From 05efd4675b1241f2cc68fd54c92a8a834699f212 Mon Sep 17 00:00:00 2001

From: "plai@redhat.com" <plai@redhat.com>

Date: Thu, 29 Jul 2021 07:42:21 -0400

Subject: [PATCH 14/39] ratelimit: protect with a mutex

RH-Author: Miroslav Rezanina <mrezanin@redhat.com>

RH-MergeRequest: 32: Synchronize with RHEL-AV 8.5 release 27 to RHEL 9

RH-Commit: [6/15] 48586bf5d422cb676a6f2d2cd0abb0822cfc17b2 (mrezanin/centos-src-qemu-kvm)

RH-Bugzilla: 1957194

RH-Acked-by: Stefano Garzarella <sgarzare@redhat.com>

RH-Acked-by: Kevin Wolf <kwolf@redhat.com>

RH-Acked-by: Igor Mammedov <imammedo@redhat.com>

RH-Acked-by: Andrew Jones <drjones@redhat.com>

Right now, rate limiting is protected by the AioContext mutex, which is

taken for example both by the block jobs and by qmp_block_job_set_speed

(via find_block_job).

We would like to remove the dependency of block layer code on the

AioContext mutex, since most drivers and the core I/O code are already

not relying on it.  However, there is no existing lock that can easily

be taken by both ratelimit_set_speed and ratelimit_calculate_delay,

especially because the latter might run in coroutine context (and

therefore under a CoMutex) but the former will not.

Since concurrent calls to ratelimit_calculate_delay are not possible,

one idea could be to use a seqlock to get a snapshot of slice_ns and

slice_quota.  But for now keep it simple, and just add a mutex to the

RateLimit struct; block jobs are generally not performance critical to

the point of optimizing the clock cycles spent in synchronization.

This also requires the introduction of init/destroy functions, so

add them to the two users of ratelimit.h.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

(cherry picked from commit 4951967d84a0acbf47895add9158e2d4c6056ea0)

Signed-off-by: Paul Lai <plai@redhat.com>

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

---

 block/block-copy.c       |  2 ++

 blockjob.c               |  3 +++

 include/qemu/ratelimit.h | 14 ++++++++++++++

 3 files changed, 19 insertions(+)

diff --git a/block/block-copy.c b/block/block-copy.c

index 39ae481c8b..9b4af00614 100644

--- a/block/block-copy.c

+++ b/block/block-copy.c

@@ -230,6 +230,7 @@ void block_copy_state_free(BlockCopyState *s)

         return;

     }

+    ratelimit_destroy(&s->rate_limit);

     bdrv_release_dirty_bitmap(s->copy_bitmap);

     shres_destroy(s->mem);

     g_free(s);

@@ -289,6 +290,7 @@ BlockCopyState *block_copy_state_new(BdrvChild *source, BdrvChild *target,

         s->copy_size = MAX(s->cluster_size, BLOCK_COPY_MAX_BUFFER);

     }

+    ratelimit_init(&s->rate_limit);

     QLIST_INIT(&s->tasks);

     QLIST_INIT(&s->calls);

diff --git a/blockjob.c b/blockjob.c

index 207e8c7fd9..46f15befe8 100644

--- a/blockjob.c

+++ b/blockjob.c

@@ -87,6 +87,7 @@ void block_job_free(Job *job)

     block_job_remove_all_bdrv(bjob);

     blk_unref(bjob->blk);

+    ratelimit_destroy(&bjob->limit);

     error_free(bjob->blocker);

 }

@@ -435,6 +436,8 @@ void *block_job_create(const char *job_id, const BlockJobDriver *driver,

     assert(job->job.driver->free == &block_job_free);

     assert(job->job.driver->user_resume == &block_job_user_resume);

+    ratelimit_init(&job->limit);

+

     job->blk = blk;

     job->finalize_cancelled_notifier.notify = block_job_event_cancelled;

diff --git a/include/qemu/ratelimit.h b/include/qemu/ratelimit.h

index 01da8d63f1..003ea6d5a3 100644

--- a/include/qemu/ratelimit.h

+++ b/include/qemu/ratelimit.h

@@ -14,9 +14,11 @@

 #ifndef QEMU_RATELIMIT_H

 #define QEMU_RATELIMIT_H

+#include "qemu/lockable.h"

 #include "qemu/timer.h"

 typedef struct {

+    QemuMutex lock;

     int64_t slice_start_time;

     int64_t slice_end_time;

     uint64_t slice_quota;

@@ -40,6 +42,7 @@ static inline int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n)

     int64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);

     double delay_slices;

+    QEMU_LOCK_GUARD(&limit->lock);

     assert(limit->slice_quota && limit->slice_ns);

     if (limit->slice_end_time < now) {

@@ -65,9 +68,20 @@ static inline int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n)

     return limit->slice_end_time - now;

 }

+static inline void ratelimit_init(RateLimit *limit)

+{

+    qemu_mutex_init(&limit->lock);

+}

+

+static inline void ratelimit_destroy(RateLimit *limit)

+{

+    qemu_mutex_destroy(&limit->lock);

+}

+

 static inline void ratelimit_set_speed(RateLimit *limit, uint64_t speed,

                                        uint64_t slice_ns)

 {

+    QEMU_LOCK_GUARD(&limit->lock);

     limit->slice_ns = slice_ns;

     limit->slice_quota = MAX(((double)speed * slice_ns) / 1000000000ULL, 1);

 }

-- 

2.27.0