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SubjectRe: [RFC][PATCH] set_page_buffer_dirty should skip unmapped buffers
Jan Kara wrote:
> Hi,
>> Jan Kara wrote:
>>> I've been looking more at the code and I have revived my patch fixing
>>> this part of the code. I've mildly tested the patch. Could you also give
>>> it a try? Thanks.
>>> Honza
>>> ------------------------------------------------------------------------
>>> Original commit code assumes, that when a buffer on BJ_SyncData list is
>>> locked,
>>> it is being written to disk. But this is not true and hence it can lead to
>>> a
>>> potential data loss on crash. Also the code didn't count with the fact that
>>> journal_dirty_data() can steal buffers from committing transaction and
>>> hence
>>> could write buffers that no longer belong to the committing transaction.
>>> Finally it could possibly happen that we tried writing out one buffer
>>> several
>>> times.
>>> The patch below tries to solve these problems by a complete rewrite of the
>>> data
>>> commit code. We go through buffers on t_sync_datalist, lock buffers needing
>>> write out and store them in an array. Buffers are also immediately refiled
>>> to
>>> BJ_Locked list or unfiled (if the write out is completed). When the array
>>> is
>>> full or we have to block on buffer lock, we submit all accumulated buffers
>>> for
>>> IO.
>>> Signed-off-by: Jan Kara <>
>> I have been running 4+ hours with this patch and seems to work fine. I
>> haven't hit any
>> assert yet :)
>> I will let it run till tomorrow. I will let you know, how it goes.
> Great, thanks. BTW: Do you have any performance tests handy? The
> changes are big enough to cause some unexpected performance regressions,
> livelocks... If you don't have anything ready, I can setup and run
> something myself. Just that I don't like this testing too much ;).
Tests are still running fine.

I don't have any performance tests handy. We have some automated tests I
can schedule
to run to verify the stability aspects.


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