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Commit da391d64 authored by William Kucharski's avatar William Kucharski Committed by Linus Torvalds
Browse files

mm: correct comments regarding do_fault_around() 

There are multiple comments surrounding do_fault_around that memtion
fault_around_pages() and fault_around_mask(), two routines that do not
exist.  These comments should be reworded to reference
fault_around_bytes, the value which is used to determine how much
do_fault_around() will attempt to read when processing a fault.

These comments should have been updated when fault_around_pages() and
fault_around_mask() were removed in commit aecd6f44 ("mm: close race
between do_fault_around() and fault_around_bytes_set()").

Fixes: aecd6f44 ("mm: close race between do_fault_around() and fault_around_bytes_set()")
Link: http://lkml.kernel.org/r/302D0B14-C7E9-44C6-8BED-033F9ACBD030@oracle.com


Signed-off-by: default avatarWilliam Kucharski <william.kucharski@oracle.com>
Reviewed-by: default avatarLarry Bassel <larry.bassel@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 859d4adc

mm/memory.c

+11 −11
Original line number Diff line number Diff line
@@ -3511,9 +3511,8 @@ static int fault_around_bytes_get(void *data, u64 *val) 
}



/*

 * fault_around_pages() and fault_around_mask() expects fault_around_bytes

 * rounded down to nearest page order. It's what do_fault_around() expects to

 * see.

 * fault_around_bytes must be rounded down to the nearest page order as it's

 * what do_fault_around() expects to see.

 */

static int fault_around_bytes_set(void *data, u64 val)

{
@@ -3556,13 +3555,14 @@ late_initcall(fault_around_debugfs); 
 * This function doesn't cross the VMA boundaries, in order to call map_pages()

 * only once.

 *

 * fault_around_pages() defines how many pages we'll try to map.

 * do_fault_around() expects it to return a power of two less than or equal to

 * PTRS_PER_PTE.

 * fault_around_bytes defines how many bytes we'll try to map.

 * do_fault_around() expects it to be set to a power of two less than or equal

 * to PTRS_PER_PTE.

 *

 * The virtual address of the area that we map is naturally aligned to the

 * fault_around_pages() value (and therefore to page order).  This way it's

 * easier to guarantee that we don't cross page table boundaries.

 * The virtual address of the area that we map is naturally aligned to

 * fault_around_bytes rounded down to the machine page size

 * (and therefore to page order).  This way it's easier to guarantee

 * that we don't cross page table boundaries.

 */

static int do_fault_around(struct vm_fault *vmf)

{
@@ -3579,8 +3579,8 @@ static int do_fault_around(struct vm_fault *vmf) 
	start_pgoff -= off;



	/*

	 *  end_pgoff is either end of page table or end of vma

	 *  or fault_around_pages() from start_pgoff, depending what is nearest.

	 *  end_pgoff is either the end of the page table, the end of

	 *  the vma or nr_pages from start_pgoff, depending what is nearest.

	 */

	end_pgoff = start_pgoff -

		((vmf->address >> PAGE_SHIFT) & (PTRS_PER_PTE - 1)) +