+ nilfs2-fix-kernel-bug-due-to-missing-clearing-of-buffer-delay-flag.patch added to mm-hotfixes-unstable branch

+ nilfs2-fix-kernel-bug-due-to-missing-clearing-of-buffer-delay-flag.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: nilfs2: fix kernel bug due to missing clearing of buffer delay flag
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     nilfs2-fix-kernel-bug-due-to-missing-clearing-of-buffer-delay-flag.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/nilfs2-fix-kernel-bug-due-to-missing-clearing-of-buffer-delay-flag.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Subject: nilfs2: fix kernel bug due to missing clearing of buffer delay flag
Date: Wed, 16 Oct 2024 06:32:07 +0900

Syzbot reported that after nilfs2 reads a corrupted file system image and
degrades to read-only, the BUG_ON check for the buffer delay flag in
submit_bh_wbc() may fail, causing a kernel bug.

This is because the buffer delay flag is not cleared when clearing the
buffer state flags to discard a page/folio or a buffer head.  So, fix
this.

This became necessary when the use of nilfs2's own page clear routine was
expanded.  This state inconsistency does not occur if the buffer is
written normally by log writing.

Link: https://lkml.kernel.org/r/20241015213300.7114-1-konishi.ryusuke@gmail.com
Fixes: 8c26c4e2694a ("nilfs2: fix issue with flush kernel thread after remount in RO mode because of driver's internal error or metadata corruption")
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Reported-by: syzbot+985ada84bf055a575c07@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=985ada84bf055a575c07
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/nilfs2/page.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/fs/nilfs2/page.c~nilfs2-fix-kernel-bug-due-to-missing-clearing-of-buffer-delay-flag
+++ a/fs/nilfs2/page.c
@@ -77,7 +77,8 @@ void nilfs_forget_buffer(struct buffer_h
 	const unsigned long clear_bits =
 		(BIT(BH_Uptodate) | BIT(BH_Dirty) | BIT(BH_Mapped) |
 		 BIT(BH_Async_Write) | BIT(BH_NILFS_Volatile) |
-		 BIT(BH_NILFS_Checked) | BIT(BH_NILFS_Redirected));
+		 BIT(BH_NILFS_Checked) | BIT(BH_NILFS_Redirected) |
+		 BIT(BH_Delay));
 
 	lock_buffer(bh);
 	set_mask_bits(&bh->b_state, clear_bits, 0);
@@ -406,7 +407,8 @@ void nilfs_clear_folio_dirty(struct foli
 		const unsigned long clear_bits =
 			(BIT(BH_Uptodate) | BIT(BH_Dirty) | BIT(BH_Mapped) |
 			 BIT(BH_Async_Write) | BIT(BH_NILFS_Volatile) |
-			 BIT(BH_NILFS_Checked) | BIT(BH_NILFS_Redirected));
+			 BIT(BH_NILFS_Checked) | BIT(BH_NILFS_Redirected) |
+			 BIT(BH_Delay));
 
 		bh = head;
 		do {
_

Patches currently in -mm which might be from konishi.ryusuke@gmail.com are

nilfs2-propagate-directory-read-errors-from-nilfs_find_entry.patch
nilfs2-fix-kernel-bug-due-to-missing-clearing-of-buffer-delay-flag.patch