Messages in this thread | | | Date | Wed, 17 Dec 2003 12:17:26 -0800 | From | Janet Morgan <> | Subject | Re: [PATCH linux-2.6.0-test10-mm1] filemap_fdatawait.patch |
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Daniel McNeil wrote:
>On Tue, 2003-12-16 at 18:03, Andrew Morton wrote: > >>Daniel McNeil <daniel@osdl.org> wrote: >> >>>I have found something else that might be causing the problem. >>>filemap_fdatawait() skips pages that are not marked PG_writeback. >>>However, when a page is going to be written, PG_dirty is cleared >>>before PG_writeback is set (while the PG_locked is set). So it >>>looks like filemap_fdatawait() can see a page just before it is >>>going to be written and not wait for it. Here is a patch that >>>makes filemap_fdatawait() wait for locked pages as well to make >>>sure it does not missed any pages. >>> >>This filemap_fdatawait() behaviour is as-designed. That function is only >>responsible for waiting on I/O which was initiated prior to it being >>invoked. Because it is designed for fsync(), fdatasync(), O_SYNC, msync(), >>sync(), etc. >> >>Now, it could be that this behaviour is not appropriate for the O_DIRECT >>sync function - the result of your testing will be interesting. >> > >My tests still failed overnight. I was thinking that maybe a >non-blocking do_writepages() was happening at the same time as >the filemap_fdatawrite()/filemap_fdatawait(), so even though the >page was dirty before the filemap_fdatawrite(), it was missed. > >Daniel > > I'm wondering if processing in generic_file_direct_IO() shouldn't look more like sys_fsync()? When I add to generic_file_direct_IO() a call to f_op->fsync() between the calls to filemap_fdatawrite() and filemap_fdatawait(), the test Daniel and I have been running no longer fails for me. This change would also seem consistent with 2.4, but I could be way off base.
-Janet
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