Re: [PATCH 6/7] khugepaged: Use a folio throughout collapse_file()

[Matthew Wilcox <willy@infradead.org>]

On Fri, Apr 05, 2024 at 02:20:28PM -0700, Vishal Moola wrote:
> On Wed, Apr 03, 2024 at 06:18:35PM +0100, Matthew Wilcox (Oracle) wrote:
> > -				page = find_lock_page(mapping, index);
> > -				if (unlikely(page == NULL)) {
> > +				folio = filemap_lock_folio(mapping, index);
> > +				if (unlikely(folio == NULL)) {
> 
> filemap_lock_folio() can return an ERR_PTR(), find_lock_page() handles
> it internally.

Argh.  I keep forgetting that when doing conversions.  Thanks.

Andrew, if you could attach this fix ...

(the unlikely() is embedded in IS_ERR() so no need to keep it here)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 6a96a85de56b..89e2624fb3ff 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1865,7 +1865,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
 				/* drain lru cache to help isolate_lru_page() */
 				lru_add_drain();
 				folio = filemap_lock_folio(mapping, index);
-				if (unlikely(folio == NULL)) {
+				if (IS_ERR(folio)) {
 					result = SCAN_FAIL;
 					goto xa_unlocked;
 				}