From c0c1147350005b47068285a288f848cf75eb60c6 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Tue, 26 Jan 2010 14:49:08 +0100 Subject: [PATCH] block: avoid creating too large iovecs in multiwrite_merge If we go over the maximum number of iovecs support by syscall we get back EINVAL from the kernel which translate to I/O errors for the guest. Add a MAX_IOV defintion for platforms that don't have it. For now we use the same 1024 define that's used on Linux and various other platforms, but until the windows block backend implements some kind of vectored I/O it doesn't matter. Signed-off-by: Christoph Hellwig Signed-off-by: Anthony Liguori --- block.c | 4 ++++ qemu-common.h | 4 ++++ 2 files changed, 8 insertions(+), 0 deletions(-) diff --git a/block.c b/block.c index 97af3f5..9697dc9 100644 --- a/block.c +++ b/block.c @@ -1669,6 +1669,10 @@ static int multiwrite_merge(BlockDriverState *bs, BlockRequest *reqs, merge = bs->drv->bdrv_merge_requests(bs, &reqs[outidx], &reqs[i]); } + if (reqs[outidx].qiov->niov + reqs[i].qiov->niov + 1 > IOV_MAX) { + merge = 0; + } + if (merge) { size_t size; QEMUIOVector *qiov = qemu_mallocz(sizeof(*qiov)); diff --git a/qemu-common.h b/qemu-common.h index 1c5c0b2..b604ddf 100644 --- a/qemu-common.h +++ b/qemu-common.h @@ -54,6 +54,10 @@ struct iovec { void *iov_base; size_t iov_len; }; +/* + * Use the same value as Linux for now. + */ +#define IOV_MAX 1024 #else #include #endif -- 1.6.6.1