sgdisk program, misc. bug fixes
diff --git a/support.cc b/support.cc
index 8ab9a2e..c30f4e7 100644
--- a/support.cc
+++ b/support.cc
@@ -27,6 +27,10 @@
#define BLKPBSZGET _IO(0x12,123)
#endif
+// Below constant corresponds to an 800GB disk -- a somewhat arbitrary
+// cutoff
+#define SMALLEST_ADVANCED_FORMAT UINT64_C(1677721600)
+
using namespace std;
// Get a numeric value from the user, between low and high (inclusive).
@@ -84,8 +88,7 @@
//value as the default if the user just hits Enter
uint64_t GetSectorNum(uint64_t low, uint64_t high, uint64_t def, char prompt[]) {
unsigned long long response;
- int num;
- int plusFlag = 0;
+ int num, plusFlag = 0;
uint64_t mult = 1;
char suffix;
char line[255];
@@ -147,7 +150,14 @@
// Adjust response based on multiplier and plus flag, if present
response *= (unsigned long long) mult;
if (plusFlag == 1) {
- response = response + (unsigned long long) low - UINT64_C(1);
+ // Recompute response based on low part of range (if default = high
+ // value, which should be the case when prompting for the end of a
+ // range) or the defaut value (if default != high, which should be
+ // the case for the first sector of a partition).
+ if (def == high)
+ response = response + (unsigned long long) low - UINT64_C(1);
+ else
+ response = response + (unsigned long long) def - UINT64_C(1);
} // if
if (plusFlag == -1) {
response = (unsigned long long) high - response;
@@ -231,29 +241,65 @@
return (result);
} // GetBlockSize()
+// My original FindAlignment() function (after this one) isn't working, since
+// the BLKPBSZGET ioctl() isn't doing what I expected (it returns 512 even on
+// a WD Advanced Format drive). Therefore, I'm using a simpler function that
+// returns 1-sector alignment for unusual sector sizes and drives smaller than
+// a size defined by SMALLEST_ADVANCED_FORMAT, and 8-sector alignment for
+// larger drives with 512-byte sectors.
+int FindAlignment(int fd) {
+ int err, result;
+
+ if ((GetBlockSize(fd) == 512) && (disksize(fd, &err) >= SMALLEST_ADVANCED_FORMAT)) {
+ result = 8; // play it safe; align for 4096-byte sectors
+ } else {
+ result = 1; // unusual sector size; assume it's the real physical size
+ } // if/else
+ return result;
+} // FindAlignment
+
// Return the partition alignment value in sectors. Right now this works
// only for Linux 2.6.32 and later, since I can't find equivalent ioctl()s
// for OS X or FreeBSD, and the Linux ioctl is new
-int FindAlignment(int fd) {
- int err = -2, result = 8, physicalSectorSize = 4096;
+/* int FindAlignment(int fd) {
+ int err = -2, errnum = 0, result = 8, physicalSectorSize = 4096;
+ uint64_t diskSize;
+ printf("Entering FindAlignment()\n");
#if defined (__linux__) && defined (BLKPBSZGET)
err = ioctl(fd, BLKPBSZGET, &physicalSectorSize);
+ printf("In FindAlignment(), physicalSectorSize = %d, err = %d\n", physicalSectorSize, err);
// printf("Tried to get hardware alignment; err is %d, sector size is %d\n", err, physicalSectorSize);
#else
err = -1;
#endif
if (err < 0) { // ioctl didn't work; have to guess....
- if (GetBlockSize(fd) == 512)
+ if (GetBlockSize(fd) == 512) {
result = 8; // play it safe; align for 4096-byte sectors
- else
- result = 1; // unusual sector size; assume it's the real physical size
+ } else {
+ result = 1; // unusual sector size; assume it's the real physical size
+ } // if/else
} else { // ioctl worked; compute alignment
result = physicalSectorSize / GetBlockSize(fd);
+ // Disks with larger physical than logical sectors must theoretically
+ // have a total disk size that's a multiple of the physical sector
+ // size; however, some such disks have compatibility jumper settings
+ // meant for one-partition MBR setups, and these reduce the total
+ // number of sectors by 1. If such a setting is used, it'll result
+ // in improper alignment, so look for this condition and warn the
+ // user if it's found....
+ diskSize = disksize(fd, &errnum);
+ if ((diskSize % (uint64_t) result) != 0) {
+ fprintf(stderr, "\aWarning! Disk size (%llu) is not a multiple of alignment\n"
+ "size (%d), but it should be! Check disk manual and jumper settings!\n",
+ (unsigned long long) diskSize, result);
+ } // if
} // if/else
+ if (result <= 0) // can happen if physical sector size < logical sector size
+ result = 1;
return result;
-} // FindAlignment(int)
+} // FindAlignment(int) */
// The same as FindAlignment(int), but opens and closes a device by filename
int FindAlignment(char deviceFilename[]) {