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

[OGAWA Hirofumi]

Jeff Layton <jlayton@xxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxx>