[PATCH] Warn if we run out of swap space

[Christoph Lameter <cl@linux-foundation.org>]

Subject: Warn if we run out of swap space

Running out of swap space means that the evicton of anonymous pages may no longer
be possible which can lead to OOM conditions.

Print a warning when swap space first becomes exhausted.

Signed-off-by: Christoph Lameter <cl@linux-foundation.org>

---
 mm/swapfile.c |    5 +++++
 1 file changed, 5 insertions(+)

Index: linux-2.6/mm/swapfile.c
===================================================================
--- linux-2.6.orig/mm/swapfile.c	2009-05-22 12:25:19.000000000 -0500
+++ linux-2.6/mm/swapfile.c	2009-05-22 13:56:10.000000000 -0500
@@ -380,6 +380,7 @@ swp_entry_t get_swap_page(void)
 	pgoff_t offset;
 	int type, next;
 	int wrapped = 0;
+	static int printed = 0;

 	spin_lock(&swap_lock);
 	if (nr_swap_pages <= 0)
@@ -410,6 +411,10 @@ swp_entry_t get_swap_page(void)
 	}

 	nr_swap_pages++;
+	if (!printed) {
+		printed = 1;
+		printk(KERN_WARNING "All of swap is in use. Some pages cannot be swapped out.");
+	}
 noswap:
 	spin_unlock(&swap_lock);
 	return (swp_entry_t) {0};

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