[PATCH 22/53] afs: use d_alloc_nonblock in afs_sillyrename()

[NeilBrown]

From: NeilBrown <neil at brown.name>

Rather than performing a normal lookup (which will be awkward with future
locking changes) use d_alloc_noblock() to find a dentry for an
unused name, and use an open-coded lookup_slow() to see if it is free on
the server.

Signed-off-by: NeilBrown <neil at brown.name>
---
 fs/afs/dir_silly.c | 51 ++++++++++++++++++++++++++++++----------------
 1 file changed, 34 insertions(+), 17 deletions(-)

diff --git a/fs/afs/dir_silly.c b/fs/afs/dir_silly.c
index 982bb6ec15f0..699143b21cdd 100644
--- a/fs/afs/dir_silly.c
+++ b/fs/afs/dir_silly.c
@@ -112,7 +112,9 @@ int afs_sillyrename(struct afs_vnode *dvnode, struct afs_vnode *vnode,
 		    struct dentry *dentry, struct key *key)
 {
 	static unsigned int sillycounter;
-	struct dentry *sdentry = NULL;
+	struct dentry *sdentry = NULL, *old;
+	struct inode *dir = dentry->d_parent->d_inode;
+	struct qstr qsilly;
 	unsigned char silly[16];
 	int ret = -EBUSY;
 
@@ -122,23 +124,38 @@ int afs_sillyrename(struct afs_vnode *dvnode, struct afs_vnode *vnode,
 	if (dentry->d_flags & DCACHE_NFSFS_RENAMED)
 		return -EBUSY;
 
-	sdentry = NULL;
-	do {
-		dput(sdentry);
-		sillycounter++;
-
-		/* Create a silly name.  Note that the ".__afs" prefix is
-		 * understood by the salvager and must not be changed.
-		 */
-		scnprintf(silly, sizeof(silly), ".__afs%04X", sillycounter);
-		sdentry = lookup_noperm(&QSTR(silly), dentry->d_parent);
+newname:
+	sillycounter++;
 
-		/* N.B. Better to return EBUSY here ... it could be dangerous
-		 * to delete the file while it's in use.
-		 */
-		if (IS_ERR(sdentry))
-			goto out;
-	} while (!d_is_negative(sdentry));
+	/* Create a silly name.  Note that the ".__afs" prefix is
+	 * understood by the salvager and must not be changed.
+	 */
+	scnprintf(silly, sizeof(silly), ".__afs%04X", sillycounter);
+	qsilly = QSTR(silly);
+	sdentry = try_lookup_noperm(&qsilly, dentry->d_parent);
+	if (!sdentry)
+		sdentry = d_alloc_noblock(dentry->d_parent, &qsilly);
+	if (sdentry == ERR_PTR(-EWOULDBLOCK))
+		/* try another name */
+		goto newname;
+	/* N.B. Better to return EBUSY here ... it could be dangerous
+	 * to delete the file while it's in use.
+	 */
+	if (IS_ERR(sdentry))
+		goto out;
+	if (d_is_positive(sdentry)) {
+		dput(sdentry);
+		goto newname;
+	}
+	/* This name isn't known locally - check on server */
+	old = dir->i_op->lookup(dir, sdentry, 0);
+	d_lookup_done(sdentry);
+	if (old || d_is_positive(sdentry)) {
+		if (!IS_ERR(old))
+			dput(old);
+		dput(sdentry);
+		goto newname;
+	}
 
 	ihold(&vnode->netfs.inode);
 
-- 
2.50.0.107.gf914562f5916.dirty