* subclass.
*/
down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING);
- s->s_count = S_BIAS;
+ s->s_count = 1;
atomic_set(&s->s_active, 1);
mutex_init(&s->s_vfs_rename_mutex);
mutex_init(&s->s_dquot.dqio_mutex);
/* Superblock refcounting */
/*
- * Drop a superblock's refcount. Returns non-zero if the superblock was
- * destroyed. The caller must hold sb_lock.
+ * Drop a superblock's refcount. The caller must hold sb_lock.
*/
-static int __put_super(struct super_block *sb)
+void __put_super(struct super_block *sb)
{
- int ret = 0;
-
if (!--sb->s_count) {
+ list_del_init(&sb->s_list);
destroy_super(sb);
- ret = 1;
}
- return ret;
-}
-
-/*
- * Drop a superblock's refcount.
- * Returns non-zero if the superblock is about to be destroyed and
- * at least is already removed from super_blocks list, so if we are
- * making a loop through super blocks then we need to restart.
- * The caller must hold sb_lock.
- */
-int __put_super_and_need_restart(struct super_block *sb)
-{
- /* check for race with generic_shutdown_super() */
- if (list_empty(&sb->s_list)) {
- /* super block is removed, need to restart... */
- __put_super(sb);
- return 1;
- }
- /* can't be the last, since s_list is still in use */
- sb->s_count--;
- BUG_ON(sb->s_count == 0);
- return 0;
}
/**
/**
- * deactivate_super - drop an active reference to superblock
+ * deactivate_locked_super - drop an active reference to superblock
* @s: superblock to deactivate
*
- * Drops an active reference to superblock, acquiring a temprory one if
- * there is no active references left. In that case we lock superblock,
+ * Drops an active reference to superblock, converting it into a temprory
+ * one if there is no other active references left. In that case we
* tell fs driver to shut it down and drop the temporary reference we
* had just acquired.
+ *
+ * Caller holds exclusive lock on superblock; that lock is released.
*/
-void deactivate_super(struct super_block *s)
+void deactivate_locked_super(struct super_block *s)
{
struct file_system_type *fs = s->s_type;
- if (atomic_dec_and_lock(&s->s_active, &sb_lock)) {
- s->s_count -= S_BIAS-1;
- spin_unlock(&sb_lock);
+ if (atomic_dec_and_test(&s->s_active)) {
vfs_dq_off(s, 0);
- down_write(&s->s_umount);
fs->kill_sb(s);
put_filesystem(fs);
put_super(s);
+ } else {
+ up_write(&s->s_umount);
}
}
-EXPORT_SYMBOL(deactivate_super);
+EXPORT_SYMBOL(deactivate_locked_super);
/**
- * deactivate_locked_super - drop an active reference to superblock
+ * deactivate_super - drop an active reference to superblock
* @s: superblock to deactivate
*
- * Equivalent of up_write(&s->s_umount); deactivate_super(s);, except that
- * it does not unlock it until it's all over. As the result, it's safe to
- * use to dispose of new superblock on ->get_sb() failure exits - nobody
- * will see the sucker until it's all over. Equivalent using up_write +
- * deactivate_super is safe for that purpose only if superblock is either
- * safe to use or has NULL ->s_root when we unlock.
+ * Variant of deactivate_locked_super(), except that superblock is *not*
+ * locked by caller. If we are going to drop the final active reference,
+ * lock will be acquired prior to that.
*/
-void deactivate_locked_super(struct super_block *s)
+void deactivate_super(struct super_block *s)
{
- struct file_system_type *fs = s->s_type;
- if (atomic_dec_and_lock(&s->s_active, &sb_lock)) {
- s->s_count -= S_BIAS-1;
- spin_unlock(&sb_lock);
- vfs_dq_off(s, 0);
- fs->kill_sb(s);
- put_filesystem(fs);
- put_super(s);
- } else {
- up_write(&s->s_umount);
+ if (!atomic_add_unless(&s->s_active, -1, 1)) {
+ down_write(&s->s_umount);
+ deactivate_locked_super(s);
}
}
-EXPORT_SYMBOL(deactivate_locked_super);
+EXPORT_SYMBOL(deactivate_super);
/**
* grab_super - acquire an active reference
*/
static int grab_super(struct super_block *s) __releases(sb_lock)
{
+ if (atomic_inc_not_zero(&s->s_active)) {
+ spin_unlock(&sb_lock);
+ down_write(&s->s_umount);
+ return 1;
+ }
+ /* it's going away */
s->s_count++;
spin_unlock(&sb_lock);
+ /* wait for it to die */
down_write(&s->s_umount);
- if (s->s_root) {
- spin_lock(&sb_lock);
- if (s->s_count > S_BIAS) {
- atomic_inc(&s->s_active);
- s->s_count--;
- spin_unlock(&sb_lock);
- return 1;
- }
- spin_unlock(&sb_lock);
- }
up_write(&s->s_umount);
put_super(s);
- yield();
return 0;
}
}
spin_lock(&sb_lock);
/* should be initialized for __put_super_and_need_restart() */
- list_del_init(&sb->s_list);
- list_del(&sb->s_instances);
+ list_del_init(&sb->s_instances);
spin_unlock(&sb_lock);
up_write(&sb->s_umount);
}
*/
void sync_supers(void)
{
- struct super_block *sb;
+ struct super_block *sb, *n;
spin_lock(&sb_lock);
-restart:
- list_for_each_entry(sb, &super_blocks, s_list) {
+ list_for_each_entry_safe(sb, n, &super_blocks, s_list) {
+ if (list_empty(&sb->s_instances))
+ continue;
if (sb->s_op->write_super && sb->s_dirt) {
sb->s_count++;
spin_unlock(&sb_lock);
up_read(&sb->s_umount);
spin_lock(&sb_lock);
- if (__put_super_and_need_restart(sb))
- goto restart;
+ __put_super(sb);
}
}
spin_unlock(&sb_lock);
}
+/**
+ * iterate_supers - call function for all active superblocks
+ * @f: function to call
+ * @arg: argument to pass to it
+ *
+ * Scans the superblock list and calls given function, passing it
+ * locked superblock and given argument.
+ */
+void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
+{
+ struct super_block *sb, *n;
+
+ spin_lock(&sb_lock);
+ list_for_each_entry_safe(sb, n, &super_blocks, s_list) {
+ if (list_empty(&sb->s_instances))
+ continue;
+ sb->s_count++;
+ spin_unlock(&sb_lock);
+
+ down_read(&sb->s_umount);
+ if (sb->s_root)
+ f(sb, arg);
+ up_read(&sb->s_umount);
+
+ spin_lock(&sb_lock);
+ __put_super(sb);
+ }
+ spin_unlock(&sb_lock);
+}
+
/**
* get_super - get the superblock of a device
* @bdev: device to get the superblock for
* mounted on the device given. %NULL is returned if no match is found.
*/
-struct super_block * get_super(struct block_device *bdev)
+struct super_block *get_super(struct block_device *bdev)
{
struct super_block *sb;
spin_lock(&sb_lock);
rescan:
list_for_each_entry(sb, &super_blocks, s_list) {
+ if (list_empty(&sb->s_instances))
+ continue;
if (sb->s_bdev == bdev) {
sb->s_count++;
spin_unlock(&sb_lock);
down_read(&sb->s_umount);
+ /* still alive? */
if (sb->s_root)
return sb;
up_read(&sb->s_umount);
- /* restart only when sb is no longer on the list */
+ /* nope, got unmounted */
spin_lock(&sb_lock);
- if (__put_super_and_need_restart(sb))
- goto rescan;
+ __put_super(sb);
+ goto rescan;
}
}
spin_unlock(&sb_lock);
if (!bdev)
return NULL;
+restart:
spin_lock(&sb_lock);
list_for_each_entry(sb, &super_blocks, s_list) {
- if (sb->s_bdev != bdev)
+ if (list_empty(&sb->s_instances))
continue;
-
- if (grab_super(sb)) /* drops sb_lock */
- return sb;
-
- spin_lock(&sb_lock);
+ if (sb->s_bdev == bdev) {
+ if (grab_super(sb)) /* drops sb_lock */
+ return sb;
+ else
+ goto restart;
+ }
}
spin_unlock(&sb_lock);
return NULL;
}
-struct super_block * user_get_super(dev_t dev)
+struct super_block *user_get_super(dev_t dev)
{
struct super_block *sb;
spin_lock(&sb_lock);
rescan:
list_for_each_entry(sb, &super_blocks, s_list) {
+ if (list_empty(&sb->s_instances))
+ continue;
if (sb->s_dev == dev) {
sb->s_count++;
spin_unlock(&sb_lock);
down_read(&sb->s_umount);
+ /* still alive? */
if (sb->s_root)
return sb;
up_read(&sb->s_umount);
- /* restart only when sb is no longer on the list */
+ /* nope, got unmounted */
spin_lock(&sb_lock);
- if (__put_super_and_need_restart(sb))
- goto rescan;
+ __put_super(sb);
+ goto rescan;
}
}
spin_unlock(&sb_lock);
static void do_emergency_remount(struct work_struct *work)
{
- struct super_block *sb;
+ struct super_block *sb, *n;
spin_lock(&sb_lock);
- list_for_each_entry(sb, &super_blocks, s_list) {
+ list_for_each_entry_safe(sb, n, &super_blocks, s_list) {
+ if (list_empty(&sb->s_instances))
+ continue;
sb->s_count++;
spin_unlock(&sb_lock);
down_write(&sb->s_umount);
do_remount_sb(sb, MS_RDONLY, NULL, 1);
}
up_write(&sb->s_umount);
- put_super(sb);
spin_lock(&sb_lock);
+ __put_super(sb);
}
spin_unlock(&sb_lock);
kfree(work);
Code Review / linux-2.6.git / blobdiff