linux-kernel - [PATCH V4 10/12] block: call __bio_free in bio

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Message-Id: <f1e84225656d403485ac5f1bd8b9f5db42bc74ca.1498666964.git.shli@fb.com>
Date:   Wed, 28 Jun 2017 09:30:00 -0700
From:   Shaohua Li <shli@...nel.org>
To:     linux-kernel@...r.kernel.org, linux-block@...r.kernel.org
Cc:     tj@...nel.org, gregkh@...uxfoundation.org, hch@....de,
        axboe@...com, rostedt@...dmis.org, lizefan@...wei.com,
        Kernel-team@...com, Shaohua Li <shli@...com>
Subject: [PATCH V4 10/12] block: call __bio_free in bio_endio

From: Shaohua Li <shli@...com>

bio_free isn't a good place to free cgroup/integrity info. There are a
lot of cases bio is allocated in special way (for example, in stack) and
never gets called by bio_put hence bio_free, we are leaking memory. This
patch moves the free to bio endio, which should be called anyway. The
__bio_free call in bio_free is kept, in case the bio never gets called
bio endio.

This assumes ->bi_end_io() doesn't access cgroup/integrity info, which
seems true in my audit. Otherwise, we probably must add a flag to
distinguish if bio will be called by bio_put.

Signed-off-by: Shaohua Li <shli@...com>
---
 block/bio-integrity.c | 1 +
 block/bio.c           | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/block/bio-integrity.c b/block/bio-integrity.c
index b8a3a65..e7fa7d0 100644
--- a/block/bio-integrity.c
+++ b/block/bio-integrity.c
@@ -120,6 +120,7 @@ void bio_integrity_free(struct bio *bio)
 	}

 	bio->bi_integrity = NULL;
+	bio->bi_opf &= ~REQ_INTEGRITY;
 }
 EXPORT_SYMBOL(bio_integrity_free);

diff --git a/block/bio.c b/block/bio.c
index 9cf98b2..4bf3a29 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1828,6 +1828,8 @@ void bio_endio(struct bio *bio)
 	}

 	blk_throtl_bio_endio(bio);
+	/* release cgroup/integrity info */
+	__bio_free(bio);
 	if (bio->bi_end_io)
 		bio->bi_end_io(bio);
 }
-- 
2.9.3