From faffaab2895914a803e011600164683bf747fee3 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Wed, 12 Apr 2023 14:06:47 -1000 Subject: blkcg: Restructure blkg_conf_prep() and friends 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 Link: https://lore.kernel.org/r/20230413000649.115785-3-tj@kernel.org Signed-off-by: Jens Axboe --- block/blk-iocost.c | 58 ++++++++++++++++++++++++++++++++---------------------- 1 file changed, 34 insertions(+), 24 deletions(-) (limited to 'block/blk-iocost.c') 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 @@ einval: 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 @@ einval: ret = -EINVAL; err: - blkdev_put_no_open(bdev); + blkg_conf_exit(&ctx); return ret; } -- cgit v1.2.3