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