Leave superblocks on s_list until the end

We used to remove from s_list and s_instances at the same
time.  So let's *not* do the former and skip superblocks
that have empty s_instances in the loops over s_list.

The next step, of course, will be to get rid of rescan logics
in those loops.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

6 files changed, 25 insertions, 4 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index c9c266db0624..021ec4da9932 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -568,6 +568,8 @@ static void do_thaw_all(struct work_struct *work)
         spin_lock(&sb_lock);
 restart:
         list_for_each_entry(sb, &super_blocks, s_list) {
+                if (list_empty(&sb->s_instances))
+                        continue;
                 sb->s_count++;
                 spin_unlock(&sb_lock);
                 down_read(&sb->s_umount);
diff --git a/fs/dcache.c b/fs/dcache.c
index 2b6f09af13ab..5afc4994bb27 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -552,6 +552,8 @@ restart:
                 prune_ratio = unused / count;
         spin_lock(&sb_lock);
         list_for_each_entry(sb, &super_blocks, s_list) {
+                if (list_empty(&sb->s_instances))
+                        continue;
                 if (sb->s_nr_dentry_unused == 0)
                         continue;
                 sb->s_count++;
diff --git a/fs/drop_caches.c b/fs/drop_caches.c
index 31f4b0e6d72c..9cd4e4a70f56 100644
--- a/fs/drop_caches.c
+++ b/fs/drop_caches.c
@@ -40,6 +40,8 @@ static void drop_pagecache(void)
         spin_lock(&sb_lock);
 restart:
         list_for_each_entry(sb, &super_blocks, s_list) {
+                if (list_empty(&sb->s_instances))
+                        continue;
                 sb->s_count++;
                 spin_unlock(&sb_lock);
                 down_read(&sb->s_umount);
diff --git a/fs/quota/quota.c b/fs/quota/quota.c
index cfc78826da90..4669e7e639bd 100644
--- a/fs/quota/quota.c
+++ b/fs/quota/quota.c
@@ -59,6 +59,8 @@ static int quota_sync_all(int type)
         spin_lock(&sb_lock);
 restart:
         list_for_each_entry(sb, &super_blocks, s_list) {
+                if (list_empty(&sb->s_instances))
+                        continue;
                 if (!sb->s_qcop || !sb->s_qcop->quota_sync)
                         continue;
 
diff --git a/fs/super.c b/fs/super.c
index 157657b32798..0390461dfca0 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -135,6 +135,7 @@ static int __put_super(struct super_block *sb)
         int ret = 0;
 
         if (!--sb->s_count) {
+                list_del_init(&sb->s_list);
                 destroy_super(sb);
                 ret = 1;
         }
@@ -151,7 +152,7 @@ static int __put_super(struct super_block *sb)
 int __put_super_and_need_restart(struct super_block *sb)
 {
         /* check for race with generic_shutdown_super() */
-        if (list_empty(&sb->s_list)) {
+        if (list_empty(&sb->s_instances)) {
                 /* super block is removed, need to restart... */
                 __put_super(sb);
                 return 1;
@@ -308,8 +309,7 @@ void generic_shutdown_super(struct super_block *sb)
         }
         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);
 }
@@ -400,6 +400,8 @@ void sync_supers(void)
         spin_lock(&sb_lock);
 restart:
         list_for_each_entry(sb, &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);
@@ -435,6 +437,8 @@ struct super_block * get_super(struct block_device *bdev)
         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);
@@ -471,6 +475,8 @@ struct super_block *get_active_super(struct block_device *bdev)
 
         spin_lock(&sb_lock);
         list_for_each_entry(sb, &super_blocks, s_list) {
+                if (list_empty(&sb->s_instances))
+                        continue;
                 if (sb->s_bdev != bdev)
                         continue;
 
@@ -490,6 +496,8 @@ struct super_block * user_get_super(dev_t dev)
         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);
@@ -600,6 +608,8 @@ static void do_emergency_remount(struct work_struct *work)
 
         spin_lock(&sb_lock);
         list_for_each_entry(sb, &super_blocks, s_list) {
+                if (list_empty(&sb->s_instances))
+                        continue;
                 sb->s_count++;
                 spin_unlock(&sb_lock);
                 down_write(&sb->s_umount);
diff --git a/fs/sync.c b/fs/sync.c
index 92b228176f7c..ad6691bae370 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -99,10 +99,13 @@ static void sync_filesystems(int wait)
         mutex_lock(&mutex);             /* Could be down_interruptible */
         spin_lock(&sb_lock);
         list_for_each_entry(sb, &super_blocks, s_list)
-                sb->s_need_sync = 1;
+                if (!list_empty(&sb->s_instances))
+                        sb->s_need_sync = 1;
 
 restart:
         list_for_each_entry(sb, &super_blocks, s_list) {
+                if (list_empty(&sb->s_instances))
+                        continue;
                 if (!sb->s_need_sync)
                         continue;
                 sb->s_need_sync = 0;