[PATCH] Btrfs: avoid unnecessarily locking inode when clearing a range

[PATCH] Btrfs: avoid unnecessarily locking inode when clearing a range

[fdmanana]

From: Filipe Manana <fdmanana@suse.com>

If the range being cleared was not marked for defrag and we are not
about to clear the range from the defrag status, we don't need to
lock and unlock the inode.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
---
 fs/btrfs/inode.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index eb495e956d53..51c45c0a8553 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1797,10 +1797,11 @@ static void btrfs_clear_bit_hook(void *private_data,
 	u64 len = state->end + 1 - state->start;
 	u32 num_extents = count_max_extents(len);
 
-	spin_lock(&inode->lock);
-	if ((state->state & EXTENT_DEFRAG) && (*bits & EXTENT_DEFRAG))
+	if ((state->state & EXTENT_DEFRAG) && (*bits & EXTENT_DEFRAG)) {
+		spin_lock(&inode->lock);
 		inode->defrag_bytes -= len;
-	spin_unlock(&inode->lock);
+		spin_unlock(&inode->lock);
+	}
 
 	/*
 	 * set_bit and clear bit hooks normally require _irqsave/restore
-- 
2.11.0

Re: [PATCH] Btrfs: avoid unnecessarily locking inode when clearing a range

[Chris Mason]

On 07/27/2017 02:52 PM, fdmanana@kernel.org wrote:
> From: Filipe Manana <fdmanana@suse.com>
> 
> If the range being cleared was not marked for defrag and we are not
> about to clear the range from the defrag status, we don't need to
> lock and unlock the inode.
> 
> Signed-off-by: Filipe Manana <fdmanana@suse.com>

Thanks Filipe, looks like it goes all the way back to:

commit 47059d930f0e002ff851beea87d738146804726d
Author: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
Date:   Thu Jul 3 18:22:07 2014 +0800

     Btrfs: make defragment work with nodatacow option

I can't see how the inode lock is required here.

Reviewed-by: Chris Mason <clm@fb.com>

-chris

> ---
>   fs/btrfs/inode.c | 7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index eb495e956d53..51c45c0a8553 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -1797,10 +1797,11 @@ static void btrfs_clear_bit_hook(void *private_data,
>   	u64 len = state->end + 1 - state->start;
>   	u32 num_extents = count_max_extents(len);
>   
> -	spin_lock(&inode->lock);
> -	if ((state->state & EXTENT_DEFRAG) && (*bits & EXTENT_DEFRAG))
> +	if ((state->state & EXTENT_DEFRAG) && (*bits & EXTENT_DEFRAG)) {
> +		spin_lock(&inode->lock);
>   		inode->defrag_bytes -= len;
> -	spin_unlock(&inode->lock);
> +		spin_unlock(&inode->lock);
> +	}
>   
>   	/*
>   	 * set_bit and clear bit hooks normally require _irqsave/restore
> 

Re: [PATCH] Btrfs: avoid unnecessarily locking inode when clearing a range

[Wang Shilong]

On Thu, Aug 3, 2017 at 11:00 PM, Chris Mason <clm@fb.com> wrote:
>
>
> On 07/27/2017 02:52 PM, fdmanana@kernel.org wrote:
>>
>> From: Filipe Manana <fdmanana@suse.com>
>>
>> If the range being cleared was not marked for defrag and we are not
>> about to clear the range from the defrag status, we don't need to
>> lock and unlock the inode.
>>
>> Signed-off-by: Filipe Manana <fdmanana@suse.com>
>
>
> Thanks Filipe, looks like it goes all the way back to:
>
> commit 47059d930f0e002ff851beea87d738146804726d
> Author: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
> Date:   Thu Jul 3 18:22:07 2014 +0800
>
>     Btrfs: make defragment work with nodatacow option
>
> I can't see how the inode lock is required here.

This blames to me, thanks for fixing it.

Reviewed-by: Wang Shilong <wangshilong1991@gmail.com>

>
> Reviewed-by: Chris Mason <clm@fb.com>
>
> -chris
>
>> ---
>>   fs/btrfs/inode.c | 7 ++++---
>>   1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
>> index eb495e956d53..51c45c0a8553 100644
>> --- a/fs/btrfs/inode.c
>> +++ b/fs/btrfs/inode.c
>> @@ -1797,10 +1797,11 @@ static void btrfs_clear_bit_hook(void
>> *private_data,
>>         u64 len = state->end + 1 - state->start;
>>         u32 num_extents = count_max_extents(len);
>>   -     spin_lock(&inode->lock);
>> -       if ((state->state & EXTENT_DEFRAG) && (*bits & EXTENT_DEFRAG))
>> +       if ((state->state & EXTENT_DEFRAG) && (*bits & EXTENT_DEFRAG)) {
>> +               spin_lock(&inode->lock);
>>                 inode->defrag_bytes -= len;
>> -       spin_unlock(&inode->lock);
>> +               spin_unlock(&inode->lock);
>> +       }
>>         /*
>>          * set_bit and clear bit hooks normally require _irqsave/restore
>>
> --
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Re: [PATCH] Btrfs: avoid unnecessarily locking inode when clearing a range

[Chris Mason]

On 08/03/2017 11:25 AM, Wang Shilong wrote:
> On Thu, Aug 3, 2017 at 11:00 PM, Chris Mason <clm@fb.com> wrote:
>>
>>
>> On 07/27/2017 02:52 PM, fdmanana@kernel.org wrote:
>>>
>>> From: Filipe Manana <fdmanana@suse.com>
>>>
>>> If the range being cleared was not marked for defrag and we are not
>>> about to clear the range from the defrag status, we don't need to
>>> lock and unlock the inode.
>>>
>>> Signed-off-by: Filipe Manana <fdmanana@suse.com>
>>
>>
>> Thanks Filipe, looks like it goes all the way back to:
>>
>> commit 47059d930f0e002ff851beea87d738146804726d
>> Author: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
>> Date:   Thu Jul 3 18:22:07 2014 +0800
>>
>>      Btrfs: make defragment work with nodatacow option
>>
>> I can't see how the inode lock is required here.
> 
> This blames to me, thanks for fixing it.

No blame ;)  I'll take code that works any day.

-chris