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Subject[PATCH] IDE disks show invalid geometries in /proc/ide/hd*/geometry
The ATA specification tells large disk drives to return C/H/S data of 
16383/16/63 regardless of their actual size (other variations on this
return include 15 heads and/or 4092 cylinders). Unfortunately these CHS
data confuse the existing IDE code and cause it to report invalid
geometries in /proc when the disk runs in LBA mode.

The invalid geometries can cause failures in the partitioning tools;
partitioning may be impossible or illogical size limitations occur. This
also leads to various forms of human confusion.
I attach a patch that fixes this problem while strongly attempting to
not break any existing side effects and await any comments.

mark

Signed-off-by: Mark Bellon <mbellon@mvista.com>

diff -Naur linux-2.6.13-rc3-git9-orig/drivers/ide/ide-disk.c linux-2.6.13-rc3-git9/drivers/ide/ide-disk.c
--- linux-2.6.13-rc3-git9-orig/drivers/ide/ide-disk.c 2005-08-01 13:48:21.000000000 -0700
+++ linux-2.6.13-rc3-git9/drivers/ide/ide-disk.c 2005-08-02 12:14:43.000000000 -0700
@@ -884,10 +884,17 @@
ide_add_setting(drive, "max_failures", SETTING_RW, -1, -1, TYPE_INT, 0, 65535, 1, 1, &drive->max_failures, NULL);
}

+static uint32_t do_div64_32 (__u64 n, uint32_t d)
+{
+ do_div(n, d);
+
+ return n;
+}
+
static void idedisk_setup (ide_drive_t *drive)
{
struct hd_driveid *id = drive->id;
- unsigned long long capacity;
+ __u64 capacity;
int barrier;

idedisk_add_settings(drive);
@@ -949,27 +956,32 @@
*/
capacity = idedisk_capacity (drive);
if (!drive->forced_geom) {
+ uint32_t cylsz, cyl;

- if (idedisk_supports_lba48(drive->id)) {
- /* compatibility */
- drive->bios_sect = 63;
- drive->bios_head = 255;
+ /*
+ * In LBA mode the geometry isn't used to talk to the drive
+ * so always create a "rational" geometry from the capacity.
+ */
+ if (drive->select.b.lba) {
+ drive->bios_sect = drive->sect = 63;
+ drive->bios_head = drive->head = 255;
+
+ cylsz = drive->bios_sect * drive->bios_head;
+ cyl = do_div64_32(capacity, cylsz);
+
+ /* "fake out" works up to ~500 GB */
+ cyl = (cyl > 65535) ? 65535 : cyl;
+ drive->bios_cyl = drive->cyl = cyl;
}

if (drive->bios_sect && drive->bios_head) {
- unsigned int cap0 = capacity; /* truncate to 32 bits */
- unsigned int cylsz, cyl;
+ cylsz = drive->bios_sect * drive->bios_head;
+ cyl = do_div64_32(capacity, cylsz);

- if (cap0 != capacity)
- drive->bios_cyl = 65535;
- else {
- cylsz = drive->bios_sect * drive->bios_head;
- cyl = cap0 / cylsz;
- if (cyl > 65535)
- cyl = 65535;
- if (cyl > drive->bios_cyl)
- drive->bios_cyl = cyl;
- }
+ if (cyl > 65535)
+ cyl = 65535;
+ if (cyl > drive->bios_cyl)
+ drive->bios_cyl = cyl;
}
}
printk(KERN_INFO "%s: %llu sectors (%llu MB)",
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