[PATCH] fix units/partition count in sd.c (2.4.x)

[Luben Tuikov]

Hi,

This patch fixes the nr_real count in sd.c, which is also used
in genhd.c to print out the partitions/units.  The problem is that
nr_real is decremented on detach, the genhd's nr_sects is
cleared but the entry is still there and is being counted
for when displaying the partitions.  Thus when nr_real
is decremented _and_ a 0-ed partition/unit is counted,
we get to not display 1 or more entries of the tail of
the list.

The solution is to not decrement nr_real on detach, effectively
never decrementing it, and so that it doesn't grow without a bound,
to throttle it on attach, incrementing it only if it would be
smaller than nr_dev.

This was observed on a RH kernel and on the current BK kernel.
Tested and fixed on 2.4.30-pre1 (BK).  This patch is against 2.4.30-pre1.

To reproduce: assume 4 scsi disks sda, sdb, sdc, sdd.
#echo "scsi remove-single-device <sdb-HCTL>" > /proc/scsi/scsi
#cat /proc/partitions
<<sdb _and_ sdd are not listed>>

Signed-off-by: Luben Tuikov <luben_tuikov@xxxxxxxxxxx>

===== sd.c 1.31 vs edited =====
--- 1.31/drivers/scsi/sd.c      2003-06-25 19:34:08 -04:00
+++ edited/sd.c 2005-02-14 17:09:43 -05:00
@@ -1332,8 +1332,8 @@

       rscsi_disks[i].device = SDp;
       rscsi_disks[i].has_part_table = 0;
-       sd_template.nr_dev++;
-       SD_GENDISK(i).nr_real++;
+       if (sd_template.nr_dev++ >= SD_GENDISK(i).nr_real)
+               SD_GENDISK(i).nr_real++;
        devnum = i % SCSI_DISKS_PER_MAJOR;
        SD_GENDISK(i).de_arr[devnum] = SDp->de;
        if (SDp->removable)
@@ -1424,9 +1424,12 @@

       for (dpnt = rscsi_disks, i = 0; i < sd_template.dev_max; i++, dpnt++)
               if (dpnt->device == SDp) {
+                       char nbuff[6];

                       /* If we are disconnecting a disk driver, sync and invalidate
                        * everything */
+                       sd_devname(i, nbuff);
+
                       sdgd = &SD_GENDISK(i);
                       max_p = sd_gendisk.max_p;
                       start = i << sd_gendisk.minor_shift;
@@ -1447,7 +1450,12 @@
                       SDp->attached--;
                       sd_template.dev_noticed--;
                       sd_template.nr_dev--;
-                       SD_GENDISK(i).nr_real--;
+
+                       printk("Detached scsi %sdisk %s at scsi%d, "
+                              "channel %d, id %d, lun %d\n",
+                              SDp->removable ? "removable " : "",
+                              nbuff, SDp->host->host_no, SDp->channel,
+                              SDp->id, SDp->lun);
                       return;
               }
       return;

	Luben
P.S. Patch attached as well, for formatting.

Attachment: sd.patch
Description: octet/stream