On Mon, Mar 5, 2012 at 1:51 AM, Hugh Dickins <hughd@xxxxxxxxxx> 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@xxxxxxxxx> > > 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>