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 B3143184113 for ; Wed, 26 Jun 2024 14:52:16 +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=1719413536; cv=none; b=HoasorGpQR56iX0WUqZBHpw9muRrk3XAzfE85URfXtAHtAy7R+hUORYai95WZoTvQOGSS6rLIJz5mNV3F8Mts4TdqO4mW6rCD7BPwjtr2ma7NPWlhRbZFUoqlihCxeaBfrHW36hbdgQYlj8ufkjjKdliBBJZV6FJ8YVAJuAlZzE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719413536; c=relaxed/simple; bh=3x9aUwLlLr35lFq9vjm9SpBmwK+WBb/nORwA4i0c9DU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=CAKEbsvval/ERKCIFrIzzwyr6Ip2EeiOL/vfNRl6NkMfOU/Il6RzjUDwDsyJSeJXLABbGpd6e8cT+WeJpxCFblDYauxSIwGWfdpsaBHapQfAA7nWsADmtYgBCgAWygJKDMIIu4TfGn9f2/8ZBDEBh7RYeH3uxPh9MvpTvwkevTM= ARC-Authentication-Results:i=1; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 2024/6/26 10:01, Zhiguo Niu wrote: > Chao Yu 于2024年6月25日周二 22:29写道： >> >> If lfs mode is on, buffered read may race w/ OPU dio write as below, >> it may cause buffered read hits unwritten data unexpectly, and for >> dio read, the race condition exists as well. >> >> Thread A Thread B >> - f2fs_file_write_iter >> - f2fs_dio_write_iter >> - __iomap_dio_rw >> - f2fs_iomap_begin >> - f2fs_map_blocks >> - __allocate_data_block >> - allocated blkaddr #x >> - iomap_dio_submit_bio >> - f2fs_file_read_iter >> - filemap_read >> - f2fs_read_data_folio >> - f2fs_mpage_readpages >> - f2fs_map_blocks >> : get blkaddr #x >> - f2fs_submit_read_bio >> IRQ >> - f2fs_read_end_io >> : read IO on blkaddr #x complete >> IRQ >> - iomap_dio_bio_end_io >> : direct write IO on blkaddr #x complete >> >> In LFS mode, if there is inflight dio, let's force read to buffered >> IO, this policy won't cover all race cases, however it is a tradeoff >> which avoids abusing lock around IO paths. >> >> Fixes: f847c699cff3 ("f2fs: allow out-place-update for direct IO in LFS mode") >> Signed-off-by: Chao Yu >> --- >> fs/f2fs/file.c | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c >> index 278573974db4..866f1a34e92b 100644 >> --- a/fs/f2fs/file.c >> +++ b/fs/f2fs/file.c >> @@ -882,6 +882,10 @@ static bool f2fs_force_buffered_io(struct inode *inode, int rw) >> return true; >> if (is_sbi_flag_set(sbi, SBI_CP_DISABLED)) >> return true; >> + /* In LFS mode, if there is inflight dio, force read to buffered IO */ >> + if (rw == READ && f2fs_lfs_mode(sbi) && >> + atomic_read(&inode->i_dio_count)) >> + return false; > Hi Chao, > A little doubt:)，force “buffered IO” should return "true"? Oops, too rush to send the patch... > another want to confirm is, "thread B" in commit msg just doing buffer > read, so this modification just cover direct read case？ Oh, the fix is incorrect, will look into it soon. Thanks, > thanks！ >> >> return false; >> } >> -- >> 2.40.1 >> >> >> >> _______________________________________________ >> Linux-f2fs-devel mailing list >> Linux-f2fs-devel@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel