fix prune_dcache()/umount() race

... and get rid of the last __put_super_and_need_restart() caller

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

1 files changed, 6 insertions, 11 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index 5afc4994bb27..d96047b4a633 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -536,7 +536,7 @@ restart:
  */
 static void prune_dcache(int count)
 {
-        struct super_block *sb;
+        struct super_block *sb, *n;
         int w_count;
         int unused = dentry_stat.nr_unused;
         int prune_ratio;
@@ -545,13 +545,12 @@ static void prune_dcache(int count)
         if (unused == 0 || count == 0)
                 return;
         spin_lock(&dcache_lock);
-restart:
         if (count >= unused)
                 prune_ratio = 1;
         else
                 prune_ratio = unused / count;
         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;
                 if (sb->s_nr_dentry_unused == 0)
@@ -592,14 +591,10 @@ restart:
                 }
                 spin_lock(&sb_lock);
                 count -= pruned;
-                /*
-                 * restart only when sb is no longer on the list and
-                 * we have more work to do.
-                 */
-                if (__put_super_and_need_restart(sb) && count > 0) {
-                        spin_unlock(&sb_lock);
-                        goto restart;
-                }
+                __put_super(sb);
+                /* more work left to do? */
+                if (count <= 0)
+                        break;
         }
         spin_unlock(&sb_lock);
         spin_unlock(&dcache_lock);