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[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>
This commit is contained in:
NeilBrown 2006-06-23 02:05:48 -07:00 committed by Linus Torvalds
parent 57ae250861
commit e0f23603fb
1 changed files with 16 additions and 6 deletions
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22
mm/truncate.c
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@ -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)) {
next++;
continue;
}
if (page->index > next)
next = page->index;
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 (PageDirty(page) || PageWriteback(page))
goto unlock;
if (page_mapped(page))