From e2a305fb13ff0f5cf6ff805555aaa90a5ed5954c 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(+) diff --git a/block.c b/block.c index 9c106a8e4d..1919d19732 100644 --- a/block.c +++ b/block.c @@ -1691,6 +1691,10 @@ 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 ae4f23b8e8..b09f71757a 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