Commit 46435364 authored Jan 30, 2016 by Hugh Dickins Committed by Linus Torvalds Feb 03, 2016

mm: retire GUP WARN_ON_ONCE that outlived its usefulness



Trinity is now hitting the WARN_ON_ONCE we added in v3.15 commit
cda540ac ("mm: get_user_pages(write,force) refuse to COW in shared
areas").  The warning has served its purpose, nobody was harmed by that
change, so just remove the warning to generate less noise from Trinity.

Which reminds me of the comment I wrongly left behind with that commit
(but was spotted at the time by Kirill), which has since moved into a
separate function, and become even more obscure: delete it.

Reported-by: Dave Jones <davej@codemonkey.org.uk>
Suggested-by: Kirill A. Shutemov <kirill@shutemov.name>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 34229b27

mm/gup.c

+1 −3

Original line number	Diff line number	Diff line
		@@ -430,11 +430,9 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
		* Anon pages in shared mappings are surprising: now
		* just reject it.
		*/
		if (!is_cow_mapping(vm_flags)) {
		WARN_ON_ONCE(vm_flags & VM_MAYWRITE);
		if (!is_cow_mapping(vm_flags))
		return -EFAULT;
		}
		}
		} else if (!(vm_flags & VM_READ)) {
		if (!(gup_flags & FOLL_FORCE))
		return -EFAULT;

mm/memory.c

+0 −5

Original line number	Diff line number	Diff line
		@@ -2237,11 +2237,6 @@ static int wp_page_shared(struct mm_struct mm, struct vm_area_struct vma,

		page_cache_get(old_page);

		/*
		* Only catch write-faults on shared writable pages,
		* read-only shared pages can get COWed by
		* get_user_pages(.write=1, .force=1).
		*/
		if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
		int tmp;

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