On Mon, Nov 4, 2013 at 12:16 PM, Alex Lyakas
<alex.btrfs@xxxxxxxxxxxxxxxxx> wrote:
> Hi Filipe,
> any luck with this patch?:)
Hey Alex,
I haven't digged further, but I remember I couldn't reproduce your
issue (with latest btrfs-next of that day) of getting the free space
inodes created even when mount option nospace_cache is given.
What kernel were you using?
>
> Alex.
>
> On Wed, Oct 23, 2013 at 5:26 PM, Filipe David Manana <fdmanana@xxxxxxxxx> wrote:
>> 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."
--
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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