Hello,
On Wed, Oct 23, 2013 at 4:35 PM, Filipe David Manana <fdmanana@xxxxxxxxx> wrote:
> On Wed, Oct 23, 2013 at 2:33 PM, Alex Lyakas
> <alex.btrfs@xxxxxxxxxxxxxxxxx> wrote:
>> 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
So here it seems that the leak can only happen in case the block-group
has a free-space inode. This is what the orphan item is added for.
Yes, here kmemleak reports.
But: if space_cache option is disabled (and nospace_cache) enabled, it
seems that btrfs still creates the FREE_SPACE inodes, although they
are empty because in cache_save_setup:
inode = lookup_free_space_inode(root, block_group, path);
if (IS_ERR(inode) && PTR_ERR(inode) != -ENOENT) {
ret = PTR_ERR(inode);
btrfs_release_path(path);
goto out;
}
if (IS_ERR(inode)) {
...
ret = create_free_space_inode(root, trans, block_group, path);
and only later it actually sets BTRFS_DC_WRITTEN if space_cache option
is disabled. Amazing!
Although this is a different issue, do you know perhaps why these
empty inodes are needed?
Thanks!
Alex.
>>>
>>> ** 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?
>
> Maybe it's not an issue on 3.8.13 and older releases.
> This was on btrfs-next from August 19.
>
> thanks for testing
>
>>
>> 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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>
>
>
> --
> Filipe David Manana,
>
> "Reasonable men adapt themselves to the world.
> Unreasonable men adapt the world to themselves.
> That's why all progress depends on unreasonable men."
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