tree 7a32b42a64a64488aee0e91ab016d53c353f9482
parent 57ae2508610d50893cb3e3bbb869ff70ff724a2a
author NeilBrown <neilb@suse.de> 1151053548 -0700
committer Linus Torvalds <torvalds@g5.osdl.org> 1151073787 -0700

[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>