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