On Fri, 8 Dec 2000, Alexander Viro wrote:
>
> I'm quite aware of that fact ;-) However, you said
>
> On the other hand, I have this suspicion that there is an even simpler
> solution: stop using the end_buffer_io_sync version for writes
> altogether.
>
> If that happens (i.e. if write requests resulting from prepare_write()/
> commit_write()/bdflush sequence become async) we must stop unlocking pages
> after commit_write(). Essentially it would become unlocker of the same
> kind as readpage() and writepage() - callers must assume that page submitted
> to commit_write() will eventually be unlocked.
You're right, we can't do that for anonymous buffers right now. Mea culpa.
Looking more at this issue, I suspect that the easiest pretty solution
that everybody can probably agree is reasonable is to either pass down the
end-of-io callback to ll_rw_block as you suggested, or, preferably by just
forcing the _caller_ to do the buffer locking, and just do the b_end_io
stuff inside the buffer lock and get rid of all the races that way
instead (and make ll_rw_block() verify that the buffers it is passed are
always locked).
Linus
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