// SPDX-License-Identifier: GPL-2.0+
/*
 * Buffer/page management specific to NILFS
 *
 * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
 *
 * Written by Ryusuke Konishi and Seiji Kihara.
 */

#include <linux/pagemap.h>
#include <linux/writeback.h>
#include <linux/swap.h>
#include <linux/bitops.h>
#include <linux/page-flags.h>
#include <linux/list.h>
#include <linux/highmem.h>
#include <linux/pagevec.h>
#include <linux/gfp.h>
#include "nilfs.h"
#include "page.h"
#include "mdt.h"


#define NILFS_BUFFER_INHERENT_BITS                                      \
        (BIT(BH_Uptodate) | BIT(BH_Mapped) | BIT(BH_NILFS_Node) |       \
         BIT(BH_NILFS_Volatile) | BIT(BH_NILFS_Checked))

static struct buffer_head *__nilfs_get_folio_block(struct folio *folio,
                unsigned long block, pgoff_t index, int blkbits,
                unsigned long b_state)

{
        unsigned long first_block;
        struct buffer_head *bh = folio_buffers(folio);

        if (!bh)
                bh = create_empty_buffers(folio, 1 << blkbits, b_state);

        first_block = (unsigned long)index << (PAGE_SHIFT - blkbits);
        bh = get_nth_bh(bh, block - first_block);

        wait_on_buffer(bh);
        return bh;
}

struct buffer_head *nilfs_grab_buffer(struct inode *inode,
                                      struct address_space *mapping,
                                      unsigned long blkoff,
                                      unsigned long b_state)
{
        int blkbits = inode->i_blkbits;
        pgoff_t index = blkoff >> (PAGE_SHIFT - blkbits);
        struct folio *folio;
        struct buffer_head *bh;

        folio = filemap_grab_folio(mapping, index);
        if (IS_ERR(folio))
                return NULL;

        bh = __nilfs_get_folio_block(folio, blkoff, index, blkbits, b_state);
        if (unlikely(!bh)) {
                folio_unlock(folio);
                folio_put(folio);
                return NULL;
        }
        bh->b_bdev = inode->i_sb->s_bdev;
        return bh;
}

/**
 * nilfs_forget_buffer - discard dirty state
 * @bh: buffer head of the buffer to be discarded
 */
void nilfs_forget_buffer(struct buffer_head *bh)
{
        struct folio *folio = bh->b_folio;
        const unsigned long clear_bits =
                (BIT(BH_Uptodate) | BIT(BH_Dirty) | BIT(BH_Mapped) |
                 BIT(BH_Async_Write) | BIT(BH_NILFS_Volatile) |
                 BIT(BH_NILFS_Checked) | BIT(BH_NILFS_Redirected) |
                 BIT(BH_Delay));

        lock_buffer(bh);
        set_mask_bits(&bh->b_state, clear_bits, 0);
        if (nilfs_folio_buffers_clean(folio))
                __nilfs_clear_folio_dirty(folio);

        bh->b_blocknr = -1;
        folio_clear_uptodate(folio);
        folio_clear_mappedtodisk(folio);
        unlock_buffer(bh);
        brelse(bh);
}

/**
 * nilfs_copy_buffer -- copy buffer data and flags
 * @dbh: destination buffer
 * @sbh: source buffer
 */
void nilfs_copy_buffer(struct buffer_head *dbh, struct buffer_head *sbh)
{
        void *saddr, *daddr;
        unsigned long bits;
        struct folio *sfolio = sbh->b_folio, *dfolio = dbh->b_folio;
        struct buffer_head *bh;

        saddr = kmap_local_folio(sfolio, bh_offset(sbh));
        daddr = kmap_local_folio(dfolio, bh_offset(dbh));
        memcpy(daddr, saddr, sbh->b_size);
        kunmap_local(daddr);
        kunmap_local(saddr);

        dbh->b_state = sbh->b_state & NILFS_BUFFER_INHERENT_BITS;
        dbh->b_blocknr = sbh->b_blocknr;
        dbh->b_bdev = sbh->b_bdev;

        bh = dbh;
        bits = sbh->b_state & (BIT(BH_Uptodate) | BIT(BH_Mapped));
        while ((bh = bh->b_this_page) != dbh) {
                lock_buffer(bh);
                bits &= bh->b_state;
                unlock_buffer(bh);
        }
        if (bits & BIT(BH_Uptodate))
                folio_mark_uptodate(dfolio);
        else
                folio_clear_uptodate(dfolio);
        if (bits & BIT(BH_Mapped))
                folio_set_mappedtodisk(dfolio);
        else
                folio_clear_mappedtodisk(dfolio);
}

/**
 * nilfs_folio_buffers_clean - Check if a folio has dirty buffers or not.
 * @folio: Folio to be checked.
 *
 * Return: false if the folio has dirty buffers, true otherwise.
 */
bool nilfs_folio_buffers_clean(struct folio *folio)
{
        struct buffer_head *bh, *head;

        bh = head = folio_buffers(folio);
        do {
                if (buffer_dirty(bh))
                        return false;
                bh = bh->b_this_page;
        } while (bh != head);
        return true;
}

void nilfs_folio_bug(struct folio *folio)
{
        struct buffer_head *bh, *head;
        struct address_space *m;
        unsigned long ino;

        if (unlikely(!folio)) {
                printk(KERN_CRIT "NILFS_FOLIO_BUG(NULL)\n");
                return;
        }

        m = folio->mapping;
        ino = m ? m->host->i_ino : 0;

        printk(KERN_CRIT "NILFS_FOLIO_BUG(%p): cnt=%d index#=%llu flags=0x%lx "
               "mapping=%p ino=%lu\n",
               folio, folio_ref_count(folio),
               (unsigned long long)folio->index, folio->flags.f, m, ino);

        head = folio_buffers(folio);
        if (head) {
                int i = 0;

                bh = head;
                do {
                        printk(KERN_CRIT
                               " BH[%d] %p: cnt=%d block#=%llu state=0x%lx\n",
                               i++, bh, atomic_read(&bh->b_count),
                               (unsigned long long)bh->b_blocknr, bh->b_state);
                        bh = bh->b_this_page;
                } while (bh != head);
        }
}

/**
 * nilfs_copy_folio -- copy the folio with buffers
 * @dst: destination folio
 * @src: source folio
 * @copy_dirty: flag whether to copy dirty states on the folio's buffer heads.
 *
 * This function is for both data folios and btnode folios.  The dirty flag
 * should be treated by caller.  The folio must not be under i/o.
 * Both src and dst folio must be locked
 */
static void nilfs_copy_folio(struct folio *dst, struct folio *src,
                bool copy_dirty)
{
        struct buffer_head *dbh, *dbufs, *sbh;
        unsigned long mask = NILFS_BUFFER_INHERENT_BITS;

        BUG_ON(folio_test_writeback(dst));

        sbh = folio_buffers(src);
        dbh = folio_buffers(dst);
        if (!dbh)
                dbh = create_empty_buffers(dst, sbh->b_size, 0);

        if (copy_dirty)
                mask |= BIT(BH_Dirty);

        dbufs = dbh;
        do {
                lock_buffer(sbh);
                lock_buffer(dbh);
                dbh->b_state = sbh->b_state & mask;
                dbh->b_blocknr = sbh->b_blocknr;
                dbh->b_bdev = sbh->b_bdev;
                sbh = sbh->b_this_page;
                dbh = dbh->b_this_page;
        } while (dbh != dbufs);

        folio_copy(dst, src);

        if (folio_test_uptodate(src) && !folio_test_uptodate(dst))
                folio_mark_uptodate(dst);
        else if (!folio_test_uptodate(src) && folio_test_uptodate(dst))
                folio_clear_uptodate(dst);
        if (folio_test_mappedtodisk(src) && !folio_test_mappedtodisk(dst))
                folio_set_mappedtodisk(dst);
        else if (!folio_test_mappedtodisk(src) && folio_test_mappedtodisk(dst))
                folio_clear_mappedtodisk(dst);

        do {
                unlock_buffer(sbh);
                unlock_buffer(dbh);
                sbh = sbh->b_this_page;
                dbh = dbh->b_this_page;
        } while (dbh != dbufs);
}

int nilfs_copy_dirty_pages(struct address_space *dmap,
                           struct address_space *smap)
{
        struct folio_batch fbatch;
        unsigned int i;
        pgoff_t index = 0;
        int err = 0;

        folio_batch_init(&fbatch);
repeat:
        if (!filemap_get_folios_tag(smap, &index, (pgoff_t)-1,
                                PAGECACHE_TAG_DIRTY, &fbatch))
                return 0;

        for (i = 0; i < folio_batch_count(&fbatch); i++) {
                struct folio *folio = fbatch.folios[i], *dfolio;

                folio_lock(folio);
                if (unlikely(!folio_test_dirty(folio)))
                        NILFS_FOLIO_BUG(folio, "inconsistent dirty state");

                dfolio = filemap_grab_folio(dmap, folio->index);
                if (IS_ERR(dfolio)) {
                        /* No empty page is added to the page cache */
                        folio_unlock(folio);
                        err = PTR_ERR(dfolio);
                        break;
                }
                if (unlikely(!folio_buffers(folio)))
                        NILFS_FOLIO_BUG(folio,
                                       "found empty page in dat page cache");

                nilfs_copy_folio(dfolio, folio, true);
                filemap_dirty_folio(folio_mapping(dfolio), dfolio);

                folio_unlock(dfolio);
                folio_put(dfolio);
                folio_unlock(folio);
        }
        folio_batch_release(&fbatch);
        cond_resched();

        if (likely(!err))
                goto repeat;
        return err;
}

/**
 * nilfs_copy_back_pages -- copy back pages to original cache from shadow cache
 * @dmap: destination page cache
 * @smap: source page cache
 *
 * No pages must be added to the cache during this process.
 * This must be ensured by the caller.
 */
void nilfs_copy_back_pages(struct address_space *dmap,
                           struct address_space *smap)
{
        struct folio_batch fbatch;
        unsigned int i, n;
        pgoff_t start = 0;

        folio_batch_init(&fbatch);
repeat:
        n = filemap_get_folios(smap, &start, ~0UL, &fbatch);
        if (!n)
                return;

        for (i = 0; i < folio_batch_count(&fbatch); i++) {
                struct folio *folio = fbatch.folios[i], *dfolio;
                pgoff_t index = folio->index;

                folio_lock(folio);
                dfolio = filemap_lock_folio(dmap, index);
                if (!IS_ERR(dfolio)) {
                        /* overwrite existing folio in the destination cache */
                        WARN_ON(folio_test_dirty(dfolio));
                        nilfs_copy_folio(dfolio, folio, false);
                        folio_unlock(dfolio);
                        folio_put(dfolio);
                        /* Do we not need to remove folio from smap here? */
                } else {
                        struct folio *f;

                        /* move the folio to the destination cache */
                        xa_lock_irq(&smap->i_pages);
                        f = __xa_erase(&smap->i_pages, index);
                        WARN_ON(folio != f);
                        smap->nrpages--;
                        xa_unlock_irq(&smap->i_pages);

                        xa_lock_irq(&dmap->i_pages);
                        f = __xa_store(&dmap->i_pages, index, folio, GFP_NOFS);
                        if (unlikely(f)) {
                                /* Probably -ENOMEM */
                                folio->mapping = NULL;
                                folio_put(folio);
                        } else {
                                folio->mapping = dmap;
                                dmap->nrpages++;
                                if (folio_test_dirty(folio))
                                        __xa_set_mark(&dmap->i_pages, index,
                                                        PAGECACHE_TAG_DIRTY);
                        }
                        xa_unlock_irq(&dmap->i_pages);
                }
                folio_unlock(folio);
        }
        folio_batch_release(&fbatch);
        cond_resched();

        goto repeat;
}

/**
 * nilfs_clear_dirty_pages - discard dirty pages in address space
 * @mapping: address space with dirty pages for discarding
 */
void nilfs_clear_dirty_pages(struct address_space *mapping)
{
        struct folio_batch fbatch;
        unsigned int i;
        pgoff_t index = 0;

        folio_batch_init(&fbatch);

        while (filemap_get_folios_tag(mapping, &index, (pgoff_t)-1,
                                PAGECACHE_TAG_DIRTY, &fbatch)) {
                for (i = 0; i < folio_batch_count(&fbatch); i++) {
                        struct folio *folio = fbatch.folios[i];

                        folio_lock(folio);

                        /*
                         * This folio may have been removed from the address
                         * space by truncation or invalidation when the lock
                         * was acquired.  Skip processing in that case.
                         */
                        if (likely(folio->mapping == mapping))
                                nilfs_clear_folio_dirty(folio);

                        folio_unlock(folio);
                }
                folio_batch_release(&fbatch);
                cond_resched();
        }
}

/**
 * nilfs_clear_folio_dirty - discard dirty folio
 * @folio: dirty folio that will be discarded
 *
 * nilfs_clear_folio_dirty() clears working states including dirty state for
 * the folio and its buffers.  If the folio has buffers, clear only if it is
 * confirmed that none of the buffer heads are busy (none have valid
 * references and none are locked).
 */
void nilfs_clear_folio_dirty(struct folio *folio)
{
        struct buffer_head *bh, *head;

        BUG_ON(!folio_test_locked(folio));

        head = folio_buffers(folio);
        if (head) {
                const unsigned long clear_bits =
                        (BIT(BH_Uptodate) | BIT(BH_Dirty) | BIT(BH_Mapped) |
                         BIT(BH_Async_Write) | BIT(BH_NILFS_Volatile) |
                         BIT(BH_NILFS_Checked) | BIT(BH_NILFS_Redirected) |
                         BIT(BH_Delay));
                bool busy, invalidated = false;

recheck_buffers:
                busy = false;
                bh = head;
                do {
                        if (atomic_read(&bh->b_count) | buffer_locked(bh)) {
                                busy = true;
                                break;
                        }
                } while (bh = bh->b_this_page, bh != head);

                if (busy) {
                        if (invalidated)
                                return;
                        invalidate_bh_lrus();
                        invalidated = true;
                        goto recheck_buffers;
                }

                bh = head;
                do {
                        lock_buffer(bh);
                        set_mask_bits(&bh->b_state, clear_bits, 0);
                        unlock_buffer(bh);
                } while (bh = bh->b_this_page, bh != head);
        }

        folio_clear_uptodate(folio);
        folio_clear_mappedtodisk(folio);
        folio_clear_checked(folio);
        __nilfs_clear_folio_dirty(folio);
}

unsigned int nilfs_page_count_clean_buffers(struct folio *folio,
                                            unsigned int from, unsigned int to)
{
        unsigned int block_start, block_end;
        struct buffer_head *bh, *head;
        unsigned int nc = 0;

        for (bh = head = folio_buffers(folio), block_start = 0;
             bh != head || !block_start;
             block_start = block_end, bh = bh->b_this_page) {
                block_end = block_start + bh->b_size;
                if (block_end > from && block_start < to && !buffer_dirty(bh))
                        nc++;
        }
        return nc;
}

/*
 * NILFS2 needs clear_page_dirty() in the following two cases:
 *
 * 1) For B-tree node pages and data pages of DAT file, NILFS2 clears dirty
 *    flag of pages when it copies back pages from shadow cache to the
 *    original cache.
 *
 * 2) Some B-tree operations like insertion or deletion may dispose buffers
 *    in dirty state, and this needs to cancel the dirty state of their pages.
 */
void __nilfs_clear_folio_dirty(struct folio *folio)
{
        struct address_space *mapping = folio->mapping;

        if (mapping) {
                xa_lock_irq(&mapping->i_pages);
                if (folio_test_dirty(folio)) {
                        __xa_clear_mark(&mapping->i_pages, folio->index,
                                             PAGECACHE_TAG_DIRTY);
                        xa_unlock_irq(&mapping->i_pages);
                        folio_clear_dirty_for_io(folio);
                        return;
                }
                xa_unlock_irq(&mapping->i_pages);
                return;
        }
        folio_clear_dirty(folio);
}

/**
 * nilfs_find_uncommitted_extent - find extent of uncommitted data
 * @inode: inode
 * @start_blk: start block offset (in)
 * @blkoff: start offset of the found extent (out)
 *
 * This function searches an extent of buffers marked "delayed" which
 * starts from a block offset equal to or larger than @start_blk.  If
 * such an extent was found, this will store the start offset in
 * @blkoff and return its length in blocks.
 *
 * Return: Length in blocks of found extent, 0 otherwise.
 */
unsigned long nilfs_find_uncommitted_extent(struct inode *inode,
                                            sector_t start_blk,
                                            sector_t *blkoff)
{
        unsigned int i, nr_folios;
        pgoff_t index;
        unsigned long length = 0;
        struct folio_batch fbatch;
        struct folio *folio;

        if (inode->i_mapping->nrpages == 0)
                return 0;

        index = start_blk >> (PAGE_SHIFT - inode->i_blkbits);

        folio_batch_init(&fbatch);

repeat:
        nr_folios = filemap_get_folios_contig(inode->i_mapping, &index, ULONG_MAX,
                        &fbatch);
        if (nr_folios == 0)
                return length;

        i = 0;
        do {
                folio = fbatch.folios[i];

                folio_lock(folio);
                if (folio_buffers(folio)) {
                        struct buffer_head *bh, *head;
                        sector_t b;

                        b = folio->index << (PAGE_SHIFT - inode->i_blkbits);
                        bh = head = folio_buffers(folio);
                        do {
                                if (b < start_blk)
                                        continue;
                                if (buffer_delay(bh)) {
                                        if (length == 0)
                                                *blkoff = b;
                                        length++;
                                } else if (length > 0) {
                                        goto out_locked;
                                }
                        } while (++b, bh = bh->b_this_page, bh != head);
                } else {
                        if (length > 0)
                                goto out_locked;
                }
                folio_unlock(folio);

        } while (++i < nr_folios);

        folio_batch_release(&fbatch);
        cond_resched();
        goto repeat;

out_locked:
        folio_unlock(folio);
        folio_batch_release(&fbatch);
        return length;
}