mmap vs mtime in 2.6.26
- From: Ferenc Wagner <wferi@xxxxxxx>
- Date: Fri, 08 May 2009 02:58:43 +0200
Hi,
I've noticed that the last modification times of our RRD files got
stuck after upgrading from 2.6.24 to 2.6.26 (Debian Etch -> Lenny).
It has some literature, most notably kernel bug #2645, but that's
closed long ago and the resulting patch
http://lkml.org/lkml/2008/1/22/370 is present in my kernel. Still,
the test program (version 3 from the bug report) gives failures:
$ ./mmap_test junk
Modifying junk...
Flushing data using sync()...
Failure: time not changed.
Not modifying junk...
Flushing data using msync()...
Success: time not changed.
Not modifying junk...
Flushing data using fsync()...
Success: time not changed.
Modifying junk...
Flushing data using msync()...
Failure: time not changed.
Modifying junk...
Flushing data using fsync()...
Failure: time not changed.
Is this as expected? I reckon the bug wasn't solved fully, but it
seems to be worse that that.
I don't know if it's related or not, but another anomaly appeared
after the upgrade: minutes-long remount times. The machine always was
under a fair load (10), but mount /usr -oremount,rw never took
noticeable time. The IO load pushes two other filesystems. Now
strace -tt shows:
[...]
01:24:08.463813 stat64("/sbin/mount.xfs", 0xbfa40eb0) = -1 ENOENT (No such file or directory)
01:24:08.463904 mount("/dev/mapper/noc7-usr", "/usr", 0x894a2c8, MS_MGC_VAL|MS_NODEV|MS_REMOUNT, NULL) = 0
01:26:58.705387 readlink("/dev", 0xbfa3ef3b, 4096) = -1 EINVAL (Invalid argument)
[...]
After this, remount ro and rw again are quick for some time.
I can not easily test newer kernels in this setup, so thought to ask
around before delving into it further. Is this a known problem
perhaps? Does it ring any bells? If already fixed, can the fix be
backported to 2.6.26 with reasonable effort? If not, how can I best
help investigate this?
--
Thanks,
Feri.
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