From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1943D335557; Tue, 6 Jan 2026 17:43:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767721414; cv=none; b=bVxDTVk6uSJbnzj+S6xETftmaVvRU4Y3WtZu+7GkrA0qnwrf+OYUYGfmcs/IT4/2fnslPEei9DWYZ2YWnRQIbvr5KqNgVWXYiSLsNS2F8zrMyWJvPyRsdPVgDrPVal7mKHMqUR0mV4OfqD4Swh/Zs3khd9JDLfu2DSgxZDvVbrw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767721414; c=relaxed/simple; bh=P+hUF9Y/T+qK2aP625SL60jeUbT/9pGm+k4Ik6TS1Og=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=oVC8dWNXglTYdWpsBw7aWtzXSor7+InkjD+QVHtYuGTVaHOgAjdzdsb6b6tTT1P/Kd82rZAUQf0T5M05kRqkyKr+KN7s3sHnN8BDBgyMakPU9USJK/JKMFh2AUN/zjw68fug3QDMOeTEKwxzS7l+DKh6CN4l4rDWP2cfhO92HY8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Kv4m4mVt; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Kv4m4mVt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 60F63C19425; Tue, 6 Jan 2026 17:43:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1767721414; bh=P+hUF9Y/T+qK2aP625SL60jeUbT/9pGm+k4Ik6TS1Og=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Kv4m4mVtBKbpSsgml6TwJCQpi3YX8Sk1zSlp/e5PSa1unjjrIaf0ocreiUkDCF3um Y5akX+s+8irJ8+YrDOj5aA+oqebwyczdXbtRlgFB9Xs4ESdjps1gtEpuv5dZu/r50b KcVc1S6gJW0bs7ZSu5ZBYBidxSQpkD/CuSTw8cXo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, stable@kernel.org, "Bai, Shuangpeng" , Chao Yu , Jaegeuk Kim , Sasha Levin Subject: [PATCH 6.12 497/567] f2fs: fix to avoid updating compression context during writeback Date: Tue, 6 Jan 2026 18:04:39 +0100 Message-ID: <20260106170509.750259301@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260106170451.332875001@linuxfoundation.org> References: <20260106170451.332875001@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chao Yu [ Upstream commit 10b591e7fb7cdc8c1e53e9c000dc0ef7069aaa76 ] Bai, Shuangpeng reported a bug as below: Oops: divide error: 0000 [#1] SMP KASAN PTI CPU: 0 UID: 0 PID: 11441 Comm: syz.0.46 Not tainted 6.17.0 #1 PREEMPT(full) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 RIP: 0010:f2fs_all_cluster_page_ready+0x106/0x550 fs/f2fs/compress.c:857 Call Trace: f2fs_write_cache_pages fs/f2fs/data.c:3078 [inline] __f2fs_write_data_pages fs/f2fs/data.c:3290 [inline] f2fs_write_data_pages+0x1c19/0x3600 fs/f2fs/data.c:3317 do_writepages+0x38e/0x640 mm/page-writeback.c:2634 filemap_fdatawrite_wbc mm/filemap.c:386 [inline] __filemap_fdatawrite_range mm/filemap.c:419 [inline] file_write_and_wait_range+0x2ba/0x3e0 mm/filemap.c:794 f2fs_do_sync_file+0x6e6/0x1b00 fs/f2fs/file.c:294 generic_write_sync include/linux/fs.h:3043 [inline] f2fs_file_write_iter+0x76e/0x2700 fs/f2fs/file.c:5259 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x7e9/0xe00 fs/read_write.c:686 ksys_write+0x19d/0x2d0 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xf7/0x470 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f The bug was triggered w/ below race condition: fsync setattr ioctl - f2fs_do_sync_file - file_write_and_wait_range - f2fs_write_cache_pages : inode is non-compressed : cc.cluster_size = F2FS_I(inode)->i_cluster_size = 0 - tag_pages_for_writeback - f2fs_setattr - truncate_setsize - f2fs_truncate - f2fs_fileattr_set - f2fs_setflags_common - set_compress_context : F2FS_I(inode)->i_cluster_size = 4 : set_inode_flag(inode, FI_COMPRESSED_FILE) - f2fs_compressed_file : return true - f2fs_all_cluster_page_ready : "pgidx % cc->cluster_size" trigger dividing 0 issue Let's change as below to fix this issue: - introduce a new atomic type variable .writeback in structure f2fs_inode_info to track the number of threads which calling f2fs_write_cache_pages(). - use .i_sem lock to protect .writeback update. - check .writeback before update compression context in f2fs_setflags_common() to avoid race w/ ->writepages. Fixes: 4c8ff7095bef ("f2fs: support data compression") Cc: stable@kernel.org Reported-by: Bai, Shuangpeng Tested-by: Bai, Shuangpeng Closes: https://lore.kernel.org/lkml/44D8F7B3-68AD-425F-9915-65D27591F93F@psu.edu Signed-off-by: Chao Yu Signed-off-by: Jaegeuk Kim Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- fs/f2fs/data.c | 17 +++++++++++++++++ fs/f2fs/f2fs.h | 3 ++- fs/f2fs/file.c | 5 +++-- fs/f2fs/super.c | 1 + 4 files changed, 23 insertions(+), 3 deletions(-) --- a/fs/f2fs/data.c +++ b/fs/f2fs/data.c @@ -3272,6 +3272,19 @@ static inline bool __should_serialize_io return false; } +static inline void account_writeback(struct inode *inode, bool inc) +{ + if (!f2fs_sb_has_compression(F2FS_I_SB(inode))) + return; + + f2fs_down_read(&F2FS_I(inode)->i_sem); + if (inc) + atomic_inc(&F2FS_I(inode)->writeback); + else + atomic_dec(&F2FS_I(inode)->writeback); + f2fs_up_read(&F2FS_I(inode)->i_sem); +} + static int __f2fs_write_data_pages(struct address_space *mapping, struct writeback_control *wbc, enum iostat_type io_type) @@ -3321,10 +3334,14 @@ static int __f2fs_write_data_pages(struc locked = true; } + account_writeback(inode, true); + blk_start_plug(&plug); ret = f2fs_write_cache_pages(mapping, wbc, io_type); blk_finish_plug(&plug); + account_writeback(inode, false); + if (locked) mutex_unlock(&sbi->writepages); --- a/fs/f2fs/f2fs.h +++ b/fs/f2fs/f2fs.h @@ -887,6 +887,7 @@ struct f2fs_inode_info { unsigned char i_compress_level; /* compress level (lz4hc,zstd) */ unsigned char i_compress_flag; /* compress flag */ unsigned int i_cluster_size; /* cluster size */ + atomic_t writeback; /* count # of writeback thread */ unsigned int atomic_write_cnt; loff_t original_i_size; /* original i_size before atomic write */ @@ -4540,7 +4541,7 @@ static inline bool f2fs_disable_compress f2fs_up_write(&fi->i_sem); return true; } - if (f2fs_is_mmap_file(inode) || + if (f2fs_is_mmap_file(inode) || atomic_read(&fi->writeback) || (S_ISREG(inode->i_mode) && F2FS_HAS_BLOCKS(inode))) { f2fs_up_write(&fi->i_sem); return false; --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -2071,8 +2071,9 @@ static int f2fs_setflags_common(struct i f2fs_down_write(&fi->i_sem); if (!f2fs_may_compress(inode) || - (S_ISREG(inode->i_mode) && - F2FS_HAS_BLOCKS(inode))) { + atomic_read(&fi->writeback) || + (S_ISREG(inode->i_mode) && + F2FS_HAS_BLOCKS(inode))) { f2fs_up_write(&fi->i_sem); return -EINVAL; } --- a/fs/f2fs/super.c +++ b/fs/f2fs/super.c @@ -1426,6 +1426,7 @@ static struct inode *f2fs_alloc_inode(st atomic_set(&fi->dirty_pages, 0); atomic_set(&fi->i_compr_blocks, 0); atomic_set(&fi->open_count, 0); + atomic_set(&fi->writeback, 0); init_f2fs_rwsem(&fi->i_sem); spin_lock_init(&fi->i_size_lock); INIT_LIST_HEAD(&fi->dirty_list);