Commit 46d6a9b4 authored by David Hildenbrand's avatar David Hildenbrand Committed by Andrew Morton
Browse files

mm/migrate: convert do_pages_stat_array() from follow_page() to folio_walk 

Let's use folio_walk instead, so we can avoid taking a folio reference
just to read the nid and get rid of another follow_page()/FOLL_DUMP user. 
Use FW_ZEROPAGE so we can return "-EFAULT" for it as documented.

The possible return values for follow_page() were confusing, especially
with FOLL_DUMP set.  We'll handle it like documented in the man page:

* -EFAULT: This is a zero page or the memory area is not mapped by the
   process.
* -ENOENT: The page is not present.

We'll keep setting -ENOENT for ZONE_DEVICE.  Maybe not the right thing to
do, but it likely doesn't really matter (just like for weird devmap,
whereby we fake "not present").

Note that the other errors (-EACCESS, -EBUSY, -EIO, -EINVAL, -ENOMEM) so
far only applied when actually moving pages, not when only querying stats.

We'll effectively drop the "secretmem" check we had in follow_page(), but
that shouldn't really matter here, we're not accessing folio/page content
after all.

Link: https://lkml.kernel.org/r/20240802155524.517137-4-david@redhat.com


Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Janosch Frank <frankja@linux.ibm.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent aa39ca69

mm/migrate.c

+15 −16
Original line number Diff line number Diff line
@@ -50,6 +50,7 @@ 
#include <linux/random.h>

#include <linux/sched/sysctl.h>

#include <linux/memory-tiers.h>

#include <linux/pagewalk.h>



#include <asm/tlbflush.h>
@@ -2331,28 +2332,26 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages, 
	for (i = 0; i < nr_pages; i++) {

		unsigned long addr = (unsigned long)(*pages);

		struct vm_area_struct *vma;

		struct page *page;

		struct folio_walk fw;

		struct folio *folio;

		int err = -EFAULT;



		vma = vma_lookup(mm, addr);

		if (!vma)

			goto set_status;



		/* FOLL_DUMP to ignore special (like zero) pages */

		page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);



		err = PTR_ERR(page);

		if (IS_ERR(page))

			goto set_status;



		folio = folio_walk_start(&fw, vma, addr, FW_ZEROPAGE);

		if (folio) {

			if (is_zero_folio(folio) || is_huge_zero_folio(folio))

				err = -EFAULT;

			else if (folio_is_zone_device(folio))

				err = -ENOENT;

		if (!page)

			goto set_status;



		if (!is_zone_device_page(page))

			err = page_to_nid(page);



		put_page(page);

			else

				err = folio_nid(folio);

			folio_walk_end(&fw, vma);

		} else {

			err = -ENOENT;

		}

set_status:

		*status = err;