Re: [Qemu-devel] [PATCH v6 07/33] util: introduce qemu_file_get_page_size()

[Xiao Guangrong]

On 11/09/2015 06:33 PM, Michael S. Tsirkin wrote:
> On Fri, Oct 30, 2015 at 01:56:01PM +0800, Xiao Guangrong wrote:
> > There are three places use the some logic to get the page size on
> > the file path or file fd
> >
> > This patch introduces qemu_file_get_page_size() to unify the code
> >
> > Signed-off-by: Xiao Guangrong <address@hidden>
> > ---
> >   include/qemu/osdep.h |  1 +
> >   target-ppc/kvm.c     | 21 +++------------------
> >   util/oslib-posix.c   | 16 ++++++++++++++++
> >   util/oslib-win32.c   |  5 +++++
> >   4 files changed, 25 insertions(+), 18 deletions(-)
> >
> > diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> > index b568424..d4dde02 100644
> > --- a/include/qemu/osdep.h
> > +++ b/include/qemu/osdep.h
> > @@ -302,4 +302,5 @@ int qemu_read_password(char *buf, int buf_size);
> >    */
> >   pid_t qemu_fork(Error **errp);
> >
> > +size_t qemu_file_get_page_size(const char *mem_path);
> >   #endif
> > diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
> > index ac70f08..c661f1c 100644
> > --- a/target-ppc/kvm.c
> > +++ b/target-ppc/kvm.c
> > @@ -308,28 +308,13 @@ static void kvm_get_smmu_info(PowerPCCPU *cpu, struct 
> > kvm_ppc_smmu_info *info)
> >
> >   static long gethugepagesize(const char *mem_path)
> >   {
> > -    struct statfs fs;
> > -    int ret;
> > -
> > -    do {
> > -        ret = statfs(mem_path, &fs);
> > -    } while (ret != 0 && errno == EINTR);
> > +    long size = qemu_file_get_page_size(mem_path);
> >
> > -    if (ret != 0) {
> > -        fprintf(stderr, "Couldn't statfs() memory path: %s\n",
> > -                strerror(errno));
> > +    if (!size) {
> >           exit(1);
> >       }
> >
> > -#define HUGETLBFS_MAGIC       0x958458f6
> > -
> > -    if (fs.f_type != HUGETLBFS_MAGIC) {
> > -        /* Explicit mempath, but it's ordinary pages */
> > -        return getpagesize();
> > -    }
> > -
> > -    /* It's hugepage, return the huge page size */
> > -    return fs.f_bsize;
> > +    return size;
> >   }
> >
> >   static int find_max_supported_pagesize(Object *obj, void *opaque)
> > diff --git a/util/oslib-posix.c b/util/oslib-posix.c
> > index 914cef5..ad94c5a 100644
> > --- a/util/oslib-posix.c
> > +++ b/util/oslib-posix.c
> > @@ -360,6 +360,22 @@ static size_t fd_getpagesize(int fd)
> >       return getpagesize();
> >   }
> >
> > +size_t qemu_file_get_page_size(const char *path)
> > +{
> > +    size_t size = 0;
> > +    int fd = qemu_open(path, O_RDONLY);
> > +
> > +    if (fd < 0) {
> > +        fprintf(stderr, "Could not open %s.\n", path);
> > +        goto exit;
> > +    }
> > +
> > +    size = fd_getpagesize(fd);
> > +    qemu_close(fd);
> > +exit:
> > +    return size;
> > +}
> > +
> >   void os_mem_prealloc(int fd, char *area, size_t memory)
> >   {
> >       int ret;
>
> So this is opening the file for the sole purpose of
> doing the fstatfs on it. Seems strange, just do statfs instead.
> In fact, maybe we want statfs_getpagesize.

It is just to reuse the code of fd_getpagesize() which already has
the logic to check pagesize.

> > diff --git a/util/oslib-win32.c b/util/oslib-win32.c
> > index 09f9e98..a18aa87 100644
> > --- a/util/oslib-win32.c
> > +++ b/util/oslib-win32.c
> > @@ -462,6 +462,11 @@ size_t getpagesize(void)
> >       return system_info.dwPageSize;
> >   }
> >
> > +size_t qemu_file_get_page_size(const char *path)
> > +{
> > +    return getpagesize();
> > +}
> > +
> >   void os_mem_prealloc(int fd, char *area, size_t memory)
> >   {
> >       int i;
>
> And why is this needed on win32?

It is not actually used, just make osdep.h happy which has
qemu_file_get_page_size() declare.

BTW, i will drop this patch for now on.