diff options
| -rw-r--r-- | fs/libfs.c | 32 |
1 files changed, 27 insertions, 5 deletions
diff --git a/fs/libfs.c b/fs/libfs.c index b05b74ae3f16..74dc8b9e7f53 100644 --- a/fs/libfs.c +++ b/fs/libfs.c @@ -89,31 +89,53 @@ static struct dentry *next_positive(struct dentry *parent, struct list_head *from, int count) { - struct dentry *res = NULL; + unsigned *seq = &parent->d_inode->i_dir_seq, n; + struct dentry *res; struct list_head *p; + bool skipped; + int i; - spin_lock(&parent->d_lock); +retry: + i = count; + skipped = false; + n = smp_load_acquire(seq) & ~1; + res = NULL; + rcu_read_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) { + if (!simple_positive(d)) { + skipped = true; + } else if (!--i) { res = d; break; } } - spin_unlock(&parent->d_lock); + rcu_read_unlock(); + if (skipped) { + smp_rmb(); + if (unlikely(*seq != n)) + goto retry; + } return res; } static void move_cursor(struct dentry *cursor, struct list_head *after) { struct dentry *parent = cursor->d_parent; - + unsigned n, *seq = &parent->d_inode->i_dir_seq; spin_lock(&parent->d_lock); + for (;;) { + n = *seq; + if (!(n & 1) && cmpxchg(seq, n, n + 1) == n) + break; + cpu_relax(); + } __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); + smp_store_release(seq, n + 2); spin_unlock(&parent->d_lock); } |