Revision 0ee931c4e31a5efb134c76440405e9219f896e33 authored by Michal Hocko on 13 September 2017, 23:28:29 UTC, committed by Linus Torvalds on 14 September 2017, 01:53:16 UTC
GFP_TEMPORARY was introduced by commit e12ba74d8ff3 ("Group short-lived
and reclaimable kernel allocations") along with __GFP_RECLAIMABLE.  It's
primary motivation was to allow users to tell that an allocation is
short lived and so the allocator can try to place such allocations close
together and prevent long term fragmentation.  As much as this sounds
like a reasonable semantic it becomes much less clear when to use the
highlevel GFP_TEMPORARY allocation flag.  How long is temporary? Can the
context holding that memory sleep? Can it take locks? It seems there is
no good answer for those questions.

The current implementation of GFP_TEMPORARY is basically GFP_KERNEL |
__GFP_RECLAIMABLE which in itself is tricky because basically none of
the existing caller provide a way to reclaim the allocated memory.  So
this is rather misleading and hard to evaluate for any benefits.

I have checked some random users and none of them has added the flag
with a specific justification.  I suspect most of them just copied from
other existing users and others just thought it might be a good idea to
use without any measuring.  This suggests that GFP_TEMPORARY just
motivates for cargo cult usage without any reasoning.

I believe that our gfp flags are quite complex already and especially
those with highlevel semantic should be clearly defined to prevent from
confusion and abuse.  Therefore I propose dropping GFP_TEMPORARY and
replace all existing users to simply use GFP_KERNEL.  Please note that
SLAB users with shrinkers will still get __GFP_RECLAIMABLE heuristic and
so they will be placed properly for memory fragmentation prevention.

I can see reasons we might want some gfp flag to reflect shorterm
allocations but I propose starting from a clear semantic definition and
only then add users with proper justification.

This was been brought up before LSF this year by Matthew [1] and it
turned out that GFP_TEMPORARY really doesn't have a clear semantic.  It
seems to be a heuristic without any measured advantage for most (if not
all) its current users.  The follow up discussion has revealed that
opinions on what might be temporary allocation differ a lot between
developers.  So rather than trying to tweak existing users into a
semantic which they haven't expected I propose to simply remove the flag
and start from scratch if we really need a semantic for short term
allocations.

[1] http://lkml.kernel.org/r/20170118054945.GD18349@bombadil.infradead.org

[akpm@linux-foundation.org: fix typo]
[akpm@linux-foundation.org: coding-style fixes]
[sfr@canb.auug.org.au: drm/i915: fix up]
  Link: http://lkml.kernel.org/r/20170816144703.378d4f4d@canb.auug.org.au
Link: http://lkml.kernel.org/r/20170728091904.14627-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Neil Brown <neilb@suse.de>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent d0dbf77
Raw File
zconf.y
%{
/*
 * Copyright (C) 2002 Roman Zippel <zippel@linux-m68k.org>
 * Released under the terms of the GNU GPL v2.0.
 */

#include <ctype.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>

#include "lkc.h"

#define printd(mask, fmt...) if (cdebug & (mask)) printf(fmt)

#define PRINTD		0x0001
#define DEBUG_PARSE	0x0002

int cdebug = PRINTD;

extern int zconflex(void);
static void zconfprint(const char *err, ...);
static void zconf_error(const char *err, ...);
static void zconferror(const char *err);
static bool zconf_endtoken(const struct kconf_id *id, int starttoken, int endtoken);

struct symbol *symbol_hash[SYMBOL_HASHSIZE];

static struct menu *current_menu, *current_entry;

%}
%expect 32

%union
{
	char *string;
	struct file *file;
	struct symbol *symbol;
	struct expr *expr;
	struct menu *menu;
	const struct kconf_id *id;
}

%token <id>T_MAINMENU
%token <id>T_MENU
%token <id>T_ENDMENU
%token <id>T_SOURCE
%token <id>T_CHOICE
%token <id>T_ENDCHOICE
%token <id>T_COMMENT
%token <id>T_CONFIG
%token <id>T_MENUCONFIG
%token <id>T_HELP
%token <string> T_HELPTEXT
%token <id>T_IF
%token <id>T_ENDIF
%token <id>T_DEPENDS
%token <id>T_OPTIONAL
%token <id>T_PROMPT
%token <id>T_TYPE
%token <id>T_DEFAULT
%token <id>T_SELECT
%token <id>T_IMPLY
%token <id>T_RANGE
%token <id>T_VISIBLE
%token <id>T_OPTION
%token <id>T_ON
%token <string> T_WORD
%token <string> T_WORD_QUOTE
%token T_UNEQUAL
%token T_LESS
%token T_LESS_EQUAL
%token T_GREATER
%token T_GREATER_EQUAL
%token T_CLOSE_PAREN
%token T_OPEN_PAREN
%token T_EOL

%left T_OR
%left T_AND
%left T_EQUAL T_UNEQUAL
%left T_LESS T_LESS_EQUAL T_GREATER T_GREATER_EQUAL
%nonassoc T_NOT

%type <string> prompt
%type <symbol> symbol
%type <expr> expr
%type <expr> if_expr
%type <id> end
%type <id> option_name
%type <menu> if_entry menu_entry choice_entry
%type <string> symbol_option_arg word_opt

%destructor {
	fprintf(stderr, "%s:%d: missing end statement for this entry\n",
		$$->file->name, $$->lineno);
	if (current_menu == $$)
		menu_end_menu();
} if_entry menu_entry choice_entry

%{
/* Include zconf_id.c here so it can see the token constants. */
#include "kconf_id.c"
%}

%%
input: nl start | start;

start: mainmenu_stmt stmt_list | stmt_list;

stmt_list:
	  /* empty */
	| stmt_list common_stmt
	| stmt_list choice_stmt
	| stmt_list menu_stmt
	| stmt_list end			{ zconf_error("unexpected end statement"); }
	| stmt_list T_WORD error T_EOL	{ zconf_error("unknown statement \"%s\"", $2); }
	| stmt_list option_name error T_EOL
{
	zconf_error("unexpected option \"%s\"", $2->name);
}
	| stmt_list error T_EOL		{ zconf_error("invalid statement"); }
;

option_name:
	T_DEPENDS | T_PROMPT | T_TYPE | T_SELECT | T_IMPLY | T_OPTIONAL | T_RANGE | T_DEFAULT | T_VISIBLE
;

common_stmt:
	  T_EOL
	| if_stmt
	| comment_stmt
	| config_stmt
	| menuconfig_stmt
	| source_stmt
;

option_error:
	  T_WORD error T_EOL		{ zconf_error("unknown option \"%s\"", $1); }
	| error T_EOL			{ zconf_error("invalid option"); }
;


/* config/menuconfig entry */

config_entry_start: T_CONFIG T_WORD T_EOL
{
	struct symbol *sym = sym_lookup($2, 0);
	sym->flags |= SYMBOL_OPTIONAL;
	menu_add_entry(sym);
	printd(DEBUG_PARSE, "%s:%d:config %s\n", zconf_curname(), zconf_lineno(), $2);
};

config_stmt: config_entry_start config_option_list
{
	menu_end_entry();
	printd(DEBUG_PARSE, "%s:%d:endconfig\n", zconf_curname(), zconf_lineno());
};

menuconfig_entry_start: T_MENUCONFIG T_WORD T_EOL
{
	struct symbol *sym = sym_lookup($2, 0);
	sym->flags |= SYMBOL_OPTIONAL;
	menu_add_entry(sym);
	printd(DEBUG_PARSE, "%s:%d:menuconfig %s\n", zconf_curname(), zconf_lineno(), $2);
};

menuconfig_stmt: menuconfig_entry_start config_option_list
{
	if (current_entry->prompt)
		current_entry->prompt->type = P_MENU;
	else
		zconfprint("warning: menuconfig statement without prompt");
	menu_end_entry();
	printd(DEBUG_PARSE, "%s:%d:endconfig\n", zconf_curname(), zconf_lineno());
};

config_option_list:
	  /* empty */
	| config_option_list config_option
	| config_option_list symbol_option
	| config_option_list depends
	| config_option_list help
	| config_option_list option_error
	| config_option_list T_EOL
;

config_option: T_TYPE prompt_stmt_opt T_EOL
{
	menu_set_type($1->stype);
	printd(DEBUG_PARSE, "%s:%d:type(%u)\n",
		zconf_curname(), zconf_lineno(),
		$1->stype);
};

config_option: T_PROMPT prompt if_expr T_EOL
{
	menu_add_prompt(P_PROMPT, $2, $3);
	printd(DEBUG_PARSE, "%s:%d:prompt\n", zconf_curname(), zconf_lineno());
};

config_option: T_DEFAULT expr if_expr T_EOL
{
	menu_add_expr(P_DEFAULT, $2, $3);
	if ($1->stype != S_UNKNOWN)
		menu_set_type($1->stype);
	printd(DEBUG_PARSE, "%s:%d:default(%u)\n",
		zconf_curname(), zconf_lineno(),
		$1->stype);
};

config_option: T_SELECT T_WORD if_expr T_EOL
{
	menu_add_symbol(P_SELECT, sym_lookup($2, 0), $3);
	printd(DEBUG_PARSE, "%s:%d:select\n", zconf_curname(), zconf_lineno());
};

config_option: T_IMPLY T_WORD if_expr T_EOL
{
	menu_add_symbol(P_IMPLY, sym_lookup($2, 0), $3);
	printd(DEBUG_PARSE, "%s:%d:imply\n", zconf_curname(), zconf_lineno());
};

config_option: T_RANGE symbol symbol if_expr T_EOL
{
	menu_add_expr(P_RANGE, expr_alloc_comp(E_RANGE,$2, $3), $4);
	printd(DEBUG_PARSE, "%s:%d:range\n", zconf_curname(), zconf_lineno());
};

symbol_option: T_OPTION symbol_option_list T_EOL
;

symbol_option_list:
	  /* empty */
	| symbol_option_list T_WORD symbol_option_arg
{
	const struct kconf_id *id = kconf_id_lookup($2, strlen($2));
	if (id && id->flags & TF_OPTION)
		menu_add_option(id->token, $3);
	else
		zconfprint("warning: ignoring unknown option %s", $2);
	free($2);
};

symbol_option_arg:
	  /* empty */		{ $$ = NULL; }
	| T_EQUAL prompt	{ $$ = $2; }
;

/* choice entry */

choice: T_CHOICE word_opt T_EOL
{
	struct symbol *sym = sym_lookup($2, SYMBOL_CHOICE);
	sym->flags |= SYMBOL_AUTO;
	menu_add_entry(sym);
	menu_add_expr(P_CHOICE, NULL, NULL);
	printd(DEBUG_PARSE, "%s:%d:choice\n", zconf_curname(), zconf_lineno());
};

choice_entry: choice choice_option_list
{
	$$ = menu_add_menu();
};

choice_end: end
{
	if (zconf_endtoken($1, T_CHOICE, T_ENDCHOICE)) {
		menu_end_menu();
		printd(DEBUG_PARSE, "%s:%d:endchoice\n", zconf_curname(), zconf_lineno());
	}
};

choice_stmt: choice_entry choice_block choice_end
;

choice_option_list:
	  /* empty */
	| choice_option_list choice_option
	| choice_option_list depends
	| choice_option_list help
	| choice_option_list T_EOL
	| choice_option_list option_error
;

choice_option: T_PROMPT prompt if_expr T_EOL
{
	menu_add_prompt(P_PROMPT, $2, $3);
	printd(DEBUG_PARSE, "%s:%d:prompt\n", zconf_curname(), zconf_lineno());
};

choice_option: T_TYPE prompt_stmt_opt T_EOL
{
	if ($1->stype == S_BOOLEAN || $1->stype == S_TRISTATE) {
		menu_set_type($1->stype);
		printd(DEBUG_PARSE, "%s:%d:type(%u)\n",
			zconf_curname(), zconf_lineno(),
			$1->stype);
	} else
		YYERROR;
};

choice_option: T_OPTIONAL T_EOL
{
	current_entry->sym->flags |= SYMBOL_OPTIONAL;
	printd(DEBUG_PARSE, "%s:%d:optional\n", zconf_curname(), zconf_lineno());
};

choice_option: T_DEFAULT T_WORD if_expr T_EOL
{
	if ($1->stype == S_UNKNOWN) {
		menu_add_symbol(P_DEFAULT, sym_lookup($2, 0), $3);
		printd(DEBUG_PARSE, "%s:%d:default\n",
			zconf_curname(), zconf_lineno());
	} else
		YYERROR;
};

choice_block:
	  /* empty */
	| choice_block common_stmt
;

/* if entry */

if_entry: T_IF expr nl
{
	printd(DEBUG_PARSE, "%s:%d:if\n", zconf_curname(), zconf_lineno());
	menu_add_entry(NULL);
	menu_add_dep($2);
	$$ = menu_add_menu();
};

if_end: end
{
	if (zconf_endtoken($1, T_IF, T_ENDIF)) {
		menu_end_menu();
		printd(DEBUG_PARSE, "%s:%d:endif\n", zconf_curname(), zconf_lineno());
	}
};

if_stmt: if_entry if_block if_end
;

if_block:
	  /* empty */
	| if_block common_stmt
	| if_block menu_stmt
	| if_block choice_stmt
;

/* mainmenu entry */

mainmenu_stmt: T_MAINMENU prompt nl
{
	menu_add_prompt(P_MENU, $2, NULL);
};

/* menu entry */

menu: T_MENU prompt T_EOL
{
	menu_add_entry(NULL);
	menu_add_prompt(P_MENU, $2, NULL);
	printd(DEBUG_PARSE, "%s:%d:menu\n", zconf_curname(), zconf_lineno());
};

menu_entry: menu visibility_list depends_list
{
	$$ = menu_add_menu();
};

menu_end: end
{
	if (zconf_endtoken($1, T_MENU, T_ENDMENU)) {
		menu_end_menu();
		printd(DEBUG_PARSE, "%s:%d:endmenu\n", zconf_curname(), zconf_lineno());
	}
};

menu_stmt: menu_entry menu_block menu_end
;

menu_block:
	  /* empty */
	| menu_block common_stmt
	| menu_block menu_stmt
	| menu_block choice_stmt
;

source_stmt: T_SOURCE prompt T_EOL
{
	printd(DEBUG_PARSE, "%s:%d:source %s\n", zconf_curname(), zconf_lineno(), $2);
	zconf_nextfile($2);
};

/* comment entry */

comment: T_COMMENT prompt T_EOL
{
	menu_add_entry(NULL);
	menu_add_prompt(P_COMMENT, $2, NULL);
	printd(DEBUG_PARSE, "%s:%d:comment\n", zconf_curname(), zconf_lineno());
};

comment_stmt: comment depends_list
{
	menu_end_entry();
};

/* help option */

help_start: T_HELP T_EOL
{
	printd(DEBUG_PARSE, "%s:%d:help\n", zconf_curname(), zconf_lineno());
	zconf_starthelp();
};

help: help_start T_HELPTEXT
{
	current_entry->help = $2;
};

/* depends option */

depends_list:
	  /* empty */
	| depends_list depends
	| depends_list T_EOL
	| depends_list option_error
;

depends: T_DEPENDS T_ON expr T_EOL
{
	menu_add_dep($3);
	printd(DEBUG_PARSE, "%s:%d:depends on\n", zconf_curname(), zconf_lineno());
};

/* visibility option */

visibility_list:
	  /* empty */
	| visibility_list visible
	| visibility_list T_EOL
;

visible: T_VISIBLE if_expr
{
	menu_add_visibility($2);
};

/* prompt statement */

prompt_stmt_opt:
	  /* empty */
	| prompt if_expr
{
	menu_add_prompt(P_PROMPT, $1, $2);
};

prompt:	  T_WORD
	| T_WORD_QUOTE
;

end:	  T_ENDMENU T_EOL	{ $$ = $1; }
	| T_ENDCHOICE T_EOL	{ $$ = $1; }
	| T_ENDIF T_EOL		{ $$ = $1; }
;

nl:
	  T_EOL
	| nl T_EOL
;

if_expr:  /* empty */			{ $$ = NULL; }
	| T_IF expr			{ $$ = $2; }
;

expr:	  symbol				{ $$ = expr_alloc_symbol($1); }
	| symbol T_LESS symbol			{ $$ = expr_alloc_comp(E_LTH, $1, $3); }
	| symbol T_LESS_EQUAL symbol		{ $$ = expr_alloc_comp(E_LEQ, $1, $3); }
	| symbol T_GREATER symbol		{ $$ = expr_alloc_comp(E_GTH, $1, $3); }
	| symbol T_GREATER_EQUAL symbol		{ $$ = expr_alloc_comp(E_GEQ, $1, $3); }
	| symbol T_EQUAL symbol			{ $$ = expr_alloc_comp(E_EQUAL, $1, $3); }
	| symbol T_UNEQUAL symbol		{ $$ = expr_alloc_comp(E_UNEQUAL, $1, $3); }
	| T_OPEN_PAREN expr T_CLOSE_PAREN	{ $$ = $2; }
	| T_NOT expr				{ $$ = expr_alloc_one(E_NOT, $2); }
	| expr T_OR expr			{ $$ = expr_alloc_two(E_OR, $1, $3); }
	| expr T_AND expr			{ $$ = expr_alloc_two(E_AND, $1, $3); }
;

symbol:	  T_WORD	{ $$ = sym_lookup($1, 0); free($1); }
	| T_WORD_QUOTE	{ $$ = sym_lookup($1, SYMBOL_CONST); free($1); }
;

word_opt: /* empty */			{ $$ = NULL; }
	| T_WORD

%%

void conf_parse(const char *name)
{
	struct symbol *sym;
	int i;

	zconf_initscan(name);

	sym_init();
	_menu_init();
	rootmenu.prompt = menu_add_prompt(P_MENU, "Linux Kernel Configuration", NULL);

	if (getenv("ZCONF_DEBUG"))
		zconfdebug = 1;
	zconfparse();
	if (zconfnerrs)
		exit(1);
	if (!modules_sym)
		modules_sym = sym_find( "n" );

	rootmenu.prompt->text = _(rootmenu.prompt->text);
	rootmenu.prompt->text = sym_expand_string_value(rootmenu.prompt->text);

	menu_finalize(&rootmenu);
	for_all_symbols(i, sym) {
		if (sym_check_deps(sym))
			zconfnerrs++;
	}
	if (zconfnerrs)
		exit(1);
	sym_set_change_count(1);
}

static const char *zconf_tokenname(int token)
{
	switch (token) {
	case T_MENU:		return "menu";
	case T_ENDMENU:		return "endmenu";
	case T_CHOICE:		return "choice";
	case T_ENDCHOICE:	return "endchoice";
	case T_IF:		return "if";
	case T_ENDIF:		return "endif";
	case T_DEPENDS:		return "depends";
	case T_VISIBLE:		return "visible";
	}
	return "<token>";
}

static bool zconf_endtoken(const struct kconf_id *id, int starttoken, int endtoken)
{
	if (id->token != endtoken) {
		zconf_error("unexpected '%s' within %s block",
			id->name, zconf_tokenname(starttoken));
		zconfnerrs++;
		return false;
	}
	if (current_menu->file != current_file) {
		zconf_error("'%s' in different file than '%s'",
			id->name, zconf_tokenname(starttoken));
		fprintf(stderr, "%s:%d: location of the '%s'\n",
			current_menu->file->name, current_menu->lineno,
			zconf_tokenname(starttoken));
		zconfnerrs++;
		return false;
	}
	return true;
}

static void zconfprint(const char *err, ...)
{
	va_list ap;

	fprintf(stderr, "%s:%d: ", zconf_curname(), zconf_lineno());
	va_start(ap, err);
	vfprintf(stderr, err, ap);
	va_end(ap);
	fprintf(stderr, "\n");
}

static void zconf_error(const char *err, ...)
{
	va_list ap;

	zconfnerrs++;
	fprintf(stderr, "%s:%d: ", zconf_curname(), zconf_lineno());
	va_start(ap, err);
	vfprintf(stderr, err, ap);
	va_end(ap);
	fprintf(stderr, "\n");
}

static void zconferror(const char *err)
{
	fprintf(stderr, "%s:%d: %s\n", zconf_curname(), zconf_lineno() + 1, err);
}

static void print_quoted_string(FILE *out, const char *str)
{
	const char *p;
	int len;

	putc('"', out);
	while ((p = strchr(str, '"'))) {
		len = p - str;
		if (len)
			fprintf(out, "%.*s", len, str);
		fputs("\\\"", out);
		str = p + 1;
	}
	fputs(str, out);
	putc('"', out);
}

static void print_symbol(FILE *out, struct menu *menu)
{
	struct symbol *sym = menu->sym;
	struct property *prop;

	if (sym_is_choice(sym))
		fprintf(out, "\nchoice\n");
	else
		fprintf(out, "\nconfig %s\n", sym->name);
	switch (sym->type) {
	case S_BOOLEAN:
		fputs("  boolean\n", out);
		break;
	case S_TRISTATE:
		fputs("  tristate\n", out);
		break;
	case S_STRING:
		fputs("  string\n", out);
		break;
	case S_INT:
		fputs("  integer\n", out);
		break;
	case S_HEX:
		fputs("  hex\n", out);
		break;
	default:
		fputs("  ???\n", out);
		break;
	}
	for (prop = sym->prop; prop; prop = prop->next) {
		if (prop->menu != menu)
			continue;
		switch (prop->type) {
		case P_PROMPT:
			fputs("  prompt ", out);
			print_quoted_string(out, prop->text);
			if (!expr_is_yes(prop->visible.expr)) {
				fputs(" if ", out);
				expr_fprint(prop->visible.expr, out);
			}
			fputc('\n', out);
			break;
		case P_DEFAULT:
			fputs( "  default ", out);
			expr_fprint(prop->expr, out);
			if (!expr_is_yes(prop->visible.expr)) {
				fputs(" if ", out);
				expr_fprint(prop->visible.expr, out);
			}
			fputc('\n', out);
			break;
		case P_CHOICE:
			fputs("  #choice value\n", out);
			break;
		case P_SELECT:
			fputs( "  select ", out);
			expr_fprint(prop->expr, out);
			fputc('\n', out);
			break;
		case P_IMPLY:
			fputs( "  imply ", out);
			expr_fprint(prop->expr, out);
			fputc('\n', out);
			break;
		case P_RANGE:
			fputs( "  range ", out);
			expr_fprint(prop->expr, out);
			fputc('\n', out);
			break;
		case P_MENU:
			fputs( "  menu ", out);
			print_quoted_string(out, prop->text);
			fputc('\n', out);
			break;
		default:
			fprintf(out, "  unknown prop %d!\n", prop->type);
			break;
		}
	}
	if (menu->help) {
		int len = strlen(menu->help);
		while (menu->help[--len] == '\n')
			menu->help[len] = 0;
		fprintf(out, "  help\n%s\n", menu->help);
	}
}

void zconfdump(FILE *out)
{
	struct property *prop;
	struct symbol *sym;
	struct menu *menu;

	menu = rootmenu.list;
	while (menu) {
		if ((sym = menu->sym))
			print_symbol(out, menu);
		else if ((prop = menu->prompt)) {
			switch (prop->type) {
			case P_COMMENT:
				fputs("\ncomment ", out);
				print_quoted_string(out, prop->text);
				fputs("\n", out);
				break;
			case P_MENU:
				fputs("\nmenu ", out);
				print_quoted_string(out, prop->text);
				fputs("\n", out);
				break;
			default:
				;
			}
			if (!expr_is_yes(prop->visible.expr)) {
				fputs("  depends ", out);
				expr_fprint(prop->visible.expr, out);
				fputc('\n', out);
			}
		}

		if (menu->list)
			menu = menu->list;
		else if (menu->next)
			menu = menu->next;
		else while ((menu = menu->parent)) {
			if (menu->prompt && menu->prompt->type == P_MENU)
				fputs("\nendmenu\n", out);
			if (menu->next) {
				menu = menu->next;
				break;
			}
		}
	}
}

#include "zconf.lex.c"
#include "util.c"
#include "confdata.c"
#include "expr.c"
#include "symbol.c"
#include "menu.c"
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