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From e776fb3350daea9851190d6445b4786f4b1f493f Mon Sep 17 00:00:00 2001
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From: Kevin Wolf <kwolf@redhat.com>
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Date: Fri, 14 Sep 2018 10:55:14 +0200
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Subject: [PATCH 23/49] block: Allow AIO_WAIT_WHILE with NULL ctx
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RH-Author: Kevin Wolf <kwolf@redhat.com>
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Message-id: <20180914105540.18077-17-kwolf@redhat.com>
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Patchwork-id: 82168
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O-Subject: [RHV-7.6 qemu-kvm-rhev PATCH 16/42] block: Allow AIO_WAIT_WHILE with NULL ctx
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Bugzilla: 1601212
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RH-Acked-by: John Snow <jsnow@redhat.com>
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RH-Acked-by: Max Reitz <mreitz@redhat.com>
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RH-Acked-by: Fam Zheng <famz@redhat.com>
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bdrv_drain_all() wants to have a single polling loop for draining the
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in-flight requests of all nodes. This means that the AIO_WAIT_WHILE()
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condition relies on activity in multiple AioContexts, which is polled
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from the mainloop context. We must therefore call AIO_WAIT_WHILE() from
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the mainloop thread and use the AioWait notification mechanism.
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Just randomly picking the AioContext of any non-mainloop thread would
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work, but instead of bothering to find such a context in the caller, we
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can just as well accept NULL for ctx.
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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(cherry picked from commit 4d22bbf4ef72583eefdf44db6bf9fc7683fbc4c2)
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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include/block/aio-wait.h | 13 +++++++++----
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1 file changed, 9 insertions(+), 4 deletions(-)
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diff --git a/include/block/aio-wait.h b/include/block/aio-wait.h
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index 783d367..c85a62f 100644
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--- a/include/block/aio-wait.h
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+++ b/include/block/aio-wait.h
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@@ -57,7 +57,8 @@ typedef struct {
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/**
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* AIO_WAIT_WHILE:
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* @wait: the aio wait object
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- * @ctx: the aio context
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+ * @ctx: the aio context, or NULL if multiple aio contexts (for which the
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+ * caller does not hold a lock) are involved in the polling condition.
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* @cond: wait while this conditional expression is true
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*
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* Wait while a condition is true. Use this to implement synchronous
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@@ -75,7 +76,7 @@ typedef struct {
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bool waited_ = false; \
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AioWait *wait_ = (wait); \
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AioContext *ctx_ = (ctx); \
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- if (in_aio_context_home_thread(ctx_)) { \
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+ if (ctx_ && in_aio_context_home_thread(ctx_)) { \
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while ((cond)) { \
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aio_poll(ctx_, true); \
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waited_ = true; \
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@@ -86,9 +87,13 @@ typedef struct {
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/* Increment wait_->num_waiters before evaluating cond. */ \
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atomic_inc(&wait_->num_waiters); \
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while ((cond)) { \
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- aio_context_release(ctx_); \
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+ if (ctx_) { \
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+ aio_context_release(ctx_); \
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+ } \
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aio_poll(qemu_get_aio_context(), true); \
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- aio_context_acquire(ctx_); \
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+ if (ctx_) { \
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+ aio_context_acquire(ctx_); \
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+ } \
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waited_ = true; \
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} \
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atomic_dec(&wait_->num_waiters); \
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--
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1.8.3.1
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