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>

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 206632887bb40ccf48bb80b96e497c2107c172d9..da379070fab56f7632b6f880fb543ced781d5772 100644 (file)
--- 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;
 }