// SPDX-License-Identifier: GPL-2.0
#include <linux/ceph/ceph_debug.h>

#include <linux/backing-dev.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/pagemap.h>
#include <linux/slab.h>
#include <linux/pagevec.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/signal.h>
#include <linux/iversion.h>
#include <linux/ktime.h>
#include <linux/netfs.h>
#include <trace/events/netfs.h>

#include "super.h"
#include "mds_client.h"
#include "cache.h"
#include "metric.h"
#include "crypto.h"
#include <linux/ceph/osd_client.h>
#include <linux/ceph/striper.h>

/*
 * Ceph address space ops.
 *
 * There are a few funny things going on here.
 *
 * The page->private field is used to reference a struct
 * ceph_snap_context for _every_ dirty page.  This indicates which
 * snapshot the page was logically dirtied in, and thus which snap
 * context needs to be associated with the osd write during writeback.
 *
 * Similarly, struct ceph_inode_info maintains a set of counters to
 * count dirty pages on the inode.  In the absence of snapshots,
 * i_wrbuffer_ref == i_wrbuffer_ref_head == the dirty page count.
 *
 * When a snapshot is taken (that is, when the client receives
 * notification that a snapshot was taken), each inode with caps and
 * with dirty pages (dirty pages implies there is a cap) gets a new
 * ceph_cap_snap in the i_cap_snaps list (which is sorted in ascending
 * order, new snaps go to the tail).  The i_wrbuffer_ref_head count is
 * moved to capsnap->dirty. (Unless a sync write is currently in
 * progress.  In that case, the capsnap is said to be "pending", new
 * writes cannot start, and the capsnap isn't "finalized" until the
 * write completes (or fails) and a final size/mtime for the inode for
 * that snap can be settled upon.)  i_wrbuffer_ref_head is reset to 0.
 *
 * On writeback, we must submit writes to the osd IN SNAP ORDER.  So,
 * we look for the first capsnap in i_cap_snaps and write out pages in
 * that snap context _only_.  Then we move on to the next capsnap,
 * eventually reaching the "live" or "head" context (i.e., pages that
 * are not yet snapped) and are writing the most recently dirtied
 * pages.
 *
 * Invalidate and so forth must take care to ensure the dirty page
 * accounting is preserved.
 */

#define CONGESTION_ON_THRESH(congestion_kb) (congestion_kb >> (PAGE_SHIFT-10))
#define CONGESTION_OFF_THRESH(congestion_kb)                            \
        (CONGESTION_ON_THRESH(congestion_kb) -                          \
         (CONGESTION_ON_THRESH(congestion_kb) >> 2))

static int ceph_netfs_check_write_begin(struct file *file, loff_t pos, unsigned int len,
                                        struct folio **foliop, void **_fsdata);

static inline struct ceph_snap_context *page_snap_context(struct page *page)
{
        if (PagePrivate(page))
                return (void *)page->private;
        return NULL;
}

/*
 * Dirty a page.  Optimistically adjust accounting, on the assumption
 * that we won't race with invalidate.  If we do, readjust.
 */
static bool ceph_dirty_folio(struct address_space *mapping, struct folio *folio)
{
        struct inode *inode = mapping->host;
        struct ceph_client *cl = ceph_inode_to_client(inode);
        struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(inode->i_sb);
        struct ceph_inode_info *ci;
        struct ceph_snap_context *snapc;

        if (folio_test_dirty(folio)) {
                doutc(cl, "%llx.%llx %p idx %lu -- already dirty\n",
                      ceph_vinop(inode), folio, folio->index);
                VM_BUG_ON_FOLIO(!folio_test_private(folio), folio);
                return false;
        }

        atomic64_inc(&mdsc->dirty_folios);

        ci = ceph_inode(inode);

        /* dirty the head */
        spin_lock(&ci->i_ceph_lock);
        if (__ceph_have_pending_cap_snap(ci)) {
                struct ceph_cap_snap *capsnap =
                                list_last_entry(&ci->i_cap_snaps,
                                                struct ceph_cap_snap,
                                                ci_item);
                snapc = ceph_get_snap_context(capsnap->context);
                capsnap->dirty_pages++;
        } else {
                BUG_ON(!ci->i_head_snapc);
                snapc = ceph_get_snap_context(ci->i_head_snapc);
                ++ci->i_wrbuffer_ref_head;
        }
        if (ci->i_wrbuffer_ref == 0)
                ihold(inode);
        ++ci->i_wrbuffer_ref;
        doutc(cl, "%llx.%llx %p idx %lu head %d/%d -> %d/%d "
              "snapc %p seq %lld (%d snaps)\n",
              ceph_vinop(inode), folio, folio->index,
              ci->i_wrbuffer_ref-1, ci->i_wrbuffer_ref_head-1,
              ci->i_wrbuffer_ref, ci->i_wrbuffer_ref_head,
              snapc, snapc->seq, snapc->num_snaps);
        spin_unlock(&ci->i_ceph_lock);

        /*
         * Reference snap context in folio->private.  Also set
         * PagePrivate so that we get invalidate_folio callback.
         */
        VM_WARN_ON_FOLIO(folio->private, folio);
        folio_attach_private(folio, snapc);

        return ceph_fscache_dirty_folio(mapping, folio);
}

/*
 * If we are truncating the full folio (i.e. offset == 0), adjust the
 * dirty folio counters appropriately.  Only called if there is private
 * data on the folio.
 */
static void ceph_invalidate_folio(struct folio *folio, size_t offset,
                                size_t length)
{
        struct inode *inode = folio->mapping->host;
        struct ceph_client *cl = ceph_inode_to_client(inode);
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_snap_context *snapc;


        if (offset != 0 || length != folio_size(folio)) {
                doutc(cl, "%llx.%llx idx %lu partial dirty page %zu~%zu\n",
                      ceph_vinop(inode), folio->index, offset, length);
                return;
        }

        WARN_ON(!folio_test_locked(folio));
        if (folio_test_private(folio)) {
                doutc(cl, "%llx.%llx idx %lu full dirty page\n",
                      ceph_vinop(inode), folio->index);

                snapc = folio_detach_private(folio);
                ceph_put_wrbuffer_cap_refs(ci, 1, snapc);
                ceph_put_snap_context(snapc);
        }

        netfs_invalidate_folio(folio, offset, length);
}

static void ceph_netfs_expand_readahead(struct netfs_io_request *rreq)
{
        struct inode *inode = rreq->inode;
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_file_layout *lo = &ci->i_layout;
        unsigned long max_pages = inode->i_sb->s_bdi->ra_pages;
        loff_t end = rreq->start + rreq->len, new_end;
        struct ceph_netfs_request_data *priv = rreq->netfs_priv;
        unsigned long max_len;
        u32 blockoff;

        if (priv) {
                /* Readahead is disabled by posix_fadvise POSIX_FADV_RANDOM */
                if (priv->file_ra_disabled)
                        max_pages = 0;
                else
                        max_pages = priv->file_ra_pages;

        }

        /* Readahead is disabled */
        if (!max_pages)
                return;

        max_len = max_pages << PAGE_SHIFT;

        /*
         * Try to expand the length forward by rounding up it to the next
         * block, but do not exceed the file size, unless the original
         * request already exceeds it.
         */
        new_end = umin(round_up(end, lo->stripe_unit), rreq->i_size);
        if (new_end > end && new_end <= rreq->start + max_len)
                rreq->len = new_end - rreq->start;

        /* Try to expand the start downward */
        div_u64_rem(rreq->start, lo->stripe_unit, &blockoff);
        if (rreq->len + blockoff <= max_len) {
                rreq->start -= blockoff;
                rreq->len += blockoff;
        }
}

static void finish_netfs_read(struct ceph_osd_request *req)
{
        struct inode *inode = req->r_inode;
        struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
        struct ceph_client *cl = fsc->client;
        struct ceph_osd_data *osd_data = osd_req_op_extent_osd_data(req, 0);
        struct netfs_io_subrequest *subreq = req->r_priv;
        struct ceph_osd_req_op *op = &req->r_ops[0];
        int err = req->r_result;
        bool sparse = (op->op == CEPH_OSD_OP_SPARSE_READ);

        ceph_update_read_metrics(&fsc->mdsc->metric, req->r_start_latency,
                                 req->r_end_latency, osd_data->length, err);

        doutc(cl, "result %d subreq->len=%zu i_size=%lld\n", req->r_result,
              subreq->len, i_size_read(req->r_inode));

        /* no object means success but no data */
        if (err == -ENOENT) {
                __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
                __set_bit(NETFS_SREQ_MADE_PROGRESS, &subreq->flags);
                err = 0;
        } else if (err == -EBLOCKLISTED) {
                fsc->blocklisted = true;
        }

        if (err >= 0) {
                if (sparse && err > 0)
                        err = ceph_sparse_ext_map_end(op);
                if (err < subreq->len &&
                    subreq->rreq->origin != NETFS_UNBUFFERED_READ &&
                    subreq->rreq->origin != NETFS_DIO_READ)
                        __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
                if (IS_ENCRYPTED(inode) && err > 0) {
                        err = ceph_fscrypt_decrypt_extents(inode,
                                        osd_data->pages, subreq->start,
                                        op->extent.sparse_ext,
                                        op->extent.sparse_ext_cnt);
                        if (err > subreq->len)
                                err = subreq->len;
                }
                if (err > 0)
                        __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
        }

        if (osd_data->type == CEPH_OSD_DATA_TYPE_PAGES) {
                ceph_put_page_vector(osd_data->pages,
                                     calc_pages_for(osd_data->alignment,
                                        osd_data->length), false);
        }
        if (err > 0) {
                subreq->transferred = err;
                err = 0;
        }
        subreq->error = err;
        trace_netfs_sreq(subreq, netfs_sreq_trace_io_progress);
        netfs_read_subreq_terminated(subreq);
        iput(req->r_inode);
        ceph_dec_osd_stopping_blocker(fsc->mdsc);
}

static bool ceph_netfs_issue_op_inline(struct netfs_io_subrequest *subreq)
{
        struct netfs_io_request *rreq = subreq->rreq;
        struct inode *inode = rreq->inode;
        struct ceph_mds_reply_info_parsed *rinfo;
        struct ceph_mds_reply_info_in *iinfo;
        struct ceph_mds_request *req;
        struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(inode->i_sb);
        struct ceph_inode_info *ci = ceph_inode(inode);
        ssize_t err = 0;
        size_t len;
        int mode;

        if (rreq->origin != NETFS_UNBUFFERED_READ &&
            rreq->origin != NETFS_DIO_READ)
                __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
        __clear_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->flags);

        if (subreq->start >= inode->i_size)
                goto out;

        /* We need to fetch the inline data. */
        mode = ceph_try_to_choose_auth_mds(inode, CEPH_STAT_CAP_INLINE_DATA);
        req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_GETATTR, mode);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto out;
        }
        req->r_ino1 = ci->i_vino;
        req->r_args.getattr.mask = cpu_to_le32(CEPH_STAT_CAP_INLINE_DATA);
        req->r_num_caps = 2;

        trace_netfs_sreq(subreq, netfs_sreq_trace_submit);
        err = ceph_mdsc_do_request(mdsc, NULL, req);
        if (err < 0)
                goto out;

        rinfo = &req->r_reply_info;
        iinfo = &rinfo->targeti;
        if (iinfo->inline_version == CEPH_INLINE_NONE) {
                /* The data got uninlined */
                ceph_mdsc_put_request(req);
                return false;
        }

        len = min_t(size_t, iinfo->inline_len - subreq->start, subreq->len);
        err = copy_to_iter(iinfo->inline_data + subreq->start, len, &subreq->io_iter);
        if (err == 0) {
                err = -EFAULT;
        } else {
                subreq->transferred += err;
                err = 0;
        }

        ceph_mdsc_put_request(req);
out:
        subreq->error = err;
        trace_netfs_sreq(subreq, netfs_sreq_trace_io_progress);
        netfs_read_subreq_terminated(subreq);
        return true;
}

static int ceph_netfs_prepare_read(struct netfs_io_subrequest *subreq)
{
        struct netfs_io_request *rreq = subreq->rreq;
        struct inode *inode = rreq->inode;
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
        u64 objno, objoff;
        u32 xlen;

        /* Truncate the extent at the end of the current block */
        ceph_calc_file_object_mapping(&ci->i_layout, subreq->start, subreq->len,
                                      &objno, &objoff, &xlen);
        rreq->io_streams[0].sreq_max_len = umin(xlen, fsc->mount_options->rsize);
        return 0;
}

static void ceph_netfs_issue_read(struct netfs_io_subrequest *subreq)
{
        struct netfs_io_request *rreq = subreq->rreq;
        struct inode *inode = rreq->inode;
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
        struct ceph_client *cl = fsc->client;
        struct ceph_osd_request *req = NULL;
        struct ceph_vino vino = ceph_vino(inode);
        int err;
        u64 len;
        bool sparse = IS_ENCRYPTED(inode) || ceph_test_mount_opt(fsc, SPARSEREAD);
        u64 off = subreq->start;
        int extent_cnt;

        if (ceph_inode_is_shutdown(inode)) {
                err = -EIO;
                goto out;
        }

        if (ceph_has_inline_data(ci) && ceph_netfs_issue_op_inline(subreq))
                return;

        // TODO: This rounding here is slightly dodgy.  It *should* work, for
        // now, as the cache only deals in blocks that are a multiple of
        // PAGE_SIZE and fscrypt blocks are at most PAGE_SIZE.  What needs to
        // happen is for the fscrypt driving to be moved into netfslib and the
        // data in the cache also to be stored encrypted.
        len = subreq->len;
        ceph_fscrypt_adjust_off_and_len(inode, &off, &len);

        req = ceph_osdc_new_request(&fsc->client->osdc, &ci->i_layout, vino,
                        off, &len, 0, 1, sparse ? CEPH_OSD_OP_SPARSE_READ : CEPH_OSD_OP_READ,
                        CEPH_OSD_FLAG_READ, NULL, ci->i_truncate_seq,
                        ci->i_truncate_size, false);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                req = NULL;
                goto out;
        }

        if (sparse) {
                extent_cnt = __ceph_sparse_read_ext_count(inode, len);
                err = ceph_alloc_sparse_ext_map(&req->r_ops[0], extent_cnt);
                if (err)
                        goto out;
        }

        doutc(cl, "%llx.%llx pos=%llu orig_len=%zu len=%llu\n",
              ceph_vinop(inode), subreq->start, subreq->len, len);

        /*
         * FIXME: For now, use CEPH_OSD_DATA_TYPE_PAGES instead of _ITER for
         * encrypted inodes. We'd need infrastructure that handles an iov_iter
         * instead of page arrays, and we don't have that as of yet. Once the
         * dust settles on the write helpers and encrypt/decrypt routines for
         * netfs, we should be able to rework this.
         */
        if (IS_ENCRYPTED(inode)) {
                struct page **pages;
                size_t page_off;

                /*
                 * FIXME: io_iter.count needs to be corrected to aligned
                 * length. Otherwise, iov_iter_get_pages_alloc2() operates
                 * with the initial unaligned length value. As a result,
                 * ceph_msg_data_cursor_init() triggers BUG_ON() in the case
                 * if msg->sparse_read_total > msg->data_length.
                 */
                subreq->io_iter.count = len;

                err = iov_iter_get_pages_alloc2(&subreq->io_iter, &pages, len, &page_off);
                if (err < 0) {
                        doutc(cl, "%llx.%llx failed to allocate pages, %d\n",
                              ceph_vinop(inode), err);
                        goto out;
                }

                /* should always give us a page-aligned read */
                WARN_ON_ONCE(page_off);
                len = err;
                err = 0;

                osd_req_op_extent_osd_data_pages(req, 0, pages, len, 0, false,
                                                 false);
        } else {
                osd_req_op_extent_osd_iter(req, 0, &subreq->io_iter);
        }
        if (!ceph_inc_osd_stopping_blocker(fsc->mdsc)) {
                err = -EIO;
                goto out;
        }
        req->r_callback = finish_netfs_read;
        req->r_priv = subreq;
        req->r_inode = inode;
        ihold(inode);

        trace_netfs_sreq(subreq, netfs_sreq_trace_submit);
        ceph_osdc_start_request(req->r_osdc, req);
out:
        ceph_osdc_put_request(req);
        if (err) {
                subreq->error = err;
                netfs_read_subreq_terminated(subreq);
        }
        doutc(cl, "%llx.%llx result %d\n", ceph_vinop(inode), err);
}

static int ceph_init_request(struct netfs_io_request *rreq, struct file *file)
{
        struct inode *inode = rreq->inode;
        struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
        struct ceph_client *cl = ceph_inode_to_client(inode);
        int got = 0, want = CEPH_CAP_FILE_CACHE;
        struct ceph_netfs_request_data *priv;
        int ret = 0;

        /* [DEPRECATED] Use PG_private_2 to mark folio being written to the cache. */
        __set_bit(NETFS_RREQ_USE_PGPRIV2, &rreq->flags);

        if (rreq->origin != NETFS_READAHEAD)
                return 0;

        priv = kzalloc_obj(*priv, GFP_NOFS);
        if (!priv)
                return -ENOMEM;

        if (file) {
                struct ceph_rw_context *rw_ctx;
                struct ceph_file_info *fi = file->private_data;

                priv->file_ra_pages = file->f_ra.ra_pages;
                priv->file_ra_disabled = file->f_mode & FMODE_RANDOM;

                rw_ctx = ceph_find_rw_context(fi);
                if (rw_ctx) {
                        rreq->netfs_priv = priv;
                        return 0;
                }
        }

        /*
         * readahead callers do not necessarily hold Fcb caps
         * (e.g. fadvise, madvise).
         */
        ret = ceph_try_get_caps(inode, CEPH_CAP_FILE_RD, want, true, &got);
        if (ret < 0) {
                doutc(cl, "%llx.%llx, error getting cap\n", ceph_vinop(inode));
                goto out;
        }

        if (!(got & want)) {
                doutc(cl, "%llx.%llx, no cache cap\n", ceph_vinop(inode));
                ret = -EACCES;
                goto out;
        }
        if (ret == 0) {
                ret = -EACCES;
                goto out;
        }

        priv->caps = got;
        rreq->netfs_priv = priv;
        rreq->io_streams[0].sreq_max_len = fsc->mount_options->rsize;

out:
        if (ret < 0) {
                if (got)
                        ceph_put_cap_refs(ceph_inode(inode), got);
                kfree(priv);
        }

        return ret;
}

static void ceph_netfs_free_request(struct netfs_io_request *rreq)
{
        struct ceph_netfs_request_data *priv = rreq->netfs_priv;

        if (!priv)
                return;

        if (priv->caps)
                ceph_put_cap_refs(ceph_inode(rreq->inode), priv->caps);
        kfree(priv);
        rreq->netfs_priv = NULL;
}

const struct netfs_request_ops ceph_netfs_ops = {
        .init_request           = ceph_init_request,
        .free_request           = ceph_netfs_free_request,
        .prepare_read           = ceph_netfs_prepare_read,
        .issue_read             = ceph_netfs_issue_read,
        .expand_readahead       = ceph_netfs_expand_readahead,
        .check_write_begin      = ceph_netfs_check_write_begin,
};

#ifdef CONFIG_CEPH_FSCACHE
static void ceph_set_page_fscache(struct page *page)
{
        folio_start_private_2(page_folio(page)); /* [DEPRECATED] */
}

static void ceph_fscache_write_terminated(void *priv, ssize_t error)
{
        struct inode *inode = priv;

        if (IS_ERR_VALUE(error) && error != -ENOBUFS)
                ceph_fscache_invalidate(inode, false);
}

static void ceph_fscache_write_to_cache(struct inode *inode, u64 off, u64 len, bool caching)
{
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct fscache_cookie *cookie = ceph_fscache_cookie(ci);

        fscache_write_to_cache(cookie, inode->i_mapping, off, len, i_size_read(inode),
                               ceph_fscache_write_terminated, inode, true, caching);
}
#else
static inline void ceph_set_page_fscache(struct page *page)
{
}

static inline void ceph_fscache_write_to_cache(struct inode *inode, u64 off, u64 len, bool caching)
{
}
#endif /* CONFIG_CEPH_FSCACHE */

struct ceph_writeback_ctl
{
        loff_t i_size;
        u64 truncate_size;
        u32 truncate_seq;
        bool size_stable;

        bool head_snapc;
        struct ceph_snap_context *snapc;
        struct ceph_snap_context *last_snapc;

        bool done;
        bool should_loop;
        bool range_whole;
        pgoff_t start_index;
        pgoff_t index;
        pgoff_t end;
        xa_mark_t tag;

        pgoff_t strip_unit_end;
        unsigned int wsize;
        unsigned int nr_folios;
        unsigned int max_pages;
        unsigned int locked_pages;

        int op_idx;
        int num_ops;
        u64 offset;
        u64 len;

        struct folio_batch fbatch;
        unsigned int processed_in_fbatch;

        bool from_pool;
        struct page **pages;
        struct page **data_pages;
};

/*
 * Get ref for the oldest snapc for an inode with dirty data... that is, the
 * only snap context we are allowed to write back.
 */
static struct ceph_snap_context *
get_oldest_context(struct inode *inode, struct ceph_writeback_ctl *ctl,
                   struct ceph_snap_context *page_snapc)
{
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_client *cl = ceph_inode_to_client(inode);
        struct ceph_snap_context *snapc = NULL;
        struct ceph_cap_snap *capsnap = NULL;

        spin_lock(&ci->i_ceph_lock);
        list_for_each_entry(capsnap, &ci->i_cap_snaps, ci_item) {
                doutc(cl, " capsnap %p snapc %p has %d dirty pages\n",
                      capsnap, capsnap->context, capsnap->dirty_pages);
                if (!capsnap->dirty_pages)
                        continue;

                /* get i_size, truncate_{seq,size} for page_snapc? */
                if (snapc && capsnap->context != page_snapc)
                        continue;

                if (ctl) {
                        if (capsnap->writing) {
                                ctl->i_size = i_size_read(inode);
                                ctl->size_stable = false;
                        } else {
                                ctl->i_size = capsnap->size;
                                ctl->size_stable = true;
                        }
                        ctl->truncate_size = capsnap->truncate_size;
                        ctl->truncate_seq = capsnap->truncate_seq;
                        ctl->head_snapc = false;
                }

                if (snapc)
                        break;

                snapc = ceph_get_snap_context(capsnap->context);
                if (!page_snapc ||
                    page_snapc == snapc ||
                    page_snapc->seq > snapc->seq)
                        break;
        }
        if (!snapc && ci->i_wrbuffer_ref_head) {
                snapc = ceph_get_snap_context(ci->i_head_snapc);
                doutc(cl, " head snapc %p has %d dirty pages\n", snapc,
                      ci->i_wrbuffer_ref_head);
                if (ctl) {
                        ctl->i_size = i_size_read(inode);
                        ctl->truncate_size = ci->i_truncate_size;
                        ctl->truncate_seq = ci->i_truncate_seq;
                        ctl->size_stable = false;
                        ctl->head_snapc = true;
                }
        }
        spin_unlock(&ci->i_ceph_lock);
        return snapc;
}

static u64 get_writepages_data_length(struct inode *inode,
                                      struct page *page, u64 start)
{
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_snap_context *snapc;
        struct ceph_cap_snap *capsnap = NULL;
        u64 end = i_size_read(inode);
        u64 ret;

        snapc = page_snap_context(ceph_fscrypt_pagecache_page(page));
        if (snapc != ci->i_head_snapc) {
                bool found = false;
                spin_lock(&ci->i_ceph_lock);
                list_for_each_entry(capsnap, &ci->i_cap_snaps, ci_item) {
                        if (capsnap->context == snapc) {
                                if (!capsnap->writing)
                                        end = capsnap->size;
                                found = true;
                                break;
                        }
                }
                spin_unlock(&ci->i_ceph_lock);
                WARN_ON(!found);
        }
        if (end > ceph_fscrypt_page_offset(page) + thp_size(page))
                end = ceph_fscrypt_page_offset(page) + thp_size(page);
        ret = end > start ? end - start : 0;
        if (ret && fscrypt_is_bounce_page(page))
                ret = round_up(ret, CEPH_FSCRYPT_BLOCK_SIZE);
        return ret;
}

/*
 * Write a folio, but leave it locked.
 *
 * If we get a write error, mark the mapping for error, but still adjust the
 * dirty page accounting (i.e., folio is no longer dirty).
 */
static int write_folio_nounlock(struct folio *folio,
                struct writeback_control *wbc)
{
        struct page *page = &folio->page;
        struct inode *inode = folio->mapping->host;
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
        struct ceph_client *cl = fsc->client;
        struct ceph_snap_context *snapc, *oldest;
        loff_t page_off = folio_pos(folio);
        int err;
        loff_t len = folio_size(folio);
        loff_t wlen;
        struct ceph_writeback_ctl ceph_wbc;
        struct ceph_osd_client *osdc = &fsc->client->osdc;
        struct ceph_osd_request *req;
        bool caching = ceph_is_cache_enabled(inode);
        struct page *bounce_page = NULL;

        doutc(cl, "%llx.%llx folio %p idx %lu\n", ceph_vinop(inode), folio,
              folio->index);

        if (ceph_inode_is_shutdown(inode))
                return -EIO;

        /* verify this is a writeable snap context */
        snapc = page_snap_context(&folio->page);
        if (!snapc) {
                doutc(cl, "%llx.%llx folio %p not dirty?\n", ceph_vinop(inode),
                      folio);
                return 0;
        }
        oldest = get_oldest_context(inode, &ceph_wbc, snapc);
        if (snapc->seq > oldest->seq) {
                doutc(cl, "%llx.%llx folio %p snapc %p not writeable - noop\n",
                      ceph_vinop(inode), folio, snapc);
                /* we should only noop if called by kswapd */
                WARN_ON(!(current->flags & PF_MEMALLOC));
                ceph_put_snap_context(oldest);
                folio_redirty_for_writepage(wbc, folio);
                return 0;
        }
        ceph_put_snap_context(oldest);

        /* is this a partial page at end of file? */
        if (page_off >= ceph_wbc.i_size) {
                doutc(cl, "%llx.%llx folio at %lu beyond eof %llu\n",
                      ceph_vinop(inode), folio->index, ceph_wbc.i_size);
                folio_invalidate(folio, 0, folio_size(folio));
                return 0;
        }

        if (ceph_wbc.i_size < page_off + len)
                len = ceph_wbc.i_size - page_off;

        wlen = IS_ENCRYPTED(inode) ? round_up(len, CEPH_FSCRYPT_BLOCK_SIZE) : len;
        doutc(cl, "%llx.%llx folio %p index %lu on %llu~%llu snapc %p seq %lld\n",
              ceph_vinop(inode), folio, folio->index, page_off, wlen, snapc,
              snapc->seq);

        if (atomic_long_inc_return(&fsc->writeback_count) >
            CONGESTION_ON_THRESH(fsc->mount_options->congestion_kb))
                fsc->write_congested = true;

        req = ceph_osdc_new_request(osdc, &ci->i_layout, ceph_vino(inode),
                                    page_off, &wlen, 0, 1, CEPH_OSD_OP_WRITE,
                                    CEPH_OSD_FLAG_WRITE, snapc,
                                    ceph_wbc.truncate_seq,
                                    ceph_wbc.truncate_size, true);
        if (IS_ERR(req)) {
                folio_redirty_for_writepage(wbc, folio);
                return PTR_ERR(req);
        }

        if (wlen < len)
                len = wlen;

        folio_start_writeback(folio);
        if (caching)
                ceph_set_page_fscache(&folio->page);
        ceph_fscache_write_to_cache(inode, page_off, len, caching);

        if (IS_ENCRYPTED(inode)) {
                bounce_page = fscrypt_encrypt_pagecache_blocks(folio,
                                                    CEPH_FSCRYPT_BLOCK_SIZE, 0,
                                                    GFP_NOFS);
                if (IS_ERR(bounce_page)) {
                        folio_redirty_for_writepage(wbc, folio);
                        folio_end_writeback(folio);
                        ceph_osdc_put_request(req);
                        return PTR_ERR(bounce_page);
                }
        }

        /* it may be a short write due to an object boundary */
        WARN_ON_ONCE(len > folio_size(folio));
        osd_req_op_extent_osd_data_pages(req, 0,
                        bounce_page ? &bounce_page : &page, wlen, 0,
                        false, false);
        doutc(cl, "%llx.%llx %llu~%llu (%llu bytes, %sencrypted)\n",
              ceph_vinop(inode), page_off, len, wlen,
              IS_ENCRYPTED(inode) ? "" : "not ");

        req->r_mtime = inode_get_mtime(inode);
        ceph_osdc_start_request(osdc, req);
        err = ceph_osdc_wait_request(osdc, req);

        ceph_update_write_metrics(&fsc->mdsc->metric, req->r_start_latency,
                                  req->r_end_latency, len, err);
        fscrypt_free_bounce_page(bounce_page);
        ceph_osdc_put_request(req);
        if (err == 0)
                err = len;

        if (err < 0) {
                struct writeback_control tmp_wbc;
                if (!wbc)
                        wbc = &tmp_wbc;
                if (err == -ERESTARTSYS) {
                        /* killed by SIGKILL */
                        doutc(cl, "%llx.%llx interrupted page %p\n",
                              ceph_vinop(inode), folio);
                        folio_redirty_for_writepage(wbc, folio);
                        folio_end_writeback(folio);
                        return err;
                }
                if (err == -EBLOCKLISTED)
                        fsc->blocklisted = true;
                doutc(cl, "%llx.%llx setting mapping error %d %p\n",
                      ceph_vinop(inode), err, folio);
                mapping_set_error(&inode->i_data, err);
                wbc->pages_skipped++;
        } else {
                doutc(cl, "%llx.%llx cleaned page %p\n",
                      ceph_vinop(inode), folio);
                err = 0;  /* vfs expects us to return 0 */
        }
        oldest = folio_detach_private(folio);
        WARN_ON_ONCE(oldest != snapc);
        folio_end_writeback(folio);
        ceph_put_wrbuffer_cap_refs(ci, 1, snapc);
        ceph_put_snap_context(snapc);  /* page's reference */

        if (atomic_long_dec_return(&fsc->writeback_count) <
            CONGESTION_OFF_THRESH(fsc->mount_options->congestion_kb))
                fsc->write_congested = false;

        return err;
}

/*
 * async writeback completion handler.
 *
 * If we get an error, set the mapping error bit, but not the individual
 * page error bits.
 */
static void writepages_finish(struct ceph_osd_request *req)
{
        struct inode *inode = req->r_inode;
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_client *cl = ceph_inode_to_client(inode);
        struct ceph_osd_data *osd_data;
        struct page *page;
        int num_pages, total_pages = 0;
        int i, j;
        int rc = req->r_result;
        struct ceph_snap_context *snapc = req->r_snapc;
        struct address_space *mapping = inode->i_mapping;
        struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
        struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(inode->i_sb);
        unsigned int len = 0;
        bool remove_page;

        doutc(cl, "%llx.%llx rc %d\n", ceph_vinop(inode), rc);
        if (rc < 0) {
                mapping_set_error(mapping, rc);
                ceph_set_error_write(ci);
                if (rc == -EBLOCKLISTED)
                        fsc->blocklisted = true;
        } else {
                ceph_clear_error_write(ci);
        }

        /*
         * We lost the cache cap, need to truncate the page before
         * it is unlocked, otherwise we'd truncate it later in the
         * page truncation thread, possibly losing some data that
         * raced its way in
         */
        remove_page = !(ceph_caps_issued(ci) &
                        (CEPH_CAP_FILE_CACHE|CEPH_CAP_FILE_LAZYIO));

        /* clean all pages */
        for (i = 0; i < req->r_num_ops; i++) {
                if (req->r_ops[i].op != CEPH_OSD_OP_WRITE) {
                        pr_warn_client(cl,
                                "%llx.%llx incorrect op %d req %p index %d tid %llu\n",
                                ceph_vinop(inode), req->r_ops[i].op, req, i,
                                req->r_tid);
                        break;
                }

                osd_data = osd_req_op_extent_osd_data(req, i);
                BUG_ON(osd_data->type != CEPH_OSD_DATA_TYPE_PAGES);
                len += osd_data->length;
                num_pages = calc_pages_for((u64)osd_data->alignment,
                                           (u64)osd_data->length);
                total_pages += num_pages;
                for (j = 0; j < num_pages; j++) {
                        page = osd_data->pages[j];
                        if (fscrypt_is_bounce_page(page)) {
                                page = fscrypt_pagecache_page(page);
                                fscrypt_free_bounce_page(osd_data->pages[j]);
                                osd_data->pages[j] = page;
                        }
                        BUG_ON(!page);
                        WARN_ON(!PageUptodate(page));

                        if (atomic_long_dec_return(&fsc->writeback_count) <
                             CONGESTION_OFF_THRESH(
                                        fsc->mount_options->congestion_kb))
                                fsc->write_congested = false;

                        ceph_put_snap_context(detach_page_private(page));
                        end_page_writeback(page);

                        if (atomic64_dec_return(&mdsc->dirty_folios) <= 0) {
                                wake_up_all(&mdsc->flush_end_wq);
                                WARN_ON(atomic64_read(&mdsc->dirty_folios) < 0);
                        }

                        doutc(cl, "unlocking %p\n", page);

                        if (remove_page)
                                generic_error_remove_folio(inode->i_mapping,
                                                          page_folio(page));

                        unlock_page(page);
                }
                doutc(cl, "%llx.%llx wrote %llu bytes cleaned %d pages\n",
                      ceph_vinop(inode), osd_data->length,
                      rc >= 0 ? num_pages : 0);

                release_pages(osd_data->pages, num_pages);
        }

        ceph_update_write_metrics(&fsc->mdsc->metric, req->r_start_latency,
                                  req->r_end_latency, len, rc);

        ceph_put_wrbuffer_cap_refs(ci, total_pages, snapc);

        osd_data = osd_req_op_extent_osd_data(req, 0);
        if (osd_data->pages_from_pool)
                mempool_free(osd_data->pages, ceph_wb_pagevec_pool);
        else
                kfree(osd_data->pages);
        ceph_osdc_put_request(req);
        ceph_dec_osd_stopping_blocker(fsc->mdsc);
}

static inline
bool is_forced_umount(struct address_space *mapping)
{
        struct inode *inode = mapping->host;
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
        struct ceph_client *cl = fsc->client;

        if (ceph_inode_is_shutdown(inode)) {
                if (ci->i_wrbuffer_ref > 0) {
                        pr_warn_ratelimited_client(cl,
                                "%llx.%llx %lld forced umount\n",
                                ceph_vinop(inode), ceph_ino(inode));
                }
                mapping_set_error(mapping, -EIO);
                return true;
        }

        return false;
}

static inline
unsigned int ceph_define_write_size(struct address_space *mapping)
{
        struct inode *inode = mapping->host;
        struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
        struct ceph_inode_info *ci = ceph_inode(inode);
        unsigned int wsize = ci->i_layout.stripe_unit;

        if (fsc->mount_options->wsize < wsize)
                wsize = fsc->mount_options->wsize;

        return wsize;
}

static inline
void ceph_folio_batch_init(struct ceph_writeback_ctl *ceph_wbc)
{
        folio_batch_init(&ceph_wbc->fbatch);
        ceph_wbc->processed_in_fbatch = 0;
}

static inline
void ceph_folio_batch_reinit(struct ceph_writeback_ctl *ceph_wbc)
{
        folio_batch_release(&ceph_wbc->fbatch);
        ceph_folio_batch_init(ceph_wbc);
}

static inline
void ceph_init_writeback_ctl(struct address_space *mapping,
                             struct writeback_control *wbc,
                             struct ceph_writeback_ctl *ceph_wbc)
{
        ceph_wbc->snapc = NULL;
        ceph_wbc->last_snapc = NULL;

        ceph_wbc->strip_unit_end = 0;
        ceph_wbc->wsize = ceph_define_write_size(mapping);

        ceph_wbc->nr_folios = 0;
        ceph_wbc->max_pages = 0;
        ceph_wbc->locked_pages = 0;

        ceph_wbc->done = false;
        ceph_wbc->should_loop = false;
        ceph_wbc->range_whole = false;

        ceph_wbc->start_index = wbc->range_cyclic ? mapping->writeback_index : 0;
        ceph_wbc->index = ceph_wbc->start_index;
        ceph_wbc->end = -1;

        ceph_wbc->tag = wbc_to_tag(wbc);

        ceph_wbc->op_idx = -1;
        ceph_wbc->num_ops = 0;
        ceph_wbc->offset = 0;
        ceph_wbc->len = 0;
        ceph_wbc->from_pool = false;

        ceph_folio_batch_init(ceph_wbc);

        ceph_wbc->pages = NULL;
        ceph_wbc->data_pages = NULL;
}

static inline
int ceph_define_writeback_range(struct address_space *mapping,
                                struct writeback_control *wbc,
                                struct ceph_writeback_ctl *ceph_wbc)
{
        struct inode *inode = mapping->host;
        struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
        struct ceph_client *cl = fsc->client;

        /* find oldest snap context with dirty data */
        ceph_wbc->snapc = get_oldest_context(inode, ceph_wbc, NULL);
        if (!ceph_wbc->snapc) {
                /* hmm, why does writepages get called when there
                   is no dirty data? */
                doutc(cl, " no snap context with dirty data?\n");
                return -ENODATA;
        }

        doutc(cl, " oldest snapc is %p seq %lld (%d snaps)\n",
              ceph_wbc->snapc, ceph_wbc->snapc->seq,
              ceph_wbc->snapc->num_snaps);

        ceph_wbc->should_loop = false;

        if (ceph_wbc->head_snapc && ceph_wbc->snapc != ceph_wbc->last_snapc) {
                /* where to start/end? */
                if (wbc->range_cyclic) {
                        ceph_wbc->index = ceph_wbc->start_index;
                        ceph_wbc->end = -1;
                        if (ceph_wbc->index > 0)
                                ceph_wbc->should_loop = true;
                        doutc(cl, " cyclic, start at %lu\n", ceph_wbc->index);
                } else {
                        ceph_wbc->index = wbc->range_start >> PAGE_SHIFT;
                        ceph_wbc->end = wbc->range_end >> PAGE_SHIFT;
                        if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
                                ceph_wbc->range_whole = true;
                        doutc(cl, " not cyclic, %lu to %lu\n",
                                ceph_wbc->index, ceph_wbc->end);
                }
        } else if (!ceph_wbc->head_snapc) {
                /* Do not respect wbc->range_{start,end}. Dirty pages
                 * in that range can be associated with newer snapc.
                 * They are not writeable until we write all dirty pages
                 * associated with 'snapc' get written */
                if (ceph_wbc->index > 0)
                        ceph_wbc->should_loop = true;
                doutc(cl, " non-head snapc, range whole\n");
        }

        ceph_put_snap_context(ceph_wbc->last_snapc);
        ceph_wbc->last_snapc = ceph_wbc->snapc;

        return 0;
}

static inline
bool has_writeback_done(struct ceph_writeback_ctl *ceph_wbc)
{
        return ceph_wbc->done && ceph_wbc->index > ceph_wbc->end;
}

static inline
bool can_next_page_be_processed(struct ceph_writeback_ctl *ceph_wbc,
                                unsigned index)
{
        return index < ceph_wbc->nr_folios &&
                ceph_wbc->locked_pages < ceph_wbc->max_pages;
}

static
int ceph_check_page_before_write(struct address_space *mapping,
                                 struct writeback_control *wbc,
                                 struct ceph_writeback_ctl *ceph_wbc,
                                 struct folio *folio)
{
        struct inode *inode = mapping->host;
        struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
        struct ceph_client *cl = fsc->client;
        struct ceph_snap_context *pgsnapc;

        /* only dirty folios, or our accounting breaks */
        if (unlikely(!folio_test_dirty(folio) || folio->mapping != mapping)) {
                doutc(cl, "!dirty or !mapping %p\n", folio);
                return -ENODATA;
        }

        /* only if matching snap context */
        pgsnapc = page_snap_context(&folio->page);
        if (pgsnapc != ceph_wbc->snapc) {
                doutc(cl, "folio snapc %p %lld != oldest %p %lld\n",
                      pgsnapc, pgsnapc->seq,
                      ceph_wbc->snapc, ceph_wbc->snapc->seq);

                if (!ceph_wbc->should_loop && !ceph_wbc->head_snapc &&
                    wbc->sync_mode != WB_SYNC_NONE)
                        ceph_wbc->should_loop = true;

                return -ENODATA;
        }

        if (folio_pos(folio) >= ceph_wbc->i_size) {
                doutc(cl, "folio at %lu beyond eof %llu\n",
                      folio->index, ceph_wbc->i_size);

                if ((ceph_wbc->size_stable ||
                    folio_pos(folio) >= i_size_read(inode)) &&
                    folio_clear_dirty_for_io(folio))
                        folio_invalidate(folio, 0, folio_size(folio));

                return -ENODATA;
        }

        if (ceph_wbc->strip_unit_end &&
            (folio->index > ceph_wbc->strip_unit_end)) {
                doutc(cl, "end of strip unit %p\n", folio);
                return -E2BIG;
        }

        return 0;
}

static inline
void __ceph_allocate_page_array(struct ceph_writeback_ctl *ceph_wbc,
                                unsigned int max_pages)
{
        ceph_wbc->pages = kmalloc_objs(*ceph_wbc->pages, max_pages, GFP_NOFS);
        if (!ceph_wbc->pages) {
                ceph_wbc->from_pool = true;
                ceph_wbc->pages = mempool_alloc(ceph_wb_pagevec_pool, GFP_NOFS);
                BUG_ON(!ceph_wbc->pages);
        }
}

static inline
void ceph_allocate_page_array(struct address_space *mapping,
                              struct ceph_writeback_ctl *ceph_wbc,
                              struct folio *folio)
{
        struct inode *inode = mapping->host;
        struct ceph_inode_info *ci = ceph_inode(inode);
        u64 objnum;
        u64 objoff;
        u32 xlen;

        /* prepare async write request */
        ceph_wbc->offset = (u64)folio_pos(folio);
        ceph_calc_file_object_mapping(&ci->i_layout,
                                        ceph_wbc->offset, ceph_wbc->wsize,
                                        &objnum, &objoff, &xlen);

        ceph_wbc->num_ops = 1;
        ceph_wbc->strip_unit_end = folio->index + ((xlen - 1) >> PAGE_SHIFT);

        BUG_ON(ceph_wbc->pages);
        ceph_wbc->max_pages = calc_pages_for(0, (u64)xlen);
        __ceph_allocate_page_array(ceph_wbc, ceph_wbc->max_pages);

        ceph_wbc->len = 0;
}

static inline
bool is_folio_index_contiguous(const struct ceph_writeback_ctl *ceph_wbc,
                              const struct folio *folio)
{
        return folio->index == (ceph_wbc->offset + ceph_wbc->len) >> PAGE_SHIFT;
}

static inline
bool is_num_ops_too_big(struct ceph_writeback_ctl *ceph_wbc)
{
        return ceph_wbc->num_ops >=
                (ceph_wbc->from_pool ?  CEPH_OSD_SLAB_OPS : CEPH_OSD_MAX_OPS);
}

static inline
bool is_write_congestion_happened(struct ceph_fs_client *fsc)
{
        return atomic_long_inc_return(&fsc->writeback_count) >
                CONGESTION_ON_THRESH(fsc->mount_options->congestion_kb);
}

static inline int move_dirty_folio_in_page_array(struct address_space *mapping,
                struct writeback_control *wbc,
                struct ceph_writeback_ctl *ceph_wbc, struct folio *folio)
{
        struct inode *inode = mapping->host;
        struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
        struct ceph_client *cl = fsc->client;
        struct page **pages = ceph_wbc->pages;
        unsigned int index = ceph_wbc->locked_pages;
        gfp_t gfp_flags = ceph_wbc->locked_pages ? GFP_NOWAIT : GFP_NOFS;

        if (IS_ENCRYPTED(inode)) {
                pages[index] = fscrypt_encrypt_pagecache_blocks(folio,
                                                                PAGE_SIZE,
                                                                0,
                                                                gfp_flags);
                if (IS_ERR(pages[index])) {
                        int err = PTR_ERR(pages[index]);

                        if (err == -EINVAL) {
                                pr_err_client(cl, "inode->i_blkbits=%hhu\n",
                                                inode->i_blkbits);
                        }

                        /* better not fail on first page! */
                        BUG_ON(ceph_wbc->locked_pages == 0);

                        pages[index] = NULL;
                        return err;
                }
        } else {
                pages[index] = &folio->page;
        }

        ceph_wbc->locked_pages++;

        return 0;
}

static
void ceph_process_folio_batch(struct address_space *mapping,
                              struct writeback_control *wbc,
                              struct ceph_writeback_ctl *ceph_wbc)
{
        struct inode *inode = mapping->host;
        struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
        struct ceph_client *cl = fsc->client;
        struct folio *folio = NULL;
        unsigned i;
        int rc;

        for (i = 0; can_next_page_be_processed(ceph_wbc, i); i++) {
                folio = ceph_wbc->fbatch.folios[i];

                if (!folio)
                        continue;

                doutc(cl, "? %p idx %lu, folio_test_writeback %#x, "
                        "folio_test_dirty %#x, folio_test_locked %#x\n",
                        folio, folio->index, folio_test_writeback(folio),
                        folio_test_dirty(folio),
                        folio_test_locked(folio));

                if (folio_test_writeback(folio) ||
                    folio_test_private_2(folio) /* [DEPRECATED] */) {
                        doutc(cl, "waiting on writeback %p\n", folio);
                        folio_wait_writeback(folio);
                        folio_wait_private_2(folio); /* [DEPRECATED] */
                        continue;
                }

                if (ceph_wbc->locked_pages == 0)
                        folio_lock(folio);
                else if (!folio_trylock(folio))
                        break;

                rc = ceph_check_page_before_write(mapping, wbc,
                                                  ceph_wbc, folio);
                if (rc == -ENODATA) {
                        folio_unlock(folio);
                        ceph_wbc->fbatch.folios[i] = NULL;
                        continue;
                } else if (rc == -E2BIG) {
                        folio_unlock(folio);
                        break;
                }

                if (!folio_clear_dirty_for_io(folio)) {
                        doutc(cl, "%p !folio_clear_dirty_for_io\n", folio);
                        folio_unlock(folio);
                        ceph_wbc->fbatch.folios[i] = NULL;
                        continue;
                }

                /*
                 * We have something to write.  If this is
                 * the first locked page this time through,
                 * calculate max possible write size and
                 * allocate a page array
                 */
                if (ceph_wbc->locked_pages == 0) {
                        ceph_allocate_page_array(mapping, ceph_wbc, folio);
                } else if (!is_folio_index_contiguous(ceph_wbc, folio)) {
                        if (is_num_ops_too_big(ceph_wbc)) {
                                folio_redirty_for_writepage(wbc, folio);
                                folio_unlock(folio);
                                break;
                        }

                        ceph_wbc->num_ops++;
                        ceph_wbc->offset = (u64)folio_pos(folio);
                        ceph_wbc->len = 0;
                }

                /* note position of first page in fbatch */
                doutc(cl, "%llx.%llx will write folio %p idx %lu\n",
                      ceph_vinop(inode), folio, folio->index);

                fsc->write_congested = is_write_congestion_happened(fsc);

                rc = move_dirty_folio_in_page_array(mapping, wbc, ceph_wbc,
                                folio);
                if (rc) {
                        folio_redirty_for_writepage(wbc, folio);
                        folio_unlock(folio);
                        break;
                }

                ceph_wbc->fbatch.folios[i] = NULL;
                ceph_wbc->len += folio_size(folio);
        }

        ceph_wbc->processed_in_fbatch = i;
}

static inline
void ceph_shift_unused_folios_left(struct folio_batch *fbatch)
{
        unsigned j, n = 0;

        /* shift unused page to beginning of fbatch */
        for (j = 0; j < folio_batch_count(fbatch); j++) {
                if (!fbatch->folios[j])
                        continue;

                if (n < j) {
                        fbatch->folios[n] = fbatch->folios[j];
                }

                n++;
        }

        fbatch->nr = n;
}

static
int ceph_submit_write(struct address_space *mapping,
                        struct writeback_control *wbc,
                        struct ceph_writeback_ctl *ceph_wbc)
{
        struct inode *inode = mapping->host;
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
        struct ceph_client *cl = fsc->client;
        struct ceph_vino vino = ceph_vino(inode);
        struct ceph_osd_request *req = NULL;
        struct page *page = NULL;
        bool caching = ceph_is_cache_enabled(inode);
        u64 offset;
        u64 len;
        unsigned i;

new_request:
        offset = ceph_fscrypt_page_offset(ceph_wbc->pages[0]);
        len = ceph_wbc->wsize;

        req = ceph_osdc_new_request(&fsc->client->osdc,
                                    &ci->i_layout, vino,
                                    offset, &len, 0, ceph_wbc->num_ops,
                                    CEPH_OSD_OP_WRITE, CEPH_OSD_FLAG_WRITE,
                                    ceph_wbc->snapc, ceph_wbc->truncate_seq,
                                    ceph_wbc->truncate_size, false);
        if (IS_ERR(req)) {
                req = ceph_osdc_new_request(&fsc->client->osdc,
                                            &ci->i_layout, vino,
                                            offset, &len, 0,
                                            min(ceph_wbc->num_ops,
                                                CEPH_OSD_SLAB_OPS),
                                            CEPH_OSD_OP_WRITE,
                                            CEPH_OSD_FLAG_WRITE,
                                            ceph_wbc->snapc,
                                            ceph_wbc->truncate_seq,
                                            ceph_wbc->truncate_size,
                                            true);
                BUG_ON(IS_ERR(req));
        }

        page = ceph_wbc->pages[ceph_wbc->locked_pages - 1];
        BUG_ON(len < ceph_fscrypt_page_offset(page) + thp_size(page) - offset);

        if (!ceph_inc_osd_stopping_blocker(fsc->mdsc)) {
                for (i = 0; i < folio_batch_count(&ceph_wbc->fbatch); i++) {
                        struct folio *folio = ceph_wbc->fbatch.folios[i];

                        if (!folio)
                                continue;

                        page = &folio->page;
                        redirty_page_for_writepage(wbc, page);
                        unlock_page(page);
                }

                for (i = 0; i < ceph_wbc->locked_pages; i++) {
                        page = ceph_fscrypt_pagecache_page(ceph_wbc->pages[i]);

                        if (!page)
                                continue;

                        redirty_page_for_writepage(wbc, page);
                        unlock_page(page);
                }

                ceph_osdc_put_request(req);
                return -EIO;
        }

        req->r_callback = writepages_finish;
        req->r_inode = inode;

        /* Format the osd request message and submit the write */
        len = 0;
        ceph_wbc->data_pages = ceph_wbc->pages;
        ceph_wbc->op_idx = 0;
        for (i = 0; i < ceph_wbc->locked_pages; i++) {
                u64 cur_offset;

                page = ceph_fscrypt_pagecache_page(ceph_wbc->pages[i]);
                cur_offset = page_offset(page);

                /*
                 * Discontinuity in page range? Ceph can handle that by just passing
                 * multiple extents in the write op.
                 */
                if (offset + len != cur_offset) {
                        /* If it's full, stop here */
                        if (ceph_wbc->op_idx + 1 == req->r_num_ops)
                                break;

                        /* Kick off an fscache write with what we have so far. */
                        ceph_fscache_write_to_cache(inode, offset, len, caching);

                        /* Start a new extent */
                        osd_req_op_extent_dup_last(req, ceph_wbc->op_idx,
                                                   cur_offset - offset);

                        doutc(cl, "got pages at %llu~%llu\n", offset, len);

                        osd_req_op_extent_osd_data_pages(req, ceph_wbc->op_idx,
                                                         ceph_wbc->data_pages,
                                                         len, 0,
                                                         ceph_wbc->from_pool,
                                                         false);
                        osd_req_op_extent_update(req, ceph_wbc->op_idx, len);

                        len = 0;
                        offset = cur_offset;
                        ceph_wbc->data_pages = ceph_wbc->pages + i;
                        ceph_wbc->op_idx++;
                }

                set_page_writeback(page);

                if (caching)
                        ceph_set_page_fscache(page);

                len += thp_size(page);
        }

        ceph_fscache_write_to_cache(inode, offset, len, caching);

        if (ceph_wbc->size_stable) {
                len = min(len, ceph_wbc->i_size - offset);
        } else if (i == ceph_wbc->locked_pages) {
                /* writepages_finish() clears writeback pages
                 * according to the data length, so make sure
                 * data length covers all locked pages */
                u64 min_len = len + 1 - thp_size(page);
                len = get_writepages_data_length(inode,
                                                 ceph_wbc->pages[i - 1],
                                                 offset);
                len = max(len, min_len);
        }

        if (IS_ENCRYPTED(inode))
                len = round_up(len, CEPH_FSCRYPT_BLOCK_SIZE);

        doutc(cl, "got pages at %llu~%llu\n", offset, len);

        if (IS_ENCRYPTED(inode) &&
            ((offset | len) & ~CEPH_FSCRYPT_BLOCK_MASK)) {
                pr_warn_client(cl,
                        "bad encrypted write offset=%lld len=%llu\n",
                        offset, len);
        }

        osd_req_op_extent_osd_data_pages(req, ceph_wbc->op_idx,
                                         ceph_wbc->data_pages, len,
                                         0, ceph_wbc->from_pool, false);
        osd_req_op_extent_update(req, ceph_wbc->op_idx, len);

        BUG_ON(ceph_wbc->op_idx + 1 != req->r_num_ops);

        ceph_wbc->from_pool = false;
        if (i < ceph_wbc->locked_pages) {
                BUG_ON(ceph_wbc->num_ops <= req->r_num_ops);
                ceph_wbc->num_ops -= req->r_num_ops;
                ceph_wbc->locked_pages -= i;

                /* allocate new pages array for next request */
                ceph_wbc->data_pages = ceph_wbc->pages;
                __ceph_allocate_page_array(ceph_wbc, ceph_wbc->locked_pages);
                memcpy(ceph_wbc->pages, ceph_wbc->data_pages + i,
                        ceph_wbc->locked_pages * sizeof(*ceph_wbc->pages));
                memset(ceph_wbc->data_pages + i, 0,
                        ceph_wbc->locked_pages * sizeof(*ceph_wbc->pages));
        } else {
                BUG_ON(ceph_wbc->num_ops != req->r_num_ops);
                /* request message now owns the pages array */
                ceph_wbc->pages = NULL;
        }

        req->r_mtime = inode_get_mtime(inode);
        ceph_osdc_start_request(&fsc->client->osdc, req);
        req = NULL;

        wbc->nr_to_write -= i;
        if (ceph_wbc->pages)
                goto new_request;

        return 0;
}

static
void ceph_wait_until_current_writes_complete(struct address_space *mapping,
                                             struct writeback_control *wbc,
                                             struct ceph_writeback_ctl *ceph_wbc)
{
        struct page *page;
        unsigned i, nr;

        if (wbc->sync_mode != WB_SYNC_NONE &&
            ceph_wbc->start_index == 0 && /* all dirty pages were checked */
            !ceph_wbc->head_snapc) {
                ceph_wbc->index = 0;

                while ((ceph_wbc->index <= ceph_wbc->end) &&
                        (nr = filemap_get_folios_tag(mapping,
                                                     &ceph_wbc->index,
                                                     (pgoff_t)-1,
                                                     PAGECACHE_TAG_WRITEBACK,
                                                     &ceph_wbc->fbatch))) {
                        for (i = 0; i < nr; i++) {
                                page = &ceph_wbc->fbatch.folios[i]->page;
                                if (page_snap_context(page) != ceph_wbc->snapc)
                                        continue;
                                wait_on_page_writeback(page);
                        }

                        folio_batch_release(&ceph_wbc->fbatch);
                        cond_resched();
                }
        }
}

/*
 * initiate async writeback
 */
static int ceph_writepages_start(struct address_space *mapping,
                                 struct writeback_control *wbc)
{
        struct inode *inode = mapping->host;
        struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
        struct ceph_client *cl = fsc->client;
        struct ceph_writeback_ctl ceph_wbc;
        int rc = 0;

        if (wbc->sync_mode == WB_SYNC_NONE && fsc->write_congested)
                return 0;

        doutc(cl, "%llx.%llx (mode=%s)\n", ceph_vinop(inode),
              wbc->sync_mode == WB_SYNC_NONE ? "NONE" :
              (wbc->sync_mode == WB_SYNC_ALL ? "ALL" : "HOLD"));

        if (is_forced_umount(mapping)) {
                /* we're in a forced umount, don't write! */
                return -EIO;
        }

        ceph_init_writeback_ctl(mapping, wbc, &ceph_wbc);

        if (!ceph_inc_osd_stopping_blocker(fsc->mdsc)) {
                rc = -EIO;
                goto out;
        }

retry:
        rc = ceph_define_writeback_range(mapping, wbc, &ceph_wbc);
        if (rc == -ENODATA) {
                /* hmm, why does writepages get called when there
                   is no dirty data? */
                rc = 0;
                goto dec_osd_stopping_blocker;
        }

        if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
                tag_pages_for_writeback(mapping, ceph_wbc.index, ceph_wbc.end);

        while (!has_writeback_done(&ceph_wbc)) {
                BUG_ON(ceph_wbc.locked_pages);
                BUG_ON(ceph_wbc.pages);

                ceph_wbc.max_pages = ceph_wbc.wsize >> PAGE_SHIFT;

get_more_pages:
                ceph_folio_batch_reinit(&ceph_wbc);

                ceph_wbc.nr_folios = filemap_get_folios_tag(mapping,
                                                            &ceph_wbc.index,
                                                            ceph_wbc.end,
                                                            ceph_wbc.tag,
                                                            &ceph_wbc.fbatch);
                doutc(cl, "pagevec_lookup_range_tag for tag %#x got %d\n",
                        ceph_wbc.tag, ceph_wbc.nr_folios);

                if (!ceph_wbc.nr_folios && !ceph_wbc.locked_pages)
                        break;

process_folio_batch:
                ceph_process_folio_batch(mapping, wbc, &ceph_wbc);
                ceph_shift_unused_folios_left(&ceph_wbc.fbatch);

                /* did we get anything? */
                if (!ceph_wbc.locked_pages)
                        goto release_folios;

                if (ceph_wbc.processed_in_fbatch) {
                        if (folio_batch_count(&ceph_wbc.fbatch) == 0 &&
                            ceph_wbc.locked_pages < ceph_wbc.max_pages) {
                                doutc(cl, "reached end fbatch, trying for more\n");
                                goto get_more_pages;
                        }
                }

                rc = ceph_submit_write(mapping, wbc, &ceph_wbc);
                if (rc)
                        goto release_folios;

                ceph_wbc.locked_pages = 0;
                ceph_wbc.strip_unit_end = 0;

                if (folio_batch_count(&ceph_wbc.fbatch) > 0) {
                        ceph_wbc.nr_folios =
                                folio_batch_count(&ceph_wbc.fbatch);
                        goto process_folio_batch;
                }

                /*
                 * We stop writing back only if we are not doing
                 * integrity sync. In case of integrity sync we have to
                 * keep going until we have written all the pages
                 * we tagged for writeback prior to entering this loop.
                 */
                if (wbc->nr_to_write <= 0 && wbc->sync_mode == WB_SYNC_NONE)
                        ceph_wbc.done = true;

release_folios:
                doutc(cl, "folio_batch release on %d folios (%p)\n",
                      (int)ceph_wbc.fbatch.nr,
                      ceph_wbc.fbatch.nr ? ceph_wbc.fbatch.folios[0] : NULL);
                folio_batch_release(&ceph_wbc.fbatch);
        }

        if (ceph_wbc.should_loop && !ceph_wbc.done) {
                /* more to do; loop back to beginning of file */
                doutc(cl, "looping back to beginning of file\n");
                /* OK even when start_index == 0 */
                ceph_wbc.end = ceph_wbc.start_index - 1;

                /* to write dirty pages associated with next snapc,
                 * we need to wait until current writes complete */
                ceph_wait_until_current_writes_complete(mapping, wbc, &ceph_wbc);

                ceph_wbc.start_index = 0;
                ceph_wbc.index = 0;
                goto retry;
        }

        if (wbc->range_cyclic || (ceph_wbc.range_whole && wbc->nr_to_write > 0))
                mapping->writeback_index = ceph_wbc.index;

dec_osd_stopping_blocker:
        ceph_dec_osd_stopping_blocker(fsc->mdsc);

out:
        ceph_put_snap_context(ceph_wbc.last_snapc);
        doutc(cl, "%llx.%llx dend - startone, rc = %d\n", ceph_vinop(inode),
              rc);

        return rc;
}

/*
 * See if a given @snapc is either writeable, or already written.
 */
static int context_is_writeable_or_written(struct inode *inode,
                                           struct ceph_snap_context *snapc)
{
        struct ceph_snap_context *oldest = get_oldest_context(inode, NULL, NULL);
        int ret = !oldest || snapc->seq <= oldest->seq;

        ceph_put_snap_context(oldest);
        return ret;
}

/**
 * ceph_find_incompatible - find an incompatible context and return it
 * @folio: folio being dirtied
 *
 * We are only allowed to write into/dirty a folio if the folio is
 * clean, or already dirty within the same snap context. Returns a
 * conflicting context if there is one, NULL if there isn't, or a
 * negative error code on other errors.
 *
 * Must be called with folio lock held.
 */
static struct ceph_snap_context *
ceph_find_incompatible(struct folio *folio)
{
        struct inode *inode = folio->mapping->host;
        struct ceph_client *cl = ceph_inode_to_client(inode);
        struct ceph_inode_info *ci = ceph_inode(inode);

        if (ceph_inode_is_shutdown(inode)) {
                doutc(cl, " %llx.%llx folio %p is shutdown\n",
                      ceph_vinop(inode), folio);
                return ERR_PTR(-ESTALE);
        }

        for (;;) {
                struct ceph_snap_context *snapc, *oldest;

                folio_wait_writeback(folio);

                snapc = page_snap_context(&folio->page);
                if (!snapc || snapc == ci->i_head_snapc)
                        break;

                /*
                 * this folio is already dirty in another (older) snap
                 * context!  is it writeable now?
                 */
                oldest = get_oldest_context(inode, NULL, NULL);
                if (snapc->seq > oldest->seq) {
                        /* not writeable -- return it for the caller to deal with */
                        ceph_put_snap_context(oldest);
                        doutc(cl, " %llx.%llx folio %p snapc %p not current or oldest\n",
                              ceph_vinop(inode), folio, snapc);
                        return ceph_get_snap_context(snapc);
                }
                ceph_put_snap_context(oldest);

                /* yay, writeable, do it now (without dropping folio lock) */
                doutc(cl, " %llx.%llx folio %p snapc %p not current, but oldest\n",
                      ceph_vinop(inode), folio, snapc);
                if (folio_clear_dirty_for_io(folio)) {
                        int r = write_folio_nounlock(folio, NULL);
                        if (r < 0)
                                return ERR_PTR(r);
                }
        }
        return NULL;
}

static int ceph_netfs_check_write_begin(struct file *file, loff_t pos, unsigned int len,
                                        struct folio **foliop, void **_fsdata)
{
        struct inode *inode = file_inode(file);
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_snap_context *snapc;

        snapc = ceph_find_incompatible(*foliop);
        if (snapc) {
                int r;

                folio_unlock(*foliop);
                folio_put(*foliop);
                *foliop = NULL;
                if (IS_ERR(snapc))
                        return PTR_ERR(snapc);

                ceph_queue_writeback(inode);
                r = wait_event_killable(ci->i_cap_wq,
                                        context_is_writeable_or_written(inode, snapc));
                ceph_put_snap_context(snapc);
                return r == 0 ? -EAGAIN : r;
        }
        return 0;
}

/*
 * We are only allowed to write into/dirty the page if the page is
 * clean, or already dirty within the same snap context.
 */
static int ceph_write_begin(const struct kiocb *iocb,
                            struct address_space *mapping,
                            loff_t pos, unsigned len,
                            struct folio **foliop, void **fsdata)
{
        struct file *file = iocb->ki_filp;
        struct inode *inode = file_inode(file);
        struct ceph_inode_info *ci = ceph_inode(inode);
        int r;

        r = netfs_write_begin(&ci->netfs, file, inode->i_mapping, pos, len, foliop, NULL);
        if (r < 0)
                return r;

        folio_wait_private_2(*foliop); /* [DEPRECATED] */
        WARN_ON_ONCE(!folio_test_locked(*foliop));
        return 0;
}

/*
 * we don't do anything in here that simple_write_end doesn't do
 * except adjust dirty page accounting
 */
static int ceph_write_end(const struct kiocb *iocb,
                          struct address_space *mapping, loff_t pos,
                          unsigned len, unsigned copied,
                          struct folio *folio, void *fsdata)
{
        struct file *file = iocb->ki_filp;
        struct inode *inode = file_inode(file);
        struct ceph_client *cl = ceph_inode_to_client(inode);
        bool check_cap = false;

        doutc(cl, "%llx.%llx file %p folio %p %d~%d (%d)\n", ceph_vinop(inode),
              file, folio, (int)pos, (int)copied, (int)len);

        if (!folio_test_uptodate(folio)) {
                /* just return that nothing was copied on a short copy */
                if (copied < len) {
                        copied = 0;
                        goto out;
                }
                folio_mark_uptodate(folio);
        }

        /* did file size increase? */
        if (pos+copied > i_size_read(inode))
                check_cap = ceph_inode_set_size(inode, pos+copied);

        folio_mark_dirty(folio);

out:
        folio_unlock(folio);
        folio_put(folio);

        if (check_cap)
                ceph_check_caps(ceph_inode(inode), CHECK_CAPS_AUTHONLY);

        return copied;
}

const struct address_space_operations ceph_aops = {
        .read_folio = netfs_read_folio,
        .readahead = netfs_readahead,
        .writepages = ceph_writepages_start,
        .write_begin = ceph_write_begin,
        .write_end = ceph_write_end,
        .dirty_folio = ceph_dirty_folio,
        .invalidate_folio = ceph_invalidate_folio,
        .release_folio = netfs_release_folio,
        .direct_IO = noop_direct_IO,
        .migrate_folio = filemap_migrate_folio,
};

static void ceph_block_sigs(sigset_t *oldset)
{
        sigset_t mask;
        siginitsetinv(&mask, sigmask(SIGKILL));
        sigprocmask(SIG_BLOCK, &mask, oldset);
}

static void ceph_restore_sigs(sigset_t *oldset)
{
        sigprocmask(SIG_SETMASK, oldset, NULL);
}

/*
 * vm ops
 */
static vm_fault_t ceph_filemap_fault(struct vm_fault *vmf)
{
        struct vm_area_struct *vma = vmf->vma;
        struct inode *inode = file_inode(vma->vm_file);
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_client *cl = ceph_inode_to_client(inode);
        struct ceph_file_info *fi = vma->vm_file->private_data;
        loff_t off = (loff_t)vmf->pgoff << PAGE_SHIFT;
        int want, got, err;
        sigset_t oldset;
        vm_fault_t ret = VM_FAULT_SIGBUS;

        if (ceph_inode_is_shutdown(inode))
                return ret;

        ceph_block_sigs(&oldset);

        doutc(cl, "%llx.%llx %llu trying to get caps\n",
              ceph_vinop(inode), off);
        if (fi->fmode & CEPH_FILE_MODE_LAZY)
                want = CEPH_CAP_FILE_CACHE | CEPH_CAP_FILE_LAZYIO;
        else
                want = CEPH_CAP_FILE_CACHE;

        got = 0;
        err = ceph_get_caps(vma->vm_file, CEPH_CAP_FILE_RD, want, -1, &got);
        if (err < 0)
                goto out_restore;

        doutc(cl, "%llx.%llx %llu got cap refs on %s\n", ceph_vinop(inode),
              off, ceph_cap_string(got));

        if ((got & (CEPH_CAP_FILE_CACHE | CEPH_CAP_FILE_LAZYIO)) ||
            !ceph_has_inline_data(ci)) {
                CEPH_DEFINE_RW_CONTEXT(rw_ctx, got);
                ceph_add_rw_context(fi, &rw_ctx);
                ret = filemap_fault(vmf);
                ceph_del_rw_context(fi, &rw_ctx);
                doutc(cl, "%llx.%llx %llu drop cap refs %s ret %x\n",
                      ceph_vinop(inode), off, ceph_cap_string(got), ret);
        } else
                err = -EAGAIN;

        ceph_put_cap_refs(ci, got);

        if (err != -EAGAIN)
                goto out_restore;

        /* read inline data */
        if (off >= PAGE_SIZE) {
                /* does not support inline data > PAGE_SIZE */
                ret = VM_FAULT_SIGBUS;
        } else {
                struct address_space *mapping = inode->i_mapping;
                struct page *page;

                filemap_invalidate_lock_shared(mapping);
                page = find_or_create_page(mapping, 0,
                                mapping_gfp_constraint(mapping, ~__GFP_FS));
                if (!page) {
                        ret = VM_FAULT_OOM;
                        goto out_inline;
                }
                err = __ceph_do_getattr(inode, page,
                                         CEPH_STAT_CAP_INLINE_DATA, true);
                if (err < 0 || off >= i_size_read(inode)) {
                        unlock_page(page);
                        put_page(page);
                        ret = vmf_error(err);
                        goto out_inline;
                }
                if (err < PAGE_SIZE)
                        zero_user_segment(page, err, PAGE_SIZE);
                else
                        flush_dcache_page(page);
                SetPageUptodate(page);
                vmf->page = page;
                ret = VM_FAULT_MAJOR | VM_FAULT_LOCKED;
out_inline:
                filemap_invalidate_unlock_shared(mapping);
                doutc(cl, "%llx.%llx %llu read inline data ret %x\n",
                      ceph_vinop(inode), off, ret);
        }
out_restore:
        ceph_restore_sigs(&oldset);
        if (err < 0)
                ret = vmf_error(err);

        return ret;
}

static vm_fault_t ceph_page_mkwrite(struct vm_fault *vmf)
{
        struct vm_area_struct *vma = vmf->vma;
        struct inode *inode = file_inode(vma->vm_file);
        struct ceph_client *cl = ceph_inode_to_client(inode);
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_file_info *fi = vma->vm_file->private_data;
        struct ceph_cap_flush *prealloc_cf;
        struct folio *folio = page_folio(vmf->page);
        loff_t off = folio_pos(folio);
        loff_t size = i_size_read(inode);
        size_t len;
        int want, got, err;
        sigset_t oldset;
        vm_fault_t ret = VM_FAULT_SIGBUS;

        if (ceph_inode_is_shutdown(inode))
                return ret;

        prealloc_cf = ceph_alloc_cap_flush();
        if (!prealloc_cf)
                return VM_FAULT_OOM;

        sb_start_pagefault(inode->i_sb);
        ceph_block_sigs(&oldset);

        if (off + folio_size(folio) <= size)
                len = folio_size(folio);
        else
                len = offset_in_folio(folio, size);

        doutc(cl, "%llx.%llx %llu~%zd getting caps i_size %llu\n",
              ceph_vinop(inode), off, len, size);
        if (fi->fmode & CEPH_FILE_MODE_LAZY)
                want = CEPH_CAP_FILE_BUFFER | CEPH_CAP_FILE_LAZYIO;
        else
                want = CEPH_CAP_FILE_BUFFER;

        got = 0;
        err = ceph_get_caps(vma->vm_file, CEPH_CAP_FILE_WR, want, off + len, &got);
        if (err < 0)
                goto out_free;

        doutc(cl, "%llx.%llx %llu~%zd got cap refs on %s\n", ceph_vinop(inode),
              off, len, ceph_cap_string(got));

        /* Update time before taking folio lock */
        file_update_time(vma->vm_file);
        inode_inc_iversion_raw(inode);

        do {
                struct ceph_snap_context *snapc;

                folio_lock(folio);

                if (folio_mkwrite_check_truncate(folio, inode) < 0) {
                        folio_unlock(folio);
                        ret = VM_FAULT_NOPAGE;
                        break;
                }

                snapc = ceph_find_incompatible(folio);
                if (!snapc) {
                        /* success.  we'll keep the folio locked. */
                        folio_mark_dirty(folio);
                        ret = VM_FAULT_LOCKED;
                        break;
                }

                folio_unlock(folio);

                if (IS_ERR(snapc)) {
                        ret = VM_FAULT_SIGBUS;
                        break;
                }

                ceph_queue_writeback(inode);
                err = wait_event_killable(ci->i_cap_wq,
                                context_is_writeable_or_written(inode, snapc));
                ceph_put_snap_context(snapc);
        } while (err == 0);

        if (ret == VM_FAULT_LOCKED) {
                int dirty;
                spin_lock(&ci->i_ceph_lock);
                dirty = __ceph_mark_dirty_caps(ci, CEPH_CAP_FILE_WR,
                                               &prealloc_cf);
                spin_unlock(&ci->i_ceph_lock);
                if (dirty)
                        __mark_inode_dirty(inode, dirty);
        }

        doutc(cl, "%llx.%llx %llu~%zd dropping cap refs on %s ret %x\n",
              ceph_vinop(inode), off, len, ceph_cap_string(got), ret);
        ceph_put_cap_refs_async(ci, got);
out_free:
        ceph_restore_sigs(&oldset);
        sb_end_pagefault(inode->i_sb);
        ceph_free_cap_flush(prealloc_cf);
        if (err < 0)
                ret = vmf_error(err);
        return ret;
}

void ceph_fill_inline_data(struct inode *inode, struct page *locked_page,
                           char *data, size_t len)
{
        struct ceph_client *cl = ceph_inode_to_client(inode);
        struct address_space *mapping = inode->i_mapping;
        struct page *page;

        if (locked_page) {
                page = locked_page;
        } else {
                if (i_size_read(inode) == 0)
                        return;
                page = find_or_create_page(mapping, 0,
                                           mapping_gfp_constraint(mapping,
                                           ~__GFP_FS));
                if (!page)
                        return;
                if (PageUptodate(page)) {
                        unlock_page(page);
                        put_page(page);
                        return;
                }
        }

        doutc(cl, "%p %llx.%llx len %zu locked_page %p\n", inode,
              ceph_vinop(inode), len, locked_page);

        if (len > 0) {
                void *kaddr = kmap_atomic(page);
                memcpy(kaddr, data, len);
                kunmap_atomic(kaddr);
        }

        if (page != locked_page) {
                if (len < PAGE_SIZE)
                        zero_user_segment(page, len, PAGE_SIZE);
                else
                        flush_dcache_page(page);

                SetPageUptodate(page);
                unlock_page(page);
                put_page(page);
        }
}

int ceph_uninline_data(struct file *file)
{
        struct inode *inode = file_inode(file);
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
        struct ceph_client *cl = fsc->client;
        struct ceph_osd_request *req = NULL;
        struct ceph_cap_flush *prealloc_cf = NULL;
        struct folio *folio = NULL;
        struct ceph_snap_context *snapc = NULL;
        u64 inline_version = CEPH_INLINE_NONE;
        struct page *pages[1];
        int err = 0;
        u64 len;

        spin_lock(&ci->i_ceph_lock);
        inline_version = ci->i_inline_version;
        spin_unlock(&ci->i_ceph_lock);

        doutc(cl, "%llx.%llx inline_version %llu\n", ceph_vinop(inode),
              inline_version);

        if (ceph_inode_is_shutdown(inode)) {
                err = -EIO;
                goto out;
        }

        if (inline_version == CEPH_INLINE_NONE)
                return 0;

        prealloc_cf = ceph_alloc_cap_flush();
        if (!prealloc_cf)
                return -ENOMEM;

        if (inline_version == 1) /* initial version, no data */
                goto out_uninline;

        down_read(&fsc->mdsc->snap_rwsem);
        spin_lock(&ci->i_ceph_lock);
        if (__ceph_have_pending_cap_snap(ci)) {
                struct ceph_cap_snap *capsnap =
                                list_last_entry(&ci->i_cap_snaps,
                                                struct ceph_cap_snap,
                                                ci_item);
                snapc = ceph_get_snap_context(capsnap->context);
        } else {
                if (!ci->i_head_snapc) {
                        ci->i_head_snapc = ceph_get_snap_context(
                                ci->i_snap_realm->cached_context);
                }
                snapc = ceph_get_snap_context(ci->i_head_snapc);
        }
        spin_unlock(&ci->i_ceph_lock);
        up_read(&fsc->mdsc->snap_rwsem);

        folio = read_mapping_folio(inode->i_mapping, 0, file);
        if (IS_ERR(folio)) {
                err = PTR_ERR(folio);
                goto out;
        }

        folio_lock(folio);

        len = i_size_read(inode);
        if (len > folio_size(folio))
                len = folio_size(folio);

        req = ceph_osdc_new_request(&fsc->client->osdc, &ci->i_layout,
                                    ceph_vino(inode), 0, &len, 0, 1,
                                    CEPH_OSD_OP_CREATE, CEPH_OSD_FLAG_WRITE,
                                    snapc, 0, 0, false);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto out_unlock;
        }

        req->r_mtime = inode_get_mtime(inode);
        ceph_osdc_start_request(&fsc->client->osdc, req);
        err = ceph_osdc_wait_request(&fsc->client->osdc, req);
        ceph_osdc_put_request(req);
        if (err < 0)
                goto out_unlock;

        req = ceph_osdc_new_request(&fsc->client->osdc, &ci->i_layout,
                                    ceph_vino(inode), 0, &len, 1, 3,
                                    CEPH_OSD_OP_WRITE, CEPH_OSD_FLAG_WRITE,
                                    snapc, ci->i_truncate_seq,
                                    ci->i_truncate_size, false);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto out_unlock;
        }

        pages[0] = folio_page(folio, 0);
        osd_req_op_extent_osd_data_pages(req, 1, pages, len, 0, false, false);

        {
                __le64 xattr_buf = cpu_to_le64(inline_version);
                err = osd_req_op_xattr_init(req, 0, CEPH_OSD_OP_CMPXATTR,
                                            "inline_version", &xattr_buf,
                                            sizeof(xattr_buf),
                                            CEPH_OSD_CMPXATTR_OP_GT,
                                            CEPH_OSD_CMPXATTR_MODE_U64);
                if (err)
                        goto out_put_req;
        }

        {
                char xattr_buf[32];
                int xattr_len = snprintf(xattr_buf, sizeof(xattr_buf),
                                         "%llu", inline_version);
                err = osd_req_op_xattr_init(req, 2, CEPH_OSD_OP_SETXATTR,
                                            "inline_version",
                                            xattr_buf, xattr_len, 0, 0);
                if (err)
                        goto out_put_req;
        }

        req->r_mtime = inode_get_mtime(inode);
        ceph_osdc_start_request(&fsc->client->osdc, req);
        err = ceph_osdc_wait_request(&fsc->client->osdc, req);

        ceph_update_write_metrics(&fsc->mdsc->metric, req->r_start_latency,
                                  req->r_end_latency, len, err);

out_uninline:
        if (!err) {
                int dirty;

                /* Set to CAP_INLINE_NONE and dirty the caps */
                down_read(&fsc->mdsc->snap_rwsem);
                spin_lock(&ci->i_ceph_lock);
                ci->i_inline_version = CEPH_INLINE_NONE;
                dirty = __ceph_mark_dirty_caps(ci, CEPH_CAP_FILE_WR, &prealloc_cf);
                spin_unlock(&ci->i_ceph_lock);
                up_read(&fsc->mdsc->snap_rwsem);
                if (dirty)
                        __mark_inode_dirty(inode, dirty);
        }
out_put_req:
        ceph_osdc_put_request(req);
        if (err == -ECANCELED)
                err = 0;
out_unlock:
        if (folio) {
                folio_unlock(folio);
                folio_put(folio);
        }
out:
        ceph_put_snap_context(snapc);
        ceph_free_cap_flush(prealloc_cf);
        doutc(cl, "%llx.%llx inline_version %llu = %d\n",
              ceph_vinop(inode), inline_version, err);
        return err;
}

static const struct vm_operations_struct ceph_vmops = {
        .fault          = ceph_filemap_fault,
        .page_mkwrite   = ceph_page_mkwrite,
};

int ceph_mmap_prepare(struct vm_area_desc *desc)
{
        struct address_space *mapping = desc->file->f_mapping;

        if (!mapping->a_ops->read_folio)
                return -ENOEXEC;
        desc->vm_ops = &ceph_vmops;
        return 0;
}

enum {
        POOL_READ       = 1,
        POOL_WRITE      = 2,
};

static int __ceph_pool_perm_get(struct ceph_inode_info *ci,
                                s64 pool, struct ceph_string *pool_ns)
{
        struct ceph_fs_client *fsc = ceph_inode_to_fs_client(&ci->netfs.inode);
        struct ceph_mds_client *mdsc = fsc->mdsc;
        struct ceph_client *cl = fsc->client;
        struct ceph_osd_request *rd_req = NULL, *wr_req = NULL;
        struct rb_node **p, *parent;
        struct ceph_pool_perm *perm;
        struct page **pages;
        size_t pool_ns_len;
        int err = 0, err2 = 0, have = 0;

        down_read(&mdsc->pool_perm_rwsem);
        p = &mdsc->pool_perm_tree.rb_node;
        while (*p) {
                perm = rb_entry(*p, struct ceph_pool_perm, node);
                if (pool < perm->pool)
                        p = &(*p)->rb_left;
                else if (pool > perm->pool)
                        p = &(*p)->rb_right;
                else {
                        int ret = ceph_compare_string(pool_ns,
                                                perm->pool_ns,
                                                perm->pool_ns_len);
                        if (ret < 0)
                                p = &(*p)->rb_left;
                        else if (ret > 0)
                                p = &(*p)->rb_right;
                        else {
                                have = perm->perm;
                                break;
                        }
                }
        }
        up_read(&mdsc->pool_perm_rwsem);
        if (*p)
                goto out;

        if (pool_ns)
                doutc(cl, "pool %lld ns %.*s no perm cached\n", pool,
                      (int)pool_ns->len, pool_ns->str);
        else
                doutc(cl, "pool %lld no perm cached\n", pool);

        down_write(&mdsc->pool_perm_rwsem);
        p = &mdsc->pool_perm_tree.rb_node;
        parent = NULL;
        while (*p) {
                parent = *p;
                perm = rb_entry(parent, struct ceph_pool_perm, node);
                if (pool < perm->pool)
                        p = &(*p)->rb_left;
                else if (pool > perm->pool)
                        p = &(*p)->rb_right;
                else {
                        int ret = ceph_compare_string(pool_ns,
                                                perm->pool_ns,
                                                perm->pool_ns_len);
                        if (ret < 0)
                                p = &(*p)->rb_left;
                        else if (ret > 0)
                                p = &(*p)->rb_right;
                        else {
                                have = perm->perm;
                                break;
                        }
                }
        }
        if (*p) {
                up_write(&mdsc->pool_perm_rwsem);
                goto out;
        }

        rd_req = ceph_osdc_alloc_request(&fsc->client->osdc, NULL,
                                         1, false, GFP_NOFS);
        if (!rd_req) {
                err = -ENOMEM;
                goto out_unlock;
        }

        rd_req->r_flags = CEPH_OSD_FLAG_READ;
        osd_req_op_init(rd_req, 0, CEPH_OSD_OP_STAT, 0);
        rd_req->r_base_oloc.pool = pool;
        if (pool_ns)
                rd_req->r_base_oloc.pool_ns = ceph_get_string(pool_ns);
        ceph_oid_printf(&rd_req->r_base_oid, "%llx.00000000", ci->i_vino.ino);

        err = ceph_osdc_alloc_messages(rd_req, GFP_NOFS);
        if (err)
                goto out_unlock;

        wr_req = ceph_osdc_alloc_request(&fsc->client->osdc, NULL,
                                         1, false, GFP_NOFS);
        if (!wr_req) {
                err = -ENOMEM;
                goto out_unlock;
        }

        wr_req->r_flags = CEPH_OSD_FLAG_WRITE;
        osd_req_op_init(wr_req, 0, CEPH_OSD_OP_CREATE, CEPH_OSD_OP_FLAG_EXCL);
        ceph_oloc_copy(&wr_req->r_base_oloc, &rd_req->r_base_oloc);
        ceph_oid_copy(&wr_req->r_base_oid, &rd_req->r_base_oid);

        err = ceph_osdc_alloc_messages(wr_req, GFP_NOFS);
        if (err)
                goto out_unlock;

        /* one page should be large enough for STAT data */
        pages = ceph_alloc_page_vector(1, GFP_KERNEL);
        if (IS_ERR(pages)) {
                err = PTR_ERR(pages);
                goto out_unlock;
        }

        osd_req_op_raw_data_in_pages(rd_req, 0, pages, PAGE_SIZE,
                                     0, false, true);
        ceph_osdc_start_request(&fsc->client->osdc, rd_req);

        wr_req->r_mtime = inode_get_mtime(&ci->netfs.inode);
        ceph_osdc_start_request(&fsc->client->osdc, wr_req);

        err = ceph_osdc_wait_request(&fsc->client->osdc, rd_req);
        err2 = ceph_osdc_wait_request(&fsc->client->osdc, wr_req);

        if (err >= 0 || err == -ENOENT)
                have |= POOL_READ;
        else if (err != -EPERM) {
                if (err == -EBLOCKLISTED)
                        fsc->blocklisted = true;
                goto out_unlock;
        }

        if (err2 == 0 || err2 == -EEXIST)
                have |= POOL_WRITE;
        else if (err2 != -EPERM) {
                if (err2 == -EBLOCKLISTED)
                        fsc->blocklisted = true;
                err = err2;
                goto out_unlock;
        }

        pool_ns_len = pool_ns ? pool_ns->len : 0;
        perm = kmalloc_flex(*perm, pool_ns, pool_ns_len + 1, GFP_NOFS);
        if (!perm) {
                err = -ENOMEM;
                goto out_unlock;
        }

        perm->pool = pool;
        perm->perm = have;
        perm->pool_ns_len = pool_ns_len;
        if (pool_ns_len > 0)
                memcpy(perm->pool_ns, pool_ns->str, pool_ns_len);
        perm->pool_ns[pool_ns_len] = 0;

        rb_link_node(&perm->node, parent, p);
        rb_insert_color(&perm->node, &mdsc->pool_perm_tree);
        err = 0;
out_unlock:
        up_write(&mdsc->pool_perm_rwsem);

        ceph_osdc_put_request(rd_req);
        ceph_osdc_put_request(wr_req);
out:
        if (!err)
                err = have;
        if (pool_ns)
                doutc(cl, "pool %lld ns %.*s result = %d\n", pool,
                      (int)pool_ns->len, pool_ns->str, err);
        else
                doutc(cl, "pool %lld result = %d\n", pool, err);
        return err;
}

int ceph_pool_perm_check(struct inode *inode, int need)
{
        struct ceph_client *cl = ceph_inode_to_client(inode);
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_string *pool_ns;
        s64 pool;
        int ret, flags;

        /* Only need to do this for regular files */
        if (!S_ISREG(inode->i_mode))
                return 0;

        if (ci->i_vino.snap != CEPH_NOSNAP) {
                /*
                 * Pool permission check needs to write to the first object.
                 * But for snapshot, head of the first object may have already
                 * been deleted. Skip check to avoid creating orphan object.
                 */
                return 0;
        }

        if (ceph_test_mount_opt(ceph_inode_to_fs_client(inode),
                                NOPOOLPERM))
                return 0;

        spin_lock(&ci->i_ceph_lock);
        flags = ci->i_ceph_flags;
        pool = ci->i_layout.pool_id;
        spin_unlock(&ci->i_ceph_lock);
check:
        if (flags & CEPH_I_POOL_PERM) {
                if ((need & CEPH_CAP_FILE_RD) && !(flags & CEPH_I_POOL_RD)) {
                        doutc(cl, "pool %lld no read perm\n", pool);
                        return -EPERM;
                }
                if ((need & CEPH_CAP_FILE_WR) && !(flags & CEPH_I_POOL_WR)) {
                        doutc(cl, "pool %lld no write perm\n", pool);
                        return -EPERM;
                }
                return 0;
        }

        pool_ns = ceph_try_get_string(ci->i_layout.pool_ns);
        ret = __ceph_pool_perm_get(ci, pool, pool_ns);
        ceph_put_string(pool_ns);
        if (ret < 0)
                return ret;

        flags = CEPH_I_POOL_PERM;
        if (ret & POOL_READ)
                flags |= CEPH_I_POOL_RD;
        if (ret & POOL_WRITE)
                flags |= CEPH_I_POOL_WR;

        spin_lock(&ci->i_ceph_lock);
        if (pool == ci->i_layout.pool_id &&
            pool_ns == rcu_dereference_raw(ci->i_layout.pool_ns)) {
                ci->i_ceph_flags |= flags;
        } else {
                pool = ci->i_layout.pool_id;
                flags = ci->i_ceph_flags;
        }
        spin_unlock(&ci->i_ceph_lock);
        goto check;
}

void ceph_pool_perm_destroy(struct ceph_mds_client *mdsc)
{
        struct ceph_pool_perm *perm;
        struct rb_node *n;

        while (!RB_EMPTY_ROOT(&mdsc->pool_perm_tree)) {
                n = rb_first(&mdsc->pool_perm_tree);
                perm = rb_entry(n, struct ceph_pool_perm, node);
                rb_erase(n, &mdsc->pool_perm_tree);
                kfree(perm);
        }
}