Messages in this thread | | | Subject | Re: [PATCH v2 RFC] f2fs: fix to force keeping write barrier for strict fsync mode | From | Chao Yu <> | Date | Fri, 2 Jul 2021 07:04:12 +0800 |
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On 2021/7/2 1:10, Jaegeuk Kim wrote: > On 06/01, Chao Yu wrote: >> [1] https://www.mail-archive.com/linux-f2fs-devel@lists.sourceforge.net/msg15126.html >> >> As [1] reported, if lower device doesn't support write barrier, in below >> case: >> >> - write page #0; persist >> - overwrite page #0 >> - fsync >> - write data page #0 OPU into device's cache >> - write inode page into device's cache >> - issue flush > > Well, we have preflush for node writes, so I don't think this is the case. > > fio.op_flags |= REQ_PREFLUSH | REQ_FUA;
This is only used for atomic write case, right?
I mean the common case which is called from f2fs_issue_flush() in f2fs_do_sync_file().
And please see do_checkpoint(), we call f2fs_flush_device_cache() and commit_checkpoint() separately to keep persistence order of CP datas.
See commit 46706d5917f4 ("f2fs: flush cp pack except cp pack 2 page at first") for details.
Thanks,
> >> >> If SPO is triggered during flush command, inode page can be persisted >> before data page #0, so that after recovery, inode page can be recovered >> with new physical block address of data page #0, however there may >> contains dummy data in new physical block address. >> >> Then what user will see is: after overwrite & fsync + SPO, old data in >> file was corrupted, if any user do care about such case, we can suggest >> user to use STRICT fsync mode, in this mode, we will force to trigger >> preflush command to persist data in device cache in prior to node >> writeback, it avoids potential data corruption during fsync(). >> >> Signed-off-by: Chao Yu <yuchao0@huawei.com> >> --- >> v2: >> - fix this by adding additional preflush command rather than using >> atomic write flow. >> fs/f2fs/file.c | 14 ++++++++++++++ >> 1 file changed, 14 insertions(+) >> >> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c >> index 7d5311d54f63..238ca2a733ac 100644 >> --- a/fs/f2fs/file.c >> +++ b/fs/f2fs/file.c >> @@ -301,6 +301,20 @@ static int f2fs_do_sync_file(struct file *file, loff_t start, loff_t end, >> f2fs_exist_written_data(sbi, ino, UPDATE_INO)) >> goto flush_out; >> goto out; >> + } else { >> + /* >> + * for OPU case, during fsync(), node can be persisted before >> + * data when lower device doesn't support write barrier, result >> + * in data corruption after SPO. >> + * So for strict fsync mode, force to trigger preflush to keep >> + * data/node write order to avoid potential data corruption. >> + */ >> + if (F2FS_OPTION(sbi).fsync_mode == FSYNC_MODE_STRICT && >> + !atomic) { >> + ret = f2fs_issue_flush(sbi, inode->i_ino); >> + if (ret) >> + goto out; >> + } >> } >> go_write: >> /* >> -- >> 2.29.2
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