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-rw-r--r--mm/filemap.c51
1 files changed, 26 insertions, 25 deletions
diff --git a/mm/filemap.c b/mm/filemap.c
index 750e779c23db..4a30de98a8c7 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -4111,28 +4111,40 @@ static void filemap_cachestat(struct address_space *mapping,
rcu_read_lock();
xas_for_each(&xas, folio, last_index) {
+ int order;
unsigned long nr_pages;
pgoff_t folio_first_index, folio_last_index;
+ /*
+ * Don't deref the folio. It is not pinned, and might
+ * get freed (and reused) underneath us.
+ *
+ * We *could* pin it, but that would be expensive for
+ * what should be a fast and lightweight syscall.
+ *
+ * Instead, derive all information of interest from
+ * the rcu-protected xarray.
+ */
+
if (xas_retry(&xas, folio))
continue;
+ order = xa_get_order(xas.xa, xas.xa_index);
+ nr_pages = 1 << order;
+ folio_first_index = round_down(xas.xa_index, 1 << order);
+ folio_last_index = folio_first_index + nr_pages - 1;
+
+ /* Folios might straddle the range boundaries, only count covered pages */
+ if (folio_first_index < first_index)
+ nr_pages -= first_index - folio_first_index;
+
+ if (folio_last_index > last_index)
+ nr_pages -= folio_last_index - last_index;
+
if (xa_is_value(folio)) {
/* page is evicted */
void *shadow = (void *)folio;
bool workingset; /* not used */
- int order = xa_get_order(xas.xa, xas.xa_index);
-
- nr_pages = 1 << order;
- folio_first_index = round_down(xas.xa_index, 1 << order);
- folio_last_index = folio_first_index + nr_pages - 1;
-
- /* Folios might straddle the range boundaries, only count covered pages */
- if (folio_first_index < first_index)
- nr_pages -= first_index - folio_first_index;
-
- if (folio_last_index > last_index)
- nr_pages -= folio_last_index - last_index;
cs->nr_evicted += nr_pages;
@@ -4150,24 +4162,13 @@ static void filemap_cachestat(struct address_space *mapping,
goto resched;
}
- nr_pages = folio_nr_pages(folio);
- folio_first_index = folio_pgoff(folio);
- folio_last_index = folio_first_index + nr_pages - 1;
-
- /* Folios might straddle the range boundaries, only count covered pages */
- if (folio_first_index < first_index)
- nr_pages -= first_index - folio_first_index;
-
- if (folio_last_index > last_index)
- nr_pages -= folio_last_index - last_index;
-
/* page is in cache */
cs->nr_cache += nr_pages;
- if (folio_test_dirty(folio))
+ if (xas_get_mark(&xas, PAGECACHE_TAG_DIRTY))
cs->nr_dirty += nr_pages;
- if (folio_test_writeback(folio))
+ if (xas_get_mark(&xas, PAGECACHE_TAG_WRITEBACK))
cs->nr_writeback += nr_pages;
resched: