Commit e0f23603 authored Jun 23, 2006 by NeilBrown Committed by Linus Torvalds Jun 23, 2006

[PATCH] Remove semi-softlockup from invalidate_mapping_pages



If invalidate_mapping_pages is called to invalidate a very large mapping
(e.g.  a very large block device) and if the only active page in that
device is near the end (or at least, at a very large index), such as, say,
the superblock of an md array, and if that page happens to be locked when
invalidate_mapping_pages is called, then

  pagevec_lookup will return this page and
  as it is locked, 'next' will be incremented and pagevec_lookup
  will be called again. and again. and again.
  while we count from 0 upto a very large number.

We should really always set 'next' to 'page->index+1' before going around
the loop again, not just if the page isn't locked.

Cc: "Steinar H. Gunderson" <sgunderson@bigfoot.com>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

parent 57ae2508

mm/truncate.c

+16 −6

Original line number	Diff line number	Diff line
		@@ -230,14 +230,24 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping,
		pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
		for (i = 0; i < pagevec_count(&pvec); i++) {
		struct page *page = pvec.pages[i];
		pgoff_t index;
		int lock_failed;

		if (TestSetPageLocked(page)) {
		lock_failed = TestSetPageLocked(page);

		/*
		* We really shouldn't be looking at the ->index of an
		* unlocked page. But we're not allowed to lock these
		* pages. So we rely upon nobody altering the ->index
		* of this (pinned-by-us) page.
		*/
		index = page->index;
		if (index > next)
		next = index;
		next++;
		if (lock_failed)
		continue;
		}
		if (page->index > next)
		next = page->index;
		next++;

		if (PageDirty(page) \|\| PageWriteback(page))
		goto unlock;
		if (page_mapped(page))