buffer: make block_write_full_page() handle large folios correctly

Keep the interface as struct page, but work entirely on the folio
internally.  Removes several PAGE_SIZE assumptions and removes some
references to page->index and page->mapping.

Link: https://lkml.kernel.org/r/20230612210141.730128-7-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Tested-by: Bob Peterson <rpeterso@redhat.com>
Reviewed-by: Bob Peterson <rpeterso@redhat.com>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/buffer.c b/fs/buffer.c
index 4d518df50fab2a1dabd3f8107f54ebc93f89cf6a..34ecf55d2f1222319a9b29879d65214f608e48fb 100644 (file)
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2678,33 +2678,31 @@ int block_write_full_page(struct page *page, get_block_t *get_block,
                        struct writeback_control *wbc)
 {
        struct folio *folio = page_folio(page);
-       struct inode * const inode = page->mapping->host;
+       struct inode * const inode = folio->mapping->host;
        loff_t i_size = i_size_read(inode);
-       const pgoff_t end_index = i_size >> PAGE_SHIFT;
-       unsigned offset;
 
-       /* Is the page fully inside i_size? */
-       if (page->index < end_index)
+       /* Is the folio fully inside i_size? */
+       if (folio_pos(folio) + folio_size(folio) <= i_size)
                return __block_write_full_folio(inode, folio, get_block, wbc,
                                               end_buffer_async_write);
 
-       /* Is the page fully outside i_size? (truncate in progress) */
-       offset = i_size & (PAGE_SIZE-1);
-       if (page->index >= end_index+1 || !offset) {
+       /* Is the folio fully outside i_size? (truncate in progress) */
+       if (folio_pos(folio) >= i_size) {
                folio_unlock(folio);
                return 0; /* don't care */
        }
 
        /*
-        * The page straddles i_size.  It must be zeroed out on each and every
+        * The folio straddles i_size.  It must be zeroed out on each and every
         * writepage invocation because it may be mmapped.  "A file is mapped
         * in multiples of the page size.  For a file that is not a multiple of
-        * the  page size, the remaining memory is zeroed when mapped, and
+        * the page size, the remaining memory is zeroed when mapped, and
         * writes to that region are not written out to the file."
         */
-       zero_user_segment(page, offset, PAGE_SIZE);
+       folio_zero_segment(folio, offset_in_folio(folio, i_size),
+                       folio_size(folio));
        return __block_write_full_folio(inode, folio, get_block, wbc,
-                                                       end_buffer_async_write);
+                       end_buffer_async_write);
 }
 EXPORT_SYMBOL(block_write_full_page);