From patchwork Thu Oct 31 07:46:17 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: mapicccy X-Patchwork-Id: 13857661 Received: from out30-101.freemail.mail.aliyun.com (out30-101.freemail.mail.aliyun.com [115.124.30.101]) (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 0D3B01494CE; Thu, 31 Oct 2024 07:46:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.101 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730360791; cv=none; b=ZFGanXeAVlyWyOeTeNSw1YhPkeXTKIxeajrcfN2PVHEfGarStghCShxHlNQyXhAphCP4o6SB22YbT7YO4mO+gm8eS5EVI4qPzJpvVQrVVmToJd0eInefE9pCNg9px784AF/OWeP/JkGEEp9RiI5jyazww4v/3i4yH2SZeZkQHkc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730360791; c=relaxed/simple; bh=JKc11Y/ePIV67BpUqe03La6lQoNdPNKgkDTdLM6TL6Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=JMbUUorjMaYCH6kDL5yUSnb8NBbRehXiL6WS6x5ruLV+C+uQdoxsnpisRSL01e27t6bAgZVIA2zdbIq6N/Gs0Te02JKW5kCM8P5tZfuO5vFVqip/UCfyZP5E737i3GYhIoDYwLG46jdNoK+XUxZYSvvqootV7laTvdhV845TcZU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=EYMqtLWX; arc=none smtp.client-ip=115.124.30.101 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="EYMqtLWX" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1730360782; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=WwNO7n6jnbJ4T0oonR+GBHNN3lnAN99Ng6tUZqHMNRg=; b=EYMqtLWXV9XPACw+3sScXDVgSOG/4Q5WaYViTs3L7aUnVU/4iWJACYLm0IbGM9610t5h1W49w17lPj9d60QncA6L73yfXtg92GDQgXj/LQljsIPQwI1dyrKc50fAkhUTbdsYRp9qa0V6WCHwFBRzx7oR4yBY8Y+WqOERHAYhE5g= Received: from localhost(mailfrom:guanjun@linux.alibaba.com fp:SMTPD_---0WIHewyR_1730360780 cluster:ay36) by smtp.aliyun-inc.com; Thu, 31 Oct 2024 15:46:20 +0800 From: 'Guanjun' To: corbet@lwn.net, axboe@kernel.dk, mst@redhat.com, jasowang@redhat.com, xuanzhuo@linux.alibaba.com, eperezma@redhat.com, vgoyal@redhat.com, stefanha@redhat.com, miklos@szeredi.hu, tglx@linutronix.de, peterz@infradead.org, akpm@linux-foundation.org, paulmck@kernel.org, thuth@redhat.com, rostedt@goodmis.org, bp@alien8.de, xiongwei.song@windriver.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, virtualization@lists.linux.dev, linux-fsdevel@vger.kernel.org Cc: guanjun@linux.alibaba.com Subject: [PATCH RFC v1 1/2] genirq/affinity: add support for limiting managed interrupts Date: Thu, 31 Oct 2024 15:46:17 +0800 Message-ID: <20241031074618.3585491-2-guanjun@linux.alibaba.com> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20241031074618.3585491-1-guanjun@linux.alibaba.com> References: <20241031074618.3585491-1-guanjun@linux.alibaba.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Guanjun Commit c410abbbacb9 (genirq/affinity: Add is_managed to struct irq_affinity_desc) introduced is_managed bit to struct irq_affinity_desc. Due to queue interrupts treated as managed interrupts, in scenarios where a large number of devices are present (using massive msix queue interrupts), an excessive number of IRQ matrix bits (about num_online_cpus() * nvecs) are reserved during interrupt allocation. This sequently leads to the situation where interrupts for some devices cannot be properly allocated. Support for limiting the number of managed interrupts on every node per allocation. Signed-off-by: Guanjun --- .../admin-guide/kernel-parameters.txt | 9 +++ block/blk-mq-cpumap.c | 2 +- drivers/virtio/virtio_vdpa.c | 2 +- fs/fuse/virtio_fs.c | 2 +- include/linux/group_cpus.h | 2 +- kernel/irq/affinity.c | 11 ++-- lib/group_cpus.c | 55 ++++++++++++++++++- 7 files changed, 73 insertions(+), 10 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 9b61097a6448..ac80f35d04c9 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3238,6 +3238,15 @@ different yeeloong laptops. Example: machtype=lemote-yeeloong-2f-7inch + managed_irqs_per_node= + [KNL,SMP] Support for limiting the number of managed + interrupts on every node to prevent the case that + interrupts cannot be properly allocated where a large + number of devices are present. The default number is 0, + that means no limit to the number of managed irqs. + Format: integer between 0 and num_possible_cpus() / num_possible_nodes() + Default: 0 + maxcpus= [SMP,EARLY] Maximum number of processors that an SMP kernel will bring up during bootup. maxcpus=n : n >= 0 limits the kernel to bring up 'n' processors. Surely after diff --git a/block/blk-mq-cpumap.c b/block/blk-mq-cpumap.c index 9638b25fd521..481c81318e00 100644 --- a/block/blk-mq-cpumap.c +++ b/block/blk-mq-cpumap.c @@ -20,7 +20,7 @@ void blk_mq_map_queues(struct blk_mq_queue_map *qmap) const struct cpumask *masks; unsigned int queue, cpu; - masks = group_cpus_evenly(qmap->nr_queues); + masks = group_cpus_evenly(qmap->nr_queues, true); if (!masks) { for_each_possible_cpu(cpu) qmap->mq_map[cpu] = qmap->queue_offset; diff --git a/drivers/virtio/virtio_vdpa.c b/drivers/virtio/virtio_vdpa.c index 7364bd53e38d..cd303ac64046 100644 --- a/drivers/virtio/virtio_vdpa.c +++ b/drivers/virtio/virtio_vdpa.c @@ -330,7 +330,7 @@ create_affinity_masks(unsigned int nvecs, struct irq_affinity *affd) for (i = 0, usedvecs = 0; i < affd->nr_sets; i++) { unsigned int this_vecs = affd->set_size[i]; int j; - struct cpumask *result = group_cpus_evenly(this_vecs); + struct cpumask *result = group_cpus_evenly(this_vecs, true); if (!result) { kfree(masks); diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c index f68527891929..41b3bcc03f9c 100644 --- a/fs/fuse/virtio_fs.c +++ b/fs/fuse/virtio_fs.c @@ -881,7 +881,7 @@ static void virtio_fs_map_queues(struct virtio_device *vdev, struct virtio_fs *f return; fallback: /* Attempt to map evenly in groups over the CPUs */ - masks = group_cpus_evenly(fs->num_request_queues); + masks = group_cpus_evenly(fs->num_request_queues, true); /* If even this fails we default to all CPUs use queue zero */ if (!masks) { for_each_possible_cpu(cpu) diff --git a/include/linux/group_cpus.h b/include/linux/group_cpus.h index e42807ec61f6..10a12b9a7ed4 100644 --- a/include/linux/group_cpus.h +++ b/include/linux/group_cpus.h @@ -9,6 +9,6 @@ #include #include -struct cpumask *group_cpus_evenly(unsigned int numgrps); +struct cpumask *group_cpus_evenly(unsigned int numgrps, bool is_managed); #endif diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c index 44a4eba80315..775ab8537ddc 100644 --- a/kernel/irq/affinity.c +++ b/kernel/irq/affinity.c @@ -64,6 +64,10 @@ irq_create_affinity_masks(unsigned int nvecs, struct irq_affinity *affd) for (curvec = 0; curvec < affd->pre_vectors; curvec++) cpumask_copy(&masks[curvec].mask, irq_default_affinity); + /* Mark the managed interrupts */ + for (i = curvec; i < nvecs - affd->post_vectors; i++) + masks[i].is_managed = 1; + /* * Spread on present CPUs starting from affd->pre_vectors. If we * have multiple sets, build each sets affinity mask separately. @@ -71,7 +75,8 @@ irq_create_affinity_masks(unsigned int nvecs, struct irq_affinity *affd) for (i = 0, usedvecs = 0; i < affd->nr_sets; i++) { unsigned int this_vecs = affd->set_size[i]; int j; - struct cpumask *result = group_cpus_evenly(this_vecs); + struct cpumask *result = group_cpus_evenly(this_vecs, + masks[curvec].is_managed); if (!result) { kfree(masks); @@ -94,10 +99,6 @@ irq_create_affinity_masks(unsigned int nvecs, struct irq_affinity *affd) for (; curvec < nvecs; curvec++) cpumask_copy(&masks[curvec].mask, irq_default_affinity); - /* Mark the managed interrupts */ - for (i = affd->pre_vectors; i < nvecs - affd->post_vectors; i++) - masks[i].is_managed = 1; - return masks; } diff --git a/lib/group_cpus.c b/lib/group_cpus.c index ee272c4cefcc..769a139491bc 100644 --- a/lib/group_cpus.c +++ b/lib/group_cpus.c @@ -11,6 +11,30 @@ #ifdef CONFIG_SMP +static unsigned int __read_mostly managed_irqs_per_node; +static struct cpumask managed_irqs_cpumsk[MAX_NUMNODES] __cacheline_aligned_in_smp = { + [0 ... MAX_NUMNODES-1] = {CPU_BITS_ALL} +}; + +static int __init irq_managed_setup(char *str) +{ + int ret; + + ret = kstrtouint(str, 10, &managed_irqs_per_node); + if (ret < 0) { + pr_warn("managed_irqs_per_node= cannot parse, ignored\n"); + return 0; + } + + if (managed_irqs_per_node * num_possible_nodes() > num_possible_cpus()) { + managed_irqs_per_node = num_possible_cpus() / num_possible_nodes(); + pr_warn("managed_irqs_per_node= cannot be larger than %u\n", + managed_irqs_per_node); + } + return 1; +} +__setup("managed_irqs_per_node=", irq_managed_setup); + static void grp_spread_init_one(struct cpumask *irqmsk, struct cpumask *nmsk, unsigned int cpus_per_grp) { @@ -246,6 +270,30 @@ static void alloc_nodes_groups(unsigned int numgrps, } } +static void __group_prepare_affinity(struct cpumask *premask, + cpumask_var_t *node_to_cpumask) +{ + nodemask_t nodemsk = NODE_MASK_NONE; + unsigned int ncpus, n; + + get_nodes_in_cpumask(node_to_cpumask, premask, &nodemsk); + + for_each_node_mask(n, nodemsk) { + cpumask_and(&managed_irqs_cpumsk[n], &managed_irqs_cpumsk[n], premask); + cpumask_and(&managed_irqs_cpumsk[n], &managed_irqs_cpumsk[n], node_to_cpumask[n]); + + ncpus = cpumask_weight(&managed_irqs_cpumsk[n]); + if (ncpus < managed_irqs_per_node) { + /* Reset node n to current node cpumask */ + cpumask_copy(&managed_irqs_cpumsk[n], node_to_cpumask[n]); + continue; + } + + grp_spread_init_one(premask, &managed_irqs_cpumsk[n], managed_irqs_per_node); + } +} + + static int __group_cpus_evenly(unsigned int startgrp, unsigned int numgrps, cpumask_var_t *node_to_cpumask, const struct cpumask *cpu_mask, @@ -332,6 +380,7 @@ static int __group_cpus_evenly(unsigned int startgrp, unsigned int numgrps, /** * group_cpus_evenly - Group all CPUs evenly per NUMA/CPU locality * @numgrps: number of groups + * @is_managed: if these groups managed by kernel * * Return: cpumask array if successful, NULL otherwise. And each element * includes CPUs assigned to this group @@ -344,7 +393,7 @@ static int __group_cpus_evenly(unsigned int startgrp, unsigned int numgrps, * We guarantee in the resulted grouping that all CPUs are covered, and * no same CPU is assigned to multiple groups */ -struct cpumask *group_cpus_evenly(unsigned int numgrps) +struct cpumask *group_cpus_evenly(unsigned int numgrps, bool is_managed) { unsigned int curgrp = 0, nr_present = 0, nr_others = 0; cpumask_var_t *node_to_cpumask; @@ -382,6 +431,10 @@ struct cpumask *group_cpus_evenly(unsigned int numgrps) */ cpumask_copy(npresmsk, data_race(cpu_present_mask)); + /* Limit the count of managed interrupts on every node */ + if (is_managed && managed_irqs_per_node) + __group_prepare_affinity(npresmsk, node_to_cpumask); + /* grouping present CPUs first */ ret = __group_cpus_evenly(curgrp, numgrps, node_to_cpumask, npresmsk, nmsk, masks); From patchwork Thu Oct 31 07:46:18 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: mapicccy X-Patchwork-Id: 13857663 Received: from out30-112.freemail.mail.aliyun.com (out30-112.freemail.mail.aliyun.com [115.124.30.112]) (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 266F814D6E1; Thu, 31 Oct 2024 07:46:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.112 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730360794; cv=none; b=iBRo/Z5C4iWWx1wBsUObJHJj4A7OADRic2RI3JF55v8Vcnelo/fNn766jqADBYKcOESUL6DrBrAetRti416IXd5cozz4/bPRpUIvDCv8vGqzlubOG0yq6PAqs7Fa+WnfjHNWZDg1KT57D2ggMLeGkyQnmuYQrOmB8n0x7l/FJnY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730360794; c=relaxed/simple; bh=33phXrmK8nmqMHKYFyD3A7lDPDZpmvZXuiUrbzomsjs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=VYY62HABN7zDxMfKgvqrOVbAssxSsxChrux8PqPdZYJq2+4llW3JA0OTTv3X2jUshcJdP/skSSXEyQeGscd3MlGbKl97+gCKpcNdbCzpoK0gsa/ijDW1W9Aoi1Ue0BDfOy6fjGvygN7BKNjT3qUU1jIPIqTVuiHxyP2IxHl6hVA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=p/9aLeKN; arc=none smtp.client-ip=115.124.30.112 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="p/9aLeKN" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1730360783; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=Yi5S3FvCJe7m8m05OvpuB+dWdFv2eUKXm00/bjW1XKs=; b=p/9aLeKNdV7LAhkpLU0Yi0xqx/6MIYfXioKHCjax2wPa3KwsB5tWyUcjtW9Xu7oHJtba19gKZmq4Fnhrrr2vsBWMbXK0Fc9sKt1PCvg/NWP+jgQYkrQb06dkPb/btpTeRmSt2OHeFVUv4c2Y84ZmSwlpVnLfXn5Fe0/S1+cw53Q= Received: from localhost(mailfrom:guanjun@linux.alibaba.com fp:SMTPD_---0WIHewz0_1730360781 cluster:ay36) by smtp.aliyun-inc.com; Thu, 31 Oct 2024 15:46:22 +0800 From: 'Guanjun' To: corbet@lwn.net, axboe@kernel.dk, mst@redhat.com, jasowang@redhat.com, xuanzhuo@linux.alibaba.com, eperezma@redhat.com, vgoyal@redhat.com, stefanha@redhat.com, miklos@szeredi.hu, tglx@linutronix.de, peterz@infradead.org, akpm@linux-foundation.org, paulmck@kernel.org, thuth@redhat.com, rostedt@goodmis.org, bp@alien8.de, xiongwei.song@windriver.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, virtualization@lists.linux.dev, linux-fsdevel@vger.kernel.org Cc: guanjun@linux.alibaba.com Subject: [PATCH RFC v1 2/2] genirq/cpuhotplug: Handle managed IRQs when the last CPU hotplug out in the affinity Date: Thu, 31 Oct 2024 15:46:18 +0800 Message-ID: <20241031074618.3585491-3-guanjun@linux.alibaba.com> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20241031074618.3585491-1-guanjun@linux.alibaba.com> References: <20241031074618.3585491-1-guanjun@linux.alibaba.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Guanjun Once we limit the number of managed interrupts, if the last online CPU in the affinity goes offline, it will result in the interrupt becoming unavailable util one of the assigned CPUs comes online again. So prevent the last online CPU in the affinity from going offline, and return -EBUSY in this situation. Signed-off-by: Guanjun --- .../admin-guide/kernel-parameters.txt | 3 ++ include/linux/irq.h | 2 + kernel/cpu.c | 2 +- kernel/irq/cpuhotplug.c | 51 +++++++++++++++++++ 4 files changed, 57 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index ac80f35d04c9..173598cbf4a6 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3244,6 +3244,9 @@ interrupts cannot be properly allocated where a large number of devices are present. The default number is 0, that means no limit to the number of managed irqs. + Once we limit the number of managed interrupts, the last + online CPU in the affinity goes offline will fail with + the error code -EBUSY. Format: integer between 0 and num_possible_cpus() / num_possible_nodes() Default: 0 diff --git a/include/linux/irq.h b/include/linux/irq.h index fa711f80957b..68ce05a74079 100644 --- a/include/linux/irq.h +++ b/include/linux/irq.h @@ -615,8 +615,10 @@ extern int irq_set_vcpu_affinity(unsigned int irq, void *vcpu_info); #if defined(CONFIG_SMP) && defined(CONFIG_GENERIC_IRQ_MIGRATION) extern void irq_migrate_all_off_this_cpu(void); extern int irq_affinity_online_cpu(unsigned int cpu); +extern int irq_affinity_offline_cpu(unsigned int cpu); #else # define irq_affinity_online_cpu NULL +# define irq_affinity_offline_cpu NULL #endif #if defined(CONFIG_SMP) && defined(CONFIG_GENERIC_PENDING_IRQ) diff --git a/kernel/cpu.c b/kernel/cpu.c index c4aaf73dec9e..672d920970b2 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -2219,7 +2219,7 @@ static struct cpuhp_step cpuhp_hp_states[] = { [CPUHP_AP_IRQ_AFFINITY_ONLINE] = { .name = "irq/affinity:online", .startup.single = irq_affinity_online_cpu, - .teardown.single = NULL, + .teardown.single = irq_affinity_offline_cpu, }, [CPUHP_AP_PERF_ONLINE] = { .name = "perf:online", diff --git a/kernel/irq/cpuhotplug.c b/kernel/irq/cpuhotplug.c index 15a7654eff68..e6f068198e4a 100644 --- a/kernel/irq/cpuhotplug.c +++ b/kernel/irq/cpuhotplug.c @@ -232,6 +232,31 @@ static void irq_restore_affinity_of_irq(struct irq_desc *desc, unsigned int cpu) irq_set_affinity_locked(data, affinity, false); } +static int irq_check_affinity_of_irq(struct irq_desc *desc, unsigned int cpu) +{ + struct irq_data *data = irq_desc_get_irq_data(desc); + const struct cpumask *affinity = irq_data_get_affinity_mask(data); + unsigned int cur; + + if (!irqd_affinity_is_managed(data) || !desc->action || + !irq_data_get_irq_chip(data) || !cpumask_test_cpu(cpu, affinity)) + return 0; + + for_each_cpu(cur, affinity) + if (cur != cpu && cpumask_test_cpu(cur, cpu_online_mask)) + return 0; + + /* + * If the onging offline CPU is the last one in the affinity, + * the managed interrupts will be unavailable until one of + * the assigned CPUs comes online. To prevent this unavailability, + * return -EBUSY directly in this case. + */ + pr_warn("Affinity %*pbl of managed IRQ%u contains only one CPU%u that online\n", + cpumask_pr_args(affinity), data->irq, cpu); + return -EBUSY; +} + /** * irq_affinity_online_cpu - Restore affinity for managed interrupts * @cpu: Upcoming CPU for which interrupts should be restored @@ -252,3 +277,29 @@ int irq_affinity_online_cpu(unsigned int cpu) return 0; } + +/** + * irq_affinity_offline_cpu - Check affinity for managed interrupts + * to prevent the unavailability caused by taking the last CPU in the + * affinity offline. + * @cpu: Upcoming CPU for which interrupts should be checked + */ +int irq_affinity_offline_cpu(unsigned int cpu) +{ + struct irq_desc *desc; + unsigned int irq; + int ret = 0; + + irq_lock_sparse(); + for_each_active_irq(irq) { + desc = irq_to_desc(irq); + raw_spin_lock_irq(&desc->lock); + ret = irq_check_affinity_of_irq(desc, cpu); + raw_spin_unlock_irq(&desc->lock); + if (ret < 0) + break; + } + irq_unlock_sparse(); + + return ret; +}