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SubjectRe: [PATCH] fix units/partition count in sd.c (2.4.x)
On Wed, Feb 16, 2005 at 11:23:53AM -0500, Luben Tuikov wrote:
> 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>>

Luben,

On James Bottomley advice I have applied Soo Lee's fix, which looks cleaner.

Also as James notice this will increase overhead of /proc/partitions which might be
a problem on higher-end systems with many devices.

Testing of it on such systems is highly appreciated.


# 05/02/26 slee@netengine1.com 1.1558
# [PATCH] Fix units/partition count in sd.c
#
# Symptom:
# When a scsi disk is removed other scsi disk with biggest minor #
# disapears in /proc/partition at the same time.
#
# Cause and fix:
# sd.c decreases nr_real on disk removal but because nr_real is not
# real # of devices but max # of devices of a major #,
# it doesn't need to be changed on disk add/remove.
#
# 2.6 has little different structure but it does like this
#
# sd.c:sd_probe()
# gd->minors = 16;
# --------------------------------------------
#
diff -Nru a/drivers/scsi/sd.c b/drivers/scsi/sd.c
--- a/drivers/scsi/sd.c Sat Feb 26 10:46:42 2005
+++ b/drivers/scsi/sd.c Sat Feb 26 10:46:42 2005
@@ -1220,7 +1220,7 @@
goto cleanup_gendisks_part;
memset(sd_gendisks[i].part, 0, (SCSI_DISKS_PER_MAJOR << 4) * sizeof(struct hd_struct));
sd_gendisks[i].sizes = sd_sizes + (i * SCSI_DISKS_PER_MAJOR << 4);
- sd_gendisks[i].nr_real = 0;
+ sd_gendisks[i].nr_real = SCSI_DISKS_PER_MAJOR;
sd_gendisks[i].real_devices =
(void *) (rscsi_disks + i * SCSI_DISKS_PER_MAJOR);
}
@@ -1333,7 +1333,6 @@
rscsi_disks[i].device = SDp;
rscsi_disks[i].has_part_table = 0;
sd_template.nr_dev++;
- SD_GENDISK(i).nr_real++;
devnum = i % SCSI_DISKS_PER_MAJOR;
SD_GENDISK(i).de_arr[devnum] = SDp->de;
if (SDp->removable)
@@ -1447,7 +1446,6 @@
SDp->attached--;
sd_template.dev_noticed--;
sd_template.nr_dev--;
- SD_GENDISK(i).nr_real--;
return;
}
return;


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