Blame SOURCES/kvm-block-introduce-bdrv_make_zero.patch.patch.patch

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From 2f7835f6ef83931dff5fb37729fd42cd7b431b17 Mon Sep 17 00:00:00 2001
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Message-Id: <2f7835f6ef83931dff5fb37729fd42cd7b431b17.1389014116.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 14:09:07 +0100
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Subject: [PATCH 19/50] block: introduce bdrv_make_zero
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RH-Author: Paolo Bonzini <pbonzini@redhat.com>
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Message-id: <1386598178-11845-22-git-send-email-pbonzini@redhat.com>
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Patchwork-id: 56058
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O-Subject: [RHEL 7.0 qemu-kvm PATCH 21/52] block: introduce bdrv_make_zero
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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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this patch adds a call to completely zero out a block device.
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the operation is sped up by checking the block status and
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only writing zeroes to the device if they currently do not
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return zeroes. optionally the zero writing can be sped up
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by setting the flag BDRV_REQ_MAY_UNMAP to emulate the zero
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write by unmapping if the driver supports it.
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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 d75cbb5e68f5a7d64248ba89399a7f2073231de5)
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---
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 block.c               | 37 +++++++++++++++++++++++++++++++++++++
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 include/block/block.h |  1 +
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 2 files changed, 38 insertions(+)
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Signed-off-by: Michal Novotny <minovotn@redhat.com>
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---
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 block.c               | 37 +++++++++++++++++++++++++++++++++++++
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 include/block/block.h |  1 +
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 2 files changed, 38 insertions(+)
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diff --git a/block.c b/block.c
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index 23dbafd..2e77763 100644
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--- a/block.c
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+++ b/block.c
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@@ -2412,6 +2412,43 @@ int bdrv_write_zeroes(BlockDriverState *bs, int64_t sector_num,
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                       BDRV_REQ_ZERO_WRITE | flags);
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 }
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+/*
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+ * Completely zero out a block device with the help of bdrv_write_zeroes.
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+ * The operation is sped up by checking the block status and only writing
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+ * zeroes to the device if they currently do not return zeroes. Optional
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+ * flags are passed through to bdrv_write_zeroes (e.g. BDRV_REQ_MAY_UNMAP).
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+ *
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+ * Returns < 0 on error, 0 on success. For error codes see bdrv_write().
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+ */
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+int bdrv_make_zero(BlockDriverState *bs, BdrvRequestFlags flags)
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+{
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+    int64_t target_size = bdrv_getlength(bs) / BDRV_SECTOR_SIZE;
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+    int64_t ret, nb_sectors, sector_num = 0;
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+    int n;
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+
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+    for (;;) {
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+        nb_sectors = target_size - sector_num;
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+        if (nb_sectors <= 0) {
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+            return 0;
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+        }
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+        if (nb_sectors > INT_MAX) {
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+            nb_sectors = INT_MAX;
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+        }
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+        ret = bdrv_get_block_status(bs, sector_num, nb_sectors, &n);
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+        if (ret & BDRV_BLOCK_ZERO) {
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+            sector_num += n;
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+            continue;
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+        }
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+        ret = bdrv_write_zeroes(bs, sector_num, n, flags);
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+        if (ret < 0) {
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+            error_report("error writing zeroes at sector %" PRId64 ": %s",
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+                         sector_num, strerror(-ret));
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+            return ret;
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+        }
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+        sector_num += n;
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+    }
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+}
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+
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 int bdrv_pread(BlockDriverState *bs, int64_t offset,
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                void *buf, int count1)
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 {
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diff --git a/include/block/block.h b/include/block/block.h
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index 1958d98..b87ed3a 100644
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--- a/include/block/block.h
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+++ b/include/block/block.h
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@@ -218,6 +218,7 @@ int bdrv_write(BlockDriverState *bs, int64_t sector_num,
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                const uint8_t *buf, int nb_sectors);
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 int bdrv_write_zeroes(BlockDriverState *bs, int64_t sector_num,
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                int nb_sectors, BdrvRequestFlags flags);
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+int bdrv_make_zero(BlockDriverState *bs, BdrvRequestFlags flags);
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 int bdrv_writev(BlockDriverState *bs, int64_t sector_num, QEMUIOVector *qiov);
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 int bdrv_pread(BlockDriverState *bs, int64_t offset,
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                void *buf, int count);
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-- 
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1.7.11.7
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