[PATCH v2 3/5] afs: use d_alloc_trylock 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_trylock() 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.c       |  6 ++----
 fs/afs/dir_silly.c | 54 +++++++++++++++++++++++++++++++---------------
 fs/afs/internal.h  |  2 ++
 3 files changed, 41 insertions(+), 21 deletions(-)

diff --git a/fs/afs/dir.c b/fs/afs/dir.c
index c790fa9432ab..1edaa7323428 100644
--- a/fs/afs/dir.c
+++ b/fs/afs/dir.c
@@ -19,8 +19,6 @@
 #include "afs_fs.h"
 #include "xdr_fs.h"
 
-static struct dentry *afs_lookup(struct inode *dir, struct dentry *dentry,
-				 unsigned int flags);
 static int afs_dir_open(struct inode *inode, struct file *file);
 static int afs_readdir(struct file *file, struct dir_context *ctx);
 static int afs_d_revalidate(struct inode *dir, const struct qstr *name,
@@ -967,8 +965,8 @@ static struct dentry *afs_lookup_atsys(struct inode *dir, struct dentry *dentry)
 /*
  * look up an entry in a directory
  */
-static struct dentry *afs_lookup(struct inode *dir, struct dentry *dentry,
-				 unsigned int flags)
+struct dentry *afs_lookup(struct inode *dir, struct dentry *dentry,
+			  unsigned int flags)
 {
 	struct afs_vnode *dvnode = AFS_FS_I(dir);
 	struct afs_fid fid = {};
diff --git a/fs/afs/dir_silly.c b/fs/afs/dir_silly.c
index 982bb6ec15f0..12cd2b340392 100644
--- a/fs/afs/dir_silly.c
+++ b/fs/afs/dir_silly.c
@@ -112,7 +112,8 @@ 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;
 	unsigned char silly[16];
 	int ret = -EBUSY;
 
@@ -122,23 +123,42 @@ 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);
+	sdentry = d_alloc_trylock(dentry->d_parent, &QSTR(silly));
+	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_in_lookup(sdentry)) {
+		if (d_really_is_negative(sdentry)) {
+			/* try to get an in-lookup dentry */
+			d_drop(sdentry);
+			sillycounter--;
+		}
+		dput(sdentry);
+		goto newname;
+	}
+	/* This name isn't known locally - check on server */
+	old = afs_lookup(dir, sdentry, 0);
+	d_lookup_done(sdentry);
+	if (IS_ERR(old))
+		goto out;
+	if (old || d_is_positive(sdentry)) {
+		dput(old);
+		dput(sdentry);
+		goto newname;
+	}
 
 	ihold(&vnode->netfs.inode);
 
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 5815ce1f1bfd..d3fd108041cf 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -1109,6 +1109,8 @@ ssize_t afs_read_dir(struct afs_vnode *dvnode, struct file *file)
 	__acquires(&dvnode->validate_lock);
 extern void afs_d_release(struct dentry *);
 extern void afs_check_for_remote_deletion(struct afs_operation *);
+extern struct dentry *afs_lookup(struct inode *dir, struct dentry *dentry,
+				 unsigned int flags);
 
 /*
  * dir_edit.c
-- 
2.50.0.107.gf914562f5916.dirty