[PATCH] autofs4 - follow_link missing funtionality

[PATCH] autofs4 - follow_link missing funtionality

[Ian Kent]

This functionality is also need for operation of autofs v5 direct mounts.

Signed-off-by: Ian Kent <raven@themaw.net>

---

--- linux-2.6.16-rc5-mm3/fs/autofs4/root.c.follow_link-ommission	2006-03-08 13:21:37.000000000 +0800
+++ linux-2.6.16-rc5-mm3/fs/autofs4/root.c	2006-03-08 13:27:47.000000000 +0800
@@ -57,6 +57,9 @@ struct inode_operations autofs4_indirect
 
 struct inode_operations autofs4_direct_root_inode_operations = {
 	.lookup		= autofs4_lookup,
+	.unlink		= autofs4_dir_unlink,
+	.mkdir		= autofs4_dir_mkdir,
+	.rmdir		= autofs4_dir_rmdir,
 	.follow_link	= autofs4_follow_link,
 };
 
@@ -337,10 +340,34 @@ static void *autofs4_follow_link(struct 
 	if (oz_mode || !lookup_type)
 		goto done;
 
+	/*
+	 * If the dentry contains directories then it is an
+	 * autofs multi-mount with no root offset. So don't
+	 * try to mount it again.
+	 */
+	spin_lock(&dcache_lock);
+	if (!list_empty(&dentry->d_subdirs)) {
+		spin_unlock(&dcache_lock);
+		goto done;
+	}
+	spin_unlock(&dcache_lock);
+
 	status = try_to_fill_dentry(dentry, 0);
 	if (status)
 		goto out_error;
 
+	/*
+	 * The mount succeeded but if there is no root mount
+	 * and directories have been created then it must
+	 * be an autofs multi-mount with no root offset.
+	 */
+	spin_lock(&dcache_lock);
+	if (!d_mountpoint(dentry) && !list_empty(&dentry->d_subdirs)) {
+		spin_unlock(&dcache_lock);
+		goto done;
+	}
+	spin_unlock(&dcache_lock);
+
 	if (!autofs4_follow_mount(&nd->mnt, &nd->dentry)) {
 		status = -ENOENT;
 		goto out_error;
--- linux-2.6.16-rc5-mm3/fs/autofs4/expire.c.follow_link-ommission	2006-03-08 14:18:25.000000000 +0800
+++ linux-2.6.16-rc5-mm3/fs/autofs4/expire.c	2006-03-08 13:28:21.000000000 +0800
@@ -113,10 +113,6 @@ static int autofs4_direct_busy(struct vf
 	DPRINTK("top %p %.*s",
 		top, (int) top->d_name.len, top->d_name.name);
 
-	/* Not a mountpoint - give up */
-	if (!d_mountpoint(top))
-		return 1;
-
 	/* If it's busy update the expiry counters */
 	if (!may_umount_tree(mnt)) {
 		struct autofs_info *ino = autofs4_dentry_ino(top);

Re: [PATCH] autofs4 - follow_link missing funtionality

[Andrew Morton]

Ian Kent <raven@themaw.net> wrote:
>
> @@ -337,10 +340,34 @@ static void *autofs4_follow_link(struct 
>  	if (oz_mode || !lookup_type)
>  		goto done;
>  
> +	/*
> +	 * If the dentry contains directories then it is an
> +	 * autofs multi-mount with no root offset. So don't
> +	 * try to mount it again.
> +	 */
> +	spin_lock(&dcache_lock);
> +	if (!list_empty(&dentry->d_subdirs)) {
> +		spin_unlock(&dcache_lock);
> +		goto done;
> +	}
> +	spin_unlock(&dcache_lock);
> +

Can list_empty(&dentry->d_subdirs) become false right here, after the lock
was dropped?  If so, what happens?


>  	status = try_to_fill_dentry(dentry, 0);

Re: [PATCH] autofs4 - follow_link missing funtionality

[Ian Kent]

On Fri, 10 Mar 2006, Andrew Morton wrote:

> Ian Kent <raven@themaw.net> wrote:
> >
> > @@ -337,10 +340,34 @@ static void *autofs4_follow_link(struct 
> >  	if (oz_mode || !lookup_type)
> >  		goto done;
> >  
> > +	/*
> > +	 * If the dentry contains directories then it is an
> > +	 * autofs multi-mount with no root offset. So don't
> > +	 * try to mount it again.
> > +	 */
> > +	spin_lock(&dcache_lock);
> > +	if (!list_empty(&dentry->d_subdirs)) {
> > +		spin_unlock(&dcache_lock);
> > +		goto done;
> > +	}
> > +	spin_unlock(&dcache_lock);
> > +
> 
> Can list_empty(&dentry->d_subdirs) become false right here, after the lock
> was dropped?  If so, what happens?

Yep. I think so.
Not what I want to happen.

> 
> 
> >  	status = try_to_fill_dentry(dentry, 0);
> 

Re: [PATCH] autofs4 - follow_link missing funtionality

[Ian Kent]

Hi Andrew,

Here is an update to this patch to address your concern below.

Basicly, I wait for pending operations to complete, the main concern is an 
expire operation causing directories to be removed. As we hold a reference 
to the vfsmount and the dentry that shouldn't happen once any that are in 
progress have completed.

At least that's what I expect.

On Fri, 10 Mar 2006, Andrew Morton wrote:

> Ian Kent <raven@themaw.net> wrote:
> >
> > @@ -337,10 +340,34 @@ static void *autofs4_follow_link(struct 
> >  	if (oz_mode || !lookup_type)
> >  		goto done;
> >  
> > +	/*
> > +	 * If the dentry contains directories then it is an
> > +	 * autofs multi-mount with no root offset. So don't
> > +	 * try to mount it again.
> > +	 */
> > +	spin_lock(&dcache_lock);
> > +	if (!list_empty(&dentry->d_subdirs)) {
> > +		spin_unlock(&dcache_lock);
> > +		goto done;
> > +	}
> > +	spin_unlock(&dcache_lock);
> > +
> 
> Can list_empty(&dentry->d_subdirs) become false right here, after the lock
> was dropped?  If so, what happens?
> 
> 
> >  	status = try_to_fill_dentry(dentry, 0);
> 

Signed-off-by: Ian Kent <raven@themaw.net>

--

--- linux-2.6.16-mm1/fs/autofs4/root.c.follow_link-expire-check	2006-03-24 12:32:16.000000000 +0800
+++ linux-2.6.16-mm1/fs/autofs4/root.c	2006-03-24 15:01:15.000000000 +0800
@@ -341,38 +341,49 @@ static void *autofs4_follow_link(struct 
 		goto done;
 
 	/*
-	 * If the dentry contains directories then it is an
-	 * autofs multi-mount with no root offset. So don't
-	 * try to mount it again.
+	 * If a request is pending wait for it.
+	 * If it's a mount then it won't be expired till at least
+	 * a liitle later and if it's an expire then we might need
+	 * to mount it again.
 	 */
-	spin_lock(&dcache_lock);
-	if (!list_empty(&dentry->d_subdirs)) {
-		spin_unlock(&dcache_lock);
-		goto done;
-	}
-	spin_unlock(&dcache_lock);
+	if (autofs4_ispending(dentry)) {
+		DPRINTK("waiting for active request %p name=%.*s",
+			dentry, dentry->d_name.len, dentry->d_name.name);
 
-	status = try_to_fill_dentry(dentry, 0);
-	if (status)
-		goto out_error;
+		status = autofs4_wait(sbi, dentry, NFY_NONE);
+
+		DPRINTK("request done status=%d", status);
+	}
 
 	/*
-	 * The mount succeeded but if there is no root mount
-	 * and directories have been created then it must
-	 * be an autofs multi-mount with no root offset.
+	 * If the dentry contains directories then it is an
+	 * autofs multi-mount with no root mount offset. So
+	 * don't try to mount it again.
 	 */
 	spin_lock(&dcache_lock);
-	if (!d_mountpoint(dentry) && !list_empty(&dentry->d_subdirs)) {
+	if (!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs)) {
 		spin_unlock(&dcache_lock);
+
+		status = try_to_fill_dentry(dentry, 0);
+		if (status)
+			goto out_error;
+
+		/*
+		 * The mount succeeded but if there is no root mount
+		 * it must be an autofs multi-mount with no root offset
+		 * so we don't need to follow the mount.
+		 */
+		if (d_mountpoint(dentry)) {
+			if (!autofs4_follow_mount(&nd->mnt, &nd->dentry)) {
+				status = -ENOENT;
+				goto out_error;
+			}
+		}
+
 		goto done;
 	}
 	spin_unlock(&dcache_lock);
 
-	if (!autofs4_follow_mount(&nd->mnt, &nd->dentry)) {
-		status = -ENOENT;
-		goto out_error;
-	}
-
 done:
 	return NULL;