btrfs: convert process_page_range() to use filemap_get_folios_contig()

Converted function to use folios throughout.  This is in preparation for
the removal of find_get_pages_contig().  Now also supports large folios.

Since we may receive more than nr_pages pages, nr_pages may underflow. 
Since nr_pages > 0 is equivalent to index <= end_index, we replaced it
with this check instead.

Also minor comment renaming for consistency in subpage.

Link: https://lkml.kernel.org/r/20220824004023.77310-5-vishal.moola@gmail.comSigned-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Acked-by: David Sterba <dsterb@suse.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Chris Mason <clm@fb.com>
Cc: David Sterba <dsterba@suse.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/btrfs/subpage.c

@@ -337,7 +337,7 @@ bool btrfs_subpage_end_and_test_writer(const struct btrfs_fs_info *fs_info,
  *
  * Even with 0 returned, the page still need extra check to make sure
  * it's really the correct page, as the caller is using
- * find_get_pages_contig(), which can race with page invalidating.
+ * filemap_get_folios_contig(), which can race with page invalidating.
  */
 int btrfs_page_start_writer_lock(const struct btrfs_fs_info *fs_info,
 		struct page *page, u64 start, u32 len)

fs/btrfs/tests/extent-io-tests.c

@@ -4,6 +4,7 @@
  */
 
 #include <linux/pagemap.h>
+#include <linux/pagevec.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/sizes.h>
@@ -20,39 +21,40 @@ static noinline int process_page_range(struct inode *inode, u64 start, u64 end,
 				       unsigned long flags)
 {
 	int ret;
-	struct page *pages[16];
+	struct folio_batch fbatch;
 	unsigned long index = start >> PAGE_SHIFT;
 	unsigned long end_index = end >> PAGE_SHIFT;
-	unsigned long nr_pages = end_index - index + 1;
 	int i;
 	int count = 0;
 	int loops = 0;
 
-	while (nr_pages > 0) {
-		ret = find_get_pages_contig(inode->i_mapping, index,
-				     min_t(unsigned long, nr_pages,
-				     ARRAY_SIZE(pages)), pages);
+	folio_batch_init(&fbatch);
+
+	while (index <= end_index) {
+		ret = filemap_get_folios_contig(inode->i_mapping, &index,
+				end_index, &fbatch);
 		for (i = 0; i < ret; i++) {
+			struct folio *folio = fbatch.folios[i];
+
 			if (flags & PROCESS_TEST_LOCKED &&
-			    !PageLocked(pages[i]))
+			    !folio_test_locked(folio))
 				count++;
-			if (flags & PROCESS_UNLOCK && PageLocked(pages[i]))
-				unlock_page(pages[i]);
-			put_page(pages[i]);
+			if (flags & PROCESS_UNLOCK && folio_test_locked(folio))
+				folio_unlock(folio);
 			if (flags & PROCESS_RELEASE)
-				put_page(pages[i]);
+				folio_put(folio);
 		}
-		nr_pages -= ret;
-		index += ret;
+		folio_batch_release(&fbatch);
 		cond_resched();
 		loops++;
 		if (loops > 100000) {
 			printk(KERN_ERR
-		"stuck in a loop, start %llu, end %llu, nr_pages %lu, ret %d\n",
-				start, end, nr_pages, ret);
+		"stuck in a loop, start %llu, end %llu, ret %d\n",
+				start, end, ret);
 			break;
 		}
 	}
+
 	return count;
 }