blkcg: reassociate bios when make_request() is called recursively

When submitting a bio, multiple recursive calls to make_request() may
occur. This causes the initial associate done in blkcg_bio_issue_check()
to be incorrect and reference the prior request_queue. This introduces
a helper to do reassociation when make_request() is recursively called.

Fixes: a7b39b4e961c ("blkcg: always associate a bio with a blkg")
Reported-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Tested-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/bio.c b/block/bio.c
index 17a8b0aa70506e094b8da3a07eca7a2c71e00826..bbfeb4ee2892fcbd9d51de450c41fab7dc466ce5 100644 (file)
--- a/block/bio.c
+++ b/block/bio.c
@@ -2083,6 +2083,26 @@ int bio_associate_create_blkg(struct request_queue *q, struct bio *bio)
        return ret;
 }
 
+/**
+ * bio_reassociate_blkg - reassociate a bio with a blkg from q
+ * @q: request_queue where bio is going
+ * @bio: target bio
+ *
+ * When submitting a bio, multiple recursive calls to make_request() may occur.
+ * This causes the initial associate done in blkcg_bio_issue_check() to be
+ * incorrect and reference the prior request_queue.  This performs reassociation
+ * when this situation happens.
+ */
+int bio_reassociate_blkg(struct request_queue *q, struct bio *bio)
+{
+       if (bio->bi_blkg) {
+               blkg_put(bio->bi_blkg);
+               bio->bi_blkg = NULL;
+       }
+
+       return bio_associate_create_blkg(q, bio);
+}
+
 /**
  * bio_disassociate_task - undo bio_associate_current()
  * @bio: target bio

diff --git a/block/blk-core.c b/block/blk-core.c
index cdfabc5646da99e3afaa60699dc33eb0b5c1fe2d..3ed60723e2429d4902fb386b66cca59561151458 100644 (file)
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2433,6 +2433,7 @@ blk_qc_t generic_make_request(struct bio *bio)
                        if (q)
                                blk_queue_exit(q);
                        q = bio->bi_disk->queue;
+                       bio_reassociate_blkg(q, bio);
                        flags = 0;
                        if (bio->bi_opf & REQ_NOWAIT)
                                flags = BLK_MQ_REQ_NOWAIT;

diff --git a/include/linux/bio.h b/include/linux/bio.h
index f447b0ebb28851a9a36039f2dc0e099d15b74487..b47c7f716731fc5ebcdf28f03db3b5eadada59e0 100644 (file)
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -514,6 +514,7 @@ int bio_associate_blkg(struct bio *bio, struct blkcg_gq *blkg);
 int bio_associate_blkg_from_css(struct bio *bio,
                                struct cgroup_subsys_state *css);
 int bio_associate_create_blkg(struct request_queue *q, struct bio *bio);
+int bio_reassociate_blkg(struct request_queue *q, struct bio *bio);
 void bio_disassociate_task(struct bio *bio);
 void bio_clone_blkg_association(struct bio *dst, struct bio *src);
 #else  /* CONFIG_BLK_CGROUP */
@@ -522,6 +523,8 @@ static inline int bio_associate_blkg_from_css(struct bio *bio,
 { return 0; }
 static inline int bio_associate_create_blkg(struct request_queue *q,
                                            struct bio *bio) { return 0; }
+static inline int bio_reassociate_blkg(struct request_queue *q, struct bio *bio)
+{ return 0; }
 static inline void bio_disassociate_task(struct bio *bio) { }
 static inline void bio_clone_blkg_association(struct bio *dst,
                                              struct bio *src) { }