btrfs: add a size parameter to btrfs_alloc_subpage()

Since we can no longer assume page sized folio for data filemap folios,
allow btrfs_alloc_subpage() to accept a new parameter, @fsize,
indicating the folio size.

This doesn't follow the regular behavior of passing a folio directly,
because this function is shared by both data and metadata folios, and
for metadata folios we have extra allocation policy to ensure no large
folios whose sizes are larger than nodesize (unless it's page sized).

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Author: adam900710

fs/btrfs/extent_io.c

@@ -3256,7 +3256,7 @@ struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
 	 * manually if we exit earlier.
 	 */
 	if (btrfs_meta_is_subpage(fs_info)) {
-		prealloc = btrfs_alloc_subpage(fs_info, BTRFS_SUBPAGE_METADATA);
+		prealloc = btrfs_alloc_subpage(fs_info, PAGE_SIZE, BTRFS_SUBPAGE_METADATA);
 		if (IS_ERR(prealloc)) {
 			ret = PTR_ERR(prealloc);
 			goto out;

fs/btrfs/subpage.c

@@ -86,7 +86,7 @@ int btrfs_attach_subpage(const struct btrfs_fs_info *fs_info,
 	if (type == BTRFS_SUBPAGE_DATA && !btrfs_is_subpage(fs_info, folio))
 		return 0;
 
-	subpage = btrfs_alloc_subpage(fs_info, type);
+	subpage = btrfs_alloc_subpage(fs_info, folio_size(folio), type);
 	if (IS_ERR(subpage))
 		return  PTR_ERR(subpage);
 
@@ -113,16 +113,16 @@ void btrfs_detach_subpage(const struct btrfs_fs_info *fs_info, struct folio *fol
 }
 
 struct btrfs_subpage *btrfs_alloc_subpage(const struct btrfs_fs_info *fs_info,
-					  enum btrfs_subpage_type type)
+				size_t fsize, enum btrfs_subpage_type type)
 {
 	struct btrfs_subpage *ret;
 	unsigned int real_size;
 
-	ASSERT(fs_info->sectorsize < PAGE_SIZE);
+	ASSERT(fs_info->sectorsize < fsize);
 
 	real_size = struct_size(ret, bitmaps,
 			BITS_TO_LONGS(btrfs_bitmap_nr_max *
-				      (PAGE_SIZE >> fs_info->sectorsize_bits)));
+				      (fsize >> fs_info->sectorsize_bits)));
 	ret = kzalloc(real_size, GFP_NOFS);
 	if (!ret)
 		return ERR_PTR(-ENOMEM);

fs/btrfs/subpage.h

@@ -112,7 +112,7 @@ void btrfs_detach_subpage(const struct btrfs_fs_info *fs_info, struct folio *fol
 
 /* Allocate additional data where page represents more than one sector */
 struct btrfs_subpage *btrfs_alloc_subpage(const struct btrfs_fs_info *fs_info,
-					  enum btrfs_subpage_type type);
+				size_t fsize, enum btrfs_subpage_type type);
 void btrfs_free_subpage(struct btrfs_subpage *subpage);
 
 void btrfs_folio_inc_eb_refs(const struct btrfs_fs_info *fs_info, struct folio *folio);