On 25.02.24 08:56, Vivek Kasireddy wrote:
This helper is the folio equivalent of check_and_migrate_movable_pages().
Therefore, all the rules that apply to check_and_migrate_movable_pages()
also apply to this one as well. Currently, this helper is only used by
memfd_pin_folios().
This patch also includes changes to rename and convert the internal
functions collect_longterm_unpinnable_pages() and
migrate_longterm_unpinnable_pages() to work on folios. Since they
are also used by check_and_migrate_movable_pages(), a temporary
array is used to collect and share the folios with these functions.
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@xxxxxxxxx>
---
mm/gup.c | 129 +++++++++++++++++++++++++++++++++++++++----------------
1 file changed, 92 insertions(+), 37 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c
index 0a45eda6aaeb..1410af954a4e 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2099,20 +2099,24 @@ struct page *get_dump_page(unsigned long addr)
#ifdef CONFIG_MIGRATION
/*
- * Returns the number of collected pages. Return value is always >= 0.
+ * Returns the number of collected folios. Return value is always >= 0.
*/
-static unsigned long collect_longterm_unpinnable_pages(
- struct list_head *movable_page_list,
- unsigned long nr_pages,
+static unsigned long collect_longterm_unpinnable_folios(
+ struct list_head *movable_folio_list,
+ unsigned long nr_folios,
+ struct folio **folios,
struct page **pages)
This function really shouldn't consume both folios and pages.
Either use "folios" and handle the conversion from pages->folios in the
caller, or handle it similar to release_pages() where we can pass either
and simply always do page_folio() on the given pointer, using
essentially an abstracted pointer type and always calling page_folio()
on that thing.
The easiest is likely to just do the page->folio conversion in the
caller by looping over the arrays once more. See below.
Temporary memory allocation can be avoided by using an abstracted
pointer type.
[...]
+ folio = folios[i];
if (folio == prev_folio)
continue;
prev_folio = folio;
@@ -2126,7 +2130,7 @@ static unsigned long collect_longterm_unpinnable_pages(
continue;
if (folio_test_hugetlb(folio)) {
- isolate_hugetlb(folio, movable_page_list);
+ isolate_hugetlb(folio, movable_folio_list);
continue;
}
@@ -2138,7 +2142,7 @@ static unsigned long collect_longterm_unpinnable_pages(
if (!folio_isolate_lru(folio))
continue;
- list_add_tail(&folio->lru, movable_page_list);
+ list_add_tail(&folio->lru, movable_folio_list);
node_stat_mod_folio(folio,
NR_ISOLATED_ANON + folio_is_file_lru(folio),
folio_nr_pages(folio));
@@ -2148,27 +2152,28 @@ static unsigned long collect_longterm_unpinnable_pages(
}
/*
- * Unpins all pages and migrates device coherent pages and movable_page_list.
- * Returns -EAGAIN if all pages were successfully migrated or -errno for failure
- * (or partial success).
+ * Unpins all folios and migrates device coherent folios and movable_folio_list.
+ * Returns -EAGAIN if all folios were successfully migrated or -errno for
+ * failure (or partial success).
*/
-static int migrate_longterm_unpinnable_pages(
- struct list_head *movable_page_list,
- unsigned long nr_pages,
- struct page **pages)
+static int migrate_longterm_unpinnable_folios(
+ struct list_head *movable_folio_list,
+ unsigned long nr_folios,
+ struct folio **folios)
{
int ret;
unsigned long i;
- for (i = 0; i < nr_pages; i++) {
- struct folio *folio = page_folio(pages[i]);
+ for (i = 0; i < nr_folios; i++) {
+ struct folio *folio = folios[i];
if (folio_is_device_coherent(folio)) {
/*
- * Migration will fail if the page is pinned, so convert
- * the pin on the source page to a normal reference.
+ * Migration will fail if the folio is pinned, so
+ * convert the pin on the source folio to a normal
+ * reference.
*/
- pages[i] = NULL;
+ folios[i] = NULL;
folio_get(folio);
gup_put_folio(folio, 1, FOLL_PIN);
@@ -2181,23 +2186,23 @@ static int migrate_longterm_unpinnable_pages(
}
/*
- * We can't migrate pages with unexpected references, so drop
+ * We can't migrate folios with unexpected references, so drop
* the reference obtained by __get_user_pages_locked().
- * Migrating pages have been added to movable_page_list after
+ * Migrating folios have been added to movable_folio_list after
* calling folio_isolate_lru() which takes a reference so the
- * page won't be freed if it's migrating.
+ * folio won't be freed if it's migrating.
*/
- unpin_user_page(pages[i]);
- pages[i] = NULL;
+ unpin_folio(folios[i]);
Aha, that's where you call unpin_folio() on an anon folio. Then simply
drop the sanity check from inside unpin_folio() in patch #1.
+ folios[i] = NULL;
}
- if (!list_empty(movable_page_list)) {
+ if (!list_empty(movable_folio_list)) {
struct migration_target_control mtc = {
.nid = NUMA_NO_NODE,
.gfp_mask = GFP_USER | __GFP_NOWARN,
};
- if (migrate_pages(movable_page_list, alloc_migration_target,
+ if (migrate_pages(movable_folio_list, alloc_migration_target,
NULL, (unsigned long)&mtc, MIGRATE_SYNC,
MR_LONGTERM_PIN, NULL)) {
ret = -ENOMEM;
@@ -2205,15 +2210,15 @@ static int migrate_longterm_unpinnable_pages(
}
}
- putback_movable_pages(movable_page_list);
+ putback_movable_pages(movable_folio_list);
This really needs a cleanup (independent of your work). We should rename
it to putback_movable_folios: it only operates on folios.
return -EAGAIN;
err:
- for (i = 0; i < nr_pages; i++)
- if (pages[i])
- unpin_user_page(pages[i]);
- putback_movable_pages(movable_page_list);
+ for (i = 0; i < nr_folios; i++)
+ if (folios[i])
+ unpin_folio(folios[i]);
Can unpin_folios() be used?
+ putback_movable_pages(movable_folio_list);
return ret;
}
@@ -2237,16 +2242,60 @@ static int migrate_longterm_unpinnable_pages(
static long check_and_migrate_movable_pages(unsigned long nr_pages,
struct page **pages)
{
+ unsigned long nr_folios = nr_pages;
unsigned long collected;
- LIST_HEAD(movable_page_list);
+ LIST_HEAD(movable_folio_list);
+ struct folio **folios;
+ long ret;
- collected = collect_longterm_unpinnable_pages(&movable_page_list,
- nr_pages, pages);
+ folios = kmalloc_array(nr_folios, sizeof(*folios), GFP_KERNEL);
+ if (!folios)
+ return -ENOMEM;
+
+ collected = collect_longterm_unpinnable_folios(&movable_folio_list,
+ nr_folios, folios,
+ pages);
+ if (!collected) {
+ kfree(folios);
+ return 0;
+ }
+
+ ret = migrate_longterm_unpinnable_folios(&movable_folio_list,
+ nr_folios, folios);
+ kfree(folios);
+ return ret;
This function should likely be a pure rapper around
check_and_migrate_movable_folios(). For example:
static long check_and_migrate_movable_pages(unsigned long nr_pages,
struct page **pages)
{
struct folio **folios;
long ret;
folios = kmalloc_array(nr_folios, sizeof(*folios), GFP_KERNEL);
if (!folios)
return -ENOMEM;
/* TODO, convert all pages to folios. */
ret = check_and_migrate_movable_folios(nr_folios, folios);
kfree(folios);
return ret;
}
+}
+
+/*
+ * Check whether all folios are *allowed* to be pinned. Rather confusingly, all
... "to be pinned possibly forever ("longterm")".
+ * folios in the range are required to be pinned via FOLL_PIN, before calling
+ * this routine.
+ *
+ * If any folios in the range are not allowed to be pinned, then this routine
+ * will migrate those folios away, unpin all the folios in the range and return
+ * -EAGAIN. The caller should re-pin the entire range with FOLL_PIN and then
+ * call this routine again.
+ *
[...]
--
Cheers,
David / dhildenb
