From: Josef Bacik josef@toxicpanda.com
commit 3c538de0f2a74d50aff7278c092f88ae59cee688 upstream.
There was a recent regression in btrfs/177 that started happening with the size class patches ("btrfs: introduce size class to block group allocator"). This however isn't a regression introduced by those patches, but rather the bug was uncovered by a change in behavior in these patches. The patches triggered more chunk allocations in the ^free-space-tree case, which uncovered a race with device shrink.
The problem is we will set the device total size to the new size, and use this to find a hole for a device extent. However during shrink we may have device extents allocated past this range, so we could potentially find a hole in a range past our new shrink size. We don't actually limit our found extent to the device size anywhere, we assume that we will not find a hole past our device size. This isn't true with shrink as we're relocating block groups and thus creating holes past the device size.
Fix this by making sure we do not search past the new device size, and if we wander into any device extents that start after our device size simply break from the loop and use whatever hole we've already found.
CC: stable@vger.kernel.org # 4.14+ Signed-off-by: Josef Bacik josef@toxicpanda.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/volumes.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
--- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -1397,7 +1397,7 @@ again: goto out; }
- while (1) { + while (search_start < search_end) { l = path->nodes[0]; slot = path->slots[0]; if (slot >= btrfs_header_nritems(l)) { @@ -1420,6 +1420,9 @@ again: if (key.type != BTRFS_DEV_EXTENT_KEY) goto next;
+ if (key.offset > search_end) + break; + if (key.offset > search_start) { hole_size = key.offset - search_start;
@@ -1494,6 +1497,7 @@ next: else ret = 0;
+ ASSERT(max_hole_start + max_hole_size <= search_end); out: btrfs_free_path(path); *start = max_hole_start;