linux-kernel - [PATCH 3/3] printk: dump full information of page flags in pGp

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Message-Id: <20210128021947.22877-4-laoar.shao@gmail.com>
Date:   Thu, 28 Jan 2021 10:19:47 +0800
From:   Yafang Shao <laoar.shao@...il.com>
To:     david@...hat.com, vbabka@...e.cz, cl@...ux.com, penberg@...nel.org,
        rientjes@...gle.com, iamjoonsoo.kim@....com,
        akpm@...ux-foundation.org, pmladek@...e.com, rostedt@...dmis.org,
        sergey.senozhatsky@...il.com, andriy.shevchenko@...ux.intel.com,
        linux@...musvillemoes.dk
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Yafang Shao <laoar.shao@...il.com>
Subject: [PATCH 3/3] printk: dump full information of page flags in pGp

Currently the pGp only shows the names of page flags, rather than
the full information including section, node, zone, last cpupid and
kasan tag. While it is not easy to parse these information manually
because there're so many flavors. Let's interpret them in pGp as well.

- Before the patch,
[ 6312.639698] ERR: Slab 0x000000006d1133b9 objects=33 used=3 fp=0x000000006d0779d1 flags=0x17ffffc0010200(slab|head)

- After the patch,
[ 6315.235783] ERR: Slab 0x000000006d1133b9 objects=33 used=3 fp=0x000000006d0779d1 flags=0x17ffffc0010200(Node 0x0,Zone 0x2,Lastcpupid 0x1fffff,slab|head)

Cc: David Hildenbrand <david@...hat.com>
Signed-off-by: Yafang Shao <laoar.shao@...il.com>
---
 lib/vsprintf.c | 42 +++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 41 insertions(+), 1 deletion(-)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 3b53c73580c5..bd809f4f1b82 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1916,6 +1916,46 @@ char *format_flags(char *buf, char *end, unsigned long flags,
 	return buf;
 }
 
+struct page_flags_layout {
+	int width;
+	int shift;
+	int mask;
+	char *name;
+};
+
+struct page_flags_layout pfl[] = {
+	{SECTIONS_WIDTH, SECTIONS_PGSHIFT, SECTIONS_MASK, "Section "},
+	{NODES_WIDTH, NODES_PGSHIFT, NODES_MASK, "Node "},
+	{ZONES_WIDTH, ZONES_PGSHIFT, ZONES_MASK, "Zone "},
+	{LAST_CPUPID_WIDTH, LAST_CPUPID_PGSHIFT, LAST_CPUPID_MASK, "Lastcpupid "},
+	{KASAN_TAG_WIDTH, KASAN_TAG_PGSHIFT, KASAN_TAG_MASK, "Kasantag "},
+};
+
+static
+char *format_layout(char *buf, char *end, unsigned long flags)
+{
+	int i;
+
+	for (i = 0; i < sizeof(pfl) / sizeof(struct page_flags_layout) && buf < end; i++) {
+		if (pfl[i].width == 0)
+			continue;
+
+		buf = string(buf, end, pfl[i].name, default_str_spec);
+
+		if (buf >= end)
+			break;
+		buf = number(buf, end, (flags >> pfl[i].shift) & pfl[i].mask,
+			     default_flag_spec);
+
+		if (buf >= end)
+			break;
+		*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)
@@ -1929,7 +1969,7 @@ char *flags_string(char *buf, char *end, void *flags_ptr,
 	switch (fmt[1]) {
 	case 'p':
 		flags = *(unsigned long *)flags_ptr;
-		/* Remove zone id */
+		buf = format_layout(buf, end, flags & ~((1UL << NR_PAGEFLAGS) - 1));
 		flags &= (1UL << NR_PAGEFLAGS) - 1;
 		names = pageflag_names;
 		break;
-- 
2.17.1