[PATCH 4/4] libmultipath: use mmap in lookup_wwid()

[mwilck]

From: Martin Wilck <mwi...@suse.com>

Replace the line-by-line reading in lookup_wwid() with mmap()
and a simple loop over the in-memory structures.

Signed-off-by: Martin Wilck <mwi...@suse.com>
---
 libmultipath/wwids.c | 71 ++++++++++++++++++++++++--------------------
 1 file changed, 38 insertions(+), 33 deletions(-)

diff --git a/libmultipath/wwids.c b/libmultipath/wwids.c
index c193b97..42455de 100644
--- a/libmultipath/wwids.c
+++ b/libmultipath/wwids.c
@@ -4,8 +4,10 @@
 #include <string.h>
 #include <limits.h>
 #include <stdio.h>
+#include <stdbool.h>
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <sys/mman.h>
 #include <fcntl.h>
 
 #include "util.h"
@@ -24,41 +26,44 @@
  * Copyright (c) 2010 Benjamin Marzinski, Redhat
  */
 
-static int
-lookup_wwid(FILE *f, const char *wwid) {
-       int c;
-       char buf[LINE_MAX];
-       int count;
+struct mem_map {
+       char *addr;
+       ssize_t len;
+};
 
-       while ((c = fgetc(f)) != EOF){
-               if (c != '/') {
-                       if (fgets(buf, LINE_MAX, f) == NULL)
-                               return 0;
-                       else
-                               continue;
-               }
-               count = 0;
-               while ((c = fgetc(f)) != '/') {
-                       if (c == EOF)
-                               return 0;
-                       if (count >= WWID_SIZE - 1)
-                               goto next;
-                       if (wwid[count] == '\0')
-                               goto next;
-                       if (c != wwid[count++])
-                               goto next;
-               }
-               if (wwid[count] == '\0')
-                       return 1;
-next:
-               if (fgets(buf, LINE_MAX, f) == NULL)
-                       return 0;
-       }
-       return 0;
+static void cleanup_mmap(struct mem_map *mm)
+{
+       if (mm->addr)
+               munmap(mm->addr, mm->len);
 }
 
-static int
-write_out_wwid(int fd, const char *wwid) {
+static bool lookup_wwid(int fd, const char *wwid)
+{
+       struct mem_map mm __attribute__((cleanup(cleanup_mmap))) = { .addr = 0 
};
+       struct stat stb;
+       ssize_t wlen;
+       const char *line;
+
+       if (fstat(fd, &stb) != 0)
+               return false;
+
+       mm.len = stb.st_size;
+       mm.addr = mmap(NULL, stb.st_size, PROT_READ, MAP_SHARED, fd, 0);
+       if (!mm.addr)
+               return false;
+
+       wlen = strlen(wwid);
+       for (line = mm.addr; line >= mm.addr && line < mm.addr + mm.len;
+            line = memchr(line, '\n', mm.addr + mm.len - line) + 1)
+               if (line[0] == '/' && (line - mm.addr + 2 + wlen <= mm.len) &&
+                   line[wlen + 1] == '/' && !strncmp(wwid, line + 1, wlen))
+                       return true;
+
+       return false;
+}
+
+static int write_out_wwid(int fd, const char *wwid)
+{
        int ret;
        off_t offset;
        char buf[WWID_SIZE + 3];
@@ -245,7 +250,7 @@ int check_wwids_file(const char *wwid, int write_wwid)
                close(fd);
                return -1;
        }
-       found = lookup_wwid(f, wwid);
+       found = lookup_wwid(fd, wwid);
        if (found) {
                ret = 0;
                goto out;
-- 
2.55.0