[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <ZdeAys9D98RBaPL1@casper.infradead.org>
Date: Thu, 22 Feb 2024 17:13:46 +0000
From: Matthew Wilcox <willy@...radead.org>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v1] mm: remove total_mapcount()
On Thu, Feb 22, 2024 at 05:09:43PM +0100, David Hildenbrand wrote:
> We always get a head page, so we can just naturally interpret is as a folio
> (similar to other code).
memfd seems rather confused about how to iterate over the page cache.
Perhaps we could sort that out and then delete total_mapcount as a
second patch?
I haven't tested this at all, but ...
Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
diff --git a/mm/memfd.c b/mm/memfd.c
index d3a1ba4208c9..45e55b0e3cbe 100644
--- a/mm/memfd.c
+++ b/mm/memfd.c
@@ -29,28 +29,29 @@
#define MEMFD_TAG_PINNED PAGECACHE_TAG_TOWRITE
#define LAST_SCAN 4 /* about 150ms max */
+static bool memfd_extra_refs(struct folio *folio)
+{
+ return folio_ref_count(folio) - folio_mapcount(folio) !=
+ folio_nr_pages(folio);
+}
+
static void memfd_tag_pins(struct xa_state *xas)
{
- struct page *page;
+ struct folio *folio;
int latency = 0;
- int cache_count;
lru_add_drain();
xas_lock_irq(xas);
- xas_for_each(xas, page, ULONG_MAX) {
- cache_count = 1;
- if (!xa_is_value(page) &&
- PageTransHuge(page) && !PageHuge(page))
- cache_count = HPAGE_PMD_NR;
-
- if (!xa_is_value(page) &&
- page_count(page) - total_mapcount(page) != cache_count)
+ xas_for_each(xas, folio, ULONG_MAX) {
+ /* Can we have shadow/swap entries in memfd? */
+ if (xa_is_value(folio))
+ continue;
+
+ if (memfd_extra_refs(folio))
xas_set_mark(xas, MEMFD_TAG_PINNED);
- if (cache_count != 1)
- xas_set(xas, page->index + cache_count);
- latency += cache_count;
+ latency++;
if (latency < XA_CHECK_SCHED)
continue;
latency = 0;
@@ -75,7 +76,6 @@ static void memfd_tag_pins(struct xa_state *xas)
static int memfd_wait_for_pins(struct address_space *mapping)
{
XA_STATE(xas, &mapping->i_pages, 0);
- struct page *page;
int error, scan;
memfd_tag_pins(&xas);
@@ -83,7 +83,7 @@ static int memfd_wait_for_pins(struct address_space *mapping)
error = 0;
for (scan = 0; scan <= LAST_SCAN; scan++) {
int latency = 0;
- int cache_count;
+ struct folio *folio;
if (!xas_marked(&xas, MEMFD_TAG_PINNED))
break;
@@ -95,16 +95,10 @@ static int memfd_wait_for_pins(struct address_space *mapping)
xas_set(&xas, 0);
xas_lock_irq(&xas);
- xas_for_each_marked(&xas, page, ULONG_MAX, MEMFD_TAG_PINNED) {
+ xas_for_each_marked(&xas, folio, ULONG_MAX, MEMFD_TAG_PINNED) {
bool clear = true;
- cache_count = 1;
- if (!xa_is_value(page) &&
- PageTransHuge(page) && !PageHuge(page))
- cache_count = HPAGE_PMD_NR;
-
- if (!xa_is_value(page) && cache_count !=
- page_count(page) - total_mapcount(page)) {
+ if (memfd_extra_refs(folio)) {
/*
* On the last scan, we clean up all those tags
* we inserted; but make a note that we still
@@ -118,8 +112,7 @@ static int memfd_wait_for_pins(struct address_space *mapping)
if (clear)
xas_clear_mark(&xas, MEMFD_TAG_PINNED);
- latency += cache_count;
- if (latency < XA_CHECK_SCHED)
+ if (++latency < XA_CHECK_SCHED)
continue;
latency = 0;
Powered by blists - more mailing lists