Bah, of course there is a write of the new data to the file just
before the fsync. The fd is also set for auto-flushing (this is a perl
script).
On Feb 8, 2010, at 3:45 PM, Robert Olson wrote:
I have a locking/fsync question..
I have an app that keeps job metadata in an XML file that resides on
a Lustre filesystem (I actually just discovered my running system
has it on NFS, but I'm seeing an anomaly on Lustre so I'll keep
writing).
It uses libxml to read and write the file, and thus has to read the
file into memory, make changes, and write back out.
The approach I'm taking to this is:
open file => fd
lock fd (using fcntl F_SETLKW)
read from fd
ftruncate fd
<make modifications>
fsync fd
unlock fd
close fd
The lustre system is a 4-OSS system and I'm running the test across
12 compute nodes, all of which have the fs mounted with the flock
option (it falls over immediately without flock). I'm at lustre 1.6.6.
What I'm seeing is that, occasionally, the file reads will pick up
an empty or partial file. This doesn't seem like it should be the
case, but I'm sure I'm missing something. I don't see any errors
showing up on the MDS.
thanks,
--bob
_______________________________________________
Lustre-discuss mailing list
[email protected]
http://lists.lustre.org/mailman/listinfo/lustre-discuss
_______________________________________________
Lustre-discuss mailing list
[email protected]
http://lists.lustre.org/mailman/listinfo/lustre-discuss
