Re: hugetlbfs not working

Marcelo Tosatti
2008-03-31T17:01:08Z

On Fri, Mar 28, 2008 at 09:41:06AM +0300, Avi Kivity wrote:
> >mmap() should fail if anything goes wrong with ftruncate and the file
> >length is not extented on tmpfs.
> >
> >--- vl.c.orig 2008-03-27 18:51:31.000000000 -0300
> >+++ vl.c 2008-03-27 18:52:40.000000000 -0300
> >@@ -8749,11 +8749,7 @@
> >
> > memory = (memory+hpagesize-1) & ~(hpagesize-1);
> >
> >- if (ftruncate(fd, memory) == -1) {
> >- perror("ftruncate");
> >- close(fd);
> >- return NULL;
> >- }
> >+ ftruncate(fd, memory);
> >
>
> I'm sure a patch will follow to add a missing error check, so how about
> a comment here?
>
> btw, we use signoffs on kvm-userspace, too.

QEMU/KVM: ftruncate() is not supported by hugetlbfs on older hosts

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/qemu/vl.c b/qemu/vl.c
index 5627862..6a240bf 100644
--- a/qemu/vl.c
+++ b/qemu/vl.c
@@ -8739,11 +8739,13 @@ void *alloc_mem_area(unsigned long memory, const char *path)

memory = (memory+hpagesize-1) & ~(hpagesize-1);

- if (ftruncate(fd, memory) == -1) {
- perror("ftruncate");
- close(fd);
- return NULL;
- }
+ /*
+ * ftruncate is not supported by hugetlbfs in older
+ * hosts, so don't bother checking for errors.
+ * If anything goes wrong with it under other filesystems,
+ * mmap will fail.
+ */
+ ftruncate(fd, memory);

area = mmap(0, memory, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0);
if (area == MAP_FAILED) {