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authorHugh Dickins <hugh.dickins@tiscali.co.uk>2009-06-23 12:36:58 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-23 12:50:05 -0700
commita5c9b696ec109bb54d547fdb437a7a0c2d514670 (patch)
treec97533e38359a2e731bcc2c65f063a27f4f629e6
parent626f380d0b264a1e40237f5a2a3dffc5d14f256e (diff)
downloadconfigs-a5c9b696ec109bb54d547fdb437a7a0c2d514670.tar.gz
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>
-rw-r--r--include/linux/swap.h12
-rw-r--r--mm/memory.c2
-rw-r--r--mm/thrash.c32
3 files changed, 22 insertions, 24 deletions
diff --git a/include/linux/swap.h b/include/linux/swap.h
index c88b36665f7..7c15334f3ff 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -298,8 +298,8 @@ extern int try_to_free_swap(struct page *);
struct backing_dev_info;
/* linux/mm/thrash.c */
-extern struct mm_struct * swap_token_mm;
-extern void grab_swap_token(void);
+extern struct mm_struct *swap_token_mm;
+extern void grab_swap_token(struct mm_struct *);
extern void __put_swap_token(struct mm_struct *);
static inline int has_swap_token(struct mm_struct *mm)
@@ -419,10 +419,10 @@ static inline swp_entry_t get_swap_page(void)
}
/* linux/mm/thrash.c */
-#define put_swap_token(x) do { } while(0)
-#define grab_swap_token() do { } while(0)
-#define has_swap_token(x) 0
-#define disable_swap_token() do { } while(0)
+#define put_swap_token(mm) do { } while (0)
+#define grab_swap_token(mm) do { } while (0)
+#define has_swap_token(mm) 0
+#define disable_swap_token() do { } while (0)
static inline void
mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent)
diff --git a/mm/memory.c b/mm/memory.c
index 50da9511aa7..f46ac18ba23 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2519,7 +2519,7 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
delayacct_set_flag(DELAYACCT_PF_SWAPIN);
page = lookup_swap_cache(entry);
if (!page) {
- grab_swap_token(); /* Contend for token _before_ read-in */
+ grab_swap_token(mm); /* Contend for token _before_ read-in */
page = swapin_readahead(entry,
GFP_HIGHUSER_MOVABLE, vma, address);
if (!page) {
diff --git a/mm/thrash.c b/mm/thrash.c
index c4c5205a9c3..2372d4ed5dd 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. */