On 06/09/2015 04:02 PM, Richard Weinberger wrote:
Am 09.06.2015 um 08:36 schrieb Artem Bityutskiy:
On Mon, 2015-06-08 at 18:07 +0800, Dongsheng Yang wrote:
Currently, ubifs does not support access time anyway. I understand
that there is a overhead to update inode in each access from user.
But for the following two reasons, I think we can make it optional
to user.
(1). More and more flash storage in server are trying to use ubifs,
it is not only for a device such as mobile phone any more, we want
to use it in more and more generic way. Then we need to compete
with some other main filesystems. From this point, access time is
necessary to us, at least as a choice to user currently.
(2). The default mount option about atime is relatime currently,
it's much relaxy compared with strictatime. Then we don't update
the inode in any accessing. So the overhead is not too much.
It's really acceptable.
Signed-off-by: Dongsheng Yang <yangds.fnst@xxxxxxxxxxxxxx>
---
It's a RESEND patch to cc to fsdevel as Artem suggested.
I would rename force_atime to enable_atime in next version.
Why do you need to introduce a custom "force_atime" option if there are
already standard "atime" and "noatime" mount option? I am fine with
adding atime support to UBIFS in general, and I'd expect this behavior
then.
I think the rationale behind force_atime was "I know atime can hurt my NAND and I know what
I'm doing". :-)
Such that possible users think of the consequences.
Thanx Richard, Yes, that's my point. :-)
In addition, the atime and noatime are non-fs dependent options.
Then these options would be parsed in userspace and vfs will
get a flags about them. vfs are treating default as atime enabled,
then vfs will set MNT_RELATIME in flags:
2592 /* Default to relatime unless overriden */
2593 if (!(flags & MS_NOATIME))
2594 mnt_flags |= MNT_RELATIME;
But ubifs is working differently. ubifs disables atime by default.
The problem is, we can not distinguish the following two case
in ubifs.
1. mount -t ubifs ... - MNT_RELATIME in flags
2. mount -t ubifs -o atime - MNT_RELATIME in flags too
In vfs, they are equal. In ubifs, we want different behaviours but we
can not distinguish them.
Therefore, I introduced a new option named as force_atime in ubifs.
That's a ubifs-dependent opiton and it works as a main switch, in
a higher level compared with atime and noatime. If force_atime, we
support the atime-related flags. Otherwise, we don't care about all of
them in flags and don't support atime anyway.
Thanx
Yang
Thanks,
//richard
.
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