From ab2aac59e8cc7172800864a28f2386d780a08016 Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Thu, 23 Jun 2016 16:37:08 -0600 Subject: [PATCH] nbd: Allow larger requests The NBD layer was breaking up request at a limit of 2040 sectors (just under 1M) to cater to old qemu-nbd. But the server limit was raised to 32M in commit 2d8214885 to match the kernel, more than three years ago; and the upstream NBD Protocol is proposing documentation that without any explicit communication to state otherwise, a client should be able to safely assume that a 32M transaction will work. It is time to rely on the larger sizing, and any downstream distro that cares about maximum interoperability to older qemu-nbd servers can just tweak the value of #define NBD_MAX_SECTORS. Signed-off-by: Eric Blake Reviewed-by: Kevin Wolf Acked-by: Paolo Bonzini Cc: qemu-stable@nongnu.org Reviewed-by: Fam Zheng Reviewed-by: Stefan Hajnoczi Signed-off-by: Kevin Wolf (cherry picked from commit 476b923c32ece0e268580776aaf1fab4ab4459a8) Conflicts: include/block/nbd.h * removed context dependency on 943cec86 Signed-off-by: Michael Roth --- block/nbd-client.c | 4 ---- include/block/nbd.h | 1 + 2 files changed, 1 insertion(+), 4 deletions(-) diff --git a/block/nbd-client.c b/block/nbd-client.c index 878e879ace..6f6df468fa 100644 --- a/block/nbd-client.c +++ b/block/nbd-client.c @@ -269,10 +269,6 @@ static int nbd_co_writev_1(BlockDriverState *bs, int64_t sector_num, return -reply.error; } -/* qemu-nbd has a limit of slightly less than 1M per request. Try to - * remain aligned to 4K. */ -#define NBD_MAX_SECTORS 2040 - int nbd_client_co_readv(BlockDriverState *bs, int64_t sector_num, int nb_sectors, QEMUIOVector *qiov) { diff --git a/include/block/nbd.h b/include/block/nbd.h index b86a976984..36dde24e51 100644 --- a/include/block/nbd.h +++ b/include/block/nbd.h @@ -76,6 +76,7 @@ enum { /* Maximum size of a single READ/WRITE data buffer */ #define NBD_MAX_BUFFER_SIZE (32 * 1024 * 1024) +#define NBD_MAX_SECTORS (NBD_MAX_BUFFER_SIZE / BDRV_SECTOR_SIZE) ssize_t nbd_wr_syncv(QIOChannel *ioc, struct iovec *iov, -- 2.11.4.GIT