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authorMatthew Wilcox (Oracle) <willy@infradead.org>2022-06-03 15:30:25 -0400
committerMatthew Wilcox (Oracle) <willy@infradead.org>2022-06-29 08:51:05 -0400
commitbe0ced5e9cb81a4c2edefd081a7794a1814fb60d (patch)
treeafc91df5848bf584e080725e48616c58992a7ef1 /mm/filemap.c
parent2bb876b58d593d7f2522ec0f41f20a74fde76822 (diff)
filemap: Add filemap_get_folios()
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@infradead.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Acked-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Diffstat (limited to 'mm/filemap.c')
-rw-r--r--mm/filemap.c59
1 files changed, 59 insertions, 0 deletions
diff --git a/mm/filemap.c b/mm/filemap.c
index 22a17ab256f7..ce3209a8ad49 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2127,6 +2127,65 @@ put:
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)) {
+ unsigned long nr = folio_nr_pages(folio);
+
+ if (folio_test_hugetlb(folio))
+ nr = 1;
+ *start = folio->index + nr;
+ 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)
{