[RFC v3 3/4] mm, printk: introduce new format %pGt for page_type

Hyeonggon Yoo
2022-12-18T10:19:42Z

%pGp format is used to print 'flags' field of struct page.
As some page flags (e.g. PG_buddy, see page-flags.h for more details)
are set in page_type field, introduce %pGt format which provides
human readable output of page_type.

Note that the sense of bits are different in page_type. if page_type is
0xffffffff, no flags are set. if PG_slab (0x00100000) flag is set,
page_type is 0xffefffff. Clearing a bit means we set the bit.

Bits in page_type are inverted when printing page type names.

Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
---
Documentation/core-api/printk-formats.rst | 3 ++-
include/trace/events/mmflags.h | 7 ++++++
lib/test_printf.c | 26 +++++++++++++++++++++++
lib/vsprintf.c | 21 ++++++++++++++++++
mm/debug.c | 5 +++++
mm/internal.h | 1 +
6 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst
index dbe1aacc79d0..582e965508eb 100644
--- a/Documentation/core-api/printk-formats.rst
+++ b/Documentation/core-api/printk-formats.rst
@@ -575,12 +575,13 @@ The field width is passed by value, the bitmap is passed by reference.
Helper macros cpumask_pr_args() and nodemask_pr_args() are available to ease
printing cpumask and nodemask.

-Flags bitfields such as page flags, gfp_flags
+Flags bitfields such as page flags, page_type, gfp_flags
---------------------------------------------

::

%pGp 0x17ffffc0002036(referenced|uptodate|lru|active|private|node=0|zone=2|lastcpupid=0x1fffff)
+ %pGt 0xffefffff(slab)
%pGg GFP_USER|GFP_DMA32|GFP_NOWARN
%pGv read|exec|mayread|maywrite|mayexec|denywrite

diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
index 8301912f8c25..57f52d00e761 100644
--- a/include/trace/events/mmflags.h
+++ b/include/trace/events/mmflags.h
@@ -138,6 +138,13 @@ IF_HAVE_PG_SKIP_KASAN_POISON(PG_skip_kasan_poison, "skip_kasan_poison")
__def_pageflag_names \
) : "none"

+#define __def_pagetype_names \
+ {PG_slab, "slab" }, \
+ {PG_offline, "offline" }, \
+ {PG_guard, "guard" }, \
+ {PG_table, "table" }, \
+ {PG_buddy, "buddy" }
+
#if defined(CONFIG_X86)
#define __VM_ARCH_SPECIFIC_1 {VM_PAT, "pat" }
#elif defined(CONFIG_PPC)
diff --git a/lib/test_printf.c b/lib/test_printf.c
index d34dc636b81c..e0d0770d5eec 100644
--- a/lib/test_printf.c
+++ b/lib/test_printf.c
@@ -642,12 +642,26 @@ page_flags_test(int section, int node, int zone, int last_cpupid,
test(cmp_buf, "%pGp", &flags);
}

+static void __init page_type_test(unsigned int page_type, const char *name,
+ char *cmp_buf)
+{
+ unsigned long size;
+
+ size = scnprintf(cmp_buf, BUF_SIZE, "%#x(", page_type);
+ if (page_type_has_type(page_type))
+ size += scnprintf(cmp_buf + size, BUF_SIZE - size, "%s", name);
+
+ snprintf(cmp_buf + size, BUF_SIZE - size, ")");
+ test(cmp_buf, "%pGt", &page_type);
+}
+
static void __init
flags(void)
{
unsigned long flags;
char *cmp_buffer;
gfp_t gfp;
+ unsigned int page_type;

cmp_buffer = kmalloc(BUF_SIZE, GFP_KERNEL);
if (!cmp_buffer)
@@ -687,6 +701,18 @@ flags(void)
gfp |= __GFP_ATOMIC;
test(cmp_buffer, "%pGg", &gfp);

+ page_type = ~0;
+ page_type_test(page_type, "", cmp_buffer);
+
+ page_type = 10;
+ page_type_test(page_type, "", cmp_buffer);
+
+ page_type = ~PG_slab;
+ page_type_test(page_type, "slab", cmp_buffer);
+
+ page_type = ~(PG_slab | PG_table | PG_buddy);
+ page_type_test(page_type, "slab|table|buddy", cmp_buffer);
+
kfree(cmp_buffer);
}

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index be71a03c936a..fbe320b5e89f 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -2052,6 +2052,25 @@ char *format_page_flags(char *buf, char *end, unsigned long flags)
return buf;
}

+static
+char *format_page_type(char *buf, char *end, unsigned int page_type)
+{
+ buf = number(buf, end, page_type, default_flag_spec);
+
+ if (buf < end)
+ *buf = '(';
+ buf++;
+
+ if (page_type_has_type(page_type))
+ buf = format_flags(buf, end, ~page_type, pagetype_names);
+
+ if (buf < end)
+ *buf = ')';
+ buf++;
+
+ return buf;
+}
+
static noinline_for_stack
char *flags_string(char *buf, char *end, void *flags_ptr,
struct printf_spec spec, const char *fmt)
@@ -2065,6 +2084,8 @@ char *flags_string(char *buf, char *end, void *flags_ptr,
switch (fmt[1]) {
case 'p':
return format_page_flags(buf, end, *(unsigned long *)flags_ptr);
+ case 't':
+ return format_page_type(buf, end, *(unsigned int *)flags_ptr);
case 'v':
flags = *(unsigned long *)flags_ptr;
names = vmaflag_names;
diff --git a/mm/debug.c b/mm/debug.c
index 7f8e5f744e42..5ce6b359004a 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -36,6 +36,11 @@ const struct trace_print_flags pageflag_names[] = {
{0, NULL}
};

+const struct trace_print_flags pagetype_names[] = {
+ __def_pagetype_names,
+ {0, NULL}
+};
+
const struct trace_print_flags gfpflag_names[] = {
__def_gfpflag_names,
{0, NULL}
diff --git a/mm/internal.h b/mm/internal.h
index bcf75a8b032d..b4ba6fd6051c 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -773,6 +773,7 @@ static inline void flush_tlb_batched_pending(struct mm_struct *mm)
#endif /* CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH */

extern const struct trace_print_flags pageflag_names[];
+extern const struct trace_print_flags pagetype_names[];
extern const struct trace_print_flags vmaflag_names[];
extern const struct trace_print_flags gfpflag_names[];

--
2.32.0