From 013989ed30ff32eedbb1a6767f0c38c85150f951 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Wed, 10 Oct 2018 20:21:39 +0100 Subject: [PATCH 13/49] block: Drain recursively with a single BDRV_POLL_WHILE() RH-Author: Kevin Wolf Message-id: <20181010202213.7372-1-kwolf@redhat.com> Patchwork-id: 82590 O-Subject: [RHEL-8 qemu-kvm PATCH 10/44] block: Drain recursively with a single BDRV_POLL_WHILE() Bugzilla: 1637976 RH-Acked-by: Max Reitz RH-Acked-by: John Snow RH-Acked-by: Thomas Huth Anything can happen inside BDRV_POLL_WHILE(), including graph changes that may interfere with its callers (e.g. child list iteration in recursive callers of bdrv_do_drained_begin). Switch to a single BDRV_POLL_WHILE() call for the whole subtree at the end of bdrv_do_drained_begin() to avoid such effects. The recursion happens now inside the loop condition. As the graph can only change between bdrv_drain_poll() calls, but not inside of it, doing the recursion here is safe. Signed-off-by: Kevin Wolf (cherry picked from commit fe4f0614ef9e361dae12012d3c400657444836cf) Signed-off-by: Kevin Wolf Signed-off-by: Danilo C. L. de Paula --- block.c | 2 +- block/io.c | 63 ++++++++++++++++++++++++++++++++++++--------------- include/block/block.h | 9 +++++--- 3 files changed, 52 insertions(+), 22 deletions(-) diff --git a/block.c b/block.c index 0d9698a..9afaf26 100644 --- a/block.c +++ b/block.c @@ -824,7 +824,7 @@ static void bdrv_child_cb_drained_begin(BdrvChild *child) static bool bdrv_child_cb_drained_poll(BdrvChild *child) { BlockDriverState *bs = child->opaque; - return bdrv_drain_poll(bs, NULL); + return bdrv_drain_poll(bs, false, NULL); } static void bdrv_child_cb_drained_end(BdrvChild *child) diff --git a/block/io.c b/block/io.c index a0e3461..442ded1 100644 --- a/block/io.c +++ b/block/io.c @@ -164,6 +164,7 @@ typedef struct { bool done; bool begin; bool recursive; + bool poll; BdrvChild *parent; } BdrvCoDrainData; @@ -199,27 +200,42 @@ static void bdrv_drain_invoke(BlockDriverState *bs, bool begin) } /* Returns true if BDRV_POLL_WHILE() should go into a blocking aio_poll() */ -bool bdrv_drain_poll(BlockDriverState *bs, BdrvChild *ignore_parent) +bool bdrv_drain_poll(BlockDriverState *bs, bool recursive, + BdrvChild *ignore_parent) { + BdrvChild *child, *next; + if (bdrv_parent_drained_poll(bs, ignore_parent)) { return true; } - return atomic_read(&bs->in_flight); + if (atomic_read(&bs->in_flight)) { + return true; + } + + if (recursive) { + QLIST_FOREACH_SAFE(child, &bs->children, next, next) { + if (bdrv_drain_poll(child->bs, recursive, child)) { + return true; + } + } + } + + return false; } -static bool bdrv_drain_poll_top_level(BlockDriverState *bs, +static bool bdrv_drain_poll_top_level(BlockDriverState *bs, bool recursive, BdrvChild *ignore_parent) { /* Execute pending BHs first and check everything else only after the BHs * have executed. */ while (aio_poll(bs->aio_context, false)); - return bdrv_drain_poll(bs, ignore_parent); + return bdrv_drain_poll(bs, recursive, ignore_parent); } static void bdrv_do_drained_begin(BlockDriverState *bs, bool recursive, - BdrvChild *parent); + BdrvChild *parent, bool poll); static void bdrv_do_drained_end(BlockDriverState *bs, bool recursive, BdrvChild *parent); @@ -231,7 +247,7 @@ static void bdrv_co_drain_bh_cb(void *opaque) bdrv_dec_in_flight(bs); if (data->begin) { - bdrv_do_drained_begin(bs, data->recursive, data->parent); + bdrv_do_drained_begin(bs, data->recursive, data->parent, data->poll); } else { bdrv_do_drained_end(bs, data->recursive, data->parent); } @@ -242,7 +258,7 @@ static void bdrv_co_drain_bh_cb(void *opaque) static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs, bool begin, bool recursive, - BdrvChild *parent) + BdrvChild *parent, bool poll) { BdrvCoDrainData data; @@ -257,6 +273,7 @@ static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs, .begin = begin, .recursive = recursive, .parent = parent, + .poll = poll, }; bdrv_inc_in_flight(bs); aio_bh_schedule_oneshot(bdrv_get_aio_context(bs), @@ -269,12 +286,12 @@ static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs, } void bdrv_do_drained_begin(BlockDriverState *bs, bool recursive, - BdrvChild *parent) + BdrvChild *parent, bool poll) { BdrvChild *child, *next; if (qemu_in_coroutine()) { - bdrv_co_yield_to_drain(bs, true, recursive, parent); + bdrv_co_yield_to_drain(bs, true, recursive, parent, poll); return; } @@ -286,25 +303,35 @@ void bdrv_do_drained_begin(BlockDriverState *bs, bool recursive, bdrv_parent_drained_begin(bs, parent); bdrv_drain_invoke(bs, true); - /* Wait for drained requests to finish */ - BDRV_POLL_WHILE(bs, bdrv_drain_poll_top_level(bs, parent)); - if (recursive) { bs->recursive_quiesce_counter++; QLIST_FOREACH_SAFE(child, &bs->children, next, next) { - bdrv_do_drained_begin(child->bs, true, child); + bdrv_do_drained_begin(child->bs, true, child, false); } } + + /* + * Wait for drained requests to finish. + * + * Calling BDRV_POLL_WHILE() only once for the top-level node is okay: The + * call is needed so things in this AioContext can make progress even + * though we don't return to the main AioContext loop - this automatically + * includes other nodes in the same AioContext and therefore all child + * nodes. + */ + if (poll) { + BDRV_POLL_WHILE(bs, bdrv_drain_poll_top_level(bs, recursive, parent)); + } } void bdrv_drained_begin(BlockDriverState *bs) { - bdrv_do_drained_begin(bs, false, NULL); + bdrv_do_drained_begin(bs, false, NULL, true); } void bdrv_subtree_drained_begin(BlockDriverState *bs) { - bdrv_do_drained_begin(bs, true, NULL); + bdrv_do_drained_begin(bs, true, NULL, true); } void bdrv_do_drained_end(BlockDriverState *bs, bool recursive, @@ -314,7 +341,7 @@ void bdrv_do_drained_end(BlockDriverState *bs, bool recursive, int old_quiesce_counter; if (qemu_in_coroutine()) { - bdrv_co_yield_to_drain(bs, false, recursive, parent); + bdrv_co_yield_to_drain(bs, false, recursive, parent, false); return; } assert(bs->quiesce_counter > 0); @@ -350,7 +377,7 @@ void bdrv_apply_subtree_drain(BdrvChild *child, BlockDriverState *new_parent) int i; for (i = 0; i < new_parent->recursive_quiesce_counter; i++) { - bdrv_do_drained_begin(child->bs, true, child); + bdrv_do_drained_begin(child->bs, true, child, true); } } @@ -420,7 +447,7 @@ void bdrv_drain_all_begin(void) AioContext *aio_context = bdrv_get_aio_context(bs); aio_context_acquire(aio_context); - bdrv_do_drained_begin(bs, true, NULL); + bdrv_do_drained_begin(bs, true, NULL, true); aio_context_release(aio_context); } diff --git a/include/block/block.h b/include/block/block.h index 8c91d4c..2bbea7c 100644 --- a/include/block/block.h +++ b/include/block/block.h @@ -598,10 +598,13 @@ void bdrv_parent_drained_end(BlockDriverState *bs, BdrvChild *ignore); /** * bdrv_drain_poll: * - * Poll for pending requests in @bs and its parents (except for - * @ignore_parent). This is part of bdrv_drained_begin. + * Poll for pending requests in @bs, its parents (except for @ignore_parent), + * and if @recursive is true its children as well. + * + * This is part of bdrv_drained_begin. */ -bool bdrv_drain_poll(BlockDriverState *bs, BdrvChild *ignore_parent); +bool bdrv_drain_poll(BlockDriverState *bs, bool recursive, + BdrvChild *ignore_parent); /** * bdrv_drained_begin: -- 1.8.3.1