This issue is simple to reproduce and observe if kmemleak is enabled.
Two simple ways to reproduce it:
** 1
$ mkfs.btrfs -f /dev/loop0
$ mount /dev/loop0 /mnt/btrfs
$ btrfs balance start /mnt/btrfs
$ umount /mnt/btrfs
** 2
$ mkfs.btrfs -f /dev/loop0
$ mount /dev/loop0 /mnt/btrfs
$ touch /mnt/btrfs/foobar
$ rm -f /mnt/btrfs/foobar
$ umount /mnt/btrfs
After a while, kmemleak reports the leak:
$ cat /sys/kernel/debug/kmemleak
unreferenced object 0xffff880402b13e00 (size 128):
comm "btrfs", pid 19621, jiffies 4341648183 (age 70057.844s)
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 fc c6 b1 04 88 ff ff 04 00 04 00 ad 4e ad de .............N..
backtrace:
[<ffffffff817275a6>] kmemleak_alloc+0x26/0x50
[<ffffffff8117832b>] kmem_cache_alloc_trace+0xeb/0x1d0
[<ffffffffa04db499>] btrfs_alloc_block_rsv+0x39/0x70 [btrfs]
[<ffffffffa04f8bad>] btrfs_orphan_add+0x13d/0x1b0 [btrfs]
[<ffffffffa04e2b13>] btrfs_remove_block_group+0x143/0x500 [btrfs]
[<ffffffffa0518158>] btrfs_relocate_chunk.isra.63+0x618/0x790 [btrfs]
[<ffffffffa051bc27>] btrfs_balance+0x8f7/0xe90 [btrfs]
[<ffffffffa05240a0>] btrfs_ioctl_balance+0x250/0x550 [btrfs]
[<ffffffffa05269ca>] btrfs_ioctl+0xdfa/0x25f0 [btrfs]
[<ffffffff8119c936>] do_vfs_ioctl+0x96/0x570
[<ffffffff8119cea1>] SyS_ioctl+0x91/0xb0
[<ffffffff81750242>] system_call_fastpath+0x16/0x1b
[<ffffffffffffffff>] 0xffffffffffffffff
This affects btrfs-next, revision be8e3cd00d7293dd177e3f8a4a1645ce09ca3acb
(Btrfs: separate out tests into their own directory).
Signed-off-by: Filipe David Borba Manana <fdmanana@xxxxxxxxx>
---
V2: removed atomic_t member in struct btrfs_block_rsv, as suggested by
Josef Bacik, and use instead the condition reserved == 0 to decide
when to free the block.
V3: simplified patch, just kfree() (and not btrfs_free_block_rsv) the
root's orphan_block_rsv when free'ing the root. Thanks Josef for
the suggestion.
V4: use btrfs_free_block_rsv() instead of kfree(). The error I was getting
in xfstests when using btrfs_free_block_rsv() was unrelated, Josef just
pointed it to me (separate issue).
V5: move the free call below the iput() call, so that btrfs_evict_node()
can process the orphan_block_rsv first to do some needed cleanup before
we free it.
fs/btrfs/disk-io.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 3b12c26..9e66543 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3430,6 +3430,8 @@ static void free_fs_root(struct btrfs_root *root)
{
iput(root->cache_inode);
WARN_ON(!RB_EMPTY_ROOT(&root->inode_tree));
+ btrfs_free_block_rsv(root, root->orphan_block_rsv);
+ root->orphan_block_rsv = NULL;
if (root->anon_dev)
free_anon_bdev(root->anon_dev);
free_extent_buffer(root->node);
--
1.7.9.5
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