Patch "block: add missing group association in bio-cloning functions" has been added to the 4.7-stable tree

[<gregkh@linuxfoundation.org>]

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

    block: add missing group association in bio-cloning functions

to the 4.7-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:
     block-add-missing-group-association-in-bio-cloning-functions.patch
and it can be found in the queue-4.7 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 20bd723ec6a3261df5e02250cd3a1fbb09a343f2 Mon Sep 17 00:00:00 2001
From: Paolo Valente <paolo.valente@linaro.org>
Date: Wed, 27 Jul 2016 07:22:05 +0200
Subject: block: add missing group association in bio-cloning functions

From: Paolo Valente <paolo.valente@linaro.org>

commit 20bd723ec6a3261df5e02250cd3a1fbb09a343f2 upstream.

When a bio is cloned, the newly created bio must be associated with
the same blkcg as the original bio (if BLK_CGROUP is enabled). If
this operation is not performed, then the new bio is not associated
with any group, and the group of the current task is returned when
the group of the bio is requested.

Depending on the cloning frequency, this may cause a large
percentage of the bios belonging to a given group to be treated
as if belonging to other groups (in most cases as if belonging to
the root group). The expected group isolation may thereby be broken.

This commit adds the missing association in bio-cloning functions.

Fixes: da2f0f74cf7d ("Btrfs: add support for blkio controllers")

Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Reviewed-by: Nikolay Borisov <kernel@kyup.com>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 block/bio.c          |   15 +++++++++++++++
 fs/btrfs/extent_io.c |    6 ------
 include/linux/bio.h  |    3 +++
 3 files changed, 18 insertions(+), 6 deletions(-)

--- a/block/bio.c
+++ b/block/bio.c
@@ -579,6 +579,8 @@ void __bio_clone_fast(struct bio *bio, s
 	bio->bi_rw = bio_src->bi_rw;
 	bio->bi_iter = bio_src->bi_iter;
 	bio->bi_io_vec = bio_src->bi_io_vec;
+
+	bio_clone_blkcg_association(bio, bio_src);
 }
 EXPORT_SYMBOL(__bio_clone_fast);
 
@@ -684,6 +686,8 @@ integrity_clone:
 		}
 	}
 
+	bio_clone_blkcg_association(bio, bio_src);
+
 	return bio;
 }
 EXPORT_SYMBOL(bio_clone_bioset);
@@ -2005,6 +2009,17 @@ void bio_disassociate_task(struct bio *b
 	}
 }
 
+/**
+ * bio_clone_blkcg_association - clone blkcg association from src to dst bio
+ * @dst: destination bio
+ * @src: source bio
+ */
+void bio_clone_blkcg_association(struct bio *dst, struct bio *src)
+{
+	if (src->bi_css)
+		WARN_ON(bio_associate_blkcg(dst, src->bi_css));
+}
+
 #endif /* CONFIG_BLK_CGROUP */
 
 static void __init biovec_init_slabs(void)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2696,12 +2696,6 @@ struct bio *btrfs_bio_clone(struct bio *
 		btrfs_bio->csum = NULL;
 		btrfs_bio->csum_allocated = NULL;
 		btrfs_bio->end_io = NULL;
-
-#ifdef CONFIG_BLK_CGROUP
-		/* FIXME, put this into bio_clone_bioset */
-		if (bio->bi_css)
-			bio_associate_blkcg(new, bio->bi_css);
-#endif
 	}
 	return new;
 }
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -527,11 +527,14 @@ extern unsigned int bvec_nr_vecs(unsigne
 int bio_associate_blkcg(struct bio *bio, struct cgroup_subsys_state *blkcg_css);
 int bio_associate_current(struct bio *bio);
 void bio_disassociate_task(struct bio *bio);
+void bio_clone_blkcg_association(struct bio *dst, struct bio *src);
 #else	/* CONFIG_BLK_CGROUP */
 static inline int bio_associate_blkcg(struct bio *bio,
 			struct cgroup_subsys_state *blkcg_css) { return 0; }
 static inline int bio_associate_current(struct bio *bio) { return -ENOENT; }
 static inline void bio_disassociate_task(struct bio *bio) { }
+static inline void bio_clone_blkcg_association(struct bio *dst,
+			struct bio *src) { }
 #endif	/* CONFIG_BLK_CGROUP */
 
 #ifdef CONFIG_HIGHMEM


Patches currently in stable-queue which might be from paolo.valente@linaro.org are

queue-4.7/block-add-missing-group-association-in-bio-cloning-functions.patch