cvs commit: src/sys/kern vfs_syscalls.c

[Alex Lyashkov]

В Птн, 23.04.2004, в 02:31, Pawel Jakub Dawidek пишет:
> On Fri, Apr 23, 2004 at 01:19:10AM +0200, Thomas Moestl wrote:
> +> On Thu, 2004/04/22 at 08:40:28 -0700, Pawel Jakub Dawidek wrote:
> +> > pjd         2004/04/22 08:40:27 PDT
> +> > 
> +> >   FreeBSD src repository
> +> > 
> +> >   Modified files:
> +> >     sys/kern             vfs_syscalls.c 
> +> >   Log:
> +> >   Look out! vn_start_write() is able to return 0 and NULL 'mp'.
> +> 
> +> Hmmm, I'm not sure, but wasn't the real bug to use the struct mount *
> +> that vn_start_write() returns instead of nd.ni_vp->v_mount (or at
> +> least, not using nd.ni_vp->v_mount if mp turns out to be NULL)? 
> +> extattrctl() chooses that way.
> +> It seems that file systems are not required to implement
> +> VOP_GETWRITEMOUNT(), but could choose to implement VFS_QUOTACTL()
> +> anyway (although IIRC there currently are none that maintain this
> +> combination), so unconditionally returning EOPNOTSUPP would be too
> +> strict.
> +> 
> +> The only case where the mount point of the vnode and the mount point
> +> returned by vn_start_write() should differ is when unionfs is
> +> involved; in that case, the correct semantics of quotactl() is a bit
> +> doubtful, and so unionfs does not support quotactl() at all; thus
> +> using the mount point of the vnode should not break anything.
> 
> Yes. Even quotactl(2) in RELENG_4 is using nd.ni_vp->v_mount.
> Anyone want to test this patch:
> 
> 	http://people.freebsd.org/~pjd/patches/vfs_syscalls.c.3.patch
After I apply this patch my test box have a panic with message "negative
refs" at vn_finish_write.
I rewrite patch for ommit this situations. 

-- 
Alex Lyashkov <umka at sevinter.net>
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Index: vfs_syscalls.c
===================================================================
RCS file: /mnt/storage/freebsd-cvs/src/sys/kern/vfs_syscalls.c,v
retrieving revision 1.344
diff -u -r1.344 vfs_syscalls.c
--- vfs_syscalls.c	22 Apr 2004 15:40:27 -0000	1.344
+++ vfs_syscalls.c	24 Apr 2004 18:16:03 -0000
@@ -184,6 +184,7 @@
 	} */ *uap;
 {
 	struct mount *mp;
+	struct mount *quota_args;
 	int error;
 	struct nameidata nd;
 
@@ -194,12 +195,11 @@
 		return (error);
 	NDFREE(&nd, NDF_ONLY_PNBUF);
 	error = vn_start_write(nd.ni_vp, &mp, V_WAIT | PCATCH);
+	quota_args = mp != NULL ? mp : nd.ni_vp->v_mount;	
 	vrele(nd.ni_vp);
 	if (error)
-		return (error);
-	if (mp == NULL)
-		return (EOPNOTSUPP);
-	error = VFS_QUOTACTL(mp, uap->cmd, uap->uid, uap->arg, td);
+		return (error);		
+	error = VFS_QUOTACTL(quota_args, uap->cmd, uap->uid, uap->arg, td);
 	vn_finished_write(mp);
 	return (error);
 }