Re: [Qemu-devel] [PATCH 01/38] exec: Fix memory allocation when memory path names new file

[Paolo Bonzini]

On 04/03/2016 19:50, Markus Armbruster wrote:
> There's another one in ivshmem_server.c, functionally identical and
> wrapped in CONFIG_LINUX.

Not quite identical, since it returns -1 for non-hugetlbfs.  It should
return getpagesize().

> Here's exec.c's:
> 
>     #define HUGETLBFS_MAGIC       0x958458f6
> 
>     static long gethugepagesize(const char *path, Error **errp)
>     {
>         struct statfs fs;
>         int ret;
> 
>         do {
>             ret = statfs(path, &fs);
>         } while (ret != 0 && errno == EINTR);
> 
>         if (ret != 0) {
>             error_setg_errno(errp, errno, "failed to get page size of file 
> %s",
>                              path);
>             return 0;
>         }
> 
>         return fs.f_bsize;
>     }
> 
> Before commit bfc2a1a, it additionally had
> 
>     if (fs.f_type != HUGETLBFS_MAGIC)
>         fprintf(stderr, "Warning: path not on HugeTLBFS: %s\n", path);
> 
> Note the lack of "if not hugetlbfs, use getpagesize()" logic.
> 
> Here's util/mmap-alloc.c's:
> 
>     #define HUGETLBFS_MAGIC       0x958458f6
> 
>     #ifdef CONFIG_LINUX
>     #include <sys/vfs.h>
>     #endif
> 
>     size_t qemu_fd_getpagesize(int fd)
>     {
>     #ifdef CONFIG_LINUX
>         struct statfs fs;
>         int ret;
> 
>         if (fd != -1) {
>             do {
>                 ret = fstatfs(fd, &fs);
>             } while (ret != 0 && errno == EINTR);
> 
>             if (ret == 0 && fs.f_type == HUGETLBFS_MAGIC) {
>                 return fs.f_bsize;
>             }
>         }
>     #endif
> 
>         return getpagesize();
>     }
> 
> Would you like me to convert the others users to this one and drop the
> dupes?

That would be great, since all of them really should use fstatfs instead
of statfs.

Paolo