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From 69e802baf506bd21a2f444cfebe4ac7f5b5d07a8 Mon Sep 17 00:00:00 2001
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Message-Id: <69e802baf506bd21a2f444cfebe4ac7f5b5d07a8.1389014116.git.minovotn@redhat.com>
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In-Reply-To: <c8cc35838d42aa286242772d97e3a9be7bb786ba.1389014116.git.minovotn@redhat.com>
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References: <c8cc35838d42aa286242772d97e3a9be7bb786ba.1389014116.git.minovotn@redhat.com>
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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Mon, 9 Dec 2013 14:09:02 +0100
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Subject: [PATCH 14/50] block: honour BlockLimits in bdrv_co_do_write_zeroes
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RH-Author: Paolo Bonzini <pbonzini@redhat.com>
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Message-id: <1386598178-11845-17-git-send-email-pbonzini@redhat.com>
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Patchwork-id: 56052
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O-Subject: [RHEL 7.0 qemu-kvm PATCH 16/52] block: honour BlockLimits in bdrv_co_do_write_zeroes
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Bugzilla: 1007815
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RH-Acked-by: Jeffrey Cody <jcody@redhat.com>
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RH-Acked-by: Fam Zheng <famz@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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From: Peter Lieven <pl@kamp.de>
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Reviewed-by: Eric Blake <eblake@redhat.com>
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Signed-off-by: Peter Lieven <pl@kamp.de>
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit c31cb70728d2c0c8900b35a66784baa446fd5147)
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---
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block.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++++----------------
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1 file changed, 49 insertions(+), 16 deletions(-)
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Signed-off-by: Michal Novotny <minovotn@redhat.com>
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---
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block.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++++----------------
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1 file changed, 49 insertions(+), 16 deletions(-)
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diff --git a/block.c b/block.c
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index 2fae459..2ed9aa9 100644
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--- a/block.c
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+++ b/block.c
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@@ -2724,32 +2724,65 @@ int coroutine_fn bdrv_co_copy_on_readv(BlockDriverState *bs,
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BDRV_REQ_COPY_ON_READ);
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}
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+/* if no limit is specified in the BlockLimits use a default
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+ * of 32768 512-byte sectors (16 MiB) per request.
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+ */
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+#define MAX_WRITE_ZEROES_DEFAULT 32768
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+
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static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs,
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int64_t sector_num, int nb_sectors, BdrvRequestFlags flags)
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{
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BlockDriver *drv = bs->drv;
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QEMUIOVector qiov;
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- struct iovec iov;
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- int ret;
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+ struct iovec iov = {0};
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+ int ret = 0;
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- /* TODO Emulate only part of misaligned requests instead of letting block
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- * drivers return -ENOTSUP and emulate everything */
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+ int max_write_zeroes = bs->bl.max_write_zeroes ?
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+ bs->bl.max_write_zeroes : MAX_WRITE_ZEROES_DEFAULT;
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- /* First try the efficient write zeroes operation */
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- if (drv->bdrv_co_write_zeroes) {
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- ret = drv->bdrv_co_write_zeroes(bs, sector_num, nb_sectors, flags);
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- if (ret != -ENOTSUP) {
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- return ret;
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+ while (nb_sectors > 0 && !ret) {
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+ int num = nb_sectors;
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+
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+ /* align request */
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+ if (bs->bl.write_zeroes_alignment &&
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+ num >= bs->bl.write_zeroes_alignment &&
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+ sector_num % bs->bl.write_zeroes_alignment) {
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+ if (num > bs->bl.write_zeroes_alignment) {
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+ num = bs->bl.write_zeroes_alignment;
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+ }
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+ num -= sector_num % bs->bl.write_zeroes_alignment;
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}
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- }
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- /* Fall back to bounce buffer if write zeroes is unsupported */
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- iov.iov_len = nb_sectors * BDRV_SECTOR_SIZE;
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- iov.iov_base = qemu_blockalign(bs, iov.iov_len);
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- memset(iov.iov_base, 0, iov.iov_len);
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- qemu_iovec_init_external(&qiov, &iov, 1);
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+ /* limit request size */
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+ if (num > max_write_zeroes) {
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+ num = max_write_zeroes;
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+ }
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+
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+ ret = -ENOTSUP;
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+ /* First try the efficient write zeroes operation */
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+ if (drv->bdrv_co_write_zeroes) {
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+ ret = drv->bdrv_co_write_zeroes(bs, sector_num, num, flags);
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+ }
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+
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+ if (ret == -ENOTSUP) {
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+ /* Fall back to bounce buffer if write zeroes is unsupported */
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+ iov.iov_len = num * BDRV_SECTOR_SIZE;
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+ if (iov.iov_base == NULL) {
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+ /* allocate bounce buffer only once and ensure that it
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+ * is big enough for this and all future requests.
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+ */
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+ size_t bufsize = num <= nb_sectors ? num : max_write_zeroes;
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+ iov.iov_base = qemu_blockalign(bs, bufsize * BDRV_SECTOR_SIZE);
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+ memset(iov.iov_base, 0, bufsize * BDRV_SECTOR_SIZE);
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+ }
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+ qemu_iovec_init_external(&qiov, &iov, 1);
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- ret = drv->bdrv_co_writev(bs, sector_num, nb_sectors, &qiov);
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+ ret = drv->bdrv_co_writev(bs, sector_num, num, &qiov);
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+ }
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+
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+ sector_num += num;
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+ nb_sectors -= num;
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+ }
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qemu_vfree(iov.iov_base);
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return ret;
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--
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1.7.11.7
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