[LTP] [PATCH v3 2/2] syscalls/ioctl_loop05: Using LOOP_CONFIGURE to set direct io

[Yang Xu]

HI Cyril
> Hi!
>>> So I guess that we will have to write a parser that reads that
>>> information line by line after all.
>> I doubt how machies will have more or zero fields in (7). But I think
>> you are right,
> 
> Well that's what I do have here.
> 
>> How about using the (3) field and second to last field. Then we can
>> avoid zero or more filed in (7). the code as below??
> 
> Actually looking into util-linux code it says that th the optional
> fields are terminated with " - ", see:
> 
> https://git.kernel.org/pub/scm/utils/util-linux/util-linux.git/tree/libmount/src/tab_parse.c#n177
> 
> So I guess the safest option would be:
> 
> * Match the line by major:minor as you do
> * Then strstr() for " - " should land us directly to field (8)
Yes, using " - " more easily and faster. code as below：

index 8d8bc5b40..bdd93f19e 100644
--- a/lib/tst_device.c
+++ b/lib/tst_device.c
@@ -497,17 +497,30 @@ unsigned long tst_dev_bytes_written(const char *dev)

  void tst_find_backing_dev(const char *path, char *dev)
  {
-       char fmt[1024];
+       char fmt[20];
         struct stat buf;
+       FILE *file;
+       char line[PATH_MAX];
+       char *pre = NULL;
+       char *next = NULL;

         if (stat(path, &buf) < 0)
                  tst_brkm(TWARN | TERRNO, NULL, "stat() failed");

-       snprintf(fmt, sizeof(fmt), "%%*i %%*i %u:%u %%*s %%*s %%*s %%*s 
%%*s %%*s %%s %%*s",
-                       major(buf.st_dev), minor(buf.st_dev));
+       snprintf(fmt, sizeof(fmt), "%u:%u", major(buf.st_dev), 
minor(buf.st_dev));
+       file = SAFE_FOPEN(NULL, "/proc/self/mountinfo", "r");

-       SAFE_FILE_LINES_SCANF(NULL, "/proc/self/mountinfo", fmt, dev);
+       while (fgets(line, sizeof(line), file)) {
+               if (strstr(line, fmt) != NULL) {
+                       pre = strstr(line, " - ");
+                       pre = strtok_r(pre, " ", &next);
+                       pre = strtok_r(NULL, " ", &next);
+                       pre = strtok_r(NULL, " ", &next);
+                       strcpy(dev, pre);
+               }
+       }

+       SAFE_FCLOSE(NULL, file);
         if (stat(dev, &buf) < 0)
                  tst_brkm(TWARN | TERRNO, NULL, "stat(%s) failed", dev);


>