Received: from eggs.gnu.org ([2001:4830:134:3::10]:37702) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eBuA9-0007c3-SE for qemu-devel@nongnu.org; Mon, 06 Nov 2017 22:02:54 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eBuA9-0003WE-59 for qemu-devel@nongnu.org; Mon, 06 Nov 2017 22:02:53 -0500 From: Eric Blake Date: Mon, 6 Nov 2017 21:02:34 -0600 Message-Id: <20171107030236.23633-7-eblake@redhat.com> In-Reply-To: <20171107030236.23633-1-eblake@redhat.com> References: <20171107030236.23633-1-eblake@redhat.com> Subject: [Qemu-devel] [PATCH 6/8] nbd-client: Short-circuit 0-length operations List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: qemu-block@nongnu.org, pbonzini@redhat.com, vsementsov@virtuozzo.com, Kevin Wolf , Max Reitz The NBD spec is being clarified to state that clients should not send 0-length requests to the server, as the server behavior is undefined. While such requests are unlikely to occur from real guest behavior, qemu-io can force the driver to perform them; avoid any questionable server implementations by short-circuiting such operations as a no-op success (we are relying on the block layer for already filtering out things like invalid offset, write to a read-only volume, and so forth). Signed-off-by: Eric Blake --- block/nbd-client.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/block/nbd-client.c b/block/nbd-client.c index c35aad59b0..d8ad2ba57c 100644 --- a/block/nbd-client.c +++ b/block/nbd-client.c @@ -673,6 +673,9 @@ int nbd_client_co_preadv(BlockDriverState *bs, uint64_t offset, assert(bytes <= NBD_MAX_BUFFER_SIZE); assert(!flags); + if (!bytes) { + return 0; + } ret = nbd_co_send_request(bs, &request, NULL); if (ret < 0) { @@ -705,6 +708,9 @@ int nbd_client_co_pwritev(BlockDriverState *bs, uint64_t offset, assert(bytes <= NBD_MAX_BUFFER_SIZE); + if (!bytes) { + return 0; + } return nbd_co_request(bs, &request, qiov); } @@ -731,6 +737,9 @@ int nbd_client_co_pwrite_zeroes(BlockDriverState *bs, int64_t offset, request.flags |= NBD_CMD_FLAG_NO_HOLE; } + if (!bytes) { + return 0; + } return nbd_co_request(bs, &request, NULL); } @@ -759,7 +768,7 @@ int nbd_client_co_pdiscard(BlockDriverState *bs, int64_t offset, int bytes) }; assert(!(client->info.flags & NBD_FLAG_READ_ONLY)); - if (!(client->info.flags & NBD_FLAG_SEND_TRIM)) { + if (!(client->info.flags & NBD_FLAG_SEND_TRIM) || !bytes) { return 0; } -- 2.13.6