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btrfs: make grab_extent_buffer_from_page() handle subpage case

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For subpage case, grab_extent_buffer() can't really get an extent buffer
just from btrfs_subpage.

We have radix tree lock protecting us from inserting the same eb into
the tree.  Thus we don't really need to do the extra hassle, just let
alloc_extent_buffer() handle the existing eb in radix tree.

Now if two ebs are being allocated as the same time, one will fail with
-EEIXST when inserting into the radix tree.

So for grab_extent_buffer(), just always return NULL for subpage case.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo 2021-01-26 16:33:49 +08:00 committed by David Sterba
parent 760f991f14
commit 819822107d
1 changed files with 11 additions and 2 deletions
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13
fs/btrfs/extent_io.c
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@ -5284,10 +5284,19 @@ free_eb:
}
#endif
static struct extent_buffer *grab_extent_buffer(struct page *page)
static struct extent_buffer *grab_extent_buffer(
struct btrfs_fs_info *fs_info, struct page *page)
{
struct extent_buffer *exists;
/*
* For subpage case, we completely rely on radix tree to ensure we
* don't try to insert two ebs for the same bytenr. So here we always
* return NULL and just continue.
*/
if (fs_info->sectorsize < PAGE_SIZE)
return NULL;
/* Page not yet attached to an extent buffer */
if (!PagePrivate(page))
return NULL;
@ -5373,7 +5382,7 @@ struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
}
spin_lock(&mapping->private_lock);
exists = grab_extent_buffer(p);
exists = grab_extent_buffer(fs_info, p);
if (exists) {
spin_unlock(&mapping->private_lock);
unlock_page(p);