mpage: convert __mpage_writepage() to use a folio more fully

This is just a conversion to the folio API.  While there are some nods
towards supporting multi-page folios in here, the blocks array is still
sized for one page's worth of blocks, and there are other assumptions such
as the blocks_per_page variable.

[willy@infradead.org: fix accidentally-triggering WARN_ON_ONCE]
Link: https://lkml.kernel.org/r/Y9kuaBgXf9lKJ8b0@casper.infradead.org
Link: https://lkml.kernel.org/r/20230126201255.1681189-3-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/mpage.c b/fs/mpage.c
index 4890369..b9b7f6d 100644 (file)
--- a/fs/mpage.c
+++ b/fs/mpage.c
@@ -443,13 +443,11 @@ void clean_page_buffers(struct page *page)
 static int __mpage_writepage(struct folio *folio, struct writeback_control *wbc,
                      void *data)
 {
-       struct page *page = &folio->page;
        struct mpage_data *mpd = data;
        struct bio *bio = mpd->bio;
-       struct address_space *mapping = page->mapping;
-       struct inode *inode = page->mapping->host;
+       struct address_space *mapping = folio->mapping;
+       struct inode *inode = mapping->host;
        const unsigned blkbits = inode->i_blkbits;
-       unsigned long end_index;
        const unsigned blocks_per_page = PAGE_SIZE >> blkbits;
        sector_t last_block;
        sector_t block_in_file;
@@ -460,13 +458,13 @@ static int __mpage_writepage(struct folio *folio, struct writeback_control *wbc,
        int boundary = 0;
        sector_t boundary_block = 0;
        struct block_device *boundary_bdev = NULL;
-       int length;
+       size_t length;
        struct buffer_head map_bh;
        loff_t i_size = i_size_read(inode);
        int ret = 0;
+       struct buffer_head *head = folio_buffers(folio);
 
-       if (page_has_buffers(page)) {
-               struct buffer_head *head = page_buffers(page);
+       if (head) {
                struct buffer_head *bh = head;
 
                /* If they're all mapped and dirty, do it */
@@ -518,8 +516,8 @@ static int __mpage_writepage(struct folio *folio, struct writeback_control *wbc,
        /*
         * The page has no buffers: map it to disk
         */
-       BUG_ON(!PageUptodate(page));
-       block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);
+       BUG_ON(!folio_test_uptodate(folio));
+       block_in_file = (sector_t)folio->index << (PAGE_SHIFT - blkbits);
        /*
         * Whole page beyond EOF? Skip allocating blocks to avoid leaking
         * space.
@@ -527,7 +525,7 @@ static int __mpage_writepage(struct folio *folio, struct writeback_control *wbc,
        if (block_in_file >= (i_size + (1 << blkbits) - 1) >> blkbits)
                goto page_is_mapped;
        last_block = (i_size - 1) >> blkbits;
-       map_bh.b_page = page;
+       map_bh.b_folio = folio;
        for (page_block = 0; page_block < blocks_per_page; ) {
 
                map_bh.b_state = 0;
@@ -556,8 +554,11 @@ static int __mpage_writepage(struct folio *folio, struct writeback_control *wbc,
        first_unmapped = page_block;
 
 page_is_mapped:
-       end_index = i_size >> PAGE_SHIFT;
-       if (page->index >= end_index) {
+       /* Don't bother writing beyond EOF, truncate will discard the folio */
+       if (folio_pos(folio) >= i_size)
+               goto confused;
+       length = folio_size(folio);
+       if (folio_pos(folio) + length > i_size) {
                /*
                 * The page straddles i_size.  It must be zeroed out on each
                 * and every writepage invocation because it may be mmapped.
@@ -566,11 +567,8 @@ page_is_mapped:
                 * is zeroed when mapped, and writes to that region are not
                 * written out to the file."
                 */
-               unsigned offset = i_size & (PAGE_SIZE - 1);
-
-               if (page->index > end_index || !offset)
-                       goto confused;
-               zero_user_segment(page, offset, PAGE_SIZE);
+               length = i_size - folio_pos(folio);
+               folio_zero_segment(folio, length, folio_size(folio));
        }
 
        /*
@@ -593,18 +591,18 @@ alloc_new:
         * the confused fail path above (OOM) will be very confused when
         * it finds all bh marked clean (i.e. it will not write anything)
         */
-       wbc_account_cgroup_owner(wbc, page, PAGE_SIZE);
+       wbc_account_cgroup_owner(wbc, &folio->page, folio_size(folio));
        length = first_unmapped << blkbits;
-       if (bio_add_page(bio, page, length, 0) < length) {
+       if (!bio_add_folio(bio, folio, length, 0)) {
                bio = mpage_bio_submit(bio);
                goto alloc_new;
        }
 
-       clean_buffers(page, first_unmapped);
+       clean_buffers(&folio->page, first_unmapped);
 
-       BUG_ON(PageWriteback(page));
-       set_page_writeback(page);
-       unlock_page(page);
+       BUG_ON(folio_test_writeback(folio));
+       folio_start_writeback(folio);
+       folio_unlock(folio);
        if (boundary || (first_unmapped != blocks_per_page)) {
                bio = mpage_bio_submit(bio);
                if (boundary_block) {
@@ -623,7 +621,7 @@ confused:
        /*
         * The caller has a ref on the inode, so *mapping is stable
         */
-       ret = block_write_full_page(page, mpd->get_block, wbc);
+       ret = block_write_full_page(&folio->page, mpd->get_block, wbc);
        mapping_set_error(mapping, ret);
 out:
        mpd->bio = bio;