GFS2: Add atomic_open support
I've restricted atomic_open to only operate on regular files, although
I still don't understand why atomic_open should not be possible also for
directories on GFS2. That can always be added in later though, if it
makes sense.
The ->atomic_open function can be passed negative dentries, which
in most cases means either ENOENT (->lookup) or a call to d_instantiate
(->create). In the GFS2 case though, we need to actually perform the
look up, since we do not know whether there has been a new inode created
on another node. The look up calls d_splice_alias which then tries to
rehash the dentry - so the solution here is to simply check for that
in d_splice_alias. The same issue is likely to affect any other cluster
filesystem implementing ->atomic_open
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: "J. Bruce Fields" <bfields fieldses org>
Cc: Jeff Layton <jlayton@redhat.com>
diff --git a/fs/dcache.c b/fs/dcache.c
index f09b908..5a23073 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1612,6 +1612,10 @@
* If a dentry was found and moved, then it is returned. Otherwise NULL
* is returned. This matches the expected return value of ->lookup.
*
+ * Cluster filesystems may call this function with a negative, hashed dentry.
+ * In that case, we know that the inode will be a regular file, and also this
+ * will only occur during atomic_open. So we need to check for the dentry
+ * being already hashed only in the final case.
*/
struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
{
@@ -1636,8 +1640,11 @@
security_d_instantiate(dentry, inode);
d_rehash(dentry);
}
- } else
- d_add(dentry, inode);
+ } else {
+ d_instantiate(dentry, inode);
+ if (d_unhashed(dentry))
+ d_rehash(dentry);
+ }
return new;
}
EXPORT_SYMBOL(d_splice_alias);