[PATCH v4 06/10] smb/client: use bsearch() to find target status code

[chenxiaosong.chenxiaosong@linux.dev]

From: ChenXiaoSong <chenxiaosong@kylinos.cn>

The smb2_error_map_table array currently has 1742 elements. When searching
for the last element, the original loop-based search method requires 1742
comparisons, while binary search algorithm requires only 10 comparisons.

Signed-off-by: ChenXiaoSong <chenxiaosong@kylinos.cn>
---
 fs/smb/client/smb2maperror.c | 26 +++++++++++++++-----------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/fs/smb/client/smb2maperror.c b/fs/smb/client/smb2maperror.c
index 1bd4196386dd..df8db12ff7a9 100644
--- a/fs/smb/client/smb2maperror.c
+++ b/fs/smb/client/smb2maperror.c
@@ -2437,9 +2437,9 @@ int
 map_smb2_to_linux_error(char *buf, bool log_err)
 {
 	struct smb2_hdr *shdr = (struct smb2_hdr *)buf;
-	unsigned int i;
 	int rc = -EIO;
 	__le32 smb2err = shdr->Status;
+	struct status_to_posix_error *err_map, key;
 
 	if (smb2err == 0) {
 		trace_smb3_cmd_done(le32_to_cpu(shdr->Id.SyncId.TreeId),
@@ -2453,17 +2453,21 @@ map_smb2_to_linux_error(char *buf, bool log_err)
 		   (smb2err != STATUS_END_OF_FILE)) ||
 		  (cifsFYI & CIFS_RC);
 
-	for (i = 0; i < sizeof(smb2_error_map_table) /
-			sizeof(struct status_to_posix_error); i++) {
-		if (smb2_error_map_table[i].smb2_status == smb2err) {
-			if (log_err)
-				pr_notice("Status code returned 0x%08x %s\n", smb2err,
-					  smb2_error_map_table[i].status_string);
-			rc = smb2_error_map_table[i].posix_error;
-			break;
-		}
-	}
+	key = (struct status_to_posix_error) {
+		.smb2_status = smb2err,
+	};
+	err_map = bsearch(&key, smb2_error_map_table, err_map_num,
+			  sizeof(struct status_to_posix_error),
+			  cmp_smb2_status);
+	if (!err_map)
+		goto out;
+
+	rc = err_map->posix_error;
+	if (log_err)
+		pr_notice("Status code returned 0x%08x %s\n", smb2err,
+			  err_map->status_string);
 
+out:
 	/* on error mapping not found  - return EIO */
 
 	cifs_dbg(FYI, "Mapping SMB2 status code 0x%08x to POSIX err %d\n",
-- 
2.43.0