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From 9a02c0bcafdbf681e76f816ad3f60dfb7dea13fb Mon Sep 17 00:00:00 2001
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From: Maxim Levitsky <mlevitsk@redhat.com>
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Date: Wed, 5 Jun 2019 13:57:03 +0200
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Subject: [PATCH 15/23] file-posix: Support BDRV_REQ_NO_FALLBACK for zero
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writes
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RH-Author: Maxim Levitsky <mlevitsk@redhat.com>
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Message-id: <20190605135705.24526-8-mlevitsk@redhat.com>
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Patchwork-id: 88560
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O-Subject: [RHEL-7.7 qemu-kvm-rhev PATCH 7/9] file-posix: Support BDRV_REQ_NO_FALLBACK for zero writes
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Bugzilla: 1648622
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RH-Acked-by: Max Reitz <mreitz@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: John Snow <jsnow@redhat.com>
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From: Kevin Wolf <kwolf@redhat.com>
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We know that the kernel implements a slow fallback code path for
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BLKZEROOUT, so if BDRV_REQ_NO_FALLBACK is given, we shouldn't call it.
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The other operations we call in the context of .bdrv_co_pwrite_zeroes
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should usually be quick, so no modification should be needed for them.
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If we ever notice that there are additional problematic cases, we can
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still make these conditional as well.
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Acked-by: Eric Blake <eblake@redhat.com>
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Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1648622
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Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
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(Cherry picked from 738301e11758171defaa5a5237d584f8226af89f)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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block/file-posix.c | 24 ++++++++++++++++--------
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include/block/raw-aio.h | 1 +
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2 files changed, 17 insertions(+), 8 deletions(-)
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diff --git a/block/file-posix.c b/block/file-posix.c
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index 90c719f..d1926b3 100644
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--- a/block/file-posix.c
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+++ b/block/file-posix.c
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@@ -632,7 +632,7 @@ static int raw_open_common(BlockDriverState *bs, QDict *options,
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}
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#endif
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- bs->supported_zero_flags = BDRV_REQ_MAY_UNMAP;
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+ bs->supported_zero_flags = BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK;
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ret = 0;
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fail:
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if (filename && (bdrv_flags & BDRV_O_TEMPORARY)) {
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@@ -1449,14 +1449,19 @@ static ssize_t handle_aiocb_write_zeroes_block(RawPosixAIOData *aiocb)
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}
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#ifdef BLKZEROOUT
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- do {
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- uint64_t range[2] = { aiocb->aio_offset, aiocb->aio_nbytes };
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- if (ioctl(aiocb->aio_fildes, BLKZEROOUT, range) == 0) {
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- return 0;
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- }
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- } while (errno == EINTR);
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+ /* The BLKZEROOUT implementation in the kernel doesn't set
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+ * BLKDEV_ZERO_NOFALLBACK, so we can't call this if we have to avoid slow
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+ * fallbacks. */
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+ if (!(aiocb->aio_type & QEMU_AIO_NO_FALLBACK)) {
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+ do {
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+ uint64_t range[2] = { aiocb->aio_offset, aiocb->aio_nbytes };
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+ if (ioctl(aiocb->aio_fildes, BLKZEROOUT, range) == 0) {
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+ return 0;
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+ }
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+ } while (errno == EINTR);
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- ret = translate_err(-errno);
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+ ret = translate_err(-errno);
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+ }
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#endif
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if (ret == -ENOTSUP) {
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@@ -2535,6 +2540,9 @@ raw_do_pwrite_zeroes(BlockDriverState *bs, int64_t offset, int bytes,
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if (blkdev) {
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acb.aio_type |= QEMU_AIO_BLKDEV;
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}
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+ if (flags & BDRV_REQ_NO_FALLBACK) {
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+ acb.aio_type |= QEMU_AIO_NO_FALLBACK;
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+ }
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if (flags & BDRV_REQ_MAY_UNMAP) {
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acb.aio_type |= QEMU_AIO_DISCARD;
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diff --git a/include/block/raw-aio.h b/include/block/raw-aio.h
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index 2ffcd9d..5a926a3 100644
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--- a/include/block/raw-aio.h
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+++ b/include/block/raw-aio.h
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@@ -40,6 +40,7 @@
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/* AIO flags */
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#define QEMU_AIO_MISALIGNED 0x1000
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#define QEMU_AIO_BLKDEV 0x2000
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+#define QEMU_AIO_NO_FALLBACK 0x4000
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/* linux-aio.c - Linux native implementation */
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--
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1.8.3.1
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