linux-kernel - [PATCH v2] block-map: added error handling for bio_copy

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Message-ID: <20211013014256epcms2p5485187a369a9f8c74c2b3ab925df88fb@epcms2p5>
Date:   Wed, 13 Oct 2021 10:42:56 +0900
From:   Jinyoung CHOI <j-young.choi@...sung.com>
To:     "axboe@...nel.dk" <axboe@...nel.dk>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "hch@...radead.org" <hch@...radead.org>
Subject: [PATCH v2] block-map: added error handling for bio_copy_kern()

When new pages are allocated to bio through alloc_page() in
bio_copy_kern(), the pages must be freed in error handling after that.
There is little chance of an error occurring in blk_rq_append_bio(), but
in the code flow, pages additionally allocated to bio must be released.

V2:
        - As pointed out by Christoph, replace int with bool

Signed-off-by: Jinyoung Choi <j-young.choi@...sung.com>
---
 block/blk-map.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/block/blk-map.c b/block/blk-map.c
index 4526adde0156..b137a2f569f8 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -628,6 +628,7 @@ int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
        int reading = rq_data_dir(rq) == READ;
        unsigned long addr = (unsigned long) kbuf;
        struct bio *bio;
+       bool do_copy;
        int ret;
        if (len > (queue_max_hw_sectors(q) << 9))
@@ -635,8 +636,9 @@ int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
        if (!len || !kbuf)
                return -EINVAL;
-       if (!blk_rq_aligned(q, addr, len) || object_is_on_stack(kbuf) ||
-           blk_queue_may_bounce(q))
+       do_copy = !blk_rq_aligned(q, addr, len) || object_is_on_stack(kbuf) ||
+               blk_queue_may_bounce(q);
+       if (do_copy)
                bio = bio_copy_kern(q, kbuf, len, gfp_mask, reading);
        else
                bio = bio_map_kern(q, kbuf, len, gfp_mask);
@@ -648,8 +650,11 @@ int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
        bio->bi_opf |= req_op(rq);
        ret = blk_rq_append_bio(rq, bio);
-       if (unlikely(ret))
+       if (unlikely(ret)) {
+               if (do_copy)
+                       bio_free_pages(bio);
                bio_put(bio);
+       }
        return ret;
 }
 EXPORT_SYMBOL(blk_rq_map_kern);
--
2.25.1