btrfs: subpage: only call btrfs_alloc_subpage() when sectorsize is smaller than PAGE_SIZE

There are two call sites of btrfs_alloc_subpage():

- btrfs_attach_subpage()
  We have ensured sectorsize is smaller than PAGE_SIZE

- alloc_extent_buffer()
  We call btrfs_alloc_subpage() unconditionally.

The alloc_extent_buffer() forces us to check the sectorsize size against
page size inside btrfs_alloc_subpage().

Since the function name, btrfs_alloc_subpage(), already indicates it
should only get called for subpage cases, do the check in
alloc_extent_buffer() and add an ASSERT() in btrfs_alloc_subpage().

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 1 insertions, 2 deletions

diff --git a/fs/btrfs/subpage.c b/fs/btrfs/subpage.c
index cb10e56ee31e..ff1c6ba34a4d 100644
--- a/fs/btrfs/subpage.c
+++ b/fs/btrfs/subpage.c
@@ -104,8 +104,7 @@ int btrfs_alloc_subpage(const struct btrfs_fs_info *fs_info,
 			struct btrfs_subpage **ret,
 			enum btrfs_subpage_type type)
 {
-	if (fs_info->sectorsize == PAGE_SIZE)
-		return 0;
+	ASSERT(fs_info->sectorsize < PAGE_SIZE);
 
 	*ret = kzalloc(sizeof(struct btrfs_subpage), GFP_NOFS);
 	if (!*ret)