fuse: prepare lookup for nfs export

Use d_splice_alias() instead of d_add() in fuse lookup code, to allow NFS
exporting.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 14 insertions, 10 deletions

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 2060bf06b906..e5217b213b44 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -239,18 +239,20 @@ int fuse_valid_type(int m)
  * Add a directory inode to a dentry, ensuring that no other dentry
  * refers to this inode.  Called with fc->inst_mutex.
  */
-static int fuse_d_add_directory(struct dentry *entry, struct inode *inode)
+static struct dentry *fuse_d_add_directory(struct dentry *entry,
+                                           struct inode *inode)
 {
         struct dentry *alias = d_find_alias(inode);
-        if (alias) {
+        if (alias && !(alias->d_flags & DCACHE_DISCONNECTED)) {
                 /* This tries to shrink the subtree below alias */
                 fuse_invalidate_entry(alias);
                 dput(alias);
                 if (!list_empty(&inode->i_dentry))
-                        return -EBUSY;
+                        return ERR_PTR(-EBUSY);
+        } else {
+                dput(alias);
         }
-        d_add(entry, inode);
-        return 0;
+        return d_splice_alias(inode, entry);
 }
 
 static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
@@ -259,6 +261,7 @@ static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
         int err;
         struct fuse_entry_out outarg;
         struct inode *inode = NULL;
+        struct dentry *newent;
         struct fuse_conn *fc = get_fuse_conn(dir);
         struct fuse_req *req;
         struct fuse_req *forget_req;
@@ -303,21 +306,22 @@ static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
 
         if (inode && S_ISDIR(inode->i_mode)) {
                 mutex_lock(&fc->inst_mutex);
-                err = fuse_d_add_directory(entry, inode);
+                newent = fuse_d_add_directory(entry, inode);
                 mutex_unlock(&fc->inst_mutex);
-                if (err) {
+                if (IS_ERR(newent)) {
                         iput(inode);
-                        return ERR_PTR(err);
+                        return newent;
                 }
         } else
-                d_add(entry, inode);
+                newent = d_splice_alias(inode, entry);
 
+        entry = newent ? newent : entry;
         entry->d_op = &fuse_dentry_operations;
         if (!err)
                 fuse_change_entry_timeout(entry, &outarg);
         else
                 fuse_invalidate_entry_cache(entry);
-        return NULL;
+        return newent;
 }
 
 /*