From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2424C218592; Sat, 4 Jul 2026 19:54:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783194896; cv=none; b=Kv3zfdhE2JDZl6GVvsf/0P4f4I2aNbhJvrzTuEUTfRSxrQhw3B/YrOBEMM4yIBrm5pI4/JXA4i3Ejl58ApGLTk/gH1Dcqi11utzu62uFZ92GW2JcS7DG/n3A5Rp5V3nE7n1D67bvU2Xqw43d3Fyl6Bmdma2Kg9MvA/GcP51jers= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783194896; c=relaxed/simple; bh=jfQpY509AcJVVE/1wLE/iWzDxJMv/h0ishaCNz6vuPg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=K8ucTnKGo2sNHPwCEhOMwzSWCfTjc/TBA+Jb3L+Z37o53NFRQlRczuP1Ud5ZJfVg9GXHmsXhhO+81jSJqn8brE+ZX60vPc5ak07WWJCy6jKz5GzLEUi/OAbraTpzjyy7wb7n7InfgFnmJsrFrW9deiqFVfsqktJZQrbqA2QFTkg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fR33eH1s; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="fR33eH1s" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CDA921F000E9; Sat, 4 Jul 2026 19:54:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783194895; bh=UpXvpcnAu5pgU9SHm7QWz6pfcN7DZMwYKXJhMRcb+Cs=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=fR33eH1sdYUEdR1Fed/6lqSA4AAIcfO+4koussb8lEDg+rQy92E+JIm7f8v6DgcAr f8Nmzxu/7v94bNlJW2EP6Zal2Rixoa6Gp43ajkdgnf6CAZ4qKac8XnT80/yOuuCiw8 c1nsIvmRP5HAOlyYcy9ZPKBljWKrrNicdmHUM2l9sUCh0XHKy+cTFZOrt+SxD6kmti i0mV/yxqS0K7EaWktFviJAlQrdNYsw7XAQ3JJqzrIv47siTqrfyEImW56Sxv6jXJIC R9OhuYPvrHSwamW/fUa9hna/OwOdTf4XOUCGEx/nAuAcz0HBxSpj4waj23dHTfIE7y DJtZttvFKeLQQ== From: Yu Kuai To: Jens Axboe , Tejun Heo Cc: Christoph Hellwig , Keith Busch , Sagi Grimberg , Alasdair Kergon , Benjamin Marzinski , Mike Snitzer , Mikulas Patocka , Dongsheng Yang , Zheng Gu , Coly Li , Kent Overstreet , Josef Bacik , Yu Kuai , Nilay Shroff , linux-block@vger.kernel.org, cgroups@vger.kernel.org, linux-nvme@lists.infradead.org, dm-devel@lists.linux.dev, linux-bcache@vger.kernel.org Subject: [RFC PATCH v1 17/17] blk-cgroup: share blkg creation between lookup and config prep Date: Sun, 5 Jul 2026 03:51:24 +0800 Message-ID: <20260704195124.1375075-18-yukuai@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260704195124.1375075-1-yukuai@kernel.org> References: <20260704195124.1375075-1-yukuai@kernel.org> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Yu Kuai blkg_conf_prep() open-codes the same parent walk and blkg creation that blkg_lookup_create() already performs. Make blkg_lookup_create() report whether the target blkg was created or found while still returning the closest existing blkg on failure, then have blkg_conf_prep() use the helper and treat errors as config failures. This keeps the bio association path's closest-blkg fallback and removes the duplicate config path loop. Signed-off-by: Yu Kuai --- block/blk-cgroup.c | 81 +++++++++++++++------------------------------- 1 file changed, 26 insertions(+), 55 deletions(-) diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index ddc9073d7ab9..ae481bcde934 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -448,17 +448,19 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg, struct gendisk *disk, * blkg_lookup_create - lookup blkg, try to create one if not there * @blkcg: blkcg of interest * @disk: gendisk of interest + * @gfp_mask: allocation mask to use + * @blkgp: out parameter for the target blkg, or closest blkg on failure * * Lookup blkg for the @blkcg - @disk pair. If it doesn't exist, try to * create one. blkg creation is performed recursively from blkcg_root such * that all non-root blkg's have access to the parent blkg. This function * must be called with @disk->queue->blkcg_mutex held. * - * Returns the blkg or the closest blkg if blkg_create() fails as it walks - * down from root. + * On success, *@blkgp points to the target blkg and 0 is returned. On + * failure, *@blkgp points to the closest blkg and the errno is returned. */ -static struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg, - struct gendisk *disk) +static int blkg_lookup_create(struct blkcg *blkcg, struct gendisk *disk, + gfp_t gfp_mask, struct blkcg_gq **blkgp) { struct request_queue *q = disk->queue; struct blkcg_gq *blkg; @@ -470,7 +472,8 @@ static struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg, blkg != rcu_dereference(blkcg->blkg_hint)) rcu_assign_pointer(blkcg->blkg_hint, blkg); rcu_read_unlock(); - return blkg; + *blkgp = blkg; + return 0; } rcu_read_unlock(); @@ -497,16 +500,16 @@ static struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg, } rcu_read_unlock(); - blkg = blkg_create(pos, disk, GFP_NOIO); + blkg = blkg_create(pos, disk, gfp_mask); if (IS_ERR(blkg)) { - blkg = ret_blkg; - break; + *blkgp = ret_blkg; + return PTR_ERR(blkg); + } + if (pos == blkcg) { + *blkgp = blkg; + return 0; } - if (pos == blkcg) - break; } - - return blkg; } static void blkg_destroy(struct blkcg_gq *blkg) @@ -839,46 +842,10 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol, goto fail_unlock; } - blkg = blkg_lookup(blkcg, q); - if (blkg) - goto success; - - /* - * Create blkgs walking down from blkcg_root to @blkcg, so that all - * non-root blkgs have access to their parents. - */ - while (true) { - struct blkcg *pos = blkcg; - struct blkcg *parent; - - parent = blkcg_parent(blkcg); - rcu_read_lock(); - while (parent && !blkg_lookup(parent, q)) { - pos = parent; - parent = blkcg_parent(parent); - } - rcu_read_unlock(); - - if (!blkcg_policy_enabled(q, pol)) { - ret = -EOPNOTSUPP; - goto fail_unlock; - } - - rcu_read_lock(); - blkg = blkg_lookup(pos, q); - rcu_read_unlock(); - if (!blkg) { - blkg = blkg_create(pos, disk, GFP_NOIO); - if (IS_ERR(blkg)) { - ret = PTR_ERR(blkg); - goto fail_unlock; - } - } + ret = blkg_lookup_create(blkcg, disk, GFP_NOIO, &blkg); + if (ret) + goto fail_unlock; - if (pos == blkcg) - goto success; - } -success: ctx->blkg = blkg; return 0; @@ -2018,6 +1985,8 @@ static inline struct blkcg_gq *blkg_tryget_closest(struct bio *bio, if (blkg) return blkg; if (nowait) { + int ret; + /* * mutex_trylock() itself does not sleep, but mutexes still * follow task-context locking rules. Keep atomic nowait callers @@ -2026,9 +1995,11 @@ static inline struct blkcg_gq *blkg_tryget_closest(struct bio *bio, if (!preemptible() || !mutex_trylock(&q->blkcg_mutex)) return NULL; - blkg = blkg_lookup_create(blkcg, bio->bi_bdev->bd_disk, - GFP_ATOMIC); - if (blkg) + ret = blkg_lookup_create(blkcg, bio->bi_bdev->bd_disk, + GFP_ATOMIC, &blkg); + if (ret) + blkg = NULL; + else if (blkg) blkg = blkg_lookup_tryget(blkg); mutex_unlock(&q->blkcg_mutex); @@ -2040,7 +2011,7 @@ static inline struct blkcg_gq *blkg_tryget_closest(struct bio *bio, * time, hold lock to create new blkg. */ mutex_lock(&q->blkcg_mutex); - blkg = blkg_lookup_create(blkcg, bio->bi_bdev->bd_disk); + blkg_lookup_create(blkcg, bio->bi_bdev->bd_disk, GFP_NOIO, &blkg); if (blkg) blkg = blkg_lookup_tryget(blkg); mutex_unlock(&q->blkcg_mutex); -- 2.51.0