Arjan noted that the list_head debugging is BUG'ing when it detects
corruption.  By causing the box to panic immediately, we're possibly
losing some bug reports.  Changing this to a WARN() should mean we at the
least start seeing reports collected at kerneloops.org

Signed-off-by: Dave Jones <davej@redhat.com>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Remove the conditional surrounding the definition of list_add() from list.h
since, if you define CONFIG_DEBUG_LIST, the definition you will subsequently
pick up from lib/list_debug.c will be absolutely identical, at which point you
can remove that redundant definition from list_debug.c as well.

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Cc: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Print the other (hopefully) known good pointer when list_head debugging
too, which may yield additional clues.

Also fix for 80-columns to win akpm brownie points.

Signed-off-by: Dave Jones <davej@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

These two BUG_ON()s are redundant and undesired: we're checking for this
condition further on in the function, only better.

Cc: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

A list_del() debugging check.  Has been in -mm for years.  Dave moved
list_del() out-of-line in the debug case, so this is now suitable for
mainline.

Cc: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Signed-off-by: Dave Jones <davej@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>