Commit fdf250db authored Aug 17, 2021 by Qu Wenruo Committed by David Sterba Oct 25, 2021

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>

parent 9675ea8c

fs/btrfs/extent_io.c

+9 −7

Original line number	Diff line number	Diff line
		@@ -6137,6 +6137,7 @@ struct extent_buffer alloc_extent_buffer(struct btrfs_fs_info fs_info,
		* page, but it may change in the future for 16K page size
		* support, so we still preallocate the memory in the loop.
		*/
		if (fs_info->sectorsize < PAGE_SIZE) {
		ret = btrfs_alloc_subpage(fs_info, &prealloc,
		BTRFS_SUBPAGE_METADATA);
		if (ret < 0) {
		@@ -6145,6 +6146,7 @@ struct extent_buffer alloc_extent_buffer(struct btrfs_fs_info fs_info,
		exists = ERR_PTR(ret);
		goto free_eb;
		}
		}

		spin_lock(&mapping->private_lock);
		exists = grab_extent_buffer(fs_info, p);

fs/btrfs/subpage.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -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)