[PATCH] NFS: Fix a write performance regression

[PATCH] NFS: Fix a write performance regression

[Trond Myklebust]

If all other conditions in nfs_can_extend_write() are met, and there
are no locks, then we should be able to assume close-to-open semantics
and the ability to extend our write to cover the whole page.

With this patch, the xfstests generic/074 test completes in 232s instead
of >1400s on my test rig.

Fixes: bd61e0a9c852 ("locks: convert posix locks to file_lock_context")
Cc: Jeff Layton <jlayton@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
---
 fs/nfs/write.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 72624dc4a623..1d6f6b43b7f4 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -1223,7 +1223,7 @@ static int nfs_can_extend_write(struct file *file, struct page *page, struct ino
 		return 1;
 	if (!flctx || (list_empty_careful(&flctx->flc_flock) &&
 		       list_empty_careful(&flctx->flc_posix)))
-		return 0;
+		return 1;
 
 	/* Check to see if there are whole file write locks */
 	ret = 0;
-- 
2.4.3

Re: [PATCH] NFS: Fix a write performance regression

[Jeff Layton]

On Thu,  1 Oct 2015 19:12:26 -0400
Trond Myklebust <trond.myklebust@primarydata.com> wrote:

> If all other conditions in nfs_can_extend_write() are met, and there
> are no locks, then we should be able to assume close-to-open semantics
> and the ability to extend our write to cover the whole page.
> 
> With this patch, the xfstests generic/074 test completes in 232s instead
> of >1400s on my test rig.
> 
> Fixes: bd61e0a9c852 ("locks: convert posix locks to file_lock_context")
> Cc: Jeff Layton <jlayton@primarydata.com>
> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
> ---
>  fs/nfs/write.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/nfs/write.c b/fs/nfs/write.c
> index 72624dc4a623..1d6f6b43b7f4 100644
> --- a/fs/nfs/write.c
> +++ b/fs/nfs/write.c
> @@ -1223,7 +1223,7 @@ static int nfs_can_extend_write(struct file *file, struct page *page, struct ino
>  		return 1;
>  	if (!flctx || (list_empty_careful(&flctx->flc_flock) &&
>  		       list_empty_careful(&flctx->flc_posix)))
> -		return 0;
> +		return 1;
>  
>  	/* Check to see if there are whole file write locks */
>  	ret = 0;


Ouch -- mea culpa. Actually broken originally in
5263e31e452fb84138b9bee061d5c06c0f359fea, I think...

In any case:

Reviewed-by: Jeff Layton <jeff.layton@primarydata.com>