qemu/qemu-v2-block-avoid-creating-too-large-iovecs-in-multiwrite_merge.patch
Justin M. Forbes 563054a863 - Avoid creating too large iovecs in multiwrite merge (#559717)
- Don't try to set max_kernel_pages during ksm init on newer kernels
    (#558281)
- Add logfile options for ksmtuned debug.
2010-02-04 15:58:29 +00:00

42 lines
1.4 KiB
Diff

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 <hch@lst.de>
Index: qemu/block.c
===================================================================
--- qemu.orig/block.c 2010-01-26 10:59:39.757004445 +0100
+++ qemu/block.c 2010-01-26 11:01:38.056023231 +0100
@@ -1689,6 +1689,10 @@ static int multiwrite_merge(BlockDriverS
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));
Index: qemu/qemu-common.h
===================================================================
--- qemu.orig/qemu-common.h 2010-01-26 14:41:40.894254285 +0100
+++ qemu/qemu-common.h 2010-01-26 14:42:27.267275698 +0100
@@ -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 <sys/uio.h>
#endif