From: Eric Blake Date: Thu, 23 Jun 2016 22:37:08 +0000 (-0600) Subject: nbd: Allow larger requests X-Git-Tag: v2.7.0-rc0~57^2~38 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=476b923c32ece0e268580776aaf1fab4ab4459a8;p=thirdparty%2Fqemu.git 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 --- diff --git a/block/nbd-client.c b/block/nbd-client.c index 4d13444409c..420bce89f3f 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 df1f8043386..eeda3ebdf7b 100644 --- a/include/block/nbd.h +++ b/include/block/nbd.h @@ -77,6 +77,8 @@ 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) + /* Maximum size of an export name. The NBD spec requires 256 and * suggests that servers support up to 4096, but we stick to only the * required size so that we can stack-allocate the names, and because