Re: [PATCH] btrfs: Fix possible softlock on single core machines
Hi, [This is an automated email] This commit has been processed because it contains a "Fixes:" tag, fixing commit: 6d74119f1a3e Btrfs: avoid taking the chunk_mutex in do_chunk_alloc. The bot has also determined it's probably a bug fixing patch. (score: 55.2868) The bot has tested the following trees: v4.16, v4.15.15, v4.14.32, v4.9.92, v4.4.126. v4.16: Build OK! v4.15.15: Build OK! v4.14.32: Build OK! v4.9.92: Build OK! v4.4.126: Build OK! -- Thanks, Sasha-- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] btrfs: Fix possible softlock on single core machines
On Thu, Apr 05, 2018 at 06:04:12PM +0300, Nikolay Borisov wrote:
>
>
> On 5.04.2018 16:55, David Sterba wrote:
> > On Thu, Apr 05, 2018 at 10:40:15AM +0300, Nikolay Borisov wrote:
> >> do_chunk_alloc implements a loop checking whether there is a pending
> >> chunk allocation and if so causes the caller do loop. Generally this
> >> loop is executed only once, however testing with btrfs/072 on a
> >> single core vm machines uncovered an extreme case where the system
> >> could loop indefinitely. This is due to a missing cond_resched when
> >> loop which doesn't give a chance to the previous chunk allocator finish
> >> its job.
> >>
> >> The fix is to simply add the missing cond_resched.
> >>
> >> Fixes: 6d74119f1a3e ("Btrfs: avoid taking the chunk_mutex in
> >> do_chunk_alloc")
> >
> > Does this commit really lead to the endless loop on UP? I don't see any
> > obvious connection.
>
> This is the commit that introduced the loop there without adding
> cond_resched, hence the fixes tag.
Makes sense, thanks.
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Re: [PATCH] btrfs: Fix possible softlock on single core machines
On 5.04.2018 16:55, David Sterba wrote:
> On Thu, Apr 05, 2018 at 10:40:15AM +0300, Nikolay Borisov wrote:
>> do_chunk_alloc implements a loop checking whether there is a pending
>> chunk allocation and if so causes the caller do loop. Generally this
>> loop is executed only once, however testing with btrfs/072 on a
>> single core vm machines uncovered an extreme case where the system
>> could loop indefinitely. This is due to a missing cond_resched when
>> loop which doesn't give a chance to the previous chunk allocator finish
>> its job.
>>
>> The fix is to simply add the missing cond_resched.
>>
>> Fixes: 6d74119f1a3e ("Btrfs: avoid taking the chunk_mutex in do_chunk_alloc")
>
> Does this commit really lead to the endless loop on UP? I don't see any
> obvious connection.
This is the commit that introduced the loop there without adding
cond_resched, hence the fixes tag.
>
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Re: [PATCH] btrfs: Fix possible softlock on single core machines
On Thu, Apr 05, 2018 at 10:40:15AM +0300, Nikolay Borisov wrote:
> do_chunk_alloc implements a loop checking whether there is a pending
> chunk allocation and if so causes the caller do loop. Generally this
> loop is executed only once, however testing with btrfs/072 on a
> single core vm machines uncovered an extreme case where the system
> could loop indefinitely. This is due to a missing cond_resched when
> loop which doesn't give a chance to the previous chunk allocator finish
> its job.
>
> The fix is to simply add the missing cond_resched.
>
> Fixes: 6d74119f1a3e ("Btrfs: avoid taking the chunk_mutex in do_chunk_alloc")
Does this commit really lead to the endless loop on UP? I don't see any
obvious connection.
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[PATCH] btrfs: Fix possible softlock on single core machines
do_chunk_alloc implements a loop checking whether there is a pending
chunk allocation and if so causes the caller do loop. Generally this
loop is executed only once, however testing with btrfs/072 on a
single core vm machines uncovered an extreme case where the system
could loop indefinitely. This is due to a missing cond_resched when
loop which doesn't give a chance to the previous chunk allocator finish
its job.
The fix is to simply add the missing cond_resched.
Fixes: 6d74119f1a3e ("Btrfs: avoid taking the chunk_mutex in do_chunk_alloc")
Signed-off-by: Nikolay Borisov
---
fs/btrfs/extent-tree.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 0cf1d4c518e9..070227b78d4e 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4645,6 +4645,7 @@ static int do_chunk_alloc(struct btrfs_trans_handle
*trans,
if (wait_for_alloc) {
mutex_unlock(&fs_info->chunk_mutex);
wait_for_alloc = 0;
+ cond_resched();
goto again;
}
--
2.7.4
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