libfs.c: new helper - next_positive()
Return nth positive child after given or NULL if there's
less than n left. dcache_readdir() and dcache_dir_lseek()
switched to it.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/libfs.c b/fs/libfs.c
index f56acb1..b05b74a 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -84,6 +84,39 @@
}
EXPORT_SYMBOL(dcache_dir_close);
+/* parent is locked at least shared */
+static struct dentry *next_positive(struct dentry *parent,
+ struct list_head *from,
+ int count)
+{
+ struct dentry *res = NULL;
+ struct list_head *p;
+
+ spin_lock(&parent->d_lock);
+ for (p = from->next; p != &parent->d_subdirs; p = p->next) {
+ struct dentry *d = list_entry(p, struct dentry, d_child);
+ if (simple_positive(d) && !--count) {
+ res = d;
+ break;
+ }
+ }
+ spin_unlock(&parent->d_lock);
+ return res;
+}
+
+static void move_cursor(struct dentry *cursor, struct list_head *after)
+{
+ struct dentry *parent = cursor->d_parent;
+
+ spin_lock(&parent->d_lock);
+ __list_del(cursor->d_child.prev, cursor->d_child.next);
+ if (after)
+ list_add(&cursor->d_child, after);
+ else
+ list_add_tail(&cursor->d_child, &parent->d_subdirs);
+ spin_unlock(&parent->d_lock);
+}
+
loff_t dcache_dir_lseek(struct file *file, loff_t offset, int whence)
{
struct dentry *dentry = file->f_path.dentry;
@@ -99,24 +132,13 @@
if (offset != file->f_pos) {
file->f_pos = offset;
if (file->f_pos >= 2) {
- struct list_head *p;
struct dentry *cursor = file->private_data;
+ struct dentry *to;
loff_t n = file->f_pos - 2;
inode_lock_shared(dentry->d_inode);
- spin_lock(&dentry->d_lock);
- /* d_lock not required for cursor */
- list_del(&cursor->d_child);
- p = dentry->d_subdirs.next;
- while (n && p != &dentry->d_subdirs) {
- struct dentry *next;
- next = list_entry(p, struct dentry, d_child);
- if (simple_positive(next))
- n--;
- p = p->next;
- }
- list_add_tail(&cursor->d_child, p);
- spin_unlock(&dentry->d_lock);
+ to = next_positive(dentry, &dentry->d_subdirs, n);
+ move_cursor(cursor, to ? &to->d_child : NULL);
inode_unlock_shared(dentry->d_inode);
}
}
@@ -140,30 +162,25 @@
{
struct dentry *dentry = file->f_path.dentry;
struct dentry *cursor = file->private_data;
- struct list_head *p, *q = &cursor->d_child;
+ struct list_head *p = &cursor->d_child;
+ struct dentry *next;
+ bool moved = false;
if (!dir_emit_dots(file, ctx))
return 0;
- spin_lock(&dentry->d_lock);
+
if (ctx->pos == 2)
- list_move(q, &dentry->d_subdirs);
-
- for (p = q->next; p != &dentry->d_subdirs; p = p->next) {
- struct dentry *next = list_entry(p, struct dentry, d_child);
- if (!simple_positive(next))
- continue;
-
- spin_unlock(&dentry->d_lock);
+ p = &dentry->d_subdirs;
+ while ((next = next_positive(dentry, p, 1)) != NULL) {
if (!dir_emit(ctx, next->d_name.name, next->d_name.len,
d_inode(next)->i_ino, dt_type(d_inode(next))))
- return 0;
- spin_lock(&dentry->d_lock);
- /* next is still alive */
- list_move(q, p);
- p = q;
+ break;
+ moved = true;
+ p = &next->d_child;
ctx->pos++;
}
- spin_unlock(&dentry->d_lock);
+ if (moved)
+ move_cursor(cursor, p);
return 0;
}
EXPORT_SYMBOL(dcache_readdir);