On Mon, Sep 09, 2013 at 01:46:47AM +0100, Al Viro wrote:
> On Sat, Sep 07, 2013 at 02:46:01PM -0400, J. Bruce Fields wrote:
> > From: "J. Bruce Fields" <bfields@xxxxxxxxxx>
> >
> > DCACHE_DISCONNECTED should not be cleared until we're sure the dentry is
> > connected all the way up to the root of the filesystem. It *shouldn't*
> > be cleared as soon as the dentry is connected to a parent. That will
> > cause bugs at least on exportable filesystems.
>
> Then you probably want this
> if (!IS_ROOT(pd)) {
> /* must have found a connected parent - great */
> spin_lock(&pd->d_lock);
> pd->d_flags &= ~DCACHE_DISCONNECTED;
> spin_unlock(&pd->d_lock);
> noprogress = 0;
> to go through all intermediates, clearing DCACHE_DISCONNECTED on all of
> them; O(depth^2) can suck when we have a long chain of directories...
I'm not sure what you mean--something like the following?
Not having seen complaints about filehandle lookup performance I'm
inclined to leave it alone, though.
--b.
diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index 5816e19..72ed705 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -90,6 +90,22 @@ find_disconnected_root(struct dentry *dentry)
return dentry;
}
+static void clear_disconnected(struct dentry *dentry)
+{
+ dget(dentry);
+ while (dentry->d_flags & DCACHE_DISCONNECTED) {
+ struct dentry *parent = dget_parent(dentry);
+
+ spin_lock(&dentry->d_lock);
+ dentry->d_flags &= ~DCACHE_DISCONNECTED;
+ spin_unlock(&dentry->d_lock);
+
+ dput(dentry);
+ dentry = parent;
+ }
+ dput(dentry);
+}
+
/*
* Make sure target_dir is fully connected to the dentry tree.
*
@@ -114,15 +130,11 @@ reconnect_path(struct vfsmount *mnt, struct dentry *target_dir, char *nbuf)
if (!IS_ROOT(pd)) {
/* must have found a connected parent - great */
- spin_lock(&pd->d_lock);
- pd->d_flags &= ~DCACHE_DISCONNECTED;
- spin_unlock(&pd->d_lock);
+ clear_disconnected(target_dir);
noprogress = 0;
} else if (pd == mnt->mnt_sb->s_root) {
printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n");
- spin_lock(&pd->d_lock);
- pd->d_flags &= ~DCACHE_DISCONNECTED;
- spin_unlock(&pd->d_lock);
+ clear_disconnected(target_dir);
noprogress = 0;
} else {
/*
--
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