Re: [PATCH -next v3] block: remove init_mutex and open-code blk_iolatency_try_init
From: Yu Kuai <hidden>
Date: 2023-08-10 13:44:12
Also in:
linux-block
ÔÚ 2023/08/10 11:51, Li Lingfeng дµÀ:
From: Li Lingfeng <redacted>
Commit a13696b83da4 ("blk-iolatency: Make initialization lazy") adds
a mutex named "init_mutex" in blk_iolatency_try_init for the race
condition of initializing RQ_QOS_LATENCY.
Now a new lock has been add to struct request_queue by commit a13bd91be223
("block/rq_qos: protect rq_qos apis with a new lock"). And it has been
held in blkg_conf_open_bdev before calling blk_iolatency_init.
So it's not necessary to keep init_mutex in blk_iolatency_try_init, just
remove it.
Since init_mutex has been removed, blk_iolatency_try_init can be
open-coded back to iolatency_set_limit() like ioc_qos_write().Reviewed-by: Yu Kuai <redacted> Thanks, Kuai
quoted hunk ↗ jump to hunk
Signed-off-by: Li Lingfeng <redacted> --- v1->v2: open-code blk_iolatency_try_init() v2->v3: add lockdep check block/blk-iolatency.c | 35 +++++++++++------------------------ 1 file changed, 11 insertions(+), 24 deletions(-)diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c index fd5fec989e39..c16aef4be036 100644 --- a/block/blk-iolatency.c +++ b/block/blk-iolatency.c@@ -824,29 +824,6 @@ static void iolatency_clear_scaling(struct blkcg_gq *blkg) } } -static int blk_iolatency_try_init(struct blkg_conf_ctx *ctx) -{ - static DEFINE_MUTEX(init_mutex); - int ret; - - ret = blkg_conf_open_bdev(ctx); - if (ret) - return ret; - - /* - * blk_iolatency_init() may fail after rq_qos_add() succeeds which can - * confuse iolat_rq_qos() test. Make the test and init atomic. - */ - mutex_lock(&init_mutex); - - if (!iolat_rq_qos(ctx->bdev->bd_queue)) - ret = blk_iolatency_init(ctx->bdev->bd_disk); - - mutex_unlock(&init_mutex); - - return ret; -} - static ssize_t iolatency_set_limit(struct kernfs_open_file *of, char *buf, size_t nbytes, loff_t off) {@@ -861,7 +838,17 @@ static ssize_t iolatency_set_limit(struct kernfs_open_file *of, char *buf, blkg_conf_init(&ctx, buf); - ret = blk_iolatency_try_init(&ctx); + ret = blkg_conf_open_bdev(&ctx); + if (ret) + goto out; + + /* + * blk_iolatency_init() may fail after rq_qos_add() succeeds which can + * confuse iolat_rq_qos() test. Make the test and init atomic. + */ + lockdep_assert_held(ctx.bdev->bd_queue->rq_qos_mutex); + if (!iolat_rq_qos(ctx.bdev->bd_queue)) + ret = blk_iolatency_init(ctx.bdev->bd_disk); if (ret) goto out;