On Wed, Oct 23, 2013 at 3:14 PM, Alex Lyakas
<alex.btrfs@xxxxxxxxxxxxxxxxx> wrote:
> 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?
Don't know if they are needed. But you have a point, it seems odd to
create the free space cache inode if mount option nospace_cache was
supplied. Thanks Alex. Testing the following patch:
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index c43ee8a..eb1b7da 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3162,6 +3162,9 @@ static int cache_save_setup(struct
btrfs_block_group_cache *block_group,
int retries = 0;
int ret = 0;
+ if (!btrfs_test_opt(root, SPACE_CACHE))
+ return 0;
+
/*
* If this block group is smaller than 100 megs don't bother caching the
* block group.
>
> 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."
--
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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