Re: [PATCH v7 05/13] fat: make fat_update_time get its own timestamp

OGAWA Hirofumi
2023-08-09T14:44:34Z

Jeff Layton <jlayton@kernel.org> writes:

> I'm a little confused too. Why do you believe this will break
> -o relatime handling? This patch changes two things:
>
> 1/ it has fat_update_time fetch its own timestamp (and ignore the "now"
> parameter). This is in line with the changes in patch #3 of this series,
> which explains the rationale for this in more detail.
>
> 2/ it changes fat_update_time to also update the i_version if any of
> S_CTIME|S_MTIME|S_VERSION are set. relatime is all about the S_ATIME,
> and it is specifically excluded from that set.
>
> The rationale for the second change is is also in patch #3, but
> basically, we can't guarantee that current_time hasn't changed since we
> last checked for inode_needs_update_time, so if any of
> S_CTIME/S_MTIME/S_VERSION have changed, then we need to assume that any
> of them may need to be changed and attempt to update all 3.
>
> That said, I think the logic in fat_update_time isn't quite right. I
> think want something like this on top of this patch to ensure that the
> S_CTIME and S_MTIME get updated, even if the flags only have S_VERSION
> set.
>
> Thoughts?

I'm not talking about "relatime" at all, I'm always talking about
"lazytime".

I_DIRTY_TIME delays to update on disk inode only if changed
timestamp. But you changed it to I_DIRTY_SYNC, i.e. always update on
disk inode by timestamp.

Thanks.

> ---------------------8<-----------------------
>
> diff --git a/fs/fat/misc.c b/fs/fat/misc.c
> index 080a5035483f..313eef02f45c 100644
> --- a/fs/fat/misc.c
> +++ b/fs/fat/misc.c
> @@ -346,15 +346,21 @@ int fat_update_time(struct inode *inode, int flags)
> if (inode->i_ino == MSDOS_ROOT_INO)
> return 0;
>
> - if (flags & (S_ATIME | S_CTIME | S_MTIME)) {
> - fat_truncate_time(inode, NULL, flags);
> - if (inode->i_sb->s_flags & SB_LAZYTIME)
> - dirty_flags |= I_DIRTY_TIME;
> - else
> - dirty_flags |= I_DIRTY_SYNC;
> - }
> + /*
> + * If any of the flags indicate an expicit change to the file, then we
> + * need to ensure that we attempt to update all of 3. We do not do
> + * this in the case of an S_ATIME-only update.
> + */
> + if (flags & (S_CTIME | S_MTIME | S_VERSION))
> + flags |= S_CTIME | S_MTIME | S_VERSION;
> +
> + fat_truncate_time(inode, NULL, flags);
> + if (inode->i_sb->s_flags & SB_LAZYTIME)
> + dirty_flags |= I_DIRTY_TIME;
> + else
> + dirty_flags |= I_DIRTY_SYNC;
>
> - if ((flags & (S_VERSION|S_CTIME|S_MTIME)) && inode_maybe_inc_iversion(inode, false))
> + if ((flags & S_VERSION) && inode_maybe_inc_iversion(inode, false))
> dirty_flags |= I_DIRTY_SYNC;
>

--
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>