Kernel/linux-stable
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git synced 2024-12-29 09:16:33 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

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

Browse Source 
Let's use folio_walk instead, so we can avoid taking a folio reference
when we won't even be trying to migrate the folio and to get rid of
another follow_page()/FOLL_DUMP user.  Use FW_ZEROPAGE so we can return
"-EFAULT" for it as documented.

We now perform the folio_likely_mapped_shared() check under PTL, which is
what we want: relying on the mapcount and friends after dropping the PTL
does not make too much sense, as the page can get unmapped concurrently
from this process.

Further, we perform the folio isolation under PTL, similar to how we
handle it for MADV_PAGEOUT.

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").

The other errros are left as is, and match the documentation in the man
page.

While at it, rename add_page_for_migration() to add_folio_for_migration().

We'll lose the "secretmem" check, but that shouldn't really matter because
these folios cannot ever be migrated.  Should vma_migratable() refuse
these VMAs?  Maybe.

Link: https://lkml.kernel.org/r/20240802155524.517137-5-david@redhat.com
Signed-off-by: David 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: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand 2024-08-02 17:55:17 +02:00 committed by Andrew Morton
parent 46d6a9b445
commit 7dff875c94
1 changed files with 47 additions and 57 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

104
mm/migrate.c
View File

@ -2112,76 +2112,66 @@ static int do_move_pages_to_node(struct list_head *pagelist, int node)
return err;
}
/*
* Resolves the given address to a struct page, isolates it from the LRU and
* puts it to the given pagelist.
* Returns:
* errno - if the page cannot be found/isolated
* 0 - when it doesn't have to be migrated because it is already on the
* target node
* 1 - when it has been queued
*/
static int add_page_for_migration(struct mm_struct *mm, const void __user *p,
int node, struct list_head *pagelist, bool migrate_all)
static int __add_folio_for_migration(struct folio *folio, int node,
struct list_head *pagelist, bool migrate_all)
{
struct vm_area_struct *vma;
unsigned long addr;
struct page *page;
struct folio *folio;
int err;
if (is_zero_folio(folio) || is_huge_zero_folio(folio))
return -EFAULT;
mmap_read_lock(mm);
addr = (unsigned long)untagged_addr_remote(mm, p);
err = -EFAULT;
vma = vma_lookup(mm, addr);
if (!vma || !vma_migratable(vma))
goto out;
/* 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 out;
err = -ENOENT;
if (!page)
goto out;
folio = page_folio(page);
if (folio_is_zone_device(folio))
goto out_putfolio;
return -ENOENT;
err = 0;
if (folio_nid(folio) == node)
goto out_putfolio;
return 0;
err = -EACCES;
if (folio_likely_mapped_shared(folio) && !migrate_all)
goto out_putfolio;
return -EACCES;
err = -EBUSY;
if (folio_test_hugetlb(folio)) {
if (isolate_hugetlb(folio, pagelist))
err = 1;
} else {
if (!folio_isolate_lru(folio))
goto out_putfolio;
err = 1;
return 1;
} else if (folio_isolate_lru(folio)) {
list_add_tail(&folio->lru, pagelist);
node_stat_mod_folio(folio,
NR_ISOLATED_ANON + folio_is_file_lru(folio),
folio_nr_pages(folio));
return 1;
}
return -EBUSY;
}
/*
* Resolves the given address to a struct folio, isolates it from the LRU and
* puts it to the given pagelist.
* Returns:
* errno - if the folio cannot be found/isolated
* 0 - when it doesn't have to be migrated because it is already on the
* target node
* 1 - when it has been queued
*/
static int add_folio_for_migration(struct mm_struct *mm, const void __user *p,
int node, struct list_head *pagelist, bool migrate_all)
{
struct vm_area_struct *vma;
struct folio_walk fw;
struct folio *folio;
unsigned long addr;
int err = -EFAULT;
mmap_read_lock(mm);
addr = (unsigned long)untagged_addr_remote(mm, p);
vma = vma_lookup(mm, addr);
if (vma && vma_migratable(vma)) {
folio = folio_walk_start(&fw, vma, addr, FW_ZEROPAGE);
if (folio) {
err = __add_folio_for_migration(folio, node, pagelist,
migrate_all);
folio_walk_end(&fw, vma);
} else {
err = -ENOENT;
}
}
out_putfolio:
/*
* Either remove the duplicate refcount from folio_isolate_lru()
* or drop the folio ref if it was not isolated.
*/
folio_put(folio);
out:
mmap_read_unlock(mm);
return err;
}
@ -2275,8 +2265,8 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
* Errors in the page lookup or isolation are not fatal and we simply
* report them via status
*/
err = add_page_for_migration(mm, p, current_node, &pagelist,
flags & MPOL_MF_MOVE_ALL);
err = add_folio_for_migration(mm, p, current_node, &pagelist,
flags & MPOL_MF_MOVE_ALL);
if (err > 0) {
/* The page is successfully queued for migration */