FAILED: patch "[PATCH] btrfs: don't double lock the subvol_sem for rename exchange" failed to apply to 4.9-stable tree

FAILED: patch "[PATCH] btrfs: don't double lock the subvol_sem for rename exchange" failed to apply to 4.9-stable tree

[gregkh]

The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 943eb3bf25f4a7b745dd799e031be276aa104d82 Mon Sep 17 00:00:00 2001
From: Josef Bacik <josef@toxicpanda.com>
Date: Tue, 19 Nov 2019 13:59:20 -0500
Subject: [PATCH] btrfs: don't double lock the subvol_sem for rename exchange

If we're rename exchanging two subvols we'll try to lock this lock
twice, which is bad.  Just lock once if either of the ino's are subvols.

Fixes: cdd1fedf8261 ("btrfs: add support for RENAME_EXCHANGE and RENAME_WHITEOUT")
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 5766c2d19896..e3c76645cad7 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -9554,9 +9554,8 @@ static int btrfs_rename_exchange(struct inode *old_dir,
 	btrfs_init_log_ctx(&ctx_dest, new_inode);
 
 	/* close the race window with snapshot create/destroy ioctl */
-	if (old_ino == BTRFS_FIRST_FREE_OBJECTID)
-		down_read(&fs_info->subvol_sem);
-	if (new_ino == BTRFS_FIRST_FREE_OBJECTID)
+	if (old_ino == BTRFS_FIRST_FREE_OBJECTID ||
+	    new_ino == BTRFS_FIRST_FREE_OBJECTID)
 		down_read(&fs_info->subvol_sem);
 
 	/*
@@ -9790,9 +9789,8 @@ static int btrfs_rename_exchange(struct inode *old_dir,
 		ret = ret ? ret : ret2;
 	}
 out_notrans:
-	if (new_ino == BTRFS_FIRST_FREE_OBJECTID)
-		up_read(&fs_info->subvol_sem);
-	if (old_ino == BTRFS_FIRST_FREE_OBJECTID)
+	if (new_ino == BTRFS_FIRST_FREE_OBJECTID ||
+	    old_ino == BTRFS_FIRST_FREE_OBJECTID)
 		up_read(&fs_info->subvol_sem);
 
 	ASSERT(list_empty(&ctx_root.list));

Re: FAILED: patch "[PATCH] btrfs: don't double lock the subvol_sem for rename exchange" failed to apply to 4.9-stable tree

[Sasha Levin]

On Mon, Dec 23, 2019 at 12:11:14PM -0500, gregkh@linuxfoundation.org wrote:
>
>The patch below does not apply to the 4.9-stable tree.
>If someone wants it applied there, or to any other stable or longterm
>tree, then please email the backport, including the original git commit
>id to <stable@vger.kernel.org>.
>
>thanks,
>
>greg k-h
>
>------------------ original commit in Linus's tree ------------------
>
>From 943eb3bf25f4a7b745dd799e031be276aa104d82 Mon Sep 17 00:00:00 2001
>From: Josef Bacik <josef@toxicpanda.com>
>Date: Tue, 19 Nov 2019 13:59:20 -0500
>Subject: [PATCH] btrfs: don't double lock the subvol_sem for rename exchange
>
>If we're rename exchanging two subvols we'll try to lock this lock
>twice, which is bad.  Just lock once if either of the ino's are subvols.
>
>Fixes: cdd1fedf8261 ("btrfs: add support for RENAME_EXCHANGE and RENAME_WHITEOUT")
>CC: stable@vger.kernel.org # 4.4+
>Signed-off-by: Josef Bacik <josef@toxicpanda.com>
>Reviewed-by: David Sterba <dsterba@suse.com>
>Signed-off-by: David Sterba <dsterba@suse.com>

I've fixed it up and queued for 4.9. I don't think it needs to go to 4.4
as cdd1fedf8261 isn't in 4.4.

-- 
Thanks,
Sasha