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[223.217.95.32]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1f44c9d89b3sm118848285ad.292.2024.05.30.07.15.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 May 2024 07:16:00 -0700 (PDT) From: Ryusuke Konishi To: Andrew Morton Cc: linux-nilfs@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] nilfs2: fix potential kernel bug due to lack of writeback flag waiting Date: Thu, 30 May 2024 23:15:56 +0900 Message-Id: <20240530141556.4411-1-konishi.ryusuke@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Destructive writes to a block device on which nilfs2 is mounted can cause a kernel bug in the folio/page writeback start routine or writeback end routine (__folio_start_writeback in the log below): kernel BUG at mm/page-writeback.c:3070! Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI ... RIP: 0010:__folio_start_writeback+0xbaa/0x10e0 Code: 25 ff 0f 00 00 0f 84 18 01 00 00 e8 40 ca c6 ff e9 17 f6 ff ff e8 36 ca c6 ff 4c 89 f7 48 c7 c6 80 c0 12 84 e8 e7 b3 0f 00 90 <0f> 0b e8 1f ca c6 ff 4c 89 f7 48 c7 c6 a0 c6 12 84 e8 d0 b3 0f 00 ... Call Trace: nilfs_segctor_do_construct+0x4654/0x69d0 [nilfs2] nilfs_segctor_construct+0x181/0x6b0 [nilfs2] nilfs_segctor_thread+0x548/0x11c0 [nilfs2] kthread+0x2f0/0x390 ret_from_fork+0x4b/0x80 ret_from_fork_asm+0x1a/0x30 This is because when the log writer starts a writeback for segment summary blocks or a super root block that use the backing device's page cache, it does not wait for the ongoing folio/page writeback, resulting in an inconsistent writeback state. Fix this issue by waiting for ongoing writebacks when putting folios/pages on the backing device into writeback state. Signed-off-by: Ryusuke Konishi Fixes: 9ff05123e3bf ("nilfs2: segment constructor") Tested-by: Ryusuke Konishi Cc: stable@vger.kernel.org --- Andrew, please apply this as a bug fix. This fixes a kernel bug that is reproducible in some destructive testing. Thanks, Ryusuke Konishi fs/nilfs2/segment.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c index 60d4f59f7665..6ea81f1d5094 100644 --- a/fs/nilfs2/segment.c +++ b/fs/nilfs2/segment.c @@ -1652,6 +1652,7 @@ static void nilfs_segctor_prepare_write(struct nilfs_= sc_info *sci) if (bh->b_folio !=3D bd_folio) { if (bd_folio) { folio_lock(bd_folio); + folio_wait_writeback(bd_folio); folio_clear_dirty_for_io(bd_folio); folio_start_writeback(bd_folio); folio_unlock(bd_folio); @@ -1665,6 +1666,7 @@ static void nilfs_segctor_prepare_write(struct nilfs_= sc_info *sci) if (bh =3D=3D segbuf->sb_super_root) { if (bh->b_folio !=3D bd_folio) { folio_lock(bd_folio); + folio_wait_writeback(bd_folio); folio_clear_dirty_for_io(bd_folio); folio_start_writeback(bd_folio); folio_unlock(bd_folio); @@ -1681,6 +1683,7 @@ static void nilfs_segctor_prepare_write(struct nilfs_= sc_info *sci) } if (bd_folio) { folio_lock(bd_folio); + folio_wait_writeback(bd_folio); folio_clear_dirty_for_io(bd_folio); folio_start_writeback(bd_folio); folio_unlock(bd_folio); --=20 2.34.1