Date: Tue, 10 Sep 2002 15:23:34 -0700 (PDT) From: Don Lewis <dl-freebsd@catspoiler.org> To: rwatson@FreeBSD.ORG Cc: current@FreeBSD.ORG, jeff@FreeBSD.ORG Subject: Re: vnode lock assertion problem in nfs_link() Message-ID: <200209102223.g8AMNYwr096282@gw.catspoiler.org> In-Reply-To: <200209100419.g8A4JTwr093971@gw.catspoiler.org>
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On 9 Sep, Don Lewis wrote:
> On 9 Sep, Robert Watson wrote:
>
>> What I'd actually like to do is lock vp on going in to the VOP. I need to
>> grab the lock in the link() code anyway to do the MAC check. UFS and
>> others all immediately lock the vnode on entry anyway...
>
> Here's a patch to implement this. It compiles and seems to work OK, but
> needs review. There are a couple of issues that definitely need a look:
> The VOP_LINK(9) man page needs would also need to be updated.
Here's a patch to the man page that also fixes a bunch of bit rot that
has accumulated:
Index: VOP_LINK.9
===================================================================
RCS file: /home/ncvs/src/share/man/man9/VOP_LINK.9,v
retrieving revision 1.13
diff -u -r1.13 VOP_LINK.9
--- VOP_LINK.9 1 Oct 2001 16:09:24 -0000 1.13
+++ VOP_LINK.9 10 Sep 2002 22:21:53 -0000
@@ -52,18 +52,13 @@
pathname information about the file
.El
.Pp
-The pathname info must be released on exit. The directory and
-file vnodes should NOT be released on exit.
+The pathname info should NOT be released on exit because it is done
+by the caller.
+The directory and file vnodes should NOT be released on exit.
.Sh LOCKS
-The directory,
-.Fa dvp
-is locked on entry and should remain locked on return.
-The file
-.Fa vp
-is not locked on entry and should remain that way on return.
-If your VOP code locks
-.Fa vp ,
-it must be sure to unlock prior to returning.
+.Xr VOP_LINK 9
+expects the directory and file vnodes to be locked on entry and will leave
+the vnodes locked on return.
.Sh RETURN VALUES
Zero is returned if the file was linked successfully, otherwise an
error is returned.
@@ -74,27 +69,14 @@
{
int error = 0;
- if (vp->v_mount != dvp->v_mount) {
- error = EXDEV;
- goto out2;
- }
- if (vp != dvp && (error = VOP_LOCK(vp))) {
- goto out2;
- }
-
- /*
- * now that we've locked vp, we have to use out1 instead of out2
- */
+ if (vp->v_mount != dvp->v_mount)
+ return (EXDEV);
- if (vp would have too many links) {
- error = EMLINK;
- goto out1;
- }
+ if (vp would have too many links)
+ return (EMLINK);
- if (vp is immutable) {
- error = EPERM;
- goto out1;
- }
+ if (vp is immutable)
+ return (EPERM);
/*
* Increment link count of vp and write back the on-disc version of it.
@@ -108,19 +90,21 @@
...;
}
- free(cnp->cn_pnbuf, M_NAMEI);
-out1:
- if (vp != dvp)
- VOP_UNLOCK(vp);
-out2:
-
return error;
}
.Ed
.Sh ERRORS
.Bl -tag -width Er
+.It Bq Er EMLINK
+the file has too many links
+.El
+.Bl -tag -width Er
.It Bq Er EPERM
the file is immutable
+.El
+.Bl -tag -width Er
+.It Bq Er EXDEV
+a hard link is not possible between different file systems
.El
.Sh SEE ALSO
.Xr vnode 9 ,
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