From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60491) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1f87T8-0007SY-LP for qemu-devel@nongnu.org; Mon, 16 Apr 2018 12:59:07 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1f87T7-0003Fp-TS for qemu-devel@nongnu.org; Mon, 16 Apr 2018 12:59:06 -0400 From: Max Reitz Date: Mon, 16 Apr 2018 18:58:42 +0200 Message-Id: <20180416165849.28864-3-mreitz@redhat.com> In-Reply-To: <20180416165849.28864-1-mreitz@redhat.com> References: <20180416165849.28864-1-mreitz@redhat.com> Subject: [Qemu-devel] [PATCH 2/9] block: BLK_PERM_WRITE includes ..._UNCHANGED List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-block@nongnu.org Cc: qemu-devel@nongnu.org, Max Reitz , Kevin Wolf , Stefan Hajnoczi , Fam Zheng Currently we never actually check whether the WRITE_UNCHANGED permission has been taken for unchanging writes. But the one check that is commented out checks both WRITE and WRITE_UNCHANGED; and considering that WRITE_UNCHANGED is already documented as being weaker then WRITE, we should probably explicitly document WRITE to include WRITE_UNCHANGED. Signed-off-by: Max Reitz --- include/block/block.h | 3 +++ 1 file changed, 3 insertions(+) diff --git a/include/block/block.h b/include/block/block.h index cdec3639a3..397b5e8d44 100644 --- a/include/block/block.h +++ b/include/block/block.h @@ -205,6 +205,9 @@ enum { * This permission (which is weaker than BLK_PERM_WRITE) is both enough and * required for writes to the block node when the caller promises that * the visible disk content doesn't change. + * + * As the BLK_PERM_WRITE permission is strictly stronger, either is + * sufficient to perform an unchanging write. */ BLK_PERM_WRITE_UNCHANGED = 0x04, -- 2.14.3