This is the equivalent of find_get_pages() but fills a folio_batch
instead of an array of pages.
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
include/linux/pagemap.h | 2 ++
mm/filemap.c | 55 +++++++++++++++++++++++++++++++++++++++++
2 files changed, 57 insertions(+)
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 5555689ea809..50e57b2d845f 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -718,6 +718,8 @@ static inline struct page *find_subpage(struct page *head, pgoff_t index)
return head + (index & (thp_nr_pages(head) - 1));
}
+unsigned filemap_get_folios(struct address_space *mapping, pgoff_t *start,
+ pgoff_t end, struct folio_batch *fbatch);
unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start,
pgoff_t end, unsigned int nr_pages,
struct page **pages);
diff --git a/mm/filemap.c b/mm/filemap.c
index 1e66eea98a7e..ea4145b7a84c 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2127,6 +2127,61 @@ unsigned find_lock_entries(struct address_space *mapping, pgoff_t start,
return folio_batch_count(fbatch);
}
+/**
+ * filemap_get_folios - Get a batch of folios
+ * @mapping: The address_space to search
+ * @start: The starting page index
+ * @end: The final page index (inclusive)
+ * @fbatch: The batch to fill.
+ *
+ * Search for and return a batch of folios in the mapping starting at
+ * index @start and up to index @end (inclusive). The folios are returned
+ * in @fbatch with an elevated reference count.
+ *
+ * The first folio may start before @start; if it does, it will contain
+ * @start. The final folio may extend beyond @end; if it does, it will
+ * contain @end. The folios have ascending indices. There may be gaps
+ * between the folios if there are indices which have no folio in the
+ * page cache. If folios are added to or removed from the page cache
+ * while this is running, they may or may not be found by this call.
+ *
+ * Return: The number of folios which were found.
+ * We also update @start to index the next folio for the traversal.
+ */
+unsigned filemap_get_folios(struct address_space *mapping, pgoff_t *start,
+ pgoff_t end, struct folio_batch *fbatch)
+{
+ XA_STATE(xas, &mapping->i_pages, *start);
+ struct folio *folio;
+
+ rcu_read_lock();
+ while ((folio = find_get_entry(&xas, end, XA_PRESENT)) != NULL) {
+ /* Skip over shadow, swap and DAX entries */
+ if (xa_is_value(folio))
+ continue;
+ if (!folio_batch_add(fbatch, folio)) {
+ *start = folio->index + folio_nr_pages(folio);
+ goto out;
+ }
+ }
+
+ /*
+ * We come here when there is no page beyond @end. We take care to not
+ * overflow the index @start as it confuses some of the callers. This
+ * breaks the iteration when there is a page at index -1 but that is
+ * already broken anyway.
+ */
+ if (end == (pgoff_t)-1)
+ *start = (pgoff_t)-1;
+ else
+ *start = end + 1;
+out:
+ rcu_read_unlock();
+
+ return folio_batch_count(fbatch);
+}
+EXPORT_SYMBOL(filemap_get_folios);
+
static inline
bool folio_more_pages(struct folio *folio, pgoff_t index, pgoff_t max)
{
--
2.35.1
