Even on 64 bit kernel, the mmap failure can happen for a 32 bit task.
Virtual memory space shortage of a task on mmap is reported to userspace
as -ENOMEM. It can be confused as physical memory shortage of overall
system.
The vm_unmapped_area can be called to by some drivers or other kernel
core system like filesystem. It can be hard to know which code layer
returns the -ENOMEM.
Print error log of vm_unmapped_area with rate limited. Without rate
limited, soft lockup ocurrs on infinite mmap sytem call.
i.e.)
<3>[ 576.024088] [6: mmap_infinite:14251] mmap: vm_unmapped_area err:-12 total_vm:0xfee08 flags:0x1 len:0xa00000 low:0x8000 high:0xf3f63000
Signed-off-by: Jaewon Kim <jaewon31.kim@xxxxxxxxxxx>
---
include/linux/mm.h | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 52269e56c514..ee822d65ebb7 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2379,10 +2379,19 @@ extern unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info);
static inline unsigned long
vm_unmapped_area(struct vm_unmapped_area_info *info)
{
+ unsigned long addr;
+
if (info->flags & VM_UNMAPPED_AREA_TOPDOWN)
- return unmapped_area_topdown(info);
+ addr = unmapped_area_topdown(info);
else
- return unmapped_area(info);
+ addr = unmapped_area(info);
+
+ if (IS_ERR_VALUE(addr) && printk_ratelimit()) {
+ pr_err("%s err:%d total_vm:0x%lx flags:0x%lx len:0x%lx low:0x%lx high:0x%lx\n",
+ __func__, addr, current->mm->total_vm, info->flags,
+ info->length, info->low_limit, info->high_limit);
+ }
+ return addr;
}
/* truncate.c */
--
2.13.7
