mm/readahead: add folio allocation helper

Just a wrapper around filemap_alloc_folio() for now, but add it in
preparation for modifying the folio based on the 'ractl' being passed in.

No functional changes in this patch.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
Reviewed-by: Kirill A. Shutemov <[email protected]>
Reviewed-by: Matthew Wilcox (Oracle) <[email protected]>
Cc: Brian Foster <[email protected]>
Cc: Chris Mason <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Johannes Weiner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: axboe

mm/readahead.c

@@ -178,6 +178,12 @@ static void read_pages(struct readahead_control *rac)
 	BUG_ON(readahead_count(rac));
 }
 
+static struct folio *ractl_alloc_folio(struct readahead_control *ractl,
+				       gfp_t gfp_mask, unsigned int order)
+{
+	return filemap_alloc_folio(gfp_mask, order);
+}
+
 /**
  * page_cache_ra_unbounded - Start unchecked readahead.
  * @ractl: Readahead control.
@@ -255,8 +261,8 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
 			continue;
 		}
 
-		folio = filemap_alloc_folio(gfp_mask,
-					    mapping_min_folio_order(mapping));
+		folio = ractl_alloc_folio(ractl, gfp_mask,
+					mapping_min_folio_order(mapping));
 		if (!folio)
 			break;
 
@@ -426,7 +432,7 @@ static inline int ra_alloc_folio(struct readahead_control *ractl, pgoff_t index,
 		pgoff_t mark, unsigned int order, gfp_t gfp)
 {
 	int err;
-	struct folio *folio = filemap_alloc_folio(gfp, order);
+	struct folio *folio = ractl_alloc_folio(ractl, gfp, order);
 
 	if (!folio)
 		return -ENOMEM;
@@ -751,7 +757,7 @@ void readahead_expand(struct readahead_control *ractl,
 		if (folio && !xa_is_value(folio))
 			return; /* Folio apparently present */
 
-		folio = filemap_alloc_folio(gfp_mask, min_order);
+		folio = ractl_alloc_folio(ractl, gfp_mask, min_order);
 		if (!folio)
 			return;
 
@@ -780,7 +786,7 @@ void readahead_expand(struct readahead_control *ractl,
 		if (folio && !xa_is_value(folio))
 			return; /* Folio apparently present */
 
-		folio = filemap_alloc_folio(gfp_mask, min_order);
+		folio = ractl_alloc_folio(ractl, gfp_mask, min_order);
 		if (!folio)
 			return;