super: use higher-level helper for {freeze,thaw}

It's not necessary to use low-level locking helpers here. Use the
higher-level locking helpers and log if the superblock is dying. Since
the caller is assumed to already hold an active reference it isn't
possible to observe a dying superblock.

Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/super.c b/fs/super.c
index 2f604a6494fb09922c723ccdc9c7e6aed278abef..a284052ebab217dc07767d5f6007e6cf9ccd374d 100644 (file)
--- a/fs/super.c
+++ b/fs/super.c
@@ -1873,8 +1873,13 @@ int freeze_super(struct super_block *sb)
 {
        int ret;
 
+       /* Since the caller must already have an active reference... */
        atomic_inc(&sb->s_active);
-       __super_lock_excl(sb);
+
+       /* ...@sb definitely can't be dying. */
+       if (!super_lock_excl(sb))
+               WARN(1, "Dying superblock while freezing!");
+
        if (sb->s_writers.frozen != SB_UNFROZEN) {
                deactivate_locked_super(sb);
                return -EBUSY;
@@ -1896,7 +1901,10 @@ int freeze_super(struct super_block *sb)
        /* Release s_umount to preserve sb_start_write -> s_umount ordering */
        super_unlock_excl(sb);
        sb_wait_write(sb, SB_FREEZE_WRITE);
-       __super_lock_excl(sb);
+
+       /* We're still holding an active reference. */
+       if (!super_lock_excl(sb))
+               WARN(1, "Dying superblock while freezing!");
 
        /* Now we go and block page faults... */
        sb->s_writers.frozen = SB_FREEZE_PAGEFAULT;
@@ -1979,7 +1987,8 @@ out:
  */
 int thaw_super(struct super_block *sb)
 {
-       __super_lock_excl(sb);
+       if (!super_lock_excl(sb))
+               WARN(1, "Dying superblock while thawing!");
        return thaw_super_locked(sb);
 }
 EXPORT_SYMBOL(thaw_super);