[PATCH v2] btrfs: use strstarts() and str_has_prefix() for prefix checks

[George Hu <integral@archlinux.org>]

Replace strncmp() prefix checks with strstarts() when only a boolean result
is needed, and with str_has_prefix() when the prefix length is needed after
a successful match.

This makes prefix checks clearer and more concise.

Signed-off-by: George Hu <integral@archlinux.org>
---
V1 -> V2:
 - Avoid replacing strncmp() with strstarts() when the parameter is
   not NUL terminated
 - Revise subject

 fs/btrfs/super.c | 5 ++---
 fs/btrfs/xattr.c | 3 +--
 2 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index ddb620ac241b..287cdc45bef8 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -263,10 +263,9 @@ static const struct fs_parameter_spec btrfs_fs_parameters[] = {
 
 static bool btrfs_match_compress_type(const char *string, const char *type, bool may_have_level)
 {
-	const int len = strlen(type);
+	const size_t len = str_has_prefix(string, type);
 
-	return (strncmp(string, type, len) == 0) &&
-		((may_have_level && string[len] == ':') || string[len] == '\0');
+	return len && ((may_have_level && string[len] == ':') || string[len] == '\0');
 }
 
 static int btrfs_parse_compress(struct btrfs_fs_context *ctx,
diff --git a/fs/btrfs/xattr.c b/fs/btrfs/xattr.c
index ab55d10bd71f..9011d8096e2d 100644
--- a/fs/btrfs/xattr.c
+++ b/fs/btrfs/xattr.c
@@ -239,8 +239,7 @@ int btrfs_setxattr_trans(struct inode *inode, const char *name,
 		 * block_rsv of the handle and trigger a warning for the start
 		 * case.
 		 */
-		ASSERT(strncmp(name, XATTR_SECURITY_PREFIX,
-			       XATTR_SECURITY_PREFIX_LEN) == 0);
+		ASSERT(strstarts(name, XATTR_SECURITY_PREFIX));
 		trans = current->journal_info;
 	}
 
-- 
2.55.0