block: make blk_crypto_rq_bio_prep() able to fail

blk_crypto_rq_bio_prep() assumes its gfp_mask argument always includes
__GFP_DIRECT_RECLAIM, so that the mempool_alloc() will always succeed.

However, blk_crypto_rq_bio_prep() might be called with GFP_ATOMIC via
setup_clone() in drivers/md/dm-rq.c.

This case isn't currently reachable with a bio that actually has an
encryption context.  However, it's fragile to rely on this.  Just make
blk_crypto_rq_bio_prep() able to fail.

Suggested-by: Satya Tangirala <satyat@google.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Reviewed-by: Satya Tangirala <satyat@google.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-core.c b/block/blk-core.c
index 4884f1e..3b01e7f 100644 (file)
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1617,8 +1617,10 @@ int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
                if (rq->bio) {
                        rq->biotail->bi_next = bio;
                        rq->biotail = bio;
-               } else
+               } else {
                        rq->bio = rq->biotail = bio;
+               }
+               bio = NULL;
        }
 
        /* Copy attributes of the original request to the clone request. */
@@ -1631,8 +1633,8 @@ int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
        rq->nr_phys_segments = rq_src->nr_phys_segments;
        rq->ioprio = rq_src->ioprio;
 
-       if (rq->bio)
-               blk_crypto_rq_bio_prep(rq, rq->bio, gfp_mask);
+       if (rq->bio && blk_crypto_rq_bio_prep(rq, rq->bio, gfp_mask) < 0)
+               goto free_and_out;
 
        return 0;
 

diff --git a/block/blk-crypto-internal.h b/block/blk-crypto-internal.h
index d2b0f56..0d36aae 100644 (file)
--- a/block/blk-crypto-internal.h
+++ b/block/blk-crypto-internal.h
@@ -142,13 +142,24 @@ static inline void blk_crypto_free_request(struct request *rq)
                __blk_crypto_free_request(rq);
 }
 
-void __blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
-                             gfp_t gfp_mask);
-static inline void blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
-                                         gfp_t gfp_mask)
+int __blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
+                            gfp_t gfp_mask);
+/**
+ * blk_crypto_rq_bio_prep - Prepare a request's crypt_ctx when its first bio
+ *                         is inserted
+ * @rq: The request to prepare
+ * @bio: The first bio being inserted into the request
+ * @gfp_mask: Memory allocation flags
+ *
+ * Return: 0 on success, -ENOMEM if out of memory.  -ENOMEM is only possible if
+ *        @gfp_mask doesn't include %__GFP_DIRECT_RECLAIM.
+ */
+static inline int blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
+                                        gfp_t gfp_mask)
 {
        if (bio_has_crypt_ctx(bio))
-               __blk_crypto_rq_bio_prep(rq, bio, gfp_mask);
+               return __blk_crypto_rq_bio_prep(rq, bio, gfp_mask);
+       return 0;
 }
 
 /**

diff --git a/block/blk-crypto.c b/block/blk-crypto.c
index a3f27a1..bbe7974 100644 (file)
--- a/block/blk-crypto.c
+++ b/block/blk-crypto.c
@@ -283,20 +283,16 @@ fail:
        return false;
 }
 
-/**
- * __blk_crypto_rq_bio_prep - Prepare a request's crypt_ctx when its first bio
- *                           is inserted
- *
- * @rq: The request to prepare
- * @bio: The first bio being inserted into the request
- * @gfp_mask: gfp mask
- */
-void __blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
-                             gfp_t gfp_mask)
+int __blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
+                            gfp_t gfp_mask)
 {
-       if (!rq->crypt_ctx)
+       if (!rq->crypt_ctx) {
                rq->crypt_ctx = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
+               if (!rq->crypt_ctx)
+                       return -ENOMEM;
+       }
        *rq->crypt_ctx = *bio->bi_crypt_context;
+       return 0;
 }
 
 /**

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 176698b..2e4b3ca 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1940,13 +1940,18 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
 static void blk_mq_bio_to_request(struct request *rq, struct bio *bio,
                unsigned int nr_segs)
 {
+       int err;
+
        if (bio->bi_opf & REQ_RAHEAD)
                rq->cmd_flags |= REQ_FAILFAST_MASK;
 
        rq->__sector = bio->bi_iter.bi_sector;
        rq->write_hint = bio->bi_write_hint;
        blk_rq_bio_prep(rq, bio, nr_segs);
-       blk_crypto_rq_bio_prep(rq, bio, GFP_NOIO);
+
+       /* This can't fail, since GFP_NOIO includes __GFP_DIRECT_RECLAIM. */
+       err = blk_crypto_rq_bio_prep(rq, bio, GFP_NOIO);
+       WARN_ON_ONCE(err);
 
        blk_account_io_start(rq);
 }