From a5c9b696ec109bb54d547fdb437a7a0c2d514670 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Tue, 23 Jun 2009 12:36:58 -0700 Subject: [PATCH] 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 Signed-off-by: Johannes Weiner Signed-off-by: Hugh Dickins Acked-by: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/swap.h | 12 ++++++------ mm/memory.c | 2 +- mm/thrash.c | 32 +++++++++++++++----------------- 3 files changed, 22 insertions(+), 24 deletions(-) diff --git a/include/linux/swap.h b/include/linux/swap.h index c88b36665f79..7c15334f3ff2 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 50da9511aa77..f46ac18ba231 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 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. */ -- 2.39.5