[PATCH][BUG]: Pure nfs client performance using odirect.

[PATCH][BUG]: Pure nfs client performance using odirect.

[Arun R Bharadwaj]

Pure nfs client performance using odirect.

When an application opens a file with O_DIRECT flag, if the size of
the data that is written is equal to wsize, the client sends a
WRITE RPC with stable flag set to UNSTABLE followed by a single
COMMIT RPC rather than sending a single WRITE RPC with the stable
flag set to FILE_SYNC. This a bug.

Patch to fix this.

Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>

Index: linux-2.6.36-rc7/fs/nfs/direct.c
===================================================================
--- linux-2.6.36-rc7.orig/fs/nfs/direct.c	2010-11-18 15:53:15.904972002 +0530
+++ linux-2.6.36-rc7/fs/nfs/direct.c	2010-11-18 15:54:01.184972001 +0530
@@ -867,7 +867,7 @@
 		goto out;
 	nfs_alloc_commit_data(dreq);
 
-	if (dreq->commit_data == NULL || count < wsize)
+	if (dreq->commit_data == NULL || count <= wsize)
 		sync = NFS_FILE_SYNC;
 
 	dreq->inode = inode;

Re: [PATCH][BUG]: Pure nfs client performance using odirect.

[Chuck Lever]

On Nov 18, 2010, at 5:36 AM, Arun R Bharadwaj wrote:

> Pure nfs client performance using odirect.
> 
> When an application opens a file with O_DIRECT flag, if the size of
> the data that is written is equal to wsize, the client sends a
> WRITE RPC with stable flag set to UNSTABLE followed by a single
> COMMIT RPC rather than sending a single WRITE RPC with the stable
> flag set to FILE_SYNC. This a bug.
> 
> Patch to fix this.
> 
> Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
> 
> Index: linux-2.6.36-rc7/fs/nfs/direct.c
> ===================================================================
> --- linux-2.6.36-rc7.orig/fs/nfs/direct.c	2010-11-18 15:53:15.904972002 +0530
> +++ linux-2.6.36-rc7/fs/nfs/direct.c	2010-11-18 15:54:01.184972001 +0530
> @@ -867,7 +867,7 @@
> 		goto out;
> 	nfs_alloc_commit_data(dreq);
> 
> -	if (dreq->commit_data == NULL || count < wsize)
> +	if (dreq->commit_data == NULL || count <= wsize)
> 		sync = NFS_FILE_SYNC;
> 
> 	dreq->inode = inode;

This looks reasonable, though I haven't looked closely at the surrounding code.  It's probably been in the code for a very long time.  I'm surprised no-one caught it sooner.

-- 
Chuck Lever
chuck[dot]lever[at]oracle[dot]com

Re: [PATCH][BUG]: Pure nfs client performance using odirect.

[Jeff Layton]

On Thu, 18 Nov 2010 16:06:43 +0530
Arun R Bharadwaj <arun@linux.vnet.ibm.com> wrote:

> Pure nfs client performance using odirect.
> 
> When an application opens a file with O_DIRECT flag, if the size of
> the data that is written is equal to wsize, the client sends a
> WRITE RPC with stable flag set to UNSTABLE followed by a single
> COMMIT RPC rather than sending a single WRITE RPC with the stable
> flag set to FILE_SYNC. This a bug.
> 
> Patch to fix this.
> 
> Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
> 
> Index: linux-2.6.36-rc7/fs/nfs/direct.c
> ===================================================================
> --- linux-2.6.36-rc7.orig/fs/nfs/direct.c	2010-11-18 15:53:15.904972002 +0530
> +++ linux-2.6.36-rc7/fs/nfs/direct.c	2010-11-18 15:54:01.184972001 +0530
> @@ -867,7 +867,7 @@
>  		goto out;
>  	nfs_alloc_commit_data(dreq);
>  
> -	if (dreq->commit_data == NULL || count < wsize)
> +	if (dreq->commit_data == NULL || count <= wsize)
>  		sync = NFS_FILE_SYNC;
>  
>  	dreq->inode = inode;
> --
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Looks right to me.

Reviewed-by: Jeff Layton <jlayton@redhat.com>