Messages in this thread | | | Date | Mon, 5 Mar 2012 20:15:38 +0800 | Subject | Re: [PATCH] mm: shmem: unlock valid page | From | Hillf Danton <> |
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On Mon, Mar 5, 2012 at 1:51 AM, Hugh Dickins <hughd@google.com> wrote: > On Sun, 4 Mar 2012, Hillf Danton wrote: >> In shmem_read_mapping_page_gfp() page is unlocked if no error returned, >> so the unlocked page has to valid. >> >> To guarantee that validity, when getting page, success result is feed >> back to caller only when page is valid. >> >> Signed-off-by: Hillf Danton <dhillf@gmail.com> > > I don't understand your description, nor its relation to the patch. > > NAK to the patch: when no page has previously been allocated, the > SGP_READ case avoids allocation and returns NULL - do_shmem_file_read > then copies the ZERO_PAGE instead, avoiding lots of unnecessary memory > allocation when reading a large sparse file. > Hi Hugh
Thanks for your review.
It was not well prepared as I missed SGP_CACHE.
-hd
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