Shared file pages are never accounted in memory overcommit code,
so it isn't reasonable to count them in a code that limits the
maximal size of a process in OVERCOMMIT_NONE mode.
If a process has few large file mappings, the consequent attempts
to allocate anonymous memory may unexpectedly fail with -ENOMEM,
while there is free memory and overcommit limit if significantly
larger than the committed amount (as displayed in /proc/meminfo).
The problem is significantly smoothed by commit c9b1d0981fcc
("mm: limit growth of 3% hardcoded other user reserve"),
which limits the impact of this check with 128Mb (tunable via sysctl),
but it can still be a problem on small machines.
Signed-off-by: Roman Gushchin <klamm@xxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andrew Shewmaker <agshew@xxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
---
mm/mmap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/mmap.c b/mm/mmap.c
index 7f684d5..151fadf 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -220,7 +220,7 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
*/
if (mm) {
reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10);
- allowed -= min(mm->total_vm / 32, reserve);
+ allowed -= min((mm->total_vm - mm->shared_vm) / 32, reserve);
}
if (percpu_counter_read_positive(&vm_committed_as) < allowed)
--
2.1.0
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