6.16-stable review patch. If anyone has any objections, please let me know.
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From: Filipe Manana fdmanana@suse.com
[ Upstream commit 71c086b30d4373a01bd5627f54516a72891a026a ]
It's hard to read the logic to break out of the while loop since it's a very long expression consisting of a logical or of two composite expressions, each one composed by a logical and. Further each one is also testing for the EXTENT_BUFFER_UNMAPPED bit, making it more verbose than necessary.
So change from this:
if ((!test_bit(EXTENT_BUFFER_UNMAPPED, &eb->bflags) && refs <= 3) || (test_bit(EXTENT_BUFFER_UNMAPPED, &eb->bflags) && refs == 1)) break;
To this:
if (test_bit(EXTENT_BUFFER_UNMAPPED, &eb->bflags)) { if (refs == 1) break; } else if (refs <= 3) { break; }
At least on x86_64 using gcc 9.3.0, this doesn't change the object size.
Reviewed-by: Boris Burkov boris@bur.io Signed-off-by: Filipe Manana fdmanana@suse.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Stable-dep-of: ad580dfa388f ("btrfs: fix subpage deadlock in try_release_subpage_extent_buffer()") Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/extent_io.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
--- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -3486,10 +3486,13 @@ void free_extent_buffer(struct extent_bu
refs = atomic_read(&eb->refs); while (1) { - if ((!test_bit(EXTENT_BUFFER_UNMAPPED, &eb->bflags) && refs <= 3) - || (test_bit(EXTENT_BUFFER_UNMAPPED, &eb->bflags) && - refs == 1)) + if (test_bit(EXTENT_BUFFER_UNMAPPED, &eb->bflags)) { + if (refs == 1) + break; + } else if (refs <= 3) { break; + } + if (atomic_try_cmpxchg(&eb->refs, &refs, refs - 1)) return; }