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[2603:800c:1a02:1bae:a7fa:157f:969a:4cde]) by smtp.gmail.com with ESMTPSA id z22-20020aa785d6000000b0062dd9a8c1b8sm28308pfn.100.2023.04.12.17.06.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 12 Apr 2023 17:06:58 -0700 (PDT) Sender: Tejun Heo From: Tejun Heo To: axboe@kernel.dk, josef@toxicpanda.com, hch@lst.de Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, yukuai1@huaweicloud.com, Tejun Heo Subject: [PATCH 2/4] blkcg: Restructure blkg_conf_prep() and friends Date: Wed, 12 Apr 2023 14:06:47 -1000 Message-Id: <20230413000649.115785-3-tj@kernel.org> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230413000649.115785-1-tj@kernel.org> References: <20230413000649.115785-1-tj@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org We want to support lazy init of rq-qos policies so that iolatency is enabled lazily on configuration instead of gendisk initialization. The way blkg config helpers are structured now is a bit awkward for that. Let's restructure: * blkcg_conf_open_bdev() is renamed to blkg_conf_open_bdev(). The blkcg_ prefix was used because the bdev opening step is blkg-independent. However, the distinction is too subtle and confuses more than helps. Let's switch to blkg prefix so that it's consistent with the type and other helper names. * struct blkg_conf_ctx now remembers the original input string and is always initialized by the new blkg_conf_init(). * blkg_conf_open_bdev() is updated to take a pointer to blkg_conf_ctx like blkg_conf_prep() and can be called multiple times safely. Instead of modifying the double pointer to input string directly, blkg_conf_open_bdev() now sets blkg_conf_ctx->body. * blkg_conf_finish() is renamed to blkg_conf_exit() for symmetry and now must be called on all blkg_conf_ctx's which were initialized with blkg_conf_init(). Combined, this allows the users to either open the bdev first or do it altogether with blkg_conf_prep() which will help implementing lazy init of rq-qos policies. blkg_conf_init/exit() will also be used implement synchronization against device removal. This is necessary because iolat / iocost are configured through cgroupfs instead of one of the files under /sys/block/DEVICE. As cgroupfs operations aren't synchronized with block layer, the lazy init and other configuration operations may race against device removal. This patch makes blkg_conf_init/exit() used consistently for all cgroup-orginating configurations making them a good place to implement explicit synchronization. Users are updated accordingly. No behavior change is intended by this patch. v2: bfq wasn't updated in v1 causing a build error. Fixed. v3: Update the description to include future use of blkg_conf_init/exit() as synchronization points. Signed-off-by: Tejun Heo Cc: Josef Bacik Cc: Christoph Hellwig Cc: Yu Kuai Reviewed-by: Christoph Hellwig --- block/bfq-cgroup.c | 8 ++-- block/blk-cgroup.c | 105 +++++++++++++++++++++++++++--------------- block/blk-cgroup.h | 10 ++-- block/blk-iocost.c | 58 +++++++++++++---------- block/blk-iolatency.c | 8 ++-- block/blk-throttle.c | 16 ++++--- 6 files changed, 127 insertions(+), 78 deletions(-) diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c index 74f7d051665b..2c90e5de0acd 100644 --- a/block/bfq-cgroup.c +++ b/block/bfq-cgroup.c @@ -1105,9 +1105,11 @@ static ssize_t bfq_io_set_device_weight(struct kernfs_open_file *of, struct bfq_group *bfqg; u64 v; - ret = blkg_conf_prep(blkcg, &blkcg_policy_bfq, buf, &ctx); + blkg_conf_init(&ctx, buf); + + ret = blkg_conf_prep(blkcg, &blkcg_policy_bfq, &ctx); if (ret) - return ret; + goto out; if (sscanf(ctx.body, "%llu", &v) == 1) { /* require "default" on dfl */ @@ -1129,7 +1131,7 @@ static ssize_t bfq_io_set_device_weight(struct kernfs_open_file *of, ret = 0; } out: - blkg_conf_finish(&ctx); + blkg_conf_exit(&ctx); return ret ?: nbytes; } diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 0a2c19d74d95..c154b08a7e92 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -653,69 +653,93 @@ u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v) EXPORT_SYMBOL_GPL(__blkg_prfill_u64); /** - * blkcg_conf_open_bdev - parse and open bdev for per-blkg config update - * @inputp: input string pointer + * blkg_conf_init - initialize a blkg_conf_ctx + * @ctx: blkg_conf_ctx to initialize + * @input: input string * - * Parse the device node prefix part, MAJ:MIN, of per-blkg config update - * from @input and get and return the matching bdev. *@inputp is - * updated to point past the device node prefix. Returns an ERR_PTR() - * value on error. + * Initialize @ctx which can be used to parse blkg config input string @input. + * Once initialized, @ctx can be used with blkg_conf_open_bdev() and + * blkg_conf_prep(), and must be cleaned up with blkg_conf_exit(). + */ +void blkg_conf_init(struct blkg_conf_ctx *ctx, char *input) +{ + *ctx = (struct blkg_conf_ctx){ .input = input }; +} +EXPORT_SYMBOL_GPL(blkg_conf_init); + +/** + * blkg_conf_open_bdev - parse and open bdev for per-blkg config update + * @ctx: blkg_conf_ctx initialized with blkg_conf_init() * - * Use this function iff blkg_conf_prep() can't be used for some reason. + * Parse the device node prefix part, MAJ:MIN, of per-blkg config update from + * @ctx->input and get and store the matching bdev in @ctx->bdev. @ctx->body is + * set to point past the device node prefix. + * + * This function may be called multiple times on @ctx and the extra calls become + * NOOPs. blkg_conf_prep() implicitly calls this function. Use this function + * explicitly if bdev access is needed without resolving the blkcg / policy part + * of @ctx->input. Returns -errno on error. */ -struct block_device *blkcg_conf_open_bdev(char **inputp) +int blkg_conf_open_bdev(struct blkg_conf_ctx *ctx) { - char *input = *inputp; + char *input = ctx->input; unsigned int major, minor; struct block_device *bdev; int key_len; + if (ctx->bdev) + return 0; + if (sscanf(input, "%u:%u%n", &major, &minor, &key_len) != 2) - return ERR_PTR(-EINVAL); + return -EINVAL; input += key_len; if (!isspace(*input)) - return ERR_PTR(-EINVAL); + return -EINVAL; input = skip_spaces(input); bdev = blkdev_get_no_open(MKDEV(major, minor)); if (!bdev) - return ERR_PTR(-ENODEV); + return -ENODEV; if (bdev_is_partition(bdev)) { blkdev_put_no_open(bdev); - return ERR_PTR(-ENODEV); + return -ENODEV; } - *inputp = input; - return bdev; + ctx->body = input; + ctx->bdev = bdev; + return 0; } /** * blkg_conf_prep - parse and prepare for per-blkg config update * @blkcg: target block cgroup * @pol: target policy - * @input: input string - * @ctx: blkg_conf_ctx to be filled + * @ctx: blkg_conf_ctx initialized with blkg_conf_init() + * + * Parse per-blkg config update from @ctx->input and initialize @ctx + * accordingly. On success, @ctx->body points to the part of @ctx->input + * following MAJ:MIN, @ctx->bdev points to the target block device and + * @ctx->blkg to the blkg being configured. * - * Parse per-blkg config update from @input and initialize @ctx with the - * result. @ctx->blkg points to the blkg to be updated and @ctx->body the - * part of @input following MAJ:MIN. This function returns with queue lock - * held and must be paired with blkg_conf_finish(). + * blkg_conf_open_bdev() may be called on @ctx beforehand. On success, this + * function returns with queue lock held and must be followed by + * blkg_conf_exit(). */ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol, - char *input, struct blkg_conf_ctx *ctx) + struct blkg_conf_ctx *ctx) __acquires(&bdev->bd_queue->queue_lock) { - struct block_device *bdev; struct gendisk *disk; struct request_queue *q; struct blkcg_gq *blkg; int ret; - bdev = blkcg_conf_open_bdev(&input); - if (IS_ERR(bdev)) - return PTR_ERR(bdev); - disk = bdev->bd_disk; + ret = blkg_conf_open_bdev(ctx); + if (ret) + return ret; + + disk = ctx->bdev->bd_disk; q = disk->queue; /* @@ -793,9 +817,7 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol, } success: blk_queue_exit(q); - ctx->bdev = bdev; ctx->blkg = blkg; - ctx->body = input; return 0; fail_preloaded: @@ -805,7 +827,6 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol, fail_exit_queue: blk_queue_exit(q); fail: - blkdev_put_no_open(bdev); /* * If queue was bypassing, we should retry. Do so after a * short msleep(). It isn't strictly necessary but queue @@ -821,19 +842,27 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol, EXPORT_SYMBOL_GPL(blkg_conf_prep); /** - * blkg_conf_finish - finish up per-blkg config update - * @ctx: blkg_conf_ctx initialized by blkg_conf_prep() + * blkg_conf_exit - clean up per-blkg config update + * @ctx: blkg_conf_ctx initialized with blkg_conf_init() * - * Finish up after per-blkg config update. This function must be paired - * with blkg_conf_prep(). + * Clean up after per-blkg config update. This function must be called on all + * blkg_conf_ctx's initialized with blkg_conf_init(). */ -void blkg_conf_finish(struct blkg_conf_ctx *ctx) +void blkg_conf_exit(struct blkg_conf_ctx *ctx) __releases(&ctx->bdev->bd_queue->queue_lock) { - spin_unlock_irq(&bdev_get_queue(ctx->bdev)->queue_lock); - blkdev_put_no_open(ctx->bdev); + if (ctx->blkg) { + spin_unlock_irq(&bdev_get_queue(ctx->bdev)->queue_lock); + ctx->blkg = NULL; + } + + if (ctx->bdev) { + blkdev_put_no_open(ctx->bdev); + ctx->body = NULL; + ctx->bdev = NULL; + } } -EXPORT_SYMBOL_GPL(blkg_conf_finish); +EXPORT_SYMBOL_GPL(blkg_conf_exit); static void blkg_iostat_set(struct blkg_iostat *dst, struct blkg_iostat *src) { diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h index 2c6788658544..d6ad3abc6eca 100644 --- a/block/blk-cgroup.h +++ b/block/blk-cgroup.h @@ -206,15 +206,17 @@ void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg, u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v); struct blkg_conf_ctx { + char *input; + char *body; struct block_device *bdev; struct blkcg_gq *blkg; - char *body; }; -struct block_device *blkcg_conf_open_bdev(char **inputp); +void blkg_conf_init(struct blkg_conf_ctx *ctx, char *input); +int blkg_conf_open_bdev(struct blkg_conf_ctx *ctx); int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol, - char *input, struct blkg_conf_ctx *ctx); -void blkg_conf_finish(struct blkg_conf_ctx *ctx); + struct blkg_conf_ctx *ctx); +void blkg_conf_exit(struct blkg_conf_ctx *ctx); /** * bio_issue_as_root_blkg - see if this bio needs to be issued as root blkg diff --git a/block/blk-iocost.c b/block/blk-iocost.c index 4442c7a85112..285ced3467ab 100644 --- a/block/blk-iocost.c +++ b/block/blk-iocost.c @@ -3106,9 +3106,11 @@ static ssize_t ioc_weight_write(struct kernfs_open_file *of, char *buf, return nbytes; } - ret = blkg_conf_prep(blkcg, &blkcg_policy_iocost, buf, &ctx); + blkg_conf_init(&ctx, buf); + + ret = blkg_conf_prep(blkcg, &blkcg_policy_iocost, &ctx); if (ret) - return ret; + goto err; iocg = blkg_to_iocg(ctx.blkg); @@ -3127,12 +3129,14 @@ static ssize_t ioc_weight_write(struct kernfs_open_file *of, char *buf, weight_updated(iocg, &now); spin_unlock(&iocg->ioc->lock); - blkg_conf_finish(&ctx); + blkg_conf_exit(&ctx); return nbytes; einval: - blkg_conf_finish(&ctx); - return -EINVAL; + ret = -EINVAL; +err: + blkg_conf_exit(&ctx); + return ret; } static u64 ioc_qos_prfill(struct seq_file *sf, struct blkg_policy_data *pd, @@ -3189,19 +3193,22 @@ static const match_table_t qos_tokens = { static ssize_t ioc_qos_write(struct kernfs_open_file *of, char *input, size_t nbytes, loff_t off) { - struct block_device *bdev; + struct blkg_conf_ctx ctx; struct gendisk *disk; struct ioc *ioc; u32 qos[NR_QOS_PARAMS]; bool enable, user; - char *p; + char *body, *p; int ret; - bdev = blkcg_conf_open_bdev(&input); - if (IS_ERR(bdev)) - return PTR_ERR(bdev); + blkg_conf_init(&ctx, input); - disk = bdev->bd_disk; + ret = blkg_conf_open_bdev(&ctx); + if (ret) + goto err; + + body = ctx.body; + disk = ctx.bdev->bd_disk; if (!queue_is_mq(disk->queue)) { ret = -EOPNOTSUPP; goto err; @@ -3223,7 +3230,7 @@ static ssize_t ioc_qos_write(struct kernfs_open_file *of, char *input, enable = ioc->enabled; user = ioc->user_qos_params; - while ((p = strsep(&input, " \t\n"))) { + while ((p = strsep(&body, " \t\n"))) { substring_t args[MAX_OPT_ARGS]; char buf[32]; int tok; @@ -3313,7 +3320,7 @@ static ssize_t ioc_qos_write(struct kernfs_open_file *of, char *input, blk_mq_unquiesce_queue(disk->queue); blk_mq_unfreeze_queue(disk->queue); - blkdev_put_no_open(bdev); + blkg_conf_exit(&ctx); return nbytes; einval: spin_unlock_irq(&ioc->lock); @@ -3323,7 +3330,7 @@ static ssize_t ioc_qos_write(struct kernfs_open_file *of, char *input, ret = -EINVAL; err: - blkdev_put_no_open(bdev); + blkg_conf_exit(&ctx); return ret; } @@ -3376,19 +3383,22 @@ static const match_table_t i_lcoef_tokens = { static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input, size_t nbytes, loff_t off) { - struct block_device *bdev; + struct blkg_conf_ctx ctx; struct request_queue *q; struct ioc *ioc; u64 u[NR_I_LCOEFS]; bool user; - char *p; + char *body, *p; int ret; - bdev = blkcg_conf_open_bdev(&input); - if (IS_ERR(bdev)) - return PTR_ERR(bdev); + blkg_conf_init(&ctx, input); + + ret = blkg_conf_open_bdev(&ctx); + if (ret) + goto err; - q = bdev_get_queue(bdev); + body = ctx.body; + q = bdev_get_queue(ctx.bdev); if (!queue_is_mq(q)) { ret = -EOPNOTSUPP; goto err; @@ -3396,7 +3406,7 @@ static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input, ioc = q_to_ioc(q); if (!ioc) { - ret = blk_iocost_init(bdev->bd_disk); + ret = blk_iocost_init(ctx.bdev->bd_disk); if (ret) goto err; ioc = q_to_ioc(q); @@ -3409,7 +3419,7 @@ static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input, memcpy(u, ioc->params.i_lcoefs, sizeof(u)); user = ioc->user_cost_model; - while ((p = strsep(&input, " \t\n"))) { + while ((p = strsep(&body, " \t\n"))) { substring_t args[MAX_OPT_ARGS]; char buf[32]; int tok; @@ -3456,7 +3466,7 @@ static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input, blk_mq_unquiesce_queue(q); blk_mq_unfreeze_queue(q); - blkdev_put_no_open(bdev); + blkg_conf_exit(&ctx); return nbytes; einval: @@ -3467,7 +3477,7 @@ static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input, ret = -EINVAL; err: - blkdev_put_no_open(bdev); + blkg_conf_exit(&ctx); return ret; } diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c index 0dc910568b31..6707164c37f1 100644 --- a/block/blk-iolatency.c +++ b/block/blk-iolatency.c @@ -836,9 +836,11 @@ static ssize_t iolatency_set_limit(struct kernfs_open_file *of, char *buf, u64 oldval; int ret; - ret = blkg_conf_prep(blkcg, &blkcg_policy_iolatency, buf, &ctx); + blkg_conf_init(&ctx, buf); + + ret = blkg_conf_prep(blkcg, &blkcg_policy_iolatency, &ctx); if (ret) - return ret; + goto out; iolat = blkg_to_lat(ctx.blkg); p = ctx.body; @@ -874,7 +876,7 @@ static ssize_t iolatency_set_limit(struct kernfs_open_file *of, char *buf, iolatency_clear_scaling(blkg); ret = 0; out: - blkg_conf_finish(&ctx); + blkg_conf_exit(&ctx); return ret ?: nbytes; } diff --git a/block/blk-throttle.c b/block/blk-throttle.c index 47e9d8be68f3..9bac95343ba0 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -1368,9 +1368,11 @@ static ssize_t tg_set_conf(struct kernfs_open_file *of, int ret; u64 v; - ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx); + blkg_conf_init(&ctx, buf); + + ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, &ctx); if (ret) - return ret; + goto out_finish; ret = -EINVAL; if (sscanf(ctx.body, "%llu", &v) != 1) @@ -1389,7 +1391,7 @@ static ssize_t tg_set_conf(struct kernfs_open_file *of, tg_conf_updated(tg, false); ret = 0; out_finish: - blkg_conf_finish(&ctx); + blkg_conf_exit(&ctx); return ret ?: nbytes; } @@ -1561,9 +1563,11 @@ static ssize_t tg_set_limit(struct kernfs_open_file *of, int ret; int index = of_cft(of)->private; - ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx); + blkg_conf_init(&ctx, buf); + + ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, &ctx); if (ret) - return ret; + goto out_finish; tg = blkg_to_tg(ctx.blkg); tg_update_carryover(tg); @@ -1662,7 +1666,7 @@ static ssize_t tg_set_limit(struct kernfs_open_file *of, tg->td->limit_valid[LIMIT_LOW]); ret = 0; out_finish: - blkg_conf_finish(&ctx); + blkg_conf_exit(&ctx); return ret ?: nbytes; }