diff options
| author | Hugh Dickins <hugh.dickins@tiscali.co.uk> | 2009-06-23 12:36:58 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-06-23 12:50:05 -0700 |
| commit | a5c9b696ec109bb54d547fdb437a7a0c2d514670 (patch) | |
| tree | c97533e38359a2e731bcc2c65f063a27f4f629e6 /mm/thrash.c | |
| parent | 626f380d0b264a1e40237f5a2a3dffc5d14f256e (diff) | |
mm: pass mm to grab_swap_token
If a kthread happens to use get_user_pages() on an mm (as KSM does),
there's a chance that it will end up trying to read in a swap page, then
oops in grab_swap_token() because the kthread has no mm: GUP passes down
the right mm, so grab_swap_token() ought to be using it.
We have not identified a stronger case than KSM's daemon (not yet in
mainline), but the issue must have come up before, since RHEL has included
a fix for this for years (though a different fix, they just back out of
grab_swap_token if current->mm is unset: which is what we first proposed,
but using the right mm here seems more correct).
Reported-by: Izik Eidus <ieidus@redhat.com>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/thrash.c')
| -rw-r--r-- | mm/thrash.c | 32 |
1 files changed, 15 insertions, 17 deletions
diff --git a/mm/thrash.c b/mm/thrash.c index c4c5205a9c35..2372d4ed5dd8 100644 --- a/mm/thrash.c +++ b/mm/thrash.c @@ -26,47 +26,45 @@ static DEFINE_SPINLOCK(swap_token_lock); struct mm_struct *swap_token_mm; static unsigned int global_faults; -void grab_swap_token(void) +void grab_swap_token(struct mm_struct *mm) { int current_interval; global_faults++; - current_interval = global_faults - current->mm->faultstamp; + current_interval = global_faults - mm->faultstamp; if (!spin_trylock(&swap_token_lock)) return; /* First come first served */ if (swap_token_mm == NULL) { - current->mm->token_priority = current->mm->token_priority + 2; - swap_token_mm = current->mm; + mm->token_priority = mm->token_priority + 2; + swap_token_mm = mm; goto out; } - if (current->mm != swap_token_mm) { - if (current_interval < current->mm->last_interval) - current->mm->token_priority++; + if (mm != swap_token_mm) { + if (current_interval < mm->last_interval) + mm->token_priority++; else { - if (likely(current->mm->token_priority > 0)) - current->mm->token_priority--; + if (likely(mm->token_priority > 0)) + mm->token_priority--; } /* Check if we deserve the token */ - if (current->mm->token_priority > - swap_token_mm->token_priority) { - current->mm->token_priority += 2; - swap_token_mm = current->mm; + if (mm->token_priority > swap_token_mm->token_priority) { + mm->token_priority += 2; + swap_token_mm = mm; } } else { /* Token holder came in again! */ - current->mm->token_priority += 2; + mm->token_priority += 2; } out: - current->mm->faultstamp = global_faults; - current->mm->last_interval = current_interval; + mm->faultstamp = global_faults; + mm->last_interval = current_interval; spin_unlock(&swap_token_lock); -return; } /* Called on process exit. */ |