Messages in this thread | | | Date | Tue, 1 May 2007 19:27:16 -0700 | From | "Nate Diller" <> | Subject | Re: [PATCH] zero_user_page uses in fs/buffer.c and fs/libfs.c |
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On 5/1/07, Nate Diller <nate.diller@gmail.com> wrote: > On 5/1/07, Christoph Lameter <clameter@sgi.com> wrote: > > On Tue, 1 May 2007, Andrew Morton wrote: > > > > > As Satyam said, this will sometimes cause us to map and unmap the page > > > twice, and to run flush_dcache_page() twice. In not-terribly-uncommon > > > circumstances in very frequently called functions. > > > > > > Doesn't seem worth it to me. > > > > Ok but we have that code three times. Should I add a variant of > > zero_user_page that zeroes everything but the section specified? > > > > zero_user_page_allbut() ? > > the function already exists, it's called simple_prepare_write(), and i > thought there were patches to convert those callsites in -mm ... > although it looks like i let a review comment on that slide by. I > need to redo a bunch of patches for re-submission anyway, so i guess > i'll deal with that tomorrow. > > NATE >
well, leave it to me to reply too quickly, sorry. i think we should leave simple_prepare_write() the way it is, since it's a library function itself. the other two callsites in your patch are buffers, which may themselves be smaller than a page so you would need a special function for just those two uses, there's no other way to avoid making two calls to flush_dcache_page(). if it's tremendously important to you to eliminate open coding of these, maybe make a 'static int buffer_prepare_write()' or some such in fs/buffer.c
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