// SPDX-License-Identifier: GPL-2.0-only
/*
 * linux/fs/nfs/read.c
 *
 * Block I/O for NFS
 *
 * Partial copy of Linus' read cache modifications to fs/nfs/file.c
 * modified for async RPC by okir@monad.swb.de
 */

#include <linux/time.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/fcntl.h>
#include <linux/stat.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/pagemap.h>
#include <linux/sunrpc/clnt.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_page.h>
#include <linux/module.h>

#include "nfs4_fs.h"
#include "internal.h"
#include "iostat.h"
#include "fscache.h"
#include "pnfs.h"
#include "nfstrace.h"
#include "delegation.h"

#define NFSDBG_FACILITY         NFSDBG_PAGECACHE

const struct nfs_pgio_completion_ops nfs_async_read_completion_ops;
static const struct nfs_rw_ops nfs_rw_read_ops;

static struct kmem_cache *nfs_rdata_cachep;

static struct nfs_pgio_header *nfs_readhdr_alloc(void)
{
        struct nfs_pgio_header *p = kmem_cache_zalloc(nfs_rdata_cachep, GFP_KERNEL);

        if (p)
                p->rw_mode = FMODE_READ;
        return p;
}

static void nfs_readhdr_free(struct nfs_pgio_header *rhdr)
{
        kfree(rhdr->res.scratch);
        kmem_cache_free(nfs_rdata_cachep, rhdr);
}

static int nfs_return_empty_folio(struct folio *folio)
{
        folio_zero_segment(folio, 0, folio_size(folio));
        folio_mark_uptodate(folio);
        if (nfs_netfs_folio_unlock(folio))
                folio_unlock(folio);
        return 0;
}

void nfs_pageio_init_read(struct nfs_pageio_descriptor *pgio,
                              struct inode *inode, bool force_mds,
                              const struct nfs_pgio_completion_ops *compl_ops)
{
        struct nfs_server *server = NFS_SERVER(inode);
        const struct nfs_pageio_ops *pg_ops = &nfs_pgio_rw_ops;

#if IS_ENABLED(CONFIG_NFS_V4)
        if (server->pnfs_curr_ld && !force_mds)
                pg_ops = server->pnfs_curr_ld->pg_read_ops;
#endif /* CONFIG_NFS_V4 */
        nfs_pageio_init(pgio, inode, pg_ops, compl_ops, &nfs_rw_read_ops,
                        server->rsize, 0);
}
EXPORT_SYMBOL_GPL(nfs_pageio_init_read);

void nfs_pageio_complete_read(struct nfs_pageio_descriptor *pgio)
{
        struct nfs_pgio_mirror *pgm;
        unsigned long npages;

        nfs_pageio_complete(pgio);

        /* It doesn't make sense to do mirrored reads! */
        WARN_ON_ONCE(pgio->pg_mirror_count != 1);

        pgm = &pgio->pg_mirrors[0];
        NFS_I(pgio->pg_inode)->read_io += pgm->pg_bytes_written;
        npages = (pgm->pg_bytes_written + PAGE_SIZE - 1) >> PAGE_SHIFT;
        nfs_add_stats(pgio->pg_inode, NFSIOS_READPAGES, npages);
}


void nfs_pageio_reset_read_mds(struct nfs_pageio_descriptor *pgio)
{
        struct nfs_pgio_mirror *mirror;

        if (pgio->pg_ops && pgio->pg_ops->pg_cleanup)
                pgio->pg_ops->pg_cleanup(pgio);

        pgio->pg_ops = &nfs_pgio_rw_ops;

        /* read path should never have more than one mirror */
        WARN_ON_ONCE(pgio->pg_mirror_count != 1);

        mirror = &pgio->pg_mirrors[0];
        mirror->pg_bsize = NFS_SERVER(pgio->pg_inode)->rsize;
}
EXPORT_SYMBOL_GPL(nfs_pageio_reset_read_mds);

bool nfs_read_alloc_scratch(struct nfs_pgio_header *hdr, size_t size)
{
        WARN_ON(hdr->res.scratch != NULL);
        hdr->res.scratch = kmalloc(size, GFP_KERNEL);
        return hdr->res.scratch != NULL;
}
EXPORT_SYMBOL_GPL(nfs_read_alloc_scratch);

static void nfs_readpage_release(struct nfs_page *req, int error)
{
        struct folio *folio = nfs_page_to_folio(req);

        if (nfs_page_group_sync_on_bit(req, PG_UNLOCKPAGE))
                if (nfs_netfs_folio_unlock(folio))
                        folio_unlock(folio);

        nfs_release_request(req);
}

static void nfs_page_group_set_uptodate(struct nfs_page *req)
{
        if (nfs_page_group_sync_on_bit(req, PG_UPTODATE))
                folio_mark_uptodate(nfs_page_to_folio(req));
}

static void nfs_read_completion(struct nfs_pgio_header *hdr)
{
        unsigned long bytes = 0;
        int error;

        if (test_bit(NFS_IOHDR_REDO, &hdr->flags))
                goto out;
        while (!list_empty(&hdr->pages)) {
                struct nfs_page *req = nfs_list_entry(hdr->pages.next);
                struct folio *folio = nfs_page_to_folio(req);
                unsigned long start = req->wb_pgbase;
                unsigned long end = req->wb_pgbase + req->wb_bytes;

                if (test_bit(NFS_IOHDR_EOF, &hdr->flags)) {
                        /* note: regions of the page not covered by a
                         * request are zeroed in nfs_read_add_folio
                         */
                        if (bytes > hdr->good_bytes) {
                                /* nothing in this request was good, so zero
                                 * the full extent of the request */
                                folio_zero_segment(folio, start, end);

                        } else if (hdr->good_bytes - bytes < req->wb_bytes) {
                                /* part of this request has good bytes, but
                                 * not all. zero the bad bytes */
                                start += hdr->good_bytes - bytes;
                                WARN_ON(start < req->wb_pgbase);
                                folio_zero_segment(folio, start, end);
                        }
                }
                error = 0;
                bytes += req->wb_bytes;
                if (test_bit(NFS_IOHDR_ERROR, &hdr->flags)) {
                        if (bytes <= hdr->good_bytes)
                                nfs_page_group_set_uptodate(req);
                        else {
                                error = hdr->error;
                                xchg(&nfs_req_openctx(req)->error, error);
                        }
                } else
                        nfs_page_group_set_uptodate(req);
                nfs_list_remove_request(req);
                nfs_readpage_release(req, error);
        }
        nfs_netfs_read_completion(hdr);

out:
        hdr->release(hdr);
}

static void nfs_initiate_read(struct nfs_pgio_header *hdr,
                              struct rpc_message *msg,
                              const struct nfs_rpc_ops *rpc_ops,
                              struct rpc_task_setup *task_setup_data, int how)
{
        rpc_ops->read_setup(hdr, msg);
        nfs_netfs_initiate_read(hdr);
        trace_nfs_initiate_read(hdr);
}

static void
nfs_async_read_error(struct list_head *head, int error)
{
        struct nfs_page *req;

        while (!list_empty(head)) {
                req = nfs_list_entry(head->next);
                nfs_list_remove_request(req);
                nfs_readpage_release(req, error);
        }
}

const struct nfs_pgio_completion_ops nfs_async_read_completion_ops = {
        .error_cleanup = nfs_async_read_error,
        .completion = nfs_read_completion,
};

/*
 * This is the callback from RPC telling us whether a reply was
 * received or some error occurred (timeout or socket shutdown).
 */
static int nfs_readpage_done(struct rpc_task *task,
                             struct nfs_pgio_header *hdr,
                             struct inode *inode)
{
        int status = NFS_PROTO(inode)->read_done(task, hdr);
        if (status != 0)
                return status;

        nfs_add_stats(inode, NFSIOS_SERVERREADBYTES, hdr->res.count);
        trace_nfs_readpage_done(task, hdr);

        if (task->tk_status == -ESTALE) {
                nfs_set_inode_stale(inode);
                nfs_mark_for_revalidate(inode);
        }
        return 0;
}

static void nfs_readpage_retry(struct rpc_task *task,
                               struct nfs_pgio_header *hdr)
{
        struct nfs_pgio_args *argp = &hdr->args;
        struct nfs_pgio_res  *resp = &hdr->res;

        /* This is a short read! */
        nfs_inc_stats(hdr->inode, NFSIOS_SHORTREAD);
        trace_nfs_readpage_short(task, hdr);

        /* Has the server at least made some progress? */
        if (resp->count == 0) {
                nfs_set_pgio_error(hdr, -EIO, argp->offset);
                return;
        }

        /* For non rpc-based layout drivers, retry-through-MDS */
        if (!task->tk_ops) {
                hdr->pnfs_error = -EAGAIN;
                return;
        }

        /* Yes, so retry the read at the end of the hdr */
        hdr->mds_offset += resp->count;
        argp->offset += resp->count;
        argp->pgbase += resp->count;
        argp->count -= resp->count;
        resp->count = 0;
        resp->eof = 0;
        rpc_restart_call_prepare(task);
}

static void nfs_readpage_result(struct rpc_task *task,
                                struct nfs_pgio_header *hdr)
{
        if (hdr->res.eof) {
                loff_t pos = hdr->args.offset + hdr->res.count;
                unsigned int new = pos - hdr->io_start;

                if (hdr->good_bytes > new) {
                        hdr->good_bytes = new;
                        set_bit(NFS_IOHDR_EOF, &hdr->flags);
                        clear_bit(NFS_IOHDR_ERROR, &hdr->flags);
                }
        } else if (hdr->res.count < hdr->args.count)
                nfs_readpage_retry(task, hdr);
}

int nfs_read_add_folio(struct nfs_pageio_descriptor *pgio,
                       struct nfs_open_context *ctx,
                       struct folio *folio)
{
        struct inode *inode = folio->mapping->host;
        struct nfs_server *server = NFS_SERVER(inode);
        size_t fsize = folio_size(folio);
        unsigned int rsize = server->rsize;
        struct nfs_page *new;
        unsigned int len, aligned_len;
        int error;

        len = nfs_folio_length(folio);
        if (len == 0)
                return nfs_return_empty_folio(folio);

        aligned_len = min_t(unsigned int, ALIGN(len, rsize), fsize);

        new = nfs_page_create_from_folio(ctx, folio, 0, aligned_len);
        if (IS_ERR(new)) {
                error = PTR_ERR(new);
                if (nfs_netfs_folio_unlock(folio))
                        folio_unlock(folio);
                goto out;
        }

        if (len < fsize)
                folio_zero_segment(folio, len, fsize);
        if (!nfs_pageio_add_request(pgio, new)) {
                nfs_list_remove_request(new);
                error = pgio->pg_error;
                nfs_readpage_release(new, error);
                goto out;
        }
        return 0;
out:
        return error;
}

/*
 * Actually read a folio over the wire.
 */
static int nfs_do_read_folio(struct file *file, struct folio *folio)
{
        struct inode *inode = file_inode(file);
        struct nfs_pageio_descriptor pgio;
        struct nfs_open_context *ctx;
        int ret;

        ctx = get_nfs_open_context(nfs_file_open_context(file));

        xchg(&ctx->error, 0);
        nfs_pageio_init_read(&pgio, inode, false,
                             &nfs_async_read_completion_ops);

        ret = nfs_read_add_folio(&pgio, ctx, folio);
        if (ret)
                goto out_put;

        nfs_pageio_complete_read(&pgio);
        nfs_update_delegated_atime(inode);
        if (pgio.pg_error < 0) {
                ret = pgio.pg_error;
                goto out_put;
        }

        ret = folio_wait_locked_killable(folio);
        if (!folio_test_uptodate(folio) && !ret)
                ret = xchg(&ctx->error, 0);

out_put:
        put_nfs_open_context(ctx);
        return ret;
}

/*
 * Synchronously read a folio.
 *
 * This is not heavily used as most users to try an asynchronous
 * large read through ->readahead first.
 */
int nfs_read_folio(struct file *file, struct folio *folio)
{
        struct inode *inode = file_inode(file);
        loff_t pos = folio_pos(folio);
        size_t len = folio_size(folio);
        int ret;

        trace_nfs_aop_readpage(inode, pos, len);
        nfs_inc_stats(inode, NFSIOS_VFSREADPAGE);
        task_io_account_read(len);

        /*
         * Try to flush any pending writes to the file..
         *
         * NOTE! Because we own the folio lock, there cannot
         * be any new pending writes generated at this point
         * for this folio (other folios can be written to).
         */
        ret = nfs_wb_folio(inode, folio);
        if (ret)
                goto out_unlock;
        if (folio_test_uptodate(folio))
                goto out_unlock;

        ret = -ESTALE;
        if (NFS_STALE(inode))
                goto out_unlock;

        ret = nfs_netfs_read_folio(file, folio);
        if (ret)
                ret = nfs_do_read_folio(file, folio);
out:
        trace_nfs_aop_readpage_done(inode, pos, len, ret);
        return ret;
out_unlock:
        folio_unlock(folio);
        goto out;
}

void nfs_readahead(struct readahead_control *ractl)
{
        struct nfs_pageio_descriptor pgio;
        struct nfs_open_context *ctx;
        unsigned int nr_pages = readahead_count(ractl);
        struct file *file = ractl->file;
        struct inode *inode = ractl->mapping->host;
        struct folio *folio;
        int ret;

        trace_nfs_aop_readahead(inode, readahead_pos(ractl), nr_pages);
        nfs_inc_stats(inode, NFSIOS_VFSREADPAGES);
        task_io_account_read(readahead_length(ractl));

        ret = -ESTALE;
        if (NFS_STALE(inode))
                goto out;

        ret = nfs_netfs_readahead(ractl);
        if (!ret)
                goto out;

        if (file == NULL) {
                ret = -EBADF;
                ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
                if (ctx == NULL)
                        goto out;
        } else
                ctx = get_nfs_open_context(nfs_file_open_context(file));

        nfs_pageio_init_read(&pgio, inode, false,
                             &nfs_async_read_completion_ops);

        while ((folio = readahead_folio(ractl)) != NULL) {
                ret = nfs_read_add_folio(&pgio, ctx, folio);
                if (ret)
                        break;
        }

        nfs_pageio_complete_read(&pgio);
        nfs_update_delegated_atime(inode);

        put_nfs_open_context(ctx);
out:
        trace_nfs_aop_readahead_done(inode, nr_pages, ret);
}

int __init nfs_init_readpagecache(void)
{
        nfs_rdata_cachep = kmem_cache_create("nfs_read_data",
                                             sizeof(struct nfs_pgio_header),
                                             0, SLAB_HWCACHE_ALIGN,
                                             NULL);
        if (nfs_rdata_cachep == NULL)
                return -ENOMEM;

        return 0;
}

void nfs_destroy_readpagecache(void)
{
        kmem_cache_destroy(nfs_rdata_cachep);
}

static const struct nfs_rw_ops nfs_rw_read_ops = {
        .rw_alloc_header        = nfs_readhdr_alloc,
        .rw_free_header         = nfs_readhdr_free,
        .rw_done                = nfs_readpage_done,
        .rw_result              = nfs_readpage_result,
        .rw_initiate            = nfs_initiate_read,
};