libfs: take cursors out of list when moving past the end of directory
that eliminates the last place where we accessed the tail of ->d_subdirs
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/libfs.c b/fs/libfs.c
index 8e023b0..540611b 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -92,14 +92,13 @@ EXPORT_SYMBOL(dcache_dir_close);
/*
* Returns an element of siblings' list.
* We are looking for <count>th positive after <p>; if
- * found, dentry is grabbed and passed to caller via *<res>.
- * If no such element exists, the anchor of list is returned
- * and *<res> is set to NULL.
+ * found, dentry is grabbed and returned to caller.
+ * If no such element exists, NULL is returned.
*/
-static struct list_head *scan_positives(struct dentry *cursor,
+static struct dentry *scan_positives(struct dentry *cursor,
struct list_head *p,
loff_t count,
- struct dentry **res)
+ struct dentry *last)
{
struct dentry *dentry = cursor->d_parent, *found = NULL;
@@ -127,9 +126,8 @@ static struct list_head *scan_positives(struct dentry *cursor,
}
}
spin_unlock(&dentry->d_lock);
- dput(*res);
- *res = found;
- return p;
+ dput(last);
+ return found;
}
loff_t dcache_dir_lseek(struct file *file, loff_t offset, int whence)
@@ -149,25 +147,22 @@ loff_t dcache_dir_lseek(struct file *file, loff_t offset, int whence)
if (offset != file->f_pos) {
struct dentry *cursor = file->private_data;
struct dentry *to = NULL;
- struct list_head *p;
- file->f_pos = offset;
inode_lock_shared(dentry->d_inode);
- if (file->f_pos > 2) {
- p = scan_positives(cursor, &dentry->d_subdirs,
- file->f_pos - 2, &to);
- spin_lock(&dentry->d_lock);
- list_move(&cursor->d_child, p);
- spin_unlock(&dentry->d_lock);
- } else {
- spin_lock(&dentry->d_lock);
+ if (offset > 2)
+ to = scan_positives(cursor, &dentry->d_subdirs,
+ offset - 2, NULL);
+ spin_lock(&dentry->d_lock);
+ if (to)
+ list_move(&cursor->d_child, &to->d_child);
+ else
list_del_init(&cursor->d_child);
- spin_unlock(&dentry->d_lock);
- }
-
+ spin_unlock(&dentry->d_lock);
dput(to);
+ file->f_pos = offset;
+
inode_unlock_shared(dentry->d_inode);
}
return offset;
@@ -199,17 +194,23 @@ int dcache_readdir(struct file *file, struct dir_context *ctx)
if (ctx->pos == 2)
p = anchor;
- else
+ else if (!list_empty(&cursor->d_child))
p = &cursor->d_child;
+ else
+ return 0;
- while ((p = scan_positives(cursor, p, 1, &next)) != anchor) {
+ while ((next = scan_positives(cursor, p, 1, next)) != NULL) {
if (!dir_emit(ctx, next->d_name.name, next->d_name.len,
d_inode(next)->i_ino, dt_type(d_inode(next))))
break;
ctx->pos++;
+ p = &next->d_child;
}
spin_lock(&dentry->d_lock);
- list_move_tail(&cursor->d_child, p);
+ if (next)
+ list_move_tail(&cursor->d_child, &next->d_child);
+ else
+ list_del_init(&cursor->d_child);
spin_unlock(&dentry->d_lock);
dput(next);
