Commit df529cab authored by Jaewon Kim's avatar Jaewon Kim Committed by Linus Torvalds
Browse files

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: default avatarJaewon Kim <jaewon31.kim@samsung.com>
Signed-off-by: default avatarAndrew 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: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent baceaf1c

include/trace/events/mmap.h

0 → 100644
+48 −0
Original line number Diff line number Diff line 
/* 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>

mm/mmap.c

+10 −2
Original line number Diff line number Diff line
@@ -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

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