[PATCH v2 2/3] mm: memblock: show all region flags in debugfs

[Meijing Zhao <zhaomeijing100@gmail.com>]

From: Meijing Zhao <zhaomeijing@lixiang.com>

Commit 493f349e38d0 ("memblock: Add flags and nid info in memblock
debugfs") made memblock_debug_show() stop after finding the first set
flag. A memblock region can carry multiple flags, so debugfs hides all
but the lowest set bit.

In particular, memory allocated for HugeTLB pages is reserved with both
MEMBLOCK_RSRV_KERN and MEMBLOCK_RSRV_HUGETLB, but debugfs only reports
RSV_KERN.

Walk all bits in the region flags and print every set flag separated by
"|". Keep walking beyond flagname[] so that a set flag without a known
name is reported as UNKNOWN rather than silently ignored.

A HugeTLB reservation is now shown as:

  RSV_KERN|RSV_HUGETLB

instead of:

  RSV_KERN

Fixes: 493f349e38d0 ("memblock: Add flags and nid info in memblock debugfs")
Signed-off-by: Meijing Zhao <zhaomeijing@lixiang.com>
---
 mm/memblock.c | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/mm/memblock.c b/mm/memblock.c
index 99f8e1bc60a8..7eddcc412618 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -2912,7 +2912,9 @@ static int memblock_debug_show(struct seq_file *m, void *private)
 	struct memblock_region *reg;
 	int i, j, nid;
 	unsigned int count = ARRAY_SIZE(flagname);
+	unsigned int flags;
 	phys_addr_t end;
+	bool first;
 
 	for (i = 0; i < type->cnt; i++) {
 		reg = &type->regions[i];
@@ -2926,16 +2928,20 @@ static int memblock_debug_show(struct seq_file *m, void *private)
 		else
 			seq_printf(m, "%4c ", 'x');
 		if (reg->flags) {
-			for (j = 0; j < count; j++) {
-				if (reg->flags & (1U << j)) {
-					seq_printf(m, "%s\n", flagname[j]);
-					break;
-				}
+			flags = reg->flags;
+			first = true;
+			for (j = 0; flags; j++, flags >>= 1) {
+				if (!(flags & 1))
+					continue;
+				if (!first)
+					seq_putc(m, '|');
+				seq_puts(m, j < count && flagname[j] ?
+					 flagname[j] : "UNKNOWN");
+				first = false;
 			}
-			if (j == count)
-				seq_printf(m, "%s\n", "UNKNOWN");
+			seq_putc(m, '\n');
 		} else {
-			seq_printf(m, "%s\n", "NONE");
+			seq_puts(m, "NONE\n");
 		}
 	}
 	return 0;
-- 
2.25.1