fuse: fix nlink after unlink

Anand Avati reports that the following sequence of system calls fail on a fuse
filesystem:


 	create("filename") => 0
 	link("filename", "linkname") => 0
 	unlink("filename") => 0
 	link("linkname", "filename") => -ENOENT ### BUG ###

vfs_link() fails with ENOENT if i_nlink is zero, this is done to prevent
resurrecting already deleted files.

Fuse clears i_nlink on unlink even if there are other links pointing to the
file.

Reported-by: Anand Avati <avati@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

1 files changed, 15 insertions, 7 deletions

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 206632887bb4..da379070fab5 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -644,13 +644,12 @@ static int fuse_unlink(struct inode *dir, struct dentry *entry)
         fuse_put_request(fc, req);
         if (!err) {
                 struct inode *inode = entry->d_inode;
+                struct fuse_inode *fi = get_fuse_inode(inode);
 
-                /*
-                 * Set nlink to zero so the inode can be cleared, if the inode
-                 * does have more links this will be discovered at the next
-                 * lookup/getattr.
-                 */
-                clear_nlink(inode);
+                spin_lock(&fc->lock);
+                fi->attr_version = ++fc->attr_version;
+                drop_nlink(inode);
+                spin_unlock(&fc->lock);
                 fuse_invalidate_attr(inode);
                 fuse_invalidate_attr(dir);
                 fuse_invalidate_entry_cache(entry);
@@ -762,8 +761,17 @@ static int fuse_link(struct dentry *entry, struct inode *newdir,
            will reflect changes in the backing inode (link count,
            etc.)
         */
-        if (!err || err == -EINTR)
+        if (!err) {
+                struct fuse_inode *fi = get_fuse_inode(inode);
+
+                spin_lock(&fc->lock);
+                fi->attr_version = ++fc->attr_version;
+                inc_nlink(inode);
+                spin_unlock(&fc->lock);
                 fuse_invalidate_attr(inode);
+        } else if (err == -EINTR) {
+                fuse_invalidate_attr(inode);
+        }
         return err;
 }