Messages in this thread | | | Subject | Re: 2.6.18 ext3 panic. | From | Badari Pulavarty <> | Date | Tue, 10 Oct 2006 15:25:06 -0700 |
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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 ?
Thanks, Badari
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