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 d814a49198eafa6163698bdd93961302f3a877a4 Mon Sep 17 00:00:00 2001

From: Ethan Lien ethanlien@synology.com Date: Mon, 2 Jul 2018 15:44:58 +0800 Subject: [PATCH] btrfs: use correct compare function of dirty_metadata_bytes

We use customized, nodesize batch value to update dirty_metadata_bytes. We should also use batch version of compare function or we will easily goto fast path and get false result from percpu_counter_compare().

Fixes: e2d845211eda ("Btrfs: use percpu counter for dirty metadata count") CC: stable@vger.kernel.org # 4.4+ Signed-off-by: Ethan Lien ethanlien@synology.com Reviewed-by: Nikolay Borisov nborisov@suse.com Signed-off-by: David Sterba dsterba@suse.com

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index 6023eed3e805..e3858b2fe014 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -959,8 +959,9 @@ static int btree_writepages(struct address_space *mapping,

fs_info = BTRFS_I(mapping->host)->root->fs_info; /* this is a bit racy, but that's ok */ - ret = percpu_counter_compare(&fs_info->dirty_metadata_bytes, - BTRFS_DIRTY_METADATA_THRESH); + ret = __percpu_counter_compare(&fs_info->dirty_metadata_bytes, + BTRFS_DIRTY_METADATA_THRESH, + fs_info->dirty_metadata_batch); if (ret < 0) return 0; } @@ -4134,8 +4135,9 @@ static void __btrfs_btree_balance_dirty(struct btrfs_fs_info *fs_info, if (flush_delayed) btrfs_balance_delayed_items(fs_info);

- ret = percpu_counter_compare(&fs_info->dirty_metadata_bytes, - BTRFS_DIRTY_METADATA_THRESH); + ret = __percpu_counter_compare(&fs_info->dirty_metadata_bytes, + BTRFS_DIRTY_METADATA_THRESH, + fs_info->dirty_metadata_batch); if (ret > 0) { balance_dirty_pages_ratelimited(fs_info->btree_inode->i_mapping); }