Re: [PATCH linux-2.6.0-test10-mm1] filemap_fdatawait.patch

[Andrew Morton]

Suparna Bhattacharya <suparna@xxxxxxxxxx> wrote:
>
>  > OK, but the thread which is running fdatawrite/fdatawait isn't interested
>  > in that page, because it must have been dirtied _after_ this thread has
>  > passed through filemap_fdatawrite(), yes?
> 
>  Not exactly. The page could actually have been dirtied _before_ this 
>  thread passes through filemap_datawrite, but is just being parallely 
>  written back by a background thread.

I still don't see it.  If the page was dirtied before this thread entered
filemap_fdatawrite() then this thread will either start writeout
immediately, or will wait on the writeout and start new writeout.  And
the page lock avoids the timing window which you have mentioned.

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