Merge branch 'work.thaw' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull vfs thaw updates from Al Viro:
 "An ancient series that has fallen through the cracks in the previous
  cycle"

* 'work.thaw' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  buffer.c: call thaw_super during emergency thaw
  vfs: factor sb iteration out of do_emergency_remount

2 files changed, 79 insertions, 51 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index f3491074b035..249b83fafe48 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -494,35 +494,12 @@ repeat:
         return err;
 }
 
-static void do_thaw_one(struct super_block *sb, void *unused)
+void emergency_thaw_bdev(struct super_block *sb)
 {
         while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
                 printk(KERN_WARNING "Emergency Thaw on %pg\n", sb->s_bdev);
 }
 
-static void do_thaw_all(struct work_struct *work)
-{
-        iterate_supers(do_thaw_one, NULL);
-        kfree(work);
-        printk(KERN_WARNING "Emergency Thaw complete\n");
-}
-
-/**
- * emergency_thaw_all -- forcibly thaw every frozen filesystem
- *
- * Used for emergency unfreeze of all filesystems via SysRq
- */
-void emergency_thaw_all(void)
-{
-        struct work_struct *work;
-
-        work = kmalloc(sizeof(*work), GFP_ATOMIC);
-        if (work) {
-                INIT_WORK(work, do_thaw_all);
-                schedule_work(work);
-        }
-}
-
 /**
  * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
  * @mapping: the mapping which wants those buffers written
diff --git a/fs/super.c b/fs/super.c
index 672538ca9831..5fa9a8d8d865 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -37,6 +37,7 @@
 #include <linux/user_namespace.h>
 #include "internal.h"
 
+static int thaw_super_locked(struct super_block *sb);
 
 static LIST_HEAD(super_blocks);
 static DEFINE_SPINLOCK(sb_lock);
@@ -574,6 +575,28 @@ void drop_super_exclusive(struct super_block *sb)
 }
 EXPORT_SYMBOL(drop_super_exclusive);
 
+static void __iterate_supers(void (*f)(struct super_block *))
+{
+        struct super_block *sb, *p = NULL;
+
+        spin_lock(&sb_lock);
+        list_for_each_entry(sb, &super_blocks, s_list) {
+                if (hlist_unhashed(&sb->s_instances))
+                        continue;
+                sb->s_count++;
+                spin_unlock(&sb_lock);
+
+                f(sb);
+
+                spin_lock(&sb_lock);
+                if (p)
+                        __put_super(p);
+                p = sb;
+        }
+        if (p)
+                __put_super(p);
+        spin_unlock(&sb_lock);
+}
 /**
  *      iterate_supers - call function for all active superblocks
  *      @f: function to call
@@ -881,33 +904,22 @@ cancel_readonly:
         return retval;
 }
 
-static void do_emergency_remount(struct work_struct *work)
+static void do_emergency_remount_callback(struct super_block *sb)
 {
-        struct super_block *sb, *p = NULL;
-
-        spin_lock(&sb_lock);
-        list_for_each_entry(sb, &super_blocks, s_list) {
-                if (hlist_unhashed(&sb->s_instances))
-                        continue;
-                sb->s_count++;
-                spin_unlock(&sb_lock);
-                down_write(&sb->s_umount);
-                if (sb->s_root && sb->s_bdev && (sb->s_flags & SB_BORN) &&
-                    !sb_rdonly(sb)) {
-                        /*
-                         * What lock protects sb->s_flags??
-                         */
-                        do_remount_sb(sb, SB_RDONLY, NULL, 1);
-                }
-                up_write(&sb->s_umount);
-                spin_lock(&sb_lock);
-                if (p)
-                        __put_super(p);
-                p = sb;
+        down_write(&sb->s_umount);
+        if (sb->s_root && sb->s_bdev && (sb->s_flags & SB_BORN) &&
+            !sb_rdonly(sb)) {
+                /*
+                 * What lock protects sb->s_flags??
+                 */
+                do_remount_sb(sb, SB_RDONLY, NULL, 1);
         }
-        if (p)
-                __put_super(p);
-        spin_unlock(&sb_lock);
+        up_write(&sb->s_umount);
+}
+
+static void do_emergency_remount(struct work_struct *work)
+{
+        __iterate_supers(do_emergency_remount_callback);
         kfree(work);
         printk("Emergency Remount complete\n");
 }
@@ -923,6 +935,40 @@ void emergency_remount(void)
         }
 }
 
+static void do_thaw_all_callback(struct super_block *sb)
+{
+        down_write(&sb->s_umount);
+        if (sb->s_root && sb->s_flags & MS_BORN) {
+                emergency_thaw_bdev(sb);
+                thaw_super_locked(sb);
+        } else {
+                up_write(&sb->s_umount);
+        }
+}
+
+static void do_thaw_all(struct work_struct *work)
+{
+        __iterate_supers(do_thaw_all_callback);
+        kfree(work);
+        printk(KERN_WARNING "Emergency Thaw complete\n");
+}
+
+/**
+ * emergency_thaw_all -- forcibly thaw every frozen filesystem
+ *
+ * Used for emergency unfreeze of all filesystems via SysRq
+ */
+void emergency_thaw_all(void)
+{
+        struct work_struct *work;
+
+        work = kmalloc(sizeof(*work), GFP_ATOMIC);
+        if (work) {
+                INIT_WORK(work, do_thaw_all);
+                schedule_work(work);
+        }
+}
+
 /*
  * Unnamed block devices are dummy devices used by virtual
  * filesystems which don't use real block-devices.  -- jrs
@@ -1492,11 +1538,10 @@ EXPORT_SYMBOL(freeze_super);
  *
  * Unlocks the filesystem and marks it writeable again after freeze_super().
  */
-int thaw_super(struct super_block *sb)
+static int thaw_super_locked(struct super_block *sb)
 {
         int error;
 
-        down_write(&sb->s_umount);
         if (sb->s_writers.frozen != SB_FREEZE_COMPLETE) {
                 up_write(&sb->s_umount);
                 return -EINVAL;
@@ -1527,4 +1572,10 @@ out:
         deactivate_locked_super(sb);
         return 0;
 }
+
+int thaw_super(struct super_block *sb)
+{
+        down_write(&sb->s_umount);
+        return thaw_super_locked(sb);
+}
 EXPORT_SYMBOL(thaw_super);