Messages in this thread | | | Date | Tue, 10 Oct 2006 20:43:35 -0500 | From | Eric Sandeen <> | Subject | Re: 2.6.18 ext3 panic. |
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Badari Pulavarty wrote: > On Tue, 2006-10-10 at 17:03 -0500, Eric Sandeen wrote: >> Jan Kara wrote: >> >>> I think it's really the 1KB block size that makes it happen. >>> I've looked at journal_dirty_data() code and I think the following can >>> happen: >>> sync() eventually ends up in journal_dirty_data(bh) as Eric writes. >>> There is finds dirty buffer attached to the comitting transaction. So it drops >>> all locks and calls sync_dirty_buffer(bh). >>> Now in other process, file is truncated so that 'bh' gets just after EOF. >>> As we have 1kb buffers, it can happen that bh is in the partially >>> truncated page. Buffer is marked unmapped and clean. But in a moment the page >>> is marked dirty and msync() is called. That eventually calls >>> set_page_dirty() and all buffers in the page are marked dirty. >>> The first process now wakes up, locks the buffer, clears the dirty bit >>> and does submit_bh() - Oops. >> Hm, just FWIW I have a couple traces* of the buffer getting unmapped >> -before- journal_submit_data_buffers ever even finds it... >> >> journal_submit_data_buffers():[fs/jbd/commit.c:242] needs writeout, >> adding to array pid 1836 >> b_state:0x114025 b_jlist:BJ_SyncData cpu:0 b_count:2 b_blocknr:27130 >> b_jbd:1 b_frozen_data:0000000000000000 >> b_committed_data:0000000000000000 >> b_transaction:1 b_next_transaction:0 b_cp_transaction:0 >> b_trans_is_running:0 >> b_trans_is_comitting:1 b_jcount:0 pg_dirty:0 >> >> so it's already unmapped at this point. Could >> journal_submit_data_buffers benefit from some buffer_mapped checks? Or >> is that just a bandaid too late... > > Hmm.. > > b_state: 0x114025 > ^ > means BH_Mapped. Isn't it ?
Whoops, I pasted in the wrong one, I guess, from earlier in the trace. Here are the ones I was looking at:
journal_submit_data_buffers():[fs/jbd/commit.c:242] needs writeout, adding to array pid 1690 b_state:0x104005 b_jlist:BJ_SyncData cpu:0 b_count:2 b_blocknr:30045 b_jbd:1 b_frozen_data:0000000000000000 b_committed_data:0000000000000000 b_transaction:1 b_next_transaction:0 b_cp_transaction:0 b_trans_is_running:0 b_trans_is_comitting:1 b_jcount:0 pg_dirty:1
and
journal_submit_data_buffers():[fs/jbd/commit.c:242] needs writeout, adding to array pid 1836 b_state:0x114005 b_jlist:BJ_SyncData cpu:1 b_count:2 b_blocknr:27130 b_jbd:1 b_frozen_data:0000000000000000 b_committed_data:0000000000000000 b_transaction:1 b_next_transaction:0 b_cp_transaction:0 b_trans_is_running:0 b_trans_is_comitting:1 b_jcount:0 pg_dirty:1
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