Linus Torvalds 89f5b7da2a Reinstate ZERO_PAGE optimization in 'get_user_pages()' and fix XIP ... KAMEZAWA Hiroyuki and Oleg Nesterov point out that since the commit 557ed1fa26 ("remove ZERO_PAGE") removed the ZERO_PAGE from the VM mappings, any users of get_user_pages() will generally now populate the VM with real empty pages needlessly. We used to get the ZERO_PAGE when we did the "handle_mm_fault()", but since fault handling no longer uses ZERO_PAGE for new anonymous pages, we now need to handle that special case in follow_page() instead. In particular, the removal of ZERO_PAGE effectively removed the core file writing optimization where we would skip writing pages that had not been populated at all, and increased memory pressure a lot by allocating all those useless newly zeroed pages. This reinstates the optimization by making the unmapped PTE case the same as for a non-existent page table, which already did this correctly. While at it, this also fixes the XIP case for follow_page(), where the caller could not differentiate between the case of a page that simply could not be used (because it had no "struct page" associated with it) and a page that just wasn't mapped. We do that by simply returning an error pointer for pages that could not be turned into a "struct page *". The error is arbitrarily picked to be EFAULT, since that was what get_user_pages() already used for the equivalent IO-mapped page case. [ Also removed an impossible test for pte_offset_map_lock() failing: that's not how that function works ] Acked-by: Oleg Nesterov <oleg@tv-sign.ru> Acked-by: Nick Piggin <npiggin@suse.de> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Hugh Dickins <hugh@veritas.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Ingo Molnar <mingo@elte.hu> Cc: Roland McGrath <roland@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2008-06-20 11:18:25 -07:00
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boot	[POWERPC] Fix bootwrapper builds with newer gcc versions	2008-06-16 15:00:52 +10:00
configs	[POWERPC] Turn on ATA_SFF so we get SATA_SVW back in defconfigs	2008-06-16 21:14:12 +10:00
kernel	Reinstate ZERO_PAGE optimization in 'get_user_pages()' and fix XIP	2008-06-20 11:18:25 -07:00
kvm	KVM: ppc: Report bad GFNs	2008-06-06 21:22:41 +03:00
lib	[POWERPC] Fix -Os kernel builds with newer gcc versions	2008-06-16 15:00:54 +10:00
math-emu	[POWERPC] Replace remaining __FUNCTION__ occurrences	2008-04-01 20:43:09 +11:00
mm	[POWERPC] Clear sub-page HPTE present bits when demoting page size	2008-06-18 21:40:43 +10:00
oprofile	Merge branch 'linux-2.6'	2008-04-14 21:11:02 +10:00
platforms	[POWERPC] Fix warning in pseries/eeh_driver.c	2008-06-16 15:00:44 +10:00
sysdev	rtc-ds1374: rename device to just "ds1374"	2008-06-06 11:29:10 -07:00
xmon	powerpc/spufs: remove class_0_dsisr from spu exception handling	2008-06-16 14:35:00 +10:00
.gitignore	[POWERPC] Add files build to .gitignore	2006-12-04 20:41:29 +11:00
Kconfig	[RAPIDIO] Add RapidIO option to kernel configuration	2008-04-29 19:40:27 +10:00
Kconfig.debug	[POWERPC] Add IRQSTACKS support on ppc32	2008-04-29 15:57:34 +10:00
Makefile	[POWERPC] Fix -Os kernel builds with newer gcc versions	2008-06-16 15:00:54 +10:00