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Date: Tue, 15 Nov 2011 15:43:57 +0000
From: Mel Gorman <mgorman@...e.de>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Colin Cross <ccross@...roid.com>,
Pekka Enberg <penberg@...helsinki.fi>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
Andrea Arcangeli <aarcange@...hat.com>,
David Rientjes <rientjes@...gle.com>,
LKML <linux-kernel@...r.kernel.org>,
Linux-MM <linux-mm@...ck.org>
Subject: Re: [PATCH] mm: avoid livelock on !__GFP_FS allocations
> <SNIP>
> It feels overkill to allocate more global storage for it when
> gfp_allowed_mask is already there but I could rename pm_suspending() to
> pm_disabled_storage(), make try_to_free_swap() use the same helper but
> leave the implementation the same. This would clarify the situation.
>
Something like this? It's on top of your comment update
==== CUT HERE ====
mm: Clarify usage of gfp_allowed_mask
This patch clarifies how gfp_allowed_mask is used and that during
run-time it is PM-specific.
Signed-off-by: Mel Gorman <mgorman@...e.de>
---
include/linux/gfp.h | 16 ++++++++++++++++
mm/page_alloc.c | 11 ++---------
mm/swapfile.c | 6 +++---
3 files changed, 21 insertions(+), 12 deletions(-)
diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 3a76faf..033f55f 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -367,9 +367,25 @@ void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp);
void drain_all_pages(void);
void drain_local_pages(void *dummy);
+/*
+ * gfp_allowed_mask is set to GFP_BOOT_MASK during early boot to restrict what
+ * GFP flags are used before interrupts are enabled. Once interrupts are
+ * enabled, it is set to __GFP_BITS_MASK while the system is running. During
+ * hibernation, it is used by PM to avoid I/O during memory allocation while
+ * devices are suspended.
+ */
extern gfp_t gfp_allowed_mask;
extern void pm_restrict_gfp_mask(void);
extern void pm_restore_gfp_mask(void);
+#ifdef CONFIG_PM_SLEEP
+extern bool pm_suspended_storage(void);
+#else
+static inline bool pm_suspended_storage(void)
+{
+ return false;
+}
+#endif /* CONFIG_PM_SLEEP */
+
#endif /* __LINUX_GFP_H */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2ee4040..4ace1e0 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -128,19 +128,12 @@ void pm_restrict_gfp_mask(void)
gfp_allowed_mask &= ~GFP_IOFS;
}
-static bool pm_suspending(void)
+bool pm_suspended_storage(void)
{
if ((gfp_allowed_mask & GFP_IOFS) == GFP_IOFS)
return false;
return true;
}
-
-#else
-
-static bool pm_suspending(void)
-{
- return false;
-}
#endif /* CONFIG_PM_SLEEP */
#ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE
@@ -2235,7 +2228,7 @@ rebalance:
* Suspend also disables storage devices so kswapd cannot save
* us. Bail if we are suspending.
*/
- if (pm_suspending())
+ if (pm_suspended_storage())
goto nopage;
}
diff --git a/mm/swapfile.c b/mm/swapfile.c
index b1cd120..9520592 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -667,10 +667,10 @@ int try_to_free_swap(struct page *page)
* original page might be freed under memory pressure, then
* later read back in from swap, now with the wrong data.
*
- * Hibernation clears bits from gfp_allowed_mask to prevent
- * memory reclaim from writing to disk, so check that here.
+ * Hibration suspends storage while it is writing the image
+ * to disk so check that here.
*/
- if (!(gfp_allowed_mask & __GFP_IO))
+ if (pm_suspended_storage())
return 0;
delete_from_swap_cache(page);
--
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