mm: mmap: add trace point of vm_unmapped_area

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.  In my platform, GPU driver calls to
vm_unmapped_area and the driver returns -ENOMEM even in GPU side shortage.
It can be hard to distinguish which code layer returns the -ENOMEM.

Create mmap trace file and add trace point of vm_unmapped_area.

i.e.)
277.156599: vm_unmapped_area: addr=77e0d03000 err=0 total_vm=0x17014b flags=0x1 len=0x400000 lo=0x8000 hi=0x7878c27000 mask=0x0 ofs=0x1
342.838740: vm_unmapped_area: addr=0 err=-12 total_vm=0xffb08 flags=0x0 len=0x100000 lo=0x40000000 hi=0xfffff000 mask=0x0 ofs=0x22

[akpm@linux-foundation.org: prefix address printk with 0x, per Matthew]
Signed-off-by: Jaewon Kim <jaewon31.kim@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michel Lespinasse <walken@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Link: http://lkml.kernel.org/r/20200320055823.27089-3-jaewon31.kim@samsung.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/trace/events/mmap.h b/include/trace/events/mmap.h
new file mode 100644 (file)
index 0000000..4661f7b
--- /dev/null
+++ b/include/trace/events/mmap.h
@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM mmap
+
+#if !defined(_TRACE_MMAP_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_MMAP_H
+
+#include <linux/tracepoint.h>
+
+TRACE_EVENT(vm_unmapped_area,
+
+       TP_PROTO(unsigned long addr, struct vm_unmapped_area_info *info),
+
+       TP_ARGS(addr, info),
+
+       TP_STRUCT__entry(
+               __field(unsigned long,  addr)
+               __field(unsigned long,  total_vm)
+               __field(unsigned long,  flags)
+               __field(unsigned long,  length)
+               __field(unsigned long,  low_limit)
+               __field(unsigned long,  high_limit)
+               __field(unsigned long,  align_mask)
+               __field(unsigned long,  align_offset)
+       ),
+
+       TP_fast_assign(
+               __entry->addr = addr;
+               __entry->total_vm = current->mm->total_vm;
+               __entry->flags = info->flags;
+               __entry->length = info->length;
+               __entry->low_limit = info->low_limit;
+               __entry->high_limit = info->high_limit;
+               __entry->align_mask = info->align_mask;
+               __entry->align_offset = info->align_offset;
+       ),
+
+       TP_printk("addr=0x%lx err=%ld total_vm=0x%lx flags=0x%lx len=0x%lx lo=0x%lx hi=0x%lx mask=0x%lx ofs=0x%lx\n",
+               IS_ERR_VALUE(__entry->addr) ? 0 : __entry->addr,
+               IS_ERR_VALUE(__entry->addr) ? __entry->addr : 0,
+               __entry->total_vm, __entry->flags, __entry->length,
+               __entry->low_limit, __entry->high_limit, __entry->align_mask,
+               __entry->align_offset)
+);
+#endif
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>

diff --git a/mm/mmap.c b/mm/mmap.c
index ba990c20ecc2c88a2cb6e1244946011d505c533e..94ae18398c59d4b34011a38f2b905935ceb36ec9 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -53,6 +53,9 @@
 #include <asm/tlb.h>
 #include <asm/mmu_context.h>
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/mmap.h>
+
 #include "internal.h"
 
 #ifndef arch_mmap_check
@@ -2061,10 +2064,15 @@ found_highest:
  */
 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);
+
+       trace_vm_unmapped_area(addr, info);
+       return addr;
 }
 
 #ifndef arch_get_mmap_end