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[2603:800c:1a02:1bae:a7fa:157f:969a:4cde]) by smtp.gmail.com with ESMTPSA id jj12-20020a170903048c00b0018996404dd5sm3284296plb.109.2022.12.10.10.33.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 10 Dec 2022 10:33:11 -0800 (PST) Sender: Tejun Heo Date: Sat, 10 Dec 2022 08:33:10 -1000 From: Tejun Heo To: Jens Axboe Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, darklight2357@icloud.com, Josef Bacik , Linus Torvalds , cgroups@vger.kernel.org Subject: [PATCH 1/2 block/for-6.2] blk-iolatency: Fix memory leak on add_disk() failures Message-ID: MIME-Version: 1.0 Content-Disposition: inline Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org When a gendisk is successfully initialized but add_disk() fails such as when a loop device has invalid number of minor device numbers specified, blkcg_init_disk() is called during init and then blkcg_exit_disk() during error handling. Unfortunately, iolatency gets initialized in the former but doesn't get cleaned up in the latter. This is because, in non-error cases, the cleanup is performed by del_gendisk() calling rq_qos_exit(), the assumption being that rq_qos policies, iolatency being one of them, can only be activated once the disk is fully registered and visible. That assumption is true for wbt and iocost, but not so for iolatency as it gets initialized before add_disk() is called. It is desirable to lazy-init rq_qos policies because they are optional features and add to hot path overhead once initialized - each IO has to walk all the registered rq_qos policies. So, we want to switch iolatency to lazy init too. However, that's a bigger change. As a fix for the immediate problem, let's just add an extra call to rq_qos_exit() in blkcg_exit_disk(). This is safe because duplicate calls to rq_qos_exit() become noop's. Signed-off-by: Tejun Heo Reported-by: darklight2357@icloud.com Cc: Josef Bacik Cc: Linus Torvalds Fixes: d70675121546 ("block: introduce blk-iolatency io controller") Cc: stable@vger.kernel.org # v4.19+ Reviewed-by: Christoph Hellwig --- Hello, I'm posting two patches for the iolatency memory leak issue after add_disk() failure. This one is the immediate fix and should be really safe. However, any change has risks and given that the bug being address is not critical at all, I still think it'd make sense to route it through 6.2-rc1 rather than applying directly to master for 6.1 release. So, it's tagged for the 6.2 merge window. Thanks. block/blk-cgroup.c | 2 ++ 1 file changed, 2 insertions(+) --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -33,6 +33,7 @@ #include "blk-cgroup.h" #include "blk-ioprio.h" #include "blk-throttle.h" +#include "blk-rq-qos.h" /* * blkcg_pol_mutex protects blkcg_policy[] and policy [de]activation. @@ -1322,6 +1323,7 @@ err_unlock: void blkcg_exit_disk(struct gendisk *disk) { blkg_destroy_all(disk); + rq_qos_exit(disk->queue); blk_throtl_exit(disk); }