From 36ac1b2b346c41910838f5d1b27d34a4ce68b616 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Wed, 27 Jan 2010 17:19:59 -0200 Subject: [PATCH 9/9] block: avoid creating too large iovecs in multiwrite_merge RH-Author: Christoph Hellwig Message-id: <1264612799.20444.11.camel@brick.lst.de> Patchwork-id: 6722 O-Subject: [RHEL6 PATCH] block: avoid creating too large iovecs in multiwrite_merge Bugzilla: 558730 RH-Acked-by: Kevin Wolf RH-Acked-by: Markus Armbruster RH-Acked-by: Juan Quintela Backport of upstream commit e2a305fb13ff0f5cf6ff805555aaa90a5ed5954c to fix bugzilla 558730. 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: Eduardo Habkost --- block.c | 4 ++++ qemu-common.h | 4 ++++ 2 files changed, 8 insertions(+), 0 deletions(-) diff --git a/block.c b/block.c index faff40e..a0d9c41 100644 --- a/block.c +++ b/block.c @@ -1687,6 +1687,10 @@ 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 5fbe0f9..8ba7ed6 100644 --- a/qemu-common.h +++ b/qemu-common.h @@ -53,6 +53,10 @@ struct iovec { void *iov_base; size_t iov_len; }; +/* + * Use the same value as Linux for now. + */ +#define IOV_MAX 1024 #else #include #endif -- 1.6.3.rc4.29.g8146