From 05efd4675b1241f2cc68fd54c92a8a834699f212 Mon Sep 17 00:00:00 2001 From: "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 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 RH-Acked-by: Kevin Wolf RH-Acked-by: Igor Mammedov RH-Acked-by: Andrew Jones 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 (cherry picked from commit 4951967d84a0acbf47895add9158e2d4c6056ea0) Signed-off-by: Paul Lai Signed-off-by: Miroslav Rezanina --- 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