[RFC 13/23] readahead: set file_ra_state->ra_pages to be at least mapping_min_order

[Pankaj Raghav]

From: Luis Chamberlain <mcgrof@xxxxxxxxxx>

Set the file_ra_state->ra_pages in file_ra_state_init() to be at least
mapping_min_order of pages if the bdi->ra_pages is less than that.

Signed-off-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
---
 mm/readahead.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/mm/readahead.c b/mm/readahead.c
index ef3b23a41973..5c4e7ee64dc1 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -138,7 +138,13 @@
 void
 file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping)
 {
+	unsigned int order = mapping_min_folio_order(mapping);
+	unsigned int min_nrpages = 1U << order;
+	unsigned int max_pages = inode_to_bdi(mapping->host)->io_pages;
+
 	ra->ra_pages = inode_to_bdi(mapping->host)->ra_pages;
+	if (ra->ra_pages < min_nrpages && min_nrpages < max_pages)
+		ra->ra_pages = min_nrpages;
 	ra->prev_pos = -1;
 }
 EXPORT_SYMBOL_GPL(file_ra_state_init);
-- 
2.40.1