From: Karel Zak <kzak@redhat.com>
To: Qu Wenruo <quwenruo@cn.fujitsu.com>
Cc: util-linux@vger.kernel.org
Subject: Re: libblkid: Idea to force given cached entry to be invalidated?
Date: Thu, 17 Apr 2014 10:21:05 +0200 [thread overview]
Message-ID: <20140417082105.GH5786@x2.net.home> (raw)
In-Reply-To: <534F2B8F.5010906@cn.fujitsu.com>
On Thu, Apr 17, 2014 at 09:17:03AM +0800, Qu Wenruo wrote:
> But after some tests, it seems that the ctime/mtime based cache seems not
> perfect due to the fact that multiple
Yes, the cache is not perfect -- it was originally introduced by Ted
in time when things was less complicated :-) The current goal is to
avoid the cache usage, so we have low-level API in libblkid to bypass
the cache at all, and in userspace we use this API or udev db. I guess
that many users have the cache empty, because it's unnecessary for
fsck, mount, lsblk, findmnt, systemd etc.
> device file can be created in different fs with same major/minor number.
> especially each of them has individual ctime/mtime timestamp.
>
> So if someone (maybe insane) use mknod to create as block device file and
> use 'btrfs dev del' on the newly created
> block device file, libblkid will still be unable to detect the change since
> the ctime/mtime of block device file in /dev/
> does not change.
Not sure if I understand, it would be nice to have complete example.
Karel
--
Karel Zak <kzak@redhat.com>
http://karelzak.blogspot.com
next prev parent reply other threads:[~2014-04-17 8:21 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-15 2:15 libblkid: Idea to force given cached entry to be invalidated? Qu Wenruo
2014-04-15 4:27 ` Theodore Ts'o
2014-04-15 4:52 ` Qu Wenruo
2014-04-15 11:21 ` Karel Zak
2014-04-16 0:53 ` Qu Wenruo
2014-04-16 9:03 ` Karel Zak
2014-04-17 1:17 ` Qu Wenruo
2014-04-17 8:21 ` Karel Zak [this message]
2014-04-17 8:29 ` Qu Wenruo
2014-04-18 11:02 ` Karel Zak
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