Hi Filipe,
On Tue, Aug 20, 2013 at 2:52 AM, Filipe David Borba Manana
<fdmanana@xxxxxxxxx> wrote:
>
> 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
I tried the second repro script on kernel 3.8.13, and kmemleak does
not report a leak (even if I force the kmemleak scan). I did not try
the balance-repro script, though. Am I missing something?
Thanks,
Alex.
>
>
> 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.
> V6: free the root's orphan_block_rsv in close_ctree() too. After a balance
> the orphan_block_rsv of the tree of tree roots was being leaked, because
> free_fs_root() is only called for filesystem trees.
>
> fs/btrfs/disk-io.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index 3b12c26..5d17163 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);
> @@ -3582,6 +3584,9 @@ int close_ctree(struct btrfs_root *root)
>
> btrfs_free_stripe_hash_table(fs_info);
>
> + btrfs_free_block_rsv(root, root->orphan_block_rsv);
> + root->orphan_block_rsv = NULL;
> +
> return 0;
> }
>
> --
> 1.7.9.5
>
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