linux-kernel - [PATCH v1 2/5] f2fs: Accounting large folio subpages before bio submission

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20260105153101.152892-3-nzzhao@126.com>
Date: Mon,  5 Jan 2026 23:30:58 +0800
From: Nanzhe Zhao <nzzhao@....com>
To: Kim Jaegeuk <jaegeuk@...nel.org>
Cc: Chao Yu <chao@...nel.org>,
	linux-f2fs-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org,
	Nanzhe Zhao <nzzhao@....com>
Subject: [PATCH v1 2/5] f2fs: Accounting large folio subpages before bio submission

In f2fs_read_data_large_folio(), read_pages_pending is incremented only
after the subpage has been added to the BIO.  With a heavily fragmented
file, each new subpage can force submission of the previous BIO.

If the BIO completes quickly, f2fs_finish_read_bio() may decrement
read_pages_pending to zero and call folio_end_read() while the read loop
is still processing other subpages of the same large folio.

Fix the ordering by incrementing read_pages_pending before any possible
BIO submission for the current subpage, matching the iomap ordering and
preventing premature folio_end_read().

Signed-off-by: Nanzhe Zhao <nzzhao@....com>
---
 fs/f2fs/data.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index ab091b294fa7..4bef04560924 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -2486,6 +2486,18 @@ static int f2fs_read_data_large_folio(struct inode *inode,
 			continue;
 		}

+		/* We must increment read_pages_pending before possible BIOs submitting
+		 * to prevent from premature folio_end_read() call on folio
+		 */
+		if (folio_test_large(folio)) {
+			ffs = ffs_find_or_alloc(folio);
+
+			/* set the bitmap to wait */
+			spin_lock_irq(&ffs->state_lock);
+			ffs->read_pages_pending++;
+			spin_unlock_irq(&ffs->state_lock);
+		}
+
 		/*
 		 * This page will go to BIO.  Do we need to send this
 		 * BIO off first?
@@ -2513,15 +2525,6 @@ static int f2fs_read_data_large_folio(struct inode *inode,
 					offset << PAGE_SHIFT))
 			goto submit_and_realloc;

-		if (folio_test_large(folio)) {
-			ffs = ffs_find_or_alloc(folio);
-
-			/* set the bitmap to wait */
-			spin_lock_irq(&ffs->state_lock);
-			ffs->read_pages_pending++;
-			spin_unlock_irq(&ffs->state_lock);
-		}
-
 		inc_page_count(F2FS_I_SB(inode), F2FS_RD_DATA);
 		f2fs_update_iostat(F2FS_I_SB(inode), NULL, FS_DATA_READ_IO,
 				F2FS_BLKSIZE);
--
2.34.1