linux-kernel - [PATCH 1/2] mm/gup: Remove unnecessary check in memfd_pin

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Message-ID: <20250430010059.892632-2-vishal.moola@gmail.com>
Date: Tue, 29 Apr 2025 18:00:58 -0700
From: "Vishal Moola (Oracle)" <vishal.moola@...il.com>
To: linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org,
	Vivek Kasireddy <vivek.kasireddy@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Vishal Moola (Oracle)" <vishal.moola@...il.com>
Subject: [PATCH 1/2] mm/gup: Remove unnecessary check in memfd_pin_folios()

Commit 89c1905d9c14 ("mm/gup: introduce memfd_pin_folios() for pinning memfd folios")
checks if filemap_get_folios_contig() returned duplicate folios to
prevent multiple attempts at pinning the same folio.

Commit 8ab1b1602396 ("mm: fix filemap_get_folios_contig returning batches of identical folios")
ensures that filemap_get_folios_contig() returns a batch of distinct folios.

We can remove the duplicate folio check to simplify the code and save
58 bytes of text.

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@...il.com>
---
 mm/gup.c | 15 +--------------
 1 file changed, 1 insertion(+), 14 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index f32168339390..1fb8f3b9a493 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -3589,7 +3589,7 @@ long memfd_pin_folios(struct file *memfd, loff_t start, loff_t end,
 {
 	unsigned int flags, nr_folios, nr_found;
 	unsigned int i, pgshift = PAGE_SHIFT;
-	pgoff_t start_idx, end_idx, next_idx;
+	pgoff_t start_idx, end_idx;
 	struct folio *folio = NULL;
 	struct folio_batch fbatch;
 	struct hstate *h;
@@ -3639,19 +3639,7 @@ long memfd_pin_folios(struct file *memfd, loff_t start, loff_t end,
 				folio = NULL;
 			}
 
-			next_idx = 0;
 			for (i = 0; i < nr_found; i++) {
-				/*
-				 * As there can be multiple entries for a
-				 * given folio in the batch returned by
-				 * filemap_get_folios_contig(), the below
-				 * check is to ensure that we pin and return a
-				 * unique set of folios between start and end.
-				 */
-				if (next_idx &&
-				    next_idx != folio_index(fbatch.folios[i]))
-					continue;
-
 				folio = page_folio(&fbatch.folios[i]->page);
 
 				if (try_grab_folio(folio, 1, FOLL_PIN)) {
@@ -3664,7 +3652,6 @@ long memfd_pin_folios(struct file *memfd, loff_t start, loff_t end,
 					*offset = offset_in_folio(folio, start);
 
 				folios[nr_folios] = folio;
-				next_idx = folio_next_index(folio);
 				if (++nr_folios == max_folios)
 					break;
 			}
-- 
2.49.0