bad page state under possibly oom situation

[Dipankar Sarma <dipankar@in.ibm.com>]

We have discussed this in private previously and I had mentioned
that I see this introduced between 2.6.9-rc1 and 2.6.9-rc2. After
spending some time doing other things, I went back to take a
look at this again and thought I would share this with a wider
audience. The basic problem is that while running the LTP rename14
test with a tmpfs /tmp, I see this -

Bad page state at prep_new_page (in process 'rename14', page ffff810008002aa8)
flags:0x4000000000000090 mapping:0000000000000000 mapcount:0 count:0
Backtrace:

Call Trace:<ffffffff80150388>{bad_page+115} <ffffffff80150bb1>{buffered_rmqueue+438}
       <ffffffff80150da8>{__alloc_pages+251} <ffffffff8022fb10>{_atomic_dec_and_lock+24}
       <ffffffff801535b3>{cache_alloc_refill+581} <ffffffff8015384f>{kmem_cache_alloc+44}
       <ffffffff8017cd55>{d_alloc+33} <ffffffff8017507e>{__lookup_hash+206}
       <ffffffff80176f4e>{sys_rename+245} <ffffffff8010e636>{system_call+126}

Trying to fix it up, but a reboot is needed

Recently, I tested this with 2.6.14 and it worked. I then tried
setting rcupdate.maxbatch=10 as it was before 2.6.14 and the bad
page state problem happened again. Looks like it happens only under
memory pressure and likely have something to do with slab.
I am wondering if that rings a bell with anyone. Manfred ?

Thanks
Dipankar
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