From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794062842; b=p/EZkTpq7O7Xxsx0PTztlyyXbhxbGUOhxwHWS+Z7TQv648HkIH2n2LeQg5HeRtPIFSqv a05MN+eO495BFgnXWlZB/2Wu/XjrGTdnf4WTYwZXXUBY+49ZF1DBI83hf0tPIvUpRfjDi ZiWSREYw5kJduLNWWqM5h4yT+sHsw4WNEn4ctnmCssiP0tOZOiUz20yYkF/UkbsI/TkFG 1TqLuDrP/WaSYVm7FnFXxKr81+iCd3WLVIOLSuDhOWRWcGa3M/yMo2jRG1E+jjgiDOT4r smgxdhYCt2fEgIMyu2RDs9pX+WfHx0tSdymy6qCn9tzgj8902gM4lOGbCHstmONrTBQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794062842; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=9q7T9KcQJKQiICxGbS8UnX/EYsWrSmNZqbZf/RZkiPI=; b=R0WGfLnq7lWHFKihwLUOq5HLz0hOwM7BzYeNpAKm6JAP1NFVsmn7Pa0wVvHf2dKuzOlm pFhUxJNIBoPiI5wVFQ4/2MTd4gK9il02ltE3GEaIbiKA3VKbD+C0zAqc5EQ+QlBCEhIhr VthK0Cp2no+ljFZB1EV/YpNcVe80cPHrzvgqdvJVkHaLpV1oSoo62eWgUWENd3njWATTq 8DSW3ZFOLfQ4IqRFetZnWcBmWBKaxDNwarf1pNavEheiMn1HSp1KlO9A16WceikwIEIWn 9rehGl229yIupbnv5dOr21Blg3lUy7pitryg/ee79sy/5zm9H3WYbFnshQQ3R9L7Iug== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=RHqmtr7S; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C7916606A334; Sat, 7 Nov 2026 14:47:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=RHqmtr7S Received: by smtp.kernel.org (Postfix) with ESMTPSA id 746A31F0089F; Sat, 7 Nov 2026 14:47:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794062841; bh=9q7T9KcQJKQiICxGbS8UnX/EYsWrSmNZqbZf/RZkiPI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=RHqmtr7SuL2mnEn93Kw0LRFSVnbw8wGFsT3KpOMrZC6/R4OoXq+QyD40sCs7aERbr i75iwdf8veLF0PfEuiLafhEYDIaLVtRA0Wnob8lTjOdWVO2RHlkgehiUyBX8kGJgUT 0JYiJ3TQAF69E9H33UndPLlg2wPvgjhIHR3i3C+U= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, stable@kernel.org, Zhiguo Niu , Chao Yu , Jaegeuk Kim , Sasha Levin Subject: [PATCH 6.18 136/869] f2fs: compress: fix to handle race between truncate and writeback Date: Sat, 7 Nov 2026 08:46:58 -0500 Message-ID: <20261107134857.035258360@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261107134852.069646174@linuxfoundation.org> References: <20261107134852.069646174@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chao Yu [ Upstream commit c0337e331b065074ce20e4258a578e07dd7e4083 ] fsstress reports a kernel BUG in f2fs_truncate_partial_cluster(): kernel BUG at fs/f2fs/compress.c:1238! RIP: 0010:f2fs_truncate_partial_cluster+0x292/0x2a0 Call Trace: f2fs_truncate+0xf6/0x210 f2fs_setattr+0x6b7/0x770 notify_change+0x33b/0x520 do_truncate+0xc2/0xf0 vfs_truncate+0x153/0x1d0 ksys_truncate+0x78/0xd0 __x64_sys_truncate+0x16/0x20 do_syscall_64+0xbe/0x540 The root cause is that Thread A (truncate) and Thread B (background writeback or fsync) can race as follows: Thread A Thread B - f2fs_setattr - f2fs_truncate - f2fs_truncate_blocks - f2fs_truncate_partial_cluster - f2fs_is_compressed_cluster return 1 - f2fs_write_cache_pages - f2fs_write_multi_pages - f2fs_write_raw_pages - f2fs_write_single_data_page dn.data_blkaddr != COMPRESS_ADDR (cluster converted to normal) - f2fs_prepare_compress_overwrite - f2fs_is_compressed_cluster return 0 - return 0 - f2fs_bug_on(sbi, err == 0): BUG! Writeback path does not acquire i_gc_rwsem or filemap_invalidate_lock. When a compressed cluster fails compression during writeback, it is overwritten with raw data blocks. If Thread A checked f2fs_is_compressed_cluster() before the conversion, but calls f2fs_prepare_compress_overwrite() after the conversion, f2fs_prepare_compress_overwrite() returns 0 because the cluster is no longer a compressed cluster. To fix this, remove the f2fs_bug_on() and retry checking the cluster status when f2fs_prepare_compress_overwrite() returns 0, so that it can fall back to f2fs_do_truncate_blocks() to handle it as a normal cluster. Cc: stable@kernel.org Fixes: 3265d3db1f16 ("f2fs: support partial truncation on compressed inode") Reviewed-by: Zhiguo Niu Signed-off-by: Chao Yu Signed-off-by: Jaegeuk Kim Signed-off-by: Sasha Levin --- fs/f2fs/compress.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c index 0399db98fccfc..8fea48dc50bad 100644 --- a/fs/f2fs/compress.c +++ b/fs/f2fs/compress.c @@ -1219,6 +1219,7 @@ int f2fs_truncate_partial_cluster(struct inode *inode, u64 from, bool lock) int i; int err; +repeat: err = f2fs_is_compressed_cluster(inode, start_idx); if (err < 0) return err; @@ -1230,12 +1231,11 @@ int f2fs_truncate_partial_cluster(struct inode *inode, u64 from, bool lock) /* truncate compressed cluster */ err = f2fs_prepare_compress_overwrite(inode, &pagep, start_idx, &fsdata); - - /* should not be a normal cluster */ - f2fs_bug_on(F2FS_I_SB(inode), err == 0); - - if (err <= 0) + if (err < 0) return err; + else if (err == 0) + /* the cluster became non-compressed one due to race case */ + goto repeat; rpages = fsdata; -- 2.53.0