linux-kernel - Re: [V9fs-developer] [PATCH] fs/9p/: don't treat error as status value in file locking

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Date:	Sun, 10 Aug 2014 13:11:43 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Sasha Levin <sasha.levin@...cle.com>, ericvh@...il.com,
	rminnich@...dia.gov, lucho@...kov.net
Cc:	v9fs-developer@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	Sasha Levin <sasha.levin@...cle.com>
Subject: Re: [V9fs-developer] [PATCH] fs/9p/: don't treat error as status value	in file locking

Sasha Levin <sasha.levin@...cle.com> writes:

> When trying to lock a file we didn't properly handle the case where a
> failure in p9_client_lock_dotl() occurs and treated the status value
> as valid instead of discarding it due to the error.
>
> This would usually trigger a BUG() since the status value would
> just be stack garbage.
>
> Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
> ---
>  fs/9p/vfs_file.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
> index 520c11c..06077f3 100644
> --- a/fs/9p/vfs_file.c
> +++ b/fs/9p/vfs_file.c
> @@ -194,7 +194,7 @@ static int v9fs_file_do_lock(struct file *filp, int cmd, struct file_lock *fl)
>  	for (;;) {
>  		res = p9_client_lock_dotl(fid, &flock, &status);
>  		if (res < 0)
> -			break;
> +			return res;
>
>  		if (status != P9_LOCK_BLOCKED)
>  			break;

We may want to do the local revert of the posix lock held. ie,

diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
index 520c11c2dcca..20ed603e60b2 100644
--- a/fs/9p/vfs_file.c
+++ b/fs/9p/vfs_file.c
@@ -194,7 +194,7 @@ static int v9fs_file_do_lock(struct file *filp, int cmd, struct file_lock *fl)
 	for (;;) {
 		res = p9_client_lock_dotl(fid, &flock, &status);
 		if (res < 0)
-			break;
+			goto err_out;
 
 		if (status != P9_LOCK_BLOCKED)
 			break;
@@ -220,6 +220,7 @@ static int v9fs_file_do_lock(struct file *filp, int cmd, struct file_lock *fl)
 		BUG();
 	}
 
+err_out:
 	/*
 	 * incase server returned error for lock request, revert
 	 * it locally

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