93 lines
3.5 KiB
Diff
93 lines
3.5 KiB
Diff
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From eaade87072e903cf550dfdb8ed1480dddc6bb0e3 Mon Sep 17 00:00:00 2001
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From: Hanna Reitz <hreitz@redhat.com>
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Date: Thu, 20 Jan 2022 15:22:59 +0100
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Subject: [PATCH 21/24] ide: Increment BB in-flight counter for TRIM BH
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: Hanna Reitz <hreitz@redhat.com>
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RH-MergeRequest: 188: ide: Increment BB in-flight counter for TRIM BH
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RH-Commit: [1/1] 1e702e735ff63f2b8b69c20cac1b309dd085cd62
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RH-Bugzilla: 2029980
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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When we still have an AIOCB registered for DMA operations, we try to
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settle the respective operation by draining the BlockBackend associated
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with the IDE device.
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However, this assumes that every DMA operation is associated with an
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increment of the BlockBackend’s in-flight counter (e.g. through some
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ongoing I/O operation), so that draining the BB until its in-flight
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counter reaches 0 will settle all DMA operations. That is not the case:
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For TRIM, the guest can issue a zero-length operation that will not
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result in any I/O operation forwarded to the BlockBackend, and also not
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increment the in-flight counter in any other way. In such a case,
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blk_drain() will be a no-op if no other operations are in flight.
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It is clear that if blk_drain() is a no-op, the value of
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s->bus->dma->aiocb will not change between checking it in the `if`
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condition and asserting that it is NULL after blk_drain().
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The particular problem is that ide_issue_trim() creates a BH
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(ide_trim_bh_cb()) to settle the TRIM request: iocb->common.cb() is
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ide_dma_cb(), which will either create a new request, or find the
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transfer to be done and call ide_set_inactive(), which clears
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s->bus->dma->aiocb. Therefore, the blk_drain() must wait for
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ide_trim_bh_cb() to run, which currently it will not always do.
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To fix this issue, we increment the BlockBackend's in-flight counter
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when the TRIM operation begins (in ide_issue_trim(), when the
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ide_trim_bh_cb() BH is created) and decrement it when ide_trim_bh_cb()
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is done.
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Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2029980
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Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
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Signed-off-by: Hanna Reitz <hreitz@redhat.com>
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Message-Id: <20220120142259.120189-1-hreitz@redhat.com>
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Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
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Reviewed-by: John Snow <jsnow@redhat.com>
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Tested-by: John Snow <jsnow@redhat.com>
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(cherry picked from commit 7e5cdb345f77d76cb4877fe6230c4e17a7d0d0ca)
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Signed-off-by: Hanna Reitz <hreitz@redhat.com>
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---
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hw/ide/core.c | 7 +++++++
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1 file changed, 7 insertions(+)
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diff --git a/hw/ide/core.c b/hw/ide/core.c
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index e28f8aad61..15138225be 100644
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--- a/hw/ide/core.c
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+++ b/hw/ide/core.c
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@@ -433,12 +433,16 @@ static const AIOCBInfo trim_aiocb_info = {
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static void ide_trim_bh_cb(void *opaque)
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{
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TrimAIOCB *iocb = opaque;
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+ BlockBackend *blk = iocb->s->blk;
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iocb->common.cb(iocb->common.opaque, iocb->ret);
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qemu_bh_delete(iocb->bh);
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iocb->bh = NULL;
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qemu_aio_unref(iocb);
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+
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+ /* Paired with an increment in ide_issue_trim() */
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+ blk_dec_in_flight(blk);
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}
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static void ide_issue_trim_cb(void *opaque, int ret)
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@@ -508,6 +512,9 @@ BlockAIOCB *ide_issue_trim(
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IDEState *s = opaque;
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TrimAIOCB *iocb;
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+ /* Paired with a decrement in ide_trim_bh_cb() */
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+ blk_inc_in_flight(s->blk);
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+
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iocb = blk_aio_get(&trim_aiocb_info, s->blk, cb, cb_opaque);
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iocb->s = s;
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iocb->bh = qemu_bh_new(ide_trim_bh_cb, iocb);
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--
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2.35.3
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