ceph: avoid d_parent in ceph_dentry_hash; fix ceph_encode_fh() hashing bug

Have caller pass in a safely-obtained reference to the parent directory
for calculating a dentry's hash valud.

While we're here, simpify the flow through ceph_encode_fh() so that there
is a single exit point and cleanup.

Also fix a bug with the dentry hash calculation: calculate the hash for the
dentry we were given, not its parent.

Reviewed-by: Yehuda Sadeh <yehuda@hq.newdream.net>
Signed-off-by: Sage Weil <sage@newdream.net>

4 files changed, 18 insertions, 13 deletions

diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
index 31d27f8f8261..33a19df72288 100644
--- a/fs/ceph/dir.c
+++ b/fs/ceph/dir.c
@@ -1244,9 +1244,8 @@ void ceph_dentry_lru_del(struct dentry *dn)
  * Return name hash for a given dentry.  This is dependent on
  * the parent directory's hash function.
  */
-unsigned ceph_dentry_hash(struct dentry *dn)
+unsigned ceph_dentry_hash(struct inode *dir, struct dentry *dn)
 {
-        struct inode *dir = dn->d_parent->d_inode;
         struct ceph_inode_info *dci = ceph_inode(dir);
 
         switch (dci->i_dir_layout.dl_dir_hash) {
diff --git a/fs/ceph/export.c b/fs/ceph/export.c
index f67b687550de..9fbcdecaaccd 100644
--- a/fs/ceph/export.c
+++ b/fs/ceph/export.c
@@ -46,7 +46,7 @@ static int ceph_encode_fh(struct dentry *dentry, u32 *rawfh, int *max_len,
         int type;
         struct ceph_nfs_fh *fh = (void *)rawfh;
         struct ceph_nfs_confh *cfh = (void *)rawfh;
-        struct dentry *parent = dentry->d_parent;
+        struct dentry *parent;
         struct inode *inode = dentry->d_inode;
         int connected_handle_length = sizeof(*cfh)/4;
         int handle_length = sizeof(*fh)/4;
@@ -55,26 +55,33 @@ static int ceph_encode_fh(struct dentry *dentry, u32 *rawfh, int *max_len,
         if (ceph_snap(inode) != CEPH_NOSNAP)
                 return -EINVAL;
 
+        spin_lock(&dentry->d_lock);
+        parent = dget(dentry->d_parent);
+        spin_unlock(&dentry->d_lock);
+
         if (*max_len >= connected_handle_length) {
                 dout("encode_fh %p connectable\n", dentry);
                 cfh->ino = ceph_ino(dentry->d_inode);
                 cfh->parent_ino = ceph_ino(parent->d_inode);
-                cfh->parent_name_hash = ceph_dentry_hash(parent);
+                cfh->parent_name_hash = ceph_dentry_hash(parent->d_inode,
+                                                         dentry);
                 *max_len = connected_handle_length;
                 type = 2;
         } else if (*max_len >= handle_length) {
                 if (connectable) {
                         *max_len = connected_handle_length;
-                        return 255;
+                        type = 255;
+                } else {
+                        dout("encode_fh %p\n", dentry);
+                        fh->ino = ceph_ino(dentry->d_inode);
+                        *max_len = handle_length;
+                        type = 1;
                 }
-                dout("encode_fh %p\n", dentry);
-                fh->ino = ceph_ino(dentry->d_inode);
-                *max_len = handle_length;
-                type = 1;
         } else {
                 *max_len = handle_length;
-                return 255;
+                type = 255;
         }
+        dput(parent);
         return type;
 }
 
@@ -123,7 +130,6 @@ static struct dentry *__fh_to_dentry(struct super_block *sb,
                 return dentry;
         }
         err = ceph_init_dentry(dentry);
-
         if (err < 0) {
                 iput(inode);
                 return ERR_PTR(err);
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 3b1e743b8c8d..8a09cd5a659e 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -670,7 +670,7 @@ static int __choose_mds(struct ceph_mds_client *mdsc,
                 } else {
                         /* dir + name */
                         inode = dir;
-                        hash = ceph_dentry_hash(req->r_dentry);
+                        hash = ceph_dentry_hash(dir, req->r_dentry);
                         is_hash = true;
                 }
         }
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index c1eb9a014b74..35dc9656e499 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -800,7 +800,7 @@ extern void ceph_dentry_lru_add(struct dentry *dn);
 extern void ceph_dentry_lru_touch(struct dentry *dn);
 extern void ceph_dentry_lru_del(struct dentry *dn);
 extern void ceph_invalidate_dentry_lease(struct dentry *dentry);
-extern unsigned ceph_dentry_hash(struct dentry *dn);
+extern unsigned ceph_dentry_hash(struct inode *dir, struct dentry *dn);
 extern struct inode *ceph_get_dentry_parent_inode(struct dentry *dentry);
 
 /*