Messages in this thread | | | From | Ferenc Wagner <> | Subject | mmap vs mtime in 2.6.26 and up | Date | Tue, 12 May 2009 14:32:38 +0200 |
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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; I also tested with 2.6.30-rc5, they are still stuck). 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 kernels. 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 couldn't test this part with 2.6.30-rc5, but again, this may be totally unrelated.)
This bug is quite serious in our environment, as it thwarts the backup software. The file system is xfs; rw,nosuid,nodev,nobarrier,noquota. -- Regards, Feri.
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