Re: + mm-mmapc-use-is_err_value-to-check-return-value-of-get_unmapped_area.patch added to -mm tree

[Michal Hocko]

On Tue 15-10-19 13:48:19, Andrew Morton wrote:
> From: Gaowei Pu <pugaowei@xxxxxxxxx>
> Subject: mm/mmap.c: use IS_ERR_VALUE to check return value of get_unmapped_area
> 
> 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.
> 
> [mhocko@xxxxxxxx: rewrite changelog]
> Link: http://lkml.kernel.org/r/20191012102512.28051-1-pugaowei@xxxxxxxxx
> Signed-off-by: Gaowei Pu <pugaowei@xxxxxxxxx>
> Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Vlastimil Babka <vbabka@xxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>

Acked-by: Michal Hocko <mhocko@xxxxxxxx>

There are few more to convert

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 94d38a39d72e..9c197a26c0f4 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1448,7 +1448,7 @@ static int xol_add_vma(struct mm_struct *mm, struct xol_area *area)
 		/* Try to map as high as possible, this is only a hint. */
 		area->vaddr = get_unmapped_area(NULL, TASK_SIZE - PAGE_SIZE,
 						PAGE_SIZE, 0, 0);
-		if (area->vaddr & ~PAGE_MASK) {
+		if (IS_ERR_VALUE(area->vaddr)) {
 			ret = area->vaddr;
 			goto fail;
 		}
diff --git a/mm/mremap.c b/mm/mremap.c
index 1fc8a29fbe3f..122938dcec15 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -558,7 +558,7 @@ static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
 	ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
 				((addr - vma->vm_start) >> PAGE_SHIFT),
 				map_flags);
-	if (offset_in_page(ret))
+	if (IS_ERR_VALUE(ret))
 		goto out1;
 
 	ret = move_vma(vma, addr, old_len, new_len, new_addr, locked, uf,
@@ -706,7 +706,7 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
 					vma->vm_pgoff +
 					((addr - vma->vm_start) >> PAGE_SHIFT),
 					map_flags);
-		if (offset_in_page(new_addr)) {
+		if (IS_ERR_VALUE(new_addr)) {
 			ret = new_addr;
 			goto out;
 		}

and also few more to consider. e.g. move_vma return value checks. I
haven't checked other offset_in_page users.

> ---
> 
>  mm/mmap.c |    9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> --- a/mm/mmap.c~mm-mmapc-use-is_err_value-to-check-return-value-of-get_unmapped_area
> +++ a/mm/mmap.c
> @@ -1417,7 +1417,7 @@ unsigned long do_mmap(struct file *file,
>  	 * 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) {
> @@ -2996,15 +2996,16 @@ static int do_brk_flags(unsigned long ad
>  	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)
> _
> 
> Patches currently in -mm which might be from pugaowei@xxxxxxxxx are
> 
> mm-mmapc-use-is_err_value-to-check-return-value-of-get_unmapped_area.patch

-- 
Michal Hocko
SUSE Labs