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[thirdparty/mdadm.git] / util.c

diff --git a/util.c b/util.c
index 9204d531f86a569def9fc20fee72550d1b1f93d2..b3dbca47f145330585fefc5a155613b2c39e292e 100644 (file)
--- a/util.c
+++ b/util.c
@@ -676,6 +676,35 @@ struct supertype *guess_super(int fd)
        return NULL;
 }
 
+unsigned long long get_component_size(int fd)
+{
+       /* Find out the component size of the array.
+        * We cannot trust GET_ARRAY_INFO ioctl as it's
+        * size field is only 32bits.
+        * So look in /sys/block/mdXXX/md/component_size
+        */
+       struct stat stb;
+       char fname[50];
+       int n;
+       if (fstat(fd, &stb)) return 0;
+       if (major(stb.st_rdev) == 9)
+               sprintf(fname, "/sys/block/md%d/component_size",
+                       minor(stb.st_rdev));
+       else
+               sprintf(fname, "/sys/block/md_d%d/component_size",
+                       minor(stb.st_rdev)/16);
+       fd = open(fname, O_RDONLY);
+       if (fd < 0)
+               return 0;
+       n = read(fd, fname, sizeof(fname));
+       close(fd);
+       if (n == sizeof(fname))
+               return 0;
+       fname[n] = 0;
+       return strtoull(fname, NULL, 10);
+}
+
+
 #ifdef __TINYC__
 /* tinyc doesn't optimize this check in ioctl.h out ... */
 unsigned int __invalid_size_argument_for_IOC = 0;