The patch below does not apply to the 4.4-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 72bd2323ec87722c115a5906bc6a1b31d11e8f54 Mon Sep 17 00:00:00 2001

From: Filipe Manana fdmanana@suse.com Date: Mon, 29 Apr 2019 13:08:14 +0100 Subject: [PATCH] Btrfs: do not abort transaction at btrfs_update_root() after failure to COW path

Currently when we fail to COW a path at btrfs_update_root() we end up always aborting the transaction. However all the current callers of btrfs_update_root() are able to deal with errors returned from it, many do end up aborting the transaction themselves (directly or not, such as the transaction commit path), other BUG_ON() or just gracefully cancel whatever they were doing.

When syncing the fsync log, we call btrfs_update_root() through tree-log.c:update_log_root(), and if it returns an -ENOSPC error, the log sync code does not abort the transaction, instead it gracefully handles the error and returns -EAGAIN to the fsync handler, so that it falls back to a transaction commit. Any other error different from -ENOSPC, makes the log sync code abort the transaction.

So remove the transaction abort from btrfs_update_log() when we fail to COW a path to update the root item, so that if an -ENOSPC failure happens we avoid aborting the current transaction and have a chance of the fsync succeeding after falling back to a transaction commit.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=203413 Fixes: 79787eaab46121 ("btrfs: replace many BUG_ONs with proper error handling") Cc: stable@vger.kernel.org # 4.4+ Signed-off-by: Filipe Manana fdmanana@suse.com Reviewed-by: Anand Jain anand.jain@oracle.com Signed-off-by: David Sterba dsterba@suse.com

diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c index 1b9a5d0de139..22124122728c 100644 --- a/fs/btrfs/root-tree.c +++ b/fs/btrfs/root-tree.c @@ -132,10 +132,8 @@ int btrfs_update_root(struct btrfs_trans_handle *trans, struct btrfs_root return -ENOMEM;

ret = btrfs_search_slot(trans, root, key, path, 0, 1); - if (ret < 0) { - btrfs_abort_transaction(trans, ret); + if (ret < 0) goto out; - }

if (ret > 0) { btrfs_crit(fs_info,