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From 9e527bd9df162b9af555106675efdb909164051e 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 16:12:05 +0200
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Subject: [PATCH 038/268] block: BLK_PERM_WRITE includes ..._UNCHANGED
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RH-Author: Max Reitz <mreitz@redhat.com>
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Message-id: <20180618161212.14444-4-mreitz@redhat.com>
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Patchwork-id: 80763
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O-Subject: [RHV-7.6 qemu-kvm-rhev PATCH 03/10] block: BLK_PERM_WRITE includes ..._UNCHANGED
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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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Currently we never actually check whether the WRITE_UNCHANGED
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permission has been taken for unchanging writes. But the one check that
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is commented out checks both WRITE and WRITE_UNCHANGED; and considering
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that WRITE_UNCHANGED is already documented as being weaker than WRITE,
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we should probably explicitly document WRITE to include WRITE_UNCHANGED.
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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: 20180421132929.21610-3-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 24b7c538fea86b598e2a335f4805a0ab50a30e98)
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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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include/block/block.h | 3 +++
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1 file changed, 3 insertions(+)
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diff --git a/include/block/block.h b/include/block/block.h
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index cdec363..397b5e8 100644
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--- a/include/block/block.h
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+++ b/include/block/block.h
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@@ -205,6 +205,9 @@ enum {
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* This permission (which is weaker than BLK_PERM_WRITE) is both enough and
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* required for writes to the block node when the caller promises that
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* the visible disk content doesn't change.
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+ *
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+ * As the BLK_PERM_WRITE permission is strictly stronger, either is
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+ * sufficient to perform an unchanging write.
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*/
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BLK_PERM_WRITE_UNCHANGED = 0x04,
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--
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1.8.3.1
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