Hi Joern，
On 2013/6/19 2:47, Joern Engel wrote:
> It is counterintuitive at best that mmap'ing a hugetlbfs file with
> MAP_HUGETLB fails, while mmap'ing it without will a) succeed and b)
> return huge pages.
>
> Signed-off-by: Joern Engel <joern@xxxxxxxxx>
> ---
> mm/mmap.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 2a594246..76eb6df 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -33,6 +33,7 @@
> #include <linux/uprobes.h>
> #include <linux/rbtree_augmented.h>
> #include <linux/sched/sysctl.h>
> +#include <linux/magic.h>
>
> #include <asm/uaccess.h>
> #include <asm/cacheflush.h>
> @@ -1313,6 +1314,11 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
> return addr;
> }
>
> +static inline int is_hugetlb_file(struct file *file)
> +{
> + return file->f_inode->i_sb->s_magic == HUGETLBFS_MAGIC;
> +}
> +
> SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
> unsigned long, prot, unsigned long, flags,
> unsigned long, fd, unsigned long, pgoff)
> @@ -1322,11 +1328,12 @@ SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
>
> if (!(flags & MAP_ANONYMOUS)) {
> audit_mmap_fd(fd, flags);
> - if (unlikely(flags & MAP_HUGETLB))
> - return -EINVAL;
> file = fget(fd);
> if (!file)
> goto out;
> + retval = -EINVAL;
> + if (unlikely(flags & MAP_HUGETLB && !is_hugetlb_file(file)))
We already have is_file_hugepages().
Thanks,
Jianguo Wu
> + goto out_fput;
> } else if (flags & MAP_HUGETLB) {
> struct user_struct *user = NULL;
> /*
> @@ -1346,6 +1353,7 @@ SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
> flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
>
> retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
> +out_fput:
> if (file)
> fput(file);
> out:
--
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