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[188.141.5.72]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43cf90424fcsm11516290f8f.32.2026.03.30.00.12.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 30 Mar 2026 00:12:35 -0700 (PDT) From: David Carlier To: David Hildenbrand , Kairui Song , Chris Li , Andrew Morton , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , Youngjun Park , NeilBrown Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, David Carlier Subject: [PATCH v2] mm/page_io: fix PSWPIN undercount for large folios in sio_read_complete() Date: Mon, 30 Mar 2026 08:12:29 +0100 Message-ID: <20260330071229.14614-1-devnexen@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit sio_read_complete() uses sio->pages to account global PSWPIN vm events, but sio->pages tracks the number of bvec entries (folios), not base pages. For large folios this undercounts compared to the per-memcg path which correctly uses folio_nr_pages(), and compared to the bdev read paths which also use folio_nr_pages(). Use sio->len >> PAGE_SHIFT instead, which gives the correct base page count since sio->len is accumulated via folio_size(folio). Fixes: a1a0dfd56f97 ("mm: handle THP in swap_*page_fs()") Signed-off-by: David Carlier --- mm/page_io.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/page_io.c b/mm/page_io.c index 63b262f4c5a9..1389cd57ca88 100644 --- a/mm/page_io.c +++ b/mm/page_io.c @@ -497,7 +497,7 @@ static void sio_read_complete(struct kiocb *iocb, long ret) folio_mark_uptodate(folio); folio_unlock(folio); } - count_vm_events(PSWPIN, sio->pages); + count_vm_events(PSWPIN, sio->len >> PAGE_SHIFT); } else { for (p = 0; p < sio->pages; p++) { struct folio *folio = page_folio(sio->bvec[p].bv_page); -- 2.53.0