memblock: Print out errors on reserve_mem parser

The parsing of kernel parameter "reserve_mem=" is subject to
multiple failures, like duplicate naming, malformed expression
or even lack of available memory. Right now, all of these fail
silently. Let's add some messages so the kernel log can provide
useful information in case of failures.

Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
Link: https://patch.msgid.link/20260324012839.1991765-1-gpiccoli@igalia.com
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

Author: guilhermepiccoli

mm/memblock.c

@@ -2642,23 +2642,25 @@ static int __init reserve_mem(char *p)
 	int len;
 
 	if (!p)
-		return -EINVAL;
+		goto err_param;
 
 	/* Check if there's room for more reserved memory */
-	if (reserved_mem_count >= RESERVE_MEM_MAX_ENTRIES)
+	if (reserved_mem_count >= RESERVE_MEM_MAX_ENTRIES) {
+		pr_err("reserve_mem: no more room for reserved memory\n");
 		return -EBUSY;
+	}
 
 	oldp = p;
 	size = memparse(p, &p);
 	if (!size || p == oldp)
-		return -EINVAL;
+		goto err_param;
 
 	if (*p != ':')
-		return -EINVAL;
+		goto err_param;
 
 	align = memparse(p+1, &p);
 	if (*p != ':')
-		return -EINVAL;
+		goto err_param;
 
 	/*
 	 * memblock_phys_alloc() doesn't like a zero size align,
@@ -2672,32 +2674,39 @@ static int __init reserve_mem(char *p)
 
 	/* name needs to have length but not too big */
 	if (!len || len >= RESERVE_MEM_NAME_SIZE)
-		return -EINVAL;
+		goto err_param;
 
 	/* Make sure that name has text */
 	for (p = name; *p; p++) {
 		if (!isspace(*p))
 			break;
 	}
 	if (!*p)
-		return -EINVAL;
+		goto err_param;
 
 	/* Make sure the name is not already used */
-	if (reserve_mem_find_by_name(name, &start, &tmp))
+	if (reserve_mem_find_by_name(name, &start, &tmp)) {
+		pr_err("reserve_mem: name \"%s\" was already used\n", name);
 		return -EBUSY;
+	}
 
 	/* Pick previous allocations up from KHO if available */
 	if (reserve_mem_kho_revive(name, size, align))
 		return 1;
 
 	/* TODO: Allocation must be outside of scratch region */
 	start = memblock_phys_alloc(size, align);
-	if (!start)
+	if (!start) {
+		pr_err("reserve_mem: memblock allocation failed\n");
 		return -ENOMEM;
+	}
 
 	reserved_mem_add(start, size, name);
 
 	return 1;
+err_param:
+	pr_err("reserve_mem: empty or malformed parameter\n");
+	return -EINVAL;
 }
 __setup("reserve_mem=", reserve_mem);