diff options
Diffstat (limited to 'fs/libfs.c')
| -rw-r--r-- | fs/libfs.c | 129 |
1 files changed, 79 insertions, 50 deletions
diff --git a/fs/libfs.c b/fs/libfs.c index f3fa82ce9..74dc8b9e7 100644 --- a/fs/libfs.c +++ b/fs/libfs.c @@ -71,9 +71,7 @@ EXPORT_SYMBOL(simple_lookup); int dcache_dir_open(struct inode *inode, struct file *file) { - static struct qstr cursor_name = QSTR_INIT(".", 1); - - file->private_data = d_alloc(file->f_path.dentry, &cursor_name); + file->private_data = d_alloc_cursor(file->f_path.dentry); return file->private_data ? 0 : -ENOMEM; } @@ -86,10 +84,64 @@ int dcache_dir_close(struct inode *inode, struct file *file) } 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) +{ + unsigned *seq = &parent->d_inode->i_dir_seq, n; + struct dentry *res; + struct list_head *p; + bool skipped; + int i; + +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)) { + skipped = true; + } else if (!--i) { + res = d; + break; + } + } + 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); +} + loff_t dcache_dir_lseek(struct file *file, loff_t offset, int whence) { struct dentry *dentry = file->f_path.dentry; - inode_lock(d_inode(dentry)); switch (whence) { case 1: offset += file->f_pos; @@ -97,34 +149,21 @@ loff_t dcache_dir_lseek(struct file *file, loff_t offset, int whence) if (offset >= 0) break; default: - inode_unlock(d_inode(dentry)); return -EINVAL; } 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; - 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); - spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED); - if (simple_positive(next)) - n--; - spin_unlock(&next->d_lock); - p = p->next; - } - list_add_tail(&cursor->d_child, p); - spin_unlock(&dentry->d_lock); + inode_lock_shared(dentry->d_inode); + to = next_positive(dentry, &dentry->d_subdirs, n); + move_cursor(cursor, to ? &to->d_child : NULL); + inode_unlock_shared(dentry->d_inode); } } - inode_unlock(d_inode(dentry)); return offset; } EXPORT_SYMBOL(dcache_dir_lseek); @@ -145,36 +184,25 @@ int dcache_readdir(struct file *file, struct dir_context *ctx) { 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); - spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED); - if (!simple_positive(next)) { - spin_unlock(&next->d_lock); - continue; - } - - spin_unlock(&next->d_lock); - spin_unlock(&dentry->d_lock); + if (ctx->pos == 2) + 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); - spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED); - /* next is still alive */ - list_move(q, p); - spin_unlock(&next->d_lock); - 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); @@ -190,7 +218,7 @@ const struct file_operations simple_dir_operations = { .release = dcache_dir_close, .llseek = dcache_dir_lseek, .read = generic_read_dir, - .iterate = dcache_readdir, + .iterate_shared = dcache_readdir, .fsync = noop_fsync, }; EXPORT_SYMBOL(simple_dir_operations); @@ -1121,14 +1149,15 @@ static int empty_dir_setattr(struct dentry *dentry, struct iattr *attr) return -EPERM; } -static int empty_dir_setxattr(struct dentry *dentry, const char *name, - const void *value, size_t size, int flags) +static int empty_dir_setxattr(struct dentry *dentry, struct inode *inode, + const char *name, const void *value, + size_t size, int flags) { return -EOPNOTSUPP; } -static ssize_t empty_dir_getxattr(struct dentry *dentry, const char *name, - void *value, size_t size) +static ssize_t empty_dir_getxattr(struct dentry *dentry, struct inode *inode, + const char *name, void *value, size_t size) { return -EOPNOTSUPP; } @@ -1169,7 +1198,7 @@ static int empty_dir_readdir(struct file *file, struct dir_context *ctx) static const struct file_operations empty_dir_operations = { .llseek = empty_dir_llseek, .read = generic_read_dir, - .iterate = empty_dir_readdir, + .iterate_shared = empty_dir_readdir, .fsync = noop_fsync, }; |