Messages in this thread |  | | From | Neil Brown <> | Date | Tue, 18 Mar 2003 16:59:53 +1100 | Subject | Re: 2.4.20: ext3/raid5 - allocating block in system zone/multiple 1 requests for sector |
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On Monday March 17, akpm@digeo.com wrote: > Neil Brown <neilb@cse.unsw.edu.au> wrote: > > > > These two symptoms strongly suggest a buffer aliasing problem. > > i.e. you have two buffers (one for data and one for metadata) > > that refer to the same location on disc. > > One is part of a file that was recently deleted, but the buffer hasn't > > been flushed yet. The other is part of a new directory. > > The old buffer and the new buffer both get written to disc at much the > > same time (hence the "multiple 1 requests"), but the old buffer hits > > the disc second and so corrupts the filesystem. > > This aliasing can happen very easily with direct-io, and it is something > which drivers should be able to cope with. > > I hope RAID is not still assuming that all requests are unique in this way?
No. RAID copes. If raid5 sees a write request for a block that it already has a pending write request for, it will print a warning and delay the second until the first complete.
In the cas in question I don't think raid5 is contributing to the problem. It is just provide extra information which might help point towards the problem - i.e. it is confirming that some sort of aliasing is happening.
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