On Sat 12-10-19 18:25:12, Gaowei Pu wrote:
> get_unmapped_area already cover the offset_in_page() check and returned
> with error ptr. So replace offset_in_page() with IS_ERR_VALUE().
I have to say that I found offset_in_page check quite unintuitive. It is
a relict from the past I suspect. A newer code seems to use
IS_ERR_VALUE. If we want to make the code consistent then I am for it.
Could you check other users as well? git grep suggests checking
kernel/events/uprobes.c, mm/mmap.c and mm/mremap.c.
I would simply use the following for the changelog
"
get_unmapped_area returns an address or -errno on failure. Historically
we have checked for the failure by offset_in_page() which is correct but
quite hard to read. Newer code started using IS_ERR_VALUE which is much
easier to read. Convert remaining users of offset_in_page as well.
This shouldn't introduce any functional changes.
"
> Signed-off-by: Gaowei Pu <pugaowei@xxxxxxxxx>
>
> V2: fix compile warnning.
> ---
> mm/mmap.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 7e8c3e8ae75f..6aebfeb6a486 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1430,7 +1430,7 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
> * that it represents a valid section of the address space.
> */
> addr = get_unmapped_area(file, addr, len, pgoff, flags);
> - if (offset_in_page(addr))
> + if (IS_ERR_VALUE(addr))
> return addr;
>
> if (flags & MAP_FIXED_NOREPLACE) {
> @@ -2990,15 +2990,16 @@ static int do_brk_flags(unsigned long addr, unsigned long len, unsigned long fla
> struct rb_node **rb_link, *rb_parent;
> pgoff_t pgoff = addr >> PAGE_SHIFT;
> int error;
> + unsigned long mapped_addr;
>
> /* Until we need other flags, refuse anything except VM_EXEC. */
> if ((flags & (~VM_EXEC)) != 0)
> return -EINVAL;
> flags |= VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
>
> - error = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED);
> - if (offset_in_page(error))
> - return error;
> + mapped_addr = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED);
> + if (IS_ERR_VALUE(mapped_addr))
> + return mapped_addr;
>
> error = mlock_future_check(mm, mm->def_flags, len);
> if (error)
> --
> 2.23.0
>
--
Michal Hocko
SUSE Labs
