Patch "Btrfs: adjust outstanding_extents counter properly when dio write is split" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

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

    Btrfs: adjust outstanding_extents counter properly when dio write is split

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     btrfs-adjust-outstanding_extents-counter-properly-when-dio-write-is-split.patch
and it can be found in the queue-4.4 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 Fri Aug  4 15:15:51 PDT 2017
From: Liu Bo <bo.li.liu@oracle.com>
Date: Thu, 22 Dec 2016 17:13:54 -0800
Subject: Btrfs: adjust outstanding_extents counter properly when dio write is split

From: Liu Bo <bo.li.liu@oracle.com>


[ Upstream commit c2931667c83ded6504b3857e99cc45b21fa496fb ]

Currently how btrfs dio deals with split dio write is not good
enough if dio write is split into several segments due to the
lack of contiguous space, a large dio write like 'dd bs=1G count=1'
can end up with incorrect outstanding_extents counter and endio
would complain loudly with an assertion.

This fixes the problem by compensating the outstanding_extents
counter in inode if a large dio write gets split.

Reported-by: Anand Jain <anand.jain@oracle.com>
Tested-by: Anand Jain <anand.jain@oracle.com>
Signed-off-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/inode.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7521,11 +7521,18 @@ static void adjust_dio_outstanding_exten
 	 * within our reservation, otherwise we need to adjust our inode
 	 * counter appropriately.
 	 */
-	if (dio_data->outstanding_extents) {
+	if (dio_data->outstanding_extents >= num_extents) {
 		dio_data->outstanding_extents -= num_extents;
 	} else {
+		/*
+		 * If dio write length has been split due to no large enough
+		 * contiguous space, we need to compensate our inode counter
+		 * appropriately.
+		 */
+		u64 num_needed = num_extents - dio_data->outstanding_extents;
+
 		spin_lock(&BTRFS_I(inode)->lock);
-		BTRFS_I(inode)->outstanding_extents += num_extents;
+		BTRFS_I(inode)->outstanding_extents += num_needed;
 		spin_unlock(&BTRFS_I(inode)->lock);
 	}
 }


Patches currently in stable-queue which might be from bo.li.liu@oracle.com are

queue-4.4/btrfs-adjust-outstanding_extents-counter-properly-when-dio-write-is-split.patch
queue-4.4/btrfs-use-down_read_nested-to-make-lockdep-silent.patch