Patch "Btrfs: fix direct IO requests not reporting IO error to user space" has been added to the 4.4-stable tree

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

Btrfs: fix direct IO requests not reporting IO error to user space

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-fix-direct-io-requests-not-reporting-io-error-to-user-space.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 <[email protected]> know about it.

From: Filipe Manana <[email protected]>
Date: Mon, 15 Feb 2016 16:20:26 +0000
Subject: Btrfs: fix direct IO requests not reporting IO error to user space

From: Filipe Manana <[email protected]>

commit 1636d1d77ef4e01e57f706a4cae3371463896136 upstream.

If a bio for a direct IO request fails, we were not setting the error in the parent bio (the main DIO bio), making us not return the error to user space in btrfs_direct_IO(), that is, it made __blockdev_direct_IO() return the number of bytes issued for IO and not the error a bio created and submitted by btrfs_submit_direct() got from the block layer. This essentially happens because when we call:

   dio_end_io(dio_bio, bio->bi_error);

It does not set dio_bio->bi_error to the value of the second argument. So just add this missing assignment in endio callbacks, just as we do in the error path at btrfs_submit_direct() when we fail to clone the dio bio or allocate its private object. This follows the convention of what is done with other similar APIs such as bio_endio() where the caller is responsible for setting the bi_error field in the bio it passes as an argument to bio_endio().

This was detected by the new generic test cases in xfstests: 271, 272, 276 and 278. Which essentially setup a dm error target, then load the error table, do a direct IO write and unload the error table. They expect the write to fail with -EIO, which was not getting reported when testing against btrfs.

---
 fs/btrfs/inode.c |    2 ++
 1 file changed, 2 insertions(+)

@@ -7997,6 +7997,7 @@ static void btrfs_endio_direct_read(stru
 
 	kfree(dip);
 
+	dio_bio->bi_error = bio->bi_error;
 	dio_end_io(dio_bio, bio->bi_error);
 
 	if (io_bio->end_io)

@@ -8042,6 +8043,7 @@ out_test:
 
 	kfree(dip);
 
+	dio_bio->bi_error = bio->bi_error;
 	dio_end_io(dio_bio, bio->bi_error);
 	bio_put(bio);
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/btrfs-fix-page-reading-in-extent_same-ioctl-leading-to-csum-errors.patch queue-4.4/btrfs-fix-fitrim-discarding-device-area-reserved-for-boot-loader-s-use.patch queue-4.4/btrfs-fix-hang-on-extent-buffer-lock-caused-by-the-inode_paths-ioctl.patch queue-4.4/btrfs-fix-invalid-page-accesses-in-extent_same-dedup-ioctl.patch queue-4.4/btrfs-fix-direct-io-requests-not-reporting-io-error-to-user-space.patch