Commit edf14cdb authored by Vlastimil Babka's avatar Vlastimil Babka Committed by Linus Torvalds
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mm, printk: introduce new format string for flags 



In mm we use several kinds of flags bitfields that are sometimes printed
for debugging purposes, or exported to userspace via sysfs.  To make
them easier to interpret independently on kernel version and config, we
want to dump also the symbolic flag names.  So far this has been done
with repeated calls to pr_cont(), which is unreliable on SMP, and not
usable for e.g.  sysfs export.

To get a more reliable and universal solution, this patch extends
printk() format string for pointers to handle the page flags (%pGp),
gfp_flags (%pGg) and vma flags (%pGv).  Existing users of
dump_flag_names() are converted and simplified.

It would be possible to pass flags by value instead of pointer, but the
%p format string for pointers already has extensions for various kernel
structures, so it's a good fit, and the extra indirection in a
non-critical path is negligible.

[linux@rasmusvillemoes.dk: lots of good implementation suggestions]
Signed-off-by: default avatarVlastimil Babka <vbabka@suse.cz>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 420adbe9

Documentation/printk-formats.txt

+18 −0
Original line number Diff line number Diff line
@@ -298,6 +298,24 @@ bitmap and its derivatives such as cpumask and nodemask: 


	Passed by reference.



Flags bitfields such as page flags, gfp_flags:



	%pGp	referenced|uptodate|lru|active|private

	%pGg	GFP_USER|GFP_DMA32|GFP_NOWARN

	%pGv	read|exec|mayread|maywrite|mayexec|denywrite



	For printing flags bitfields as a collection of symbolic constants that

	would construct the value. The type of flags is given by the third

	character. Currently supported are [p]age flags, [v]ma_flags (both

	expect unsigned long *) and [g]fp_flags (expects gfp_t *). The flag

	names and print order depends on the particular	type.



	Note that this format should not be used directly in TP_printk() part

	of a tracepoint. Instead, use the show_*_flags() functions from

	<trace/events/mmflags.h>.



	Passed by reference.



Network device features:



	%pNF	0x000000000000c000

lib/test_printf.c

+53 −0
Original line number Diff line number Diff line
@@ -17,6 +17,9 @@ 
#include <linux/socket.h>

#include <linux/in.h>



#include <linux/gfp.h>

#include <linux/mm.h>



#define BUF_SIZE 256

#define PAD_SIZE 16

#define FILL_CHAR '$'
@@ -410,6 +413,55 @@ netdev_features(void) 
{

}



static void __init

flags(void)

{

	unsigned long flags;

	gfp_t gfp;

	char *cmp_buffer;



	flags = 0;

	test("", "%pGp", &flags);



	/* Page flags should filter the zone id */

	flags = 1UL << NR_PAGEFLAGS;

	test("", "%pGp", &flags);



	flags |= 1UL << PG_uptodate | 1UL << PG_dirty | 1UL << PG_lru

		| 1UL << PG_active | 1UL << PG_swapbacked;

	test("uptodate|dirty|lru|active|swapbacked", "%pGp", &flags);





	flags = VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC

			| VM_DENYWRITE;

	test("read|exec|mayread|maywrite|mayexec|denywrite", "%pGv", &flags);



	gfp = GFP_TRANSHUGE;

	test("GFP_TRANSHUGE", "%pGg", &gfp);



	gfp = GFP_ATOMIC|__GFP_DMA;

	test("GFP_ATOMIC|GFP_DMA", "%pGg", &gfp);



	gfp = __GFP_ATOMIC;

	test("__GFP_ATOMIC", "%pGg", &gfp);



	cmp_buffer = kmalloc(BUF_SIZE, GFP_KERNEL);

	if (!cmp_buffer)

		return;



	/* Any flags not translated by the table should remain numeric */

	gfp = ~__GFP_BITS_MASK;

	snprintf(cmp_buffer, BUF_SIZE, "%#lx", (unsigned long) gfp);

	test(cmp_buffer, "%pGg", &gfp);



	snprintf(cmp_buffer, BUF_SIZE, "__GFP_ATOMIC|%#lx",

							(unsigned long) gfp);

	gfp |= __GFP_ATOMIC;

	test(cmp_buffer, "%pGg", &gfp);



	kfree(cmp_buffer);

}



static void __init

test_pointer(void)

{
@@ -428,6 +480,7 @@ test_pointer(void) 
	struct_clk();

	bitmap();

	netdev_features();

	flags();

}



static int __init

lib/vsprintf.c

+75 −0
Original line number Diff line number Diff line
@@ -35,6 +35,8 @@ 
#include <linux/blkdev.h>

#endif



#include "../mm/internal.h"	/* For the trace_print_flags arrays */



#include <asm/page.h>		/* for PAGE_SIZE */

#include <asm/sections.h>	/* for dereference_function_descriptor() */

#include <asm/byteorder.h>	/* cpu_to_le16 */
@@ -1407,6 +1409,72 @@ char *clock(char *buf, char *end, struct clk *clk, struct printf_spec spec, 
	}

}



static

char *format_flags(char *buf, char *end, unsigned long flags,

					const struct trace_print_flags *names)

{

	unsigned long mask;

	const struct printf_spec strspec = {

		.field_width = -1,

		.precision = -1,

	};

	const struct printf_spec numspec = {

		.flags = SPECIAL|SMALL,

		.field_width = -1,

		.precision = -1,

		.base = 16,

	};



	for ( ; flags && names->name; names++) {

		mask = names->mask;

		if ((flags & mask) != mask)

			continue;



		buf = string(buf, end, names->name, strspec);



		flags &= ~mask;

		if (flags) {

			if (buf < end)

				*buf = '|';

			buf++;

		}

	}



	if (flags)

		buf = number(buf, end, flags, numspec);



	return buf;

}



static noinline_for_stack

char *flags_string(char *buf, char *end, void *flags_ptr, const char *fmt)

{

	unsigned long flags;

	const struct trace_print_flags *names;



	switch (fmt[1]) {

	case 'p':

		flags = *(unsigned long *)flags_ptr;

		/* Remove zone id */

		flags &= (1UL << NR_PAGEFLAGS) - 1;

		names = pageflag_names;

		break;

	case 'v':

		flags = *(unsigned long *)flags_ptr;

		names = vmaflag_names;

		break;

	case 'g':

		flags = *(gfp_t *)flags_ptr;

		names = gfpflag_names;

		break;

	default:

		WARN_ONCE(1, "Unsupported flags modifier: %c\n", fmt[1]);

		return buf;

	}



	return format_flags(buf, end, flags, names);

}



int kptr_restrict __read_mostly;



/*
@@ -1495,6 +1563,11 @@ int kptr_restrict __read_mostly; 
 * - 'Cn' For a clock, it prints the name (Common Clock Framework) or address

 *        (legacy clock framework) of the clock

 * - 'Cr' For a clock, it prints the current rate of the clock

 * - 'G' For flags to be printed as a collection of symbolic strings that would

 *       construct the specific value. Supported flags given by option:

 *       p page flags (see struct page) given as pointer to unsigned long

 *       g gfp flags (GFP_* and __GFP_*) given as pointer to gfp_t

 *       v vma flags (VM_*) given as pointer to unsigned long

 *

 * ** Please update also Documentation/printk-formats.txt when making changes **

 *
@@ -1648,6 +1721,8 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr, 
		return bdev_name(buf, end, ptr, spec, fmt);

#endif



	case 'G':

		return flags_string(buf, end, ptr, fmt);

	}

	spec.flags |= SMALL;

	if (spec.field_width == -1) {

mm/debug.c

+20 −14
Original line number Diff line number Diff line
@@ -11,12 +11,21 @@ 
#include <linux/memcontrol.h>

#include <trace/events/mmflags.h>



static const struct trace_print_flags pageflag_names[] = {

	__def_pageflag_names

#include "internal.h"



const struct trace_print_flags pageflag_names[] = {

	__def_pageflag_names,

	{0, NULL}

};



const struct trace_print_flags gfpflag_names[] = {

	__def_gfpflag_names,

	{0, NULL}

};



static const struct trace_print_flags gfpflag_names[] = {

	__def_gfpflag_names

const struct trace_print_flags vmaflag_names[] = {

	__def_vmaflag_names,

	{0, NULL}

};



static void dump_flags(unsigned long flags,
@@ -58,14 +67,15 @@ void dump_page_badflags(struct page *page, const char *reason, 
	if (PageCompound(page))

		pr_cont(" compound_mapcount: %d", compound_mapcount(page));

	pr_cont("\n");

	BUILD_BUG_ON(ARRAY_SIZE(pageflag_names) != __NR_PAGEFLAGS);

	dump_flags(page->flags, pageflag_names, ARRAY_SIZE(pageflag_names));

	BUILD_BUG_ON(ARRAY_SIZE(pageflag_names) != __NR_PAGEFLAGS + 1);

	dump_flags(page->flags, pageflag_names,

					ARRAY_SIZE(pageflag_names) - 1);

	if (reason)

		pr_alert("page dumped because: %s\n", reason);

	if (page->flags & badflags) {

		pr_alert("bad because of flags:\n");

		dump_flags(page->flags & badflags,

				pageflag_names, ARRAY_SIZE(pageflag_names));

		dump_flags(page->flags & badflags, pageflag_names,

					ARRAY_SIZE(pageflag_names) - 1);

	}

#ifdef CONFIG_MEMCG

	if (page->mem_cgroup)
@@ -81,10 +91,6 @@ EXPORT_SYMBOL(dump_page); 


#ifdef CONFIG_DEBUG_VM



static const struct trace_print_flags vmaflag_names[] = {

	__def_vmaflag_names

};



void dump_vma(const struct vm_area_struct *vma)

{

	pr_emerg("vma %p start %p end %p\n"
@@ -96,7 +102,7 @@ void dump_vma(const struct vm_area_struct *vma) 
		(unsigned long)pgprot_val(vma->vm_page_prot),

		vma->anon_vma, vma->vm_ops, vma->vm_pgoff,

		vma->vm_file, vma->vm_private_data);

	dump_flags(vma->vm_flags, vmaflag_names, ARRAY_SIZE(vmaflag_names));

	dump_flags(vma->vm_flags, vmaflag_names, ARRAY_SIZE(vmaflag_names) - 1);

}

EXPORT_SYMBOL(dump_vma);
@@ -168,7 +174,7 @@ void dump_mm(const struct mm_struct *mm) 
		);



		dump_flags(mm->def_flags, vmaflag_names,

				ARRAY_SIZE(vmaflag_names));

				ARRAY_SIZE(vmaflag_names) - 1);

}



#endif		/* CONFIG_DEBUG_VM */

mm/internal.h

+6 −0
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ 
#include <linux/fs.h>

#include <linux/mm.h>

#include <linux/pagemap.h>

#include <linux/tracepoint-defs.h>



/*

 * The set of flags that only affect watermark checking and reclaim
@@ -466,4 +467,9 @@ static inline void try_to_unmap_flush_dirty(void) 
}



#endif /* CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH */



extern const struct trace_print_flags pageflag_names[];

extern const struct trace_print_flags vmaflag_names[];

extern const struct trace_print_flags gfpflag_names[];



#endif	/* __MM_INTERNAL_H */

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