linux-kernel - [RFC v2 3/6] fs: add a helper for thaw_super

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Date:   Sat, 17 Apr 2021 00:10:23 +0000
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     rafael@...nel.org, gregkh@...uxfoundation.org,
        viro@...iv.linux.org.uk, jack@...e.cz, bvanassche@....org,
        jeyu@...nel.org, ebiederm@...ssion.com
Cc:     mchehab@...nel.org, keescook@...omium.org,
        linux-fsdevel@...r.kernel.org, kernel@...force.de,
        kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Luis Chamberlain <mcgrof@...nel.org>
Subject: [RFC v2 3/6] fs: add a helper for thaw_super_locked() which does not unlock

The thaw_super_locked() expects the caller to hold the sb->s_umount
semaphore. It also handles the unlocking of the semaphore for you.
Allow for cases where the caller will do the unlocking of the semaphore.

Signed-off-by: Luis Chamberlain <mcgrof@...nel.org>
---
 fs/super.c | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/fs/super.c b/fs/super.c
index 72b445a69a45..744b2399a272 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -1730,14 +1730,13 @@ int freeze_super(struct super_block *sb)
 }
 EXPORT_SYMBOL(freeze_super);
 
-static int thaw_super_locked(struct super_block *sb)
+/* Caller deals with the sb->s_umount */
+static int __thaw_super_locked(struct super_block *sb)
 {
 	int error;
 
-	if (!sb_is_frozen(sb)) {
-		up_write(&sb->s_umount);
+	if (!sb_is_frozen(sb))
 		return -EINVAL;
-	}
 
 	if (sb_rdonly(sb)) {
 		sb->s_writers.frozen = SB_UNFROZEN;
@@ -1752,7 +1751,6 @@ static int thaw_super_locked(struct super_block *sb)
 			printk(KERN_ERR
 				"VFS:Filesystem thaw failed\n");
 			lockdep_sb_freeze_release(sb);
-			up_write(&sb->s_umount);
 			return error;
 		}
 	}
@@ -1761,10 +1759,25 @@ static int thaw_super_locked(struct super_block *sb)
 	sb_freeze_unlock(sb);
 out:
 	wake_up(&sb->s_writers.wait_unfrozen);
-	deactivate_locked_super(sb);
 	return 0;
 }
 
+/* Handles unlocking of sb->s_umount for you */
+static int thaw_super_locked(struct super_block *sb)
+{
+	int error;
+
+	error = __thaw_super_locked(sb);
+	if (error) {
+		up_write(&sb->s_umount);
+		return error;
+	}
+
+	deactivate_locked_super(sb);
+
+	return 0;
+ }
+
 /**
  * thaw_super -- unlock filesystem
  * @sb: the super to thaw
-- 
2.29.2