[PATCH] meminfo: add Cached underflow check

Working on some code lately I've been getting huge values for "Cached".
The cause is that get_page_cache_size() is an approximate value, and for a
sufficiently small returned value of get_page_cache_size() the value
underflows.

Signed-off-by:  Martin Hicks <mort@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/fs/proc/proc_misc.c b/fs/proc/proc_misc.c
index 1d75d6ab6897..a60a3b3d8a7b 100644
--- a/fs/proc/proc_misc.c
+++ b/fs/proc/proc_misc.c
@@ -126,6 +126,7 @@ static int meminfo_read_proc(char *page, char **start, off_t off,
         unsigned long committed;
         unsigned long allowed;
         struct vmalloc_info vmi;
+        long cached;
 
         get_page_state(&ps);
         get_zone_counts(&active, &inactive, &free);
@@ -140,6 +141,10 @@ static int meminfo_read_proc(char *page, char **start, off_t off,
         allowed = ((totalram_pages - hugetlb_total_pages())
                 * sysctl_overcommit_ratio / 100) + total_swap_pages;
 
+        cached = get_page_cache_size() - total_swapcache_pages - i.bufferram;
+        if (cached < 0)
+                cached = 0;
+
         get_vmalloc_info(&vmi);
 
         /*
@@ -172,7 +177,7 @@ static int meminfo_read_proc(char *page, char **start, off_t off,
                 K(i.totalram),
                 K(i.freeram),
                 K(i.bufferram),
-                K(get_page_cache_size()-total_swapcache_pages-i.bufferram),
+                K(cached),
                 K(total_swapcache_pages),
                 K(active),
                 K(inactive),