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[46.116.102.127]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-441b2bb3f72sm35455665e9.21.2025.04.30.13.37.20 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Wed, 30 Apr 2025 13:37:21 -0700 (PDT) From: Nir Soffer To: qemu-devel@nongnu.org Cc: Eric Blake , qemu-block@nongnu.org, Markus Armbruster , Kevin Wolf , Fam Zheng , Hanna Reitz , Nir Soffer Subject: [PATCH v2 1/2] block/null: Report DATA if not reading zeroes Date: Wed, 30 Apr 2025 23:37:16 +0300 Message-Id: <20250430203717.16359-2-nirsof@gmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) In-Reply-To: <20250430203717.16359-1-nirsof@gmail.com> References: <20250430203717.16359-1-nirsof@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::330; envelope-from=nirsof@gmail.com; helo=mail-wm1-x330.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org If read-zeroes is not set, we did not report BDRV_BLOCK_DATA or BDRV_BLOCK_ZERO. This is not consistent with other drivers and can confuse users or other programs: % qemu-img map --output json "json:{'driver': 'raw', 'file': {'driver': 'null-co', 'size': '1g'}}" [{ "start": 0, "length": 1073741824, "depth": 0, "present": false, "zero": false, "data": false, "compressed": false}] % qemu-nbd "json:{'driver': 'raw', 'file': {'driver': 'null-co', 'size': '1g'}}" & % nbdinfo --map nbd://127.0.0.1 0 1073741824 1 hole With this change we report DATA in this case: % ./qemu-img map --output json "json:{'driver': 'raw', 'file': {'driver': 'null-co', 'size': '1g'}}" [{ "start": 0, "length": 1073741824, "depth": 0, "present": true, "zero": false, "data": true, "compressed": false, "offset": 0}] % ./qemu-nbd "json:{'driver': 'raw', 'file': {'driver': 'null-co', 'size': '1g'}}" & % nbdinfo --map nbd://127.0.0.1 0 1073741824 0 data Signed-off-by: Nir Soffer --- block/null.c | 4 +--- qapi/block-core.json | 5 +++-- 2 files changed, 4 insertions(+), 5 deletions(-) diff --git a/block/null.c b/block/null.c index dc0b1fdbd9..7ba87bd9a9 100644 --- a/block/null.c +++ b/block/null.c @@ -239,9 +239,7 @@ static int coroutine_fn null_co_block_status(BlockDriverState *bs, *map = offset; *file = bs; - if (s->read_zeroes) { - ret |= BDRV_BLOCK_ZERO; - } + ret |= s->read_zeroes ? BDRV_BLOCK_ZERO : BDRV_BLOCK_DATA; return ret; } diff --git a/qapi/block-core.json b/qapi/block-core.json index b1937780e1..7c95c9e36a 100644 --- a/qapi/block-core.json +++ b/qapi/block-core.json @@ -3293,8 +3293,9 @@ # requests. Default to zero which completes requests immediately. # (Since 2.4) # -# @read-zeroes: if true, reads from the device produce zeroes; if -# false, the buffer is left unchanged. +# @read-zeroes: if true, emulate a sparse image, and reads from the +# device produce zeroes; if false, emulate an allocated image but +# reads from the device leave the buffer unchanged. # (default: false; since: 4.1) # # Since: 2.9 -- 2.39.5 (Apple Git-154)