lkml.org 
[lkml]   [2003]   [Aug]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [PATCH] autofs4 doesn't expire
On Tue, Aug 05, 2003 at 04:49:04PM -0700, Andrew Morton wrote:
> spam@streefland.xs4all.nl (Dick Streefland) wrote:
> >
> > In linux-2.6.0-test1, lookup_mnt() was changed to increment the ref
> > count of the returned vfsmount struct. This breaks expiration of
> > autofs4 mounts, because lookup_mnt() is called in check_vfsmnt()
> > without decrementing the ref count afterwards. The following patch
> > fixes this:
> >
>
> Neat, thanks.
>
> Probably we should hold onto that ref because we play with the vfsmount
> later on. So something like this?
>
>
> diff -puN fs/autofs4/expire.c~autofs4-expiry-fix fs/autofs4/expire.c
> --- 25/fs/autofs4/expire.c~autofs4-expiry-fix 2003-08-05 16:44:41.000000000 -0700
> +++ 25-akpm/fs/autofs4/expire.c 2003-08-05 16:48:20.000000000 -0700
> @@ -25,7 +25,7 @@ static inline int is_vfsmnt_tree_busy(st
> struct list_head *next;
> int count;
>
> - count = atomic_read(&mnt->mnt_count) - 1;
> + count = atomic_read(&mnt->mnt_count) - 1 - 1;
>
> repeat:
> next = this_parent->mnt_mounts.next;
> @@ -70,8 +70,11 @@ static int check_vfsmnt(struct vfsmount
> int ret = dentry->d_mounted;
> struct vfsmount *vfs = lookup_mnt(mnt, dentry);
>
> - if (vfs && is_vfsmnt_tree_busy(vfs))
> - ret--;
> + if (vfs) {
> + if (is_vfsmnt_tree_busy(vfs))
> + ret = 0;
> + mntput(vfs);
> + }
> DPRINTK(("check_vfsmnt: ret=%d\n", ret));
> return ret;
> }
>
> _

Sorry, I don't think it is correct. This code is called under dcache_lock,
taken in is_tree_busy(). mntput() calls dput() and which can lead to deadlock.

I was thinking of some clean solution and trying to understand autofs4 but
some what lost in user mode utility, version 3 and 4, etc etc.

Dick, can you test the appended patch whether it works for you or not.

Thanks
Maneesh

diff -puN fs/autofs4/expire.c~autofs4-vfsmount-fix fs/autofs4/expire.c
--- linux-2.6.0-test2/fs/autofs4/expire.c~autofs4-vfsmount-fix 2003-08-06 09:10:49.000000000 +0530
+++ linux-2.6.0-test2-maneesh/fs/autofs4/expire.c 2003-08-06 09:24:07.000000000 +0530
@@ -25,7 +25,10 @@ static inline int is_vfsmnt_tree_busy(st
struct list_head *next;
int count;

- count = atomic_read(&mnt->mnt_count) - 1;
+ /* -1 for vfsmount's normal count,
+ * -1 for ref taken in lookup_mnt()
+ */
+ count = atomic_read(&mnt->mnt_count) - 1 - 1;

repeat:
next = this_parent->mnt_mounts.next;
@@ -71,7 +74,8 @@ static int check_vfsmnt(struct vfsmount
struct vfsmount *vfs = lookup_mnt(mnt, dentry);

if (vfs && is_vfsmnt_tree_busy(vfs))
- ret--;
+ ret = 0;
+ mntput(vfs);
DPRINTK(("check_vfsmnt: ret=%d\n", ret));
return ret;
}
@@ -96,8 +100,11 @@ static int is_tree_busy(struct vfsmount
DPRINTK(("is_tree_busy: autofs; count=%d\n", count));
}

- if (d_mountpoint(top))
+ if (d_mountpoint(top)) {
+ spin_unlock(&dcache_lock);
count -= check_vfsmnt(topmnt, top);
+ spin_lock(&dcache_lock);
+ }

repeat:
next = this_parent->d_subdirs.next;
@@ -110,8 +117,11 @@ static int is_tree_busy(struct vfsmount

count += atomic_read(&dentry->d_count) - 1;

- if (d_mountpoint(dentry))
+ if (d_mountpoint(dentry)) {
+ spin_unlock(&dcache_lock);
adj += check_vfsmnt(topmnt, dentry);
+ spin_lock(&dcache_lock);
+ }

if (is_autofs4_dentry(dentry)) {
adj++;
_
_

--
Maneesh Soni
IBM Linux Technology Center,
IBM India Software Lab, Bangalore.
Phone: +91-80-5044999 email: maneesh@in.ibm.com
http://lse.sourceforge.net/
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:47    [from the cache]
©2003-2011 Jasper Spaans