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From b48a7b70caf3883782f8e90fb58b7f46ef6ace88 Mon Sep 17 00:00:00 2001
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From: Max Reitz <mreitz@redhat.com>
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Date: Mon, 18 Jun 2018 16:12:06 +0200
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Subject: [PATCH 039/268] block: Add BDRV_REQ_WRITE_UNCHANGED flag
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RH-Author: Max Reitz <mreitz@redhat.com>
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Message-id: <20180618161212.14444-5-mreitz@redhat.com>
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Patchwork-id: 80764
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O-Subject: [RHV-7.6 qemu-kvm-rhev PATCH 04/10] block: Add BDRV_REQ_WRITE_UNCHANGED flag
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Bugzilla: 1518738
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RH-Acked-by: John Snow <jsnow@redhat.com>
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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This flag signifies that a write request will not change the visible
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disk content. With this flag set, it is sufficient to have the
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BLK_PERM_WRITE_UNCHANGED permission instead of BLK_PERM_WRITE.
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Signed-off-by: Max Reitz <mreitz@redhat.com>
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Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
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Reviewed-by: Alberto Garcia <berto@igalia.com>
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Message-id: 20180421132929.21610-4-mreitz@redhat.com
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Reviewed-by: Kevin Wolf <kwolf@redhat.com>
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Signed-off-by: Max Reitz <mreitz@redhat.com>
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(cherry picked from commit c6035964f8316b504060618d05b5dd434f18595b)
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Signed-off-by: Max Reitz <mreitz@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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block/io.c | 6 +++++-
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include/block/block.h | 6 +++++-
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2 files changed, 10 insertions(+), 2 deletions(-)
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diff --git a/block/io.c b/block/io.c
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index bd9a19a..134b2a4 100644
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--- a/block/io.c
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+++ b/block/io.c
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@@ -1501,7 +1501,11 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChild *child,
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assert(!waited || !req->serialising);
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assert(req->overlap_offset <= offset);
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assert(offset + bytes <= req->overlap_offset + req->overlap_bytes);
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- assert(child->perm & BLK_PERM_WRITE);
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+ if (flags & BDRV_REQ_WRITE_UNCHANGED) {
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+ assert(child->perm & (BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE));
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+ } else {
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+ assert(child->perm & BLK_PERM_WRITE);
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+ }
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assert(end_sector <= bs->total_sectors || child->perm & BLK_PERM_RESIZE);
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ret = notifier_with_return_list_notify(&bs->before_write_notifiers, req);
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diff --git a/include/block/block.h b/include/block/block.h
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index 397b5e8..3894edd 100644
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--- a/include/block/block.h
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+++ b/include/block/block.h
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@@ -54,8 +54,12 @@ typedef enum {
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BDRV_REQ_FUA = 0x10,
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BDRV_REQ_WRITE_COMPRESSED = 0x20,
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+ /* Signifies that this write request will not change the visible disk
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+ * content. */
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+ BDRV_REQ_WRITE_UNCHANGED = 0x40,
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+
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/* Mask of valid flags */
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- BDRV_REQ_MASK = 0x3f,
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+ BDRV_REQ_MASK = 0x7f,
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} BdrvRequestFlags;
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typedef struct BlockSizes {
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--
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1.8.3.1
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