From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48824) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bLeNb-0002Zf-73 for qemu-devel@nongnu.org; Fri, 08 Jul 2016 18:36:16 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bLeNY-0006dr-KH for qemu-devel@nongnu.org; Fri, 08 Jul 2016 18:36:14 -0400 Received: from resqmta-po-05v.sys.comcast.net ([2001:558:fe16:19:96:114:154:164]:34880) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bLeNY-0006d2-EY for qemu-devel@nongnu.org; Fri, 08 Jul 2016 18:36:12 -0400 From: Eric Blake Date: Fri, 8 Jul 2016 16:36:02 -0600 Message-Id: <1468017364-25980-5-git-send-email-eblake@redhat.com> In-Reply-To: <1468017364-25980-1-git-send-email-eblake@redhat.com> References: <1468017364-25980-1-git-send-email-eblake@redhat.com> Subject: [Qemu-devel] [PATCH v2 4/6] nbd: Rely on block layer to break up large requests List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: qemu-block@nongnu.org, kwolf@redhat.com, famz@redhat.com, Paolo Bonzini , Max Reitz Now that the block layer will honor max_transfer, we can simplify our code to rely on that guarantee. The readv code can call directly into nbd-client, just as the writev code has done since commit 52a4650. Interestingly enough, while qemu-io 'w 0 40m' splits into a 32M and 8M transaction, 'w -z 0 40m' splits into two 16M and an 8M, because the block layer caps the bounce buffer for writing zeroes at 16M. When we later introduce support for NBD_CMD_WRITE_ZEROES, we can get a full 32M zero write (or larger, if the client and server negotiate that write zeroes can use a larger size than ordinary writes). Signed-off-by: Eric Blake Reviewed-by: Fam Zheng --- block/nbd-client.c | 51 ++++++++------------------------------------------- block/nbd.c | 12 +++--------- 2 files changed, 11 insertions(+), 52 deletions(-) diff --git a/block/nbd-client.c b/block/nbd-client.c index 4cc408d..f1fb58b 100644 --- a/block/nbd-client.c +++ b/block/nbd-client.c @@ -217,15 +217,15 @@ static void nbd_coroutine_end(NbdClientSession *s, } } -static int nbd_co_readv_1(BlockDriverState *bs, int64_t sector_num, - int nb_sectors, QEMUIOVector *qiov, - int offset) +int nbd_client_co_readv(BlockDriverState *bs, int64_t sector_num, + int nb_sectors, QEMUIOVector *qiov) { NbdClientSession *client = nbd_get_client_session(bs); struct nbd_request request = { .type = NBD_CMD_READ }; struct nbd_reply reply; ssize_t ret; + assert(nb_sectors <= NBD_MAX_SECTORS); request.from = sector_num * 512; request.len = nb_sectors * 512; @@ -234,16 +234,15 @@ static int nbd_co_readv_1(BlockDriverState *bs, int64_t sector_num, if (ret < 0) { reply.error = -ret; } else { - nbd_co_receive_reply(client, &request, &reply, qiov, offset); + nbd_co_receive_reply(client, &request, &reply, qiov, 0); } nbd_coroutine_end(client, &request); return -reply.error; } -static int nbd_co_writev_1(BlockDriverState *bs, int64_t sector_num, - int nb_sectors, QEMUIOVector *qiov, - int offset, int flags) +int nbd_client_co_writev(BlockDriverState *bs, int64_t sector_num, + int nb_sectors, QEMUIOVector *qiov, int flags) { NbdClientSession *client = nbd_get_client_session(bs); struct nbd_request request = { .type = NBD_CMD_WRITE }; @@ -255,11 +254,12 @@ static int nbd_co_writev_1(BlockDriverState *bs, int64_t sector_num, request.type |= NBD_CMD_FLAG_FUA; } + assert(nb_sectors <= NBD_MAX_SECTORS); request.from = sector_num * 512; request.len = nb_sectors * 512; nbd_coroutine_start(client, &request); - ret = nbd_co_send_request(bs, &request, qiov, offset); + ret = nbd_co_send_request(bs, &request, qiov, 0); if (ret < 0) { reply.error = -ret; } else { @@ -269,41 +269,6 @@ static int nbd_co_writev_1(BlockDriverState *bs, int64_t sector_num, return -reply.error; } -int nbd_client_co_readv(BlockDriverState *bs, int64_t sector_num, - int nb_sectors, QEMUIOVector *qiov) -{ - int offset = 0; - int ret; - while (nb_sectors > NBD_MAX_SECTORS) { - ret = nbd_co_readv_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset); - if (ret < 0) { - return ret; - } - offset += NBD_MAX_SECTORS * 512; - sector_num += NBD_MAX_SECTORS; - nb_sectors -= NBD_MAX_SECTORS; - } - return nbd_co_readv_1(bs, sector_num, nb_sectors, qiov, offset); -} - -int nbd_client_co_writev(BlockDriverState *bs, int64_t sector_num, - int nb_sectors, QEMUIOVector *qiov, int flags) -{ - int offset = 0; - int ret; - while (nb_sectors > NBD_MAX_SECTORS) { - ret = nbd_co_writev_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset, - flags); - if (ret < 0) { - return ret; - } - offset += NBD_MAX_SECTORS * 512; - sector_num += NBD_MAX_SECTORS; - nb_sectors -= NBD_MAX_SECTORS; - } - return nbd_co_writev_1(bs, sector_num, nb_sectors, qiov, offset, flags); -} - int nbd_client_co_flush(BlockDriverState *bs) { NbdClientSession *client = nbd_get_client_session(bs); diff --git a/block/nbd.c b/block/nbd.c index 08e5b67..8a13078 100644 --- a/block/nbd.c +++ b/block/nbd.c @@ -349,12 +349,6 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags, return ret; } -static int nbd_co_readv(BlockDriverState *bs, int64_t sector_num, - int nb_sectors, QEMUIOVector *qiov) -{ - return nbd_client_co_readv(bs, sector_num, nb_sectors, qiov); -} - static int nbd_co_flush(BlockDriverState *bs) { return nbd_client_co_flush(bs); @@ -450,7 +444,7 @@ static BlockDriver bdrv_nbd = { .instance_size = sizeof(BDRVNBDState), .bdrv_parse_filename = nbd_parse_filename, .bdrv_file_open = nbd_open, - .bdrv_co_readv = nbd_co_readv, + .bdrv_co_readv = nbd_client_co_readv, .bdrv_co_writev_flags = nbd_client_co_writev, .bdrv_close = nbd_close, .bdrv_co_flush_to_os = nbd_co_flush, @@ -468,7 +462,7 @@ static BlockDriver bdrv_nbd_tcp = { .instance_size = sizeof(BDRVNBDState), .bdrv_parse_filename = nbd_parse_filename, .bdrv_file_open = nbd_open, - .bdrv_co_readv = nbd_co_readv, + .bdrv_co_readv = nbd_client_co_readv, .bdrv_co_writev_flags = nbd_client_co_writev, .bdrv_close = nbd_close, .bdrv_co_flush_to_os = nbd_co_flush, @@ -486,7 +480,7 @@ static BlockDriver bdrv_nbd_unix = { .instance_size = sizeof(BDRVNBDState), .bdrv_parse_filename = nbd_parse_filename, .bdrv_file_open = nbd_open, - .bdrv_co_readv = nbd_co_readv, + .bdrv_co_readv = nbd_client_co_readv, .bdrv_co_writev_flags = nbd_client_co_writev, .bdrv_close = nbd_close, .bdrv_co_flush_to_os = nbd_co_flush, -- 2.5.5