get rid of restarts in sync_filesystems()
At the same time we can kill s_need_restart and local mutex in there.
__put_super() made public for a while; will be gone later.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/super.c b/fs/super.c
index 0390461..ba99524 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -130,7 +130,7 @@
* Drop a superblock's refcount. Returns non-zero if the superblock was
* destroyed. The caller must hold sb_lock.
*/
-static int __put_super(struct super_block *sb)
+int __put_super(struct super_block *sb)
{
int ret = 0;
diff --git a/fs/sync.c b/fs/sync.c
index ad6691b..f3f0a0e 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -80,35 +80,15 @@
/*
* Sync all the data for all the filesystems (called by sys_sync() and
* emergency sync)
- *
- * This operation is careful to avoid the livelock which could easily happen
- * if two or more filesystems are being continuously dirtied. s_need_sync
- * is used only here. We set it against all filesystems and then clear it as
- * we sync them. So redirtied filesystems are skipped.
- *
- * But if process A is currently running sync_filesystems and then process B
- * calls sync_filesystems as well, process B will set all the s_need_sync
- * flags again, which will cause process A to resync everything. Fix that with
- * a local mutex.
*/
static void sync_filesystems(int wait)
{
- struct super_block *sb;
- static DEFINE_MUTEX(mutex);
+ struct super_block *sb, *n;
- mutex_lock(&mutex); /* Could be down_interruptible */
spin_lock(&sb_lock);
- list_for_each_entry(sb, &super_blocks, s_list)
- if (!list_empty(&sb->s_instances))
- sb->s_need_sync = 1;
-
-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_need_sync)
- continue;
- sb->s_need_sync = 0;
sb->s_count++;
spin_unlock(&sb_lock);
@@ -119,11 +99,9 @@
/* restart only when sb is no longer on the list */
spin_lock(&sb_lock);
- if (__put_super_and_need_restart(sb))
- goto restart;
+ __put_super(sb);
}
spin_unlock(&sb_lock);
- mutex_unlock(&mutex);
}
/*
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 62f84d9..e1c7427 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1332,7 +1332,6 @@
struct rw_semaphore s_umount;
struct mutex s_lock;
int s_count;
- int s_need_sync;
atomic_t s_active;
#ifdef CONFIG_SECURITY
void *s_security;
@@ -1780,6 +1779,7 @@
struct vfsmount *mnt);
extern void simple_set_mnt(struct vfsmount *mnt, struct super_block *sb);
int __put_super_and_need_restart(struct super_block *sb);
+int __put_super(struct super_block *sb);
void put_super(struct super_block *sb);
/* Alas, no aliases. Too much hassle with bringing module.h everywhere */