This is a note to let you know that I've just added the patch titled

btrfs: fix false EIO for missing device

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: btrfs-fix-false-eio-for-missing-device.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Mon Dec 18 13:28:59 CET 2017

From: Anand Jain anand.jain@oracle.com Date: Sat, 14 Oct 2017 08:34:02 +0800 Subject: btrfs: fix false EIO for missing device

From: Anand Jain anand.jain@oracle.com

[ Upstream commit 102ed2c5ff932439bbbe74c7bd63e6d5baa9f732 ]

When one of the device is missing, bbio_error() takes care of setting the error status. And if its only IO that is pending in that stripe, it fails to check the status of the other IO at %bbio_error before setting the error %bi_status for the %orig_bio. Fix this by checking if %bbio->error has exceeded the %bbio->max_errors.

Reproducer as below fdatasync error is seen intermittently.

mount -o degraded /dev/sdc /btrfs dd status=none if=/dev/zero of=$(mktemp /btrfs/XXX) bs=4096 count=1 conv=fdatasync

dd: fdatasync failed for ‘/btrfs/LSe’: Input/output error

The reason for the intermittences of the problem is because the following conditions have to be met, which depends on timing: In btrfs_map_bio() - the RAID1 the missing device has to be at %dev_nr = 1 In bbio_error() . before bbio_error() is called the bio of the not-missing device at %dev_nr = 0 must be completed so that the below condition is true if (atomic_dec_and_test(&bbio->stripes_pending)) {

Signed-off-by: Anand Jain anand.jain@oracle.com Reviewed-by: Liu Bo bo.li.liu@oracle.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Sasha Levin alexander.levin@verizon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/volumes.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -6144,7 +6144,10 @@ static void bbio_error(struct btrfs_bio

btrfs_io_bio(bio)->mirror_num = bbio->mirror_num; bio->bi_iter.bi_sector = logical >> 9; - bio->bi_status = BLK_STS_IOERR; + if (atomic_read(&bbio->error) > bbio->max_errors) + bio->bi_status = BLK_STS_IOERR; + else + bio->bi_status = BLK_STS_OK; btrfs_end_bbio(bbio, bio); } }

Patches currently in stable-queue which might be from anand.jain@oracle.com are

queue-4.14/btrfs-undo-writable-superblocke-when-sprouting-fails.patch queue-4.14/btrfs-fix-false-eio-for-missing-device.patch