thaw_super may be called with superblock lock already taken (fsfreeze's
emergency thaw being one example), so we need an unlocked version to avoid
lockups.
Cc: Josef Bacik <jbacik@xxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Dave Chinner <dchinner@xxxxxxxxxx>
Reviewed-by: Eric Sandeen <sandeen@xxxxxxxxxx>
Signed-off-by: Fernando Luis Vazquez Cao <fernando@xxxxxxxxxxxxx>
---
diff -urNp linux-3.6-rc5-orig/fs/super.c linux-3.6-rc5/fs/super.c
--- linux-3.6-rc5-orig/fs/super.c 2012-09-14 12:35:48.076847666 +0900
+++ linux-3.6-rc5/fs/super.c 2012-09-14 12:41:01.596850005 +0900
@@ -1437,40 +1437,59 @@ int freeze_super(struct super_block *sb)
EXPORT_SYMBOL(freeze_super);
/**
- * thaw_super -- unlock filesystem
+ * __thaw_super -- unlock filesystem
* @sb: the super to thaw
*
- * Unlocks the filesystem and marks it writeable again after freeze_super().
+ * Unlocks the filesystem and marks it writeable again.
+ *
+ * This is the unlocked version of thaw_super, so it is the caller's job to
+ * to protect the superblock by grabbing the s_umount semaphore in write mode
+ * and release it again on return. See thaw_super() for an example.
*/
-int thaw_super(struct super_block *sb)
+int __thaw_super(struct super_block *sb)
{
- int error;
+ int error = 0;
- down_write(&sb->s_umount);
if (sb->s_writers.frozen == SB_UNFROZEN) {
- up_write(&sb->s_umount);
- return -EINVAL;
+ error = -EINVAL;
+ goto out;
}
if (sb->s_flags & MS_RDONLY)
- goto out;
+ goto out_thaw;
if (sb->s_op->unfreeze_fs) {
error = sb->s_op->unfreeze_fs(sb);
if (error) {
printk(KERN_ERR
"VFS:Filesystem thaw failed\n");
- up_write(&sb->s_umount);
- return error;
+ goto out;
}
}
-out:
+out_thaw:
sb->s_writers.frozen = SB_UNFROZEN;
smp_wmb();
wake_up(&sb->s_writers.wait_unfrozen);
- deactivate_locked_super(sb);
+out:
+ return error;
+}
- return 0;
+/**
+ * thaw_super -- unlock filesystem
+ * @sb: the super to thaw
+ *
+ * Unlocks the filesystem and marks it writeable again after freeze_super().
+ */
+int thaw_super(struct super_block *sb)
+{
+ int res;
+ down_write(&sb->s_umount);
+ res = __thaw_super(sb);
+ if (!res)
+ deactivate_locked_super(sb);
+ else
+ up_write(&sb->s_umount);
+ return res;
}
EXPORT_SYMBOL(thaw_super);
diff -urNp linux-3.6-rc5-orig/include/linux/fs.h linux-3.6-rc5/include/linux/fs.h
--- linux-3.6-rc5-orig/include/linux/fs.h 2012-09-14 12:35:48.076847666 +0900
+++ linux-3.6-rc5/include/linux/fs.h 2012-09-14 12:37:39.304848651 +0900
@@ -2082,6 +2082,7 @@ extern int user_statfs(const char __user
extern int fd_statfs(int, struct kstatfs *);
extern int vfs_ustat(dev_t, struct kstatfs *);
extern int freeze_super(struct super_block *super);
+extern int __thaw_super(struct super_block *super);
extern int thaw_super(struct super_block *super);
extern bool our_mnt(struct vfsmount *mnt);
--
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