linux-kernel - [PATCH 09/20] lib/string_helpers: string_get

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Message-Id: <20230712211115.2174650-10-kent.overstreet@linux.dev>
Date:   Wed, 12 Jul 2023 17:11:04 -0400
From:   Kent Overstreet <kent.overstreet@...ux.dev>
To:     linux-bcachefs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Kent Overstreet <kent.overstreet@...il.com>,
        Kent Overstreet <kent.overstreet@...ux.dev>
Subject: [PATCH 09/20] lib/string_helpers: string_get_size() now returns characters wrote

From: Kent Overstreet <kent.overstreet@...il.com>

printbuf now needs to know the number of characters that would have been
written if the buffer was too small, like snprintf(); this changes
string_get_size() to return the the return value of snprintf().

Signed-off-by: Kent Overstreet <kent.overstreet@...ux.dev>
---
 include/linux/string_helpers.h |  4 ++--
 lib/string_helpers.c           | 10 ++++++----
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/include/linux/string_helpers.h b/include/linux/string_helpers.h
index fae6beaaa2..44148f8feb 100644
--- a/include/linux/string_helpers.h
+++ b/include/linux/string_helpers.h
@@ -23,8 +23,8 @@ enum string_size_units {
 	STRING_UNITS_2,		/* use binary powers of 2^10 */
 };
 
-void string_get_size(u64 size, u64 blk_size, enum string_size_units units,
-		     char *buf, int len);
+int string_get_size(u64 size, u64 blk_size, enum string_size_units units,
+		    char *buf, int len);
 
 int parse_int_array_user(const char __user *from, size_t count, int **array);
 
diff --git a/lib/string_helpers.c b/lib/string_helpers.c
index 230020a2e0..b9a34eb386 100644
--- a/lib/string_helpers.c
+++ b/lib/string_helpers.c
@@ -31,9 +31,11 @@
  * giving the size in the required units.  @buf should have room for
  * at least 9 bytes and will always be zero terminated.
  *
+ * Return value: number of characters of output that would have been written
+ * (which may be greater than len, if output was truncated).
  */
-void string_get_size(u64 size, u64 blk_size, const enum string_size_units units,
-		     char *buf, int len)
+int string_get_size(u64 size, u64 blk_size, const enum string_size_units units,
+		    char *buf, int len)
 {
 	static const char *const units_10[] = {
 		"B", "kB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB"
@@ -126,8 +128,8 @@ void string_get_size(u64 size, u64 blk_size, const enum string_size_units units,
 	else
 		unit = units_str[units][i];
 
-	snprintf(buf, len, "%u%s %s", (u32)size,
-		 tmp, unit);
+	return snprintf(buf, len, "%u%s %s", (u32)size,
+			tmp, unit);
 }
 EXPORT_SYMBOL(string_get_size);
 
-- 
2.40.1