block: Introduce the ioprio rq-qos policy
Introduce an rq-qos policy that assigns an I/O priority to requests based on blk-cgroup configuration settings. This policy has the following advantages over the ioprio_set() system call: - This policy is cgroup based so it has all the advantages of cgroups. - While ioprio_set() does not affect page cache writeback I/O, this rq-qos controller affects page cache writeback I/O for filesystems that support assiociating a cgroup with writeback I/O. See also Documentation/admin-guide/cgroup-v2.rst. Cc: Damien Le Moal <damien.lemoal@wdc.com> Cc: Hannes Reinecke <hare@suse.de> Cc: Christoph Hellwig <hch@lst.de> Cc: Ming Lei <ming.lei@redhat.com> Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com> Cc: Himanshu Madhani <himanshu.madhani@oracle.com> Signed-off-by: Bart Van Assche <bvanassche@acm.org> Link: https://lore.kernel.org/r/20210618004456.7280-5-bvanassche@acm.org Signed-off-by: Jens Axboe <axboe@kernel.dk>
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@ -56,6 +56,7 @@ v1 is available under :ref:`Documentation/admin-guide/cgroup-v1/index.rst <cgrou
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5-3-3. IO Latency
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5-3-3-1. How IO Latency Throttling Works
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5-3-3-2. IO Latency Interface Files
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5-3-4. IO Priority
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5-4. PID
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5-4-1. PID Interface Files
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5-5. Cpuset
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@ -1866,6 +1867,60 @@ IO Latency Interface Files
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duration of time between evaluation events. Windows only elapse
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with IO activity. Idle periods extend the most recent window.
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IO Priority
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~~~~~~~~~~~
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A single attribute controls the behavior of the I/O priority cgroup policy,
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namely the blkio.prio.class attribute. The following values are accepted for
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that attribute:
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no-change
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Do not modify the I/O priority class.
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none-to-rt
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For requests that do not have an I/O priority class (NONE),
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change the I/O priority class into RT. Do not modify
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the I/O priority class of other requests.
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restrict-to-be
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For requests that do not have an I/O priority class or that have I/O
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priority class RT, change it into BE. Do not modify the I/O priority
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class of requests that have priority class IDLE.
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idle
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Change the I/O priority class of all requests into IDLE, the lowest
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I/O priority class.
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The following numerical values are associated with the I/O priority policies:
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+-------------+---+
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| no-change | 0 |
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+-------------+---+
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| none-to-rt | 1 |
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+-------------+---+
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| rt-to-be | 2 |
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+-------------+---+
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| all-to-idle | 3 |
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+-------------+---+
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The numerical value that corresponds to each I/O priority class is as follows:
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+-------------------------------+---+
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| IOPRIO_CLASS_NONE | 0 |
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+-------------------------------+---+
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| IOPRIO_CLASS_RT (real-time) | 1 |
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+-------------------------------+---+
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| IOPRIO_CLASS_BE (best effort) | 2 |
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+-------------------------------+---+
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| IOPRIO_CLASS_IDLE | 3 |
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+-------------------------------+---+
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The algorithm to set the I/O priority class for a request is as follows:
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- Translate the I/O priority class policy into a number.
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- Change the request I/O priority class into the maximum of the I/O priority
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class policy number and the numerical I/O priority class.
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PID
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---
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@ -162,6 +162,15 @@ config BLK_CGROUP_IOCOST
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distributes IO capacity between different groups based on
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their share of the overall weight distribution.
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config BLK_CGROUP_IOPRIO
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bool "Cgroup I/O controller for assigning an I/O priority class"
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depends on BLK_CGROUP
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help
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Enable the .prio interface for assigning an I/O priority class to
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requests. The I/O priority class affects the order in which an I/O
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scheduler and block devices process requests. Only some I/O schedulers
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and some block devices support I/O priorities.
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config BLK_DEBUG_FS
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bool "Block layer debugging information in debugfs"
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default y
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@ -17,6 +17,7 @@ obj-$(CONFIG_BLK_DEV_BSGLIB) += bsg-lib.o
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obj-$(CONFIG_BLK_CGROUP) += blk-cgroup.o
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obj-$(CONFIG_BLK_CGROUP_RWSTAT) += blk-cgroup-rwstat.o
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obj-$(CONFIG_BLK_DEV_THROTTLING) += blk-throttle.o
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obj-$(CONFIG_BLK_CGROUP_IOPRIO) += blk-ioprio.o
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obj-$(CONFIG_BLK_CGROUP_IOLATENCY) += blk-iolatency.o
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obj-$(CONFIG_BLK_CGROUP_IOCOST) += blk-iocost.o
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obj-$(CONFIG_MQ_IOSCHED_DEADLINE) += mq-deadline.o
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@ -31,6 +31,7 @@
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#include <linux/tracehook.h>
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#include <linux/psi.h>
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#include "blk.h"
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#include "blk-ioprio.h"
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/*
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* blkcg_pol_mutex protects blkcg_policy[] and policy [de]activation.
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@ -1187,6 +1188,10 @@ int blkcg_init_queue(struct request_queue *q)
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if (ret)
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goto err_destroy_all;
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ret = blk_ioprio_init(q);
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if (ret)
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goto err_destroy_all;
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ret = blk_throtl_init(q);
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if (ret)
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goto err_destroy_all;
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@ -0,0 +1,262 @@
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// SPDX-License-Identifier: GPL-2.0
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/*
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* Block rq-qos policy for assigning an I/O priority class to requests.
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*
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* Using an rq-qos policy for assigning I/O priority class has two advantages
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* over using the ioprio_set() system call:
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*
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* - This policy is cgroup based so it has all the advantages of cgroups.
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* - While ioprio_set() does not affect page cache writeback I/O, this rq-qos
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* controller affects page cache writeback I/O for filesystems that support
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* assiociating a cgroup with writeback I/O. See also
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* Documentation/admin-guide/cgroup-v2.rst.
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*/
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#include <linux/blk-cgroup.h>
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#include <linux/blk-mq.h>
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#include <linux/blk_types.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include "blk-ioprio.h"
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#include "blk-rq-qos.h"
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/**
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* enum prio_policy - I/O priority class policy.
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* @POLICY_NO_CHANGE: (default) do not modify the I/O priority class.
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* @POLICY_NONE_TO_RT: modify IOPRIO_CLASS_NONE into IOPRIO_CLASS_RT.
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* @POLICY_RESTRICT_TO_BE: modify IOPRIO_CLASS_NONE and IOPRIO_CLASS_RT into
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* IOPRIO_CLASS_BE.
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* @POLICY_ALL_TO_IDLE: change the I/O priority class into IOPRIO_CLASS_IDLE.
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*
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* See also <linux/ioprio.h>.
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*/
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enum prio_policy {
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POLICY_NO_CHANGE = 0,
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POLICY_NONE_TO_RT = 1,
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POLICY_RESTRICT_TO_BE = 2,
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POLICY_ALL_TO_IDLE = 3,
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};
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static const char *policy_name[] = {
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[POLICY_NO_CHANGE] = "no-change",
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[POLICY_NONE_TO_RT] = "none-to-rt",
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[POLICY_RESTRICT_TO_BE] = "restrict-to-be",
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[POLICY_ALL_TO_IDLE] = "idle",
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};
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static struct blkcg_policy ioprio_policy;
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/**
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* struct ioprio_blkg - Per (cgroup, request queue) data.
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* @pd: blkg_policy_data structure.
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*/
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struct ioprio_blkg {
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struct blkg_policy_data pd;
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};
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/**
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* struct ioprio_blkcg - Per cgroup data.
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* @cpd: blkcg_policy_data structure.
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* @prio_policy: One of the IOPRIO_CLASS_* values. See also <linux/ioprio.h>.
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*/
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struct ioprio_blkcg {
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struct blkcg_policy_data cpd;
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enum prio_policy prio_policy;
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};
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static inline struct ioprio_blkg *pd_to_ioprio(struct blkg_policy_data *pd)
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{
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return pd ? container_of(pd, struct ioprio_blkg, pd) : NULL;
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}
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static struct ioprio_blkcg *blkcg_to_ioprio_blkcg(struct blkcg *blkcg)
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{
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return container_of(blkcg_to_cpd(blkcg, &ioprio_policy),
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struct ioprio_blkcg, cpd);
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}
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static struct ioprio_blkcg *
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ioprio_blkcg_from_css(struct cgroup_subsys_state *css)
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{
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return blkcg_to_ioprio_blkcg(css_to_blkcg(css));
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}
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static struct ioprio_blkcg *ioprio_blkcg_from_bio(struct bio *bio)
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{
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struct blkg_policy_data *pd = blkg_to_pd(bio->bi_blkg, &ioprio_policy);
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if (!pd)
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return NULL;
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return blkcg_to_ioprio_blkcg(pd->blkg->blkcg);
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}
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static int ioprio_show_prio_policy(struct seq_file *sf, void *v)
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{
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struct ioprio_blkcg *blkcg = ioprio_blkcg_from_css(seq_css(sf));
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seq_printf(sf, "%s\n", policy_name[blkcg->prio_policy]);
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return 0;
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}
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static ssize_t ioprio_set_prio_policy(struct kernfs_open_file *of, char *buf,
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size_t nbytes, loff_t off)
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{
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struct ioprio_blkcg *blkcg = ioprio_blkcg_from_css(of_css(of));
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int ret;
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if (off != 0)
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return -EIO;
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/* kernfs_fop_write_iter() terminates 'buf' with '\0'. */
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ret = sysfs_match_string(policy_name, buf);
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if (ret < 0)
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return ret;
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blkcg->prio_policy = ret;
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return nbytes;
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}
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static struct blkg_policy_data *
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ioprio_alloc_pd(gfp_t gfp, struct request_queue *q, struct blkcg *blkcg)
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{
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struct ioprio_blkg *ioprio_blkg;
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ioprio_blkg = kzalloc(sizeof(*ioprio_blkg), gfp);
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if (!ioprio_blkg)
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return NULL;
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return &ioprio_blkg->pd;
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}
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static void ioprio_free_pd(struct blkg_policy_data *pd)
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{
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struct ioprio_blkg *ioprio_blkg = pd_to_ioprio(pd);
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kfree(ioprio_blkg);
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}
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static struct blkcg_policy_data *ioprio_alloc_cpd(gfp_t gfp)
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{
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struct ioprio_blkcg *blkcg;
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blkcg = kzalloc(sizeof(*blkcg), gfp);
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if (!blkcg)
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return NULL;
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blkcg->prio_policy = POLICY_NO_CHANGE;
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return &blkcg->cpd;
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}
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static void ioprio_free_cpd(struct blkcg_policy_data *cpd)
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{
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struct ioprio_blkcg *blkcg = container_of(cpd, typeof(*blkcg), cpd);
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kfree(blkcg);
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}
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#define IOPRIO_ATTRS \
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{ \
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.name = "prio.class", \
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.seq_show = ioprio_show_prio_policy, \
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.write = ioprio_set_prio_policy, \
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}, \
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{ } /* sentinel */
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/* cgroup v2 attributes */
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static struct cftype ioprio_files[] = {
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IOPRIO_ATTRS
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};
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/* cgroup v1 attributes */
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static struct cftype ioprio_legacy_files[] = {
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IOPRIO_ATTRS
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};
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||||
static struct blkcg_policy ioprio_policy = {
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.dfl_cftypes = ioprio_files,
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.legacy_cftypes = ioprio_legacy_files,
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||||
.cpd_alloc_fn = ioprio_alloc_cpd,
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||||
.cpd_free_fn = ioprio_free_cpd,
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||||
|
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.pd_alloc_fn = ioprio_alloc_pd,
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.pd_free_fn = ioprio_free_pd,
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};
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||||
|
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struct blk_ioprio {
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struct rq_qos rqos;
|
||||
};
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||||
|
||||
static void blkcg_ioprio_track(struct rq_qos *rqos, struct request *rq,
|
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struct bio *bio)
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{
|
||||
struct ioprio_blkcg *blkcg = ioprio_blkcg_from_bio(bio);
|
||||
|
||||
/*
|
||||
* Except for IOPRIO_CLASS_NONE, higher I/O priority numbers
|
||||
* correspond to a lower priority. Hence, the max_t() below selects
|
||||
* the lower priority of bi_ioprio and the cgroup I/O priority class.
|
||||
* If the cgroup policy has been set to POLICY_NO_CHANGE == 0, the
|
||||
* bio I/O priority is not modified. If the bio I/O priority equals
|
||||
* IOPRIO_CLASS_NONE, the cgroup I/O priority is assigned to the bio.
|
||||
*/
|
||||
bio->bi_ioprio = max_t(u16, bio->bi_ioprio,
|
||||
IOPRIO_PRIO_VALUE(blkcg->prio_policy, 0));
|
||||
}
|
||||
|
||||
static void blkcg_ioprio_exit(struct rq_qos *rqos)
|
||||
{
|
||||
struct blk_ioprio *blkioprio_blkg =
|
||||
container_of(rqos, typeof(*blkioprio_blkg), rqos);
|
||||
|
||||
blkcg_deactivate_policy(rqos->q, &ioprio_policy);
|
||||
kfree(blkioprio_blkg);
|
||||
}
|
||||
|
||||
static struct rq_qos_ops blkcg_ioprio_ops = {
|
||||
.track = blkcg_ioprio_track,
|
||||
.exit = blkcg_ioprio_exit,
|
||||
};
|
||||
|
||||
int blk_ioprio_init(struct request_queue *q)
|
||||
{
|
||||
struct blk_ioprio *blkioprio_blkg;
|
||||
struct rq_qos *rqos;
|
||||
int ret;
|
||||
|
||||
blkioprio_blkg = kzalloc(sizeof(*blkioprio_blkg), GFP_KERNEL);
|
||||
if (!blkioprio_blkg)
|
||||
return -ENOMEM;
|
||||
|
||||
ret = blkcg_activate_policy(q, &ioprio_policy);
|
||||
if (ret) {
|
||||
kfree(blkioprio_blkg);
|
||||
return ret;
|
||||
}
|
||||
|
||||
rqos = &blkioprio_blkg->rqos;
|
||||
rqos->id = RQ_QOS_IOPRIO;
|
||||
rqos->ops = &blkcg_ioprio_ops;
|
||||
rqos->q = q;
|
||||
|
||||
/*
|
||||
* Registering the rq-qos policy after activating the blk-cgroup
|
||||
* policy guarantees that ioprio_blkcg_from_bio(bio) != NULL in the
|
||||
* rq-qos callbacks.
|
||||
*/
|
||||
rq_qos_add(q, rqos);
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
static int __init ioprio_init(void)
|
||||
{
|
||||
return blkcg_policy_register(&ioprio_policy);
|
||||
}
|
||||
|
||||
static void __exit ioprio_exit(void)
|
||||
{
|
||||
blkcg_policy_unregister(&ioprio_policy);
|
||||
}
|
||||
|
||||
module_init(ioprio_init);
|
||||
module_exit(ioprio_exit);
|
|
@ -0,0 +1,19 @@
|
|||
/* SPDX-License-Identifier: GPL-2.0 */
|
||||
|
||||
#ifndef _BLK_IOPRIO_H_
|
||||
#define _BLK_IOPRIO_H_
|
||||
|
||||
#include <linux/kconfig.h>
|
||||
|
||||
struct request_queue;
|
||||
|
||||
#ifdef CONFIG_BLK_CGROUP_IOPRIO
|
||||
int blk_ioprio_init(struct request_queue *q);
|
||||
#else
|
||||
static inline int blk_ioprio_init(struct request_queue *q)
|
||||
{
|
||||
return 0;
|
||||
}
|
||||
#endif
|
||||
|
||||
#endif /* _BLK_IOPRIO_H_ */
|
|
@ -946,6 +946,8 @@ static const char *rq_qos_id_to_name(enum rq_qos_id id)
|
|||
return "latency";
|
||||
case RQ_QOS_COST:
|
||||
return "cost";
|
||||
case RQ_QOS_IOPRIO:
|
||||
return "ioprio";
|
||||
}
|
||||
return "unknown";
|
||||
}
|
||||
|
|
|
@ -17,6 +17,7 @@ enum rq_qos_id {
|
|||
RQ_QOS_WBT,
|
||||
RQ_QOS_LATENCY,
|
||||
RQ_QOS_COST,
|
||||
RQ_QOS_IOPRIO,
|
||||
};
|
||||
|
||||
struct rq_wait {
|
||||
|
|
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