linux-kernel - [PATCH 27/30] hpsa: fix bug in adjust_hpsa_scsi

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Message-ID: <20100204144341.10406.14452.stgit@beardog.cce.hp.com>
Date:	Thu, 04 Feb 2010 08:43:41 -0600
From:	"Stephen M. Cameron" <scameron@...rdog.cce.hp.com>
To:	James.Bottomley@...senPartnership.com, akpm@...ux-foundation.org
Cc:	mikem@...rdog.cce.hp.com, brace@...rdog.cce.hp.com,
	matthew.gates@...com, linux-scsi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 27/30] hpsa: fix bug in adjust_hpsa_scsi_table

From: Stephen M. Cameron <scameron@...rdog.cce.hp.com>

hpsa: fix bug in adjust_hpsa_scsi_table which caused devices
which have changed size, etc. to do the wrong thing.

The problem was as follows:

The driver maintains its current idea of what devices are present
in the h->dev[] array.  When it updates this array, it scans the
hardware, and produces a new list of devices, call it sd[], for
scsi devices.

Then, it compares each item in h->dev[] vs. sd[], and any items which
are not present sd it removes from h->dev[], and any items present
in sd[], but different, it modifies in h->dev[].

Then, it looks for items in sd[] which are not present in h->dev[],
and adds those items into h->dev[].  All the while, it keeps track
of what items were added and removed to/from h->dev[].

Finally, it updates the SCSI mid-layer by removing and adding
the same devices it removed and added to/from h->dev[]. (modified
devices count as a remove then add.)

originally, when a "changed" device was discovered, it was
removed then added to h->dev[].  The item was added to the *end*
of h->dev[].  And, the item was removed from sd[] as well
(nulled out).  As it processed h->dev[], these newly added items
at the end of the list were encountered, and sd[] was searched,
but those items were nulled out.  So they ended up getting removed
immediately after they were added.

The solution is to have a way to replace items in the h->dev[]
array instead of doing a remove + add.  Then the "changed" items.
are not encountered a second time, and removed.

Signed-off-by: Stephen M. Cameron <scameron@...rdog.cce.hp.com>
---
 drivers/scsi/hpsa.c |   26 ++++++++++++++++++++------
 1 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/drivers/scsi/hpsa.c b/drivers/scsi/hpsa.c
index 2764cb6..6b40221 100644
--- a/drivers/scsi/hpsa.c
+++ b/drivers/scsi/hpsa.c
@@ -675,6 +675,24 @@ lun_assigned:
 	return 0;
 }

+/* Replace an entry from h->dev[] array. */
+static void hpsa_scsi_replace_entry(struct ctlr_info *h, int hostno,
+	int entry, struct hpsa_scsi_dev_t *new_entry,
+	struct hpsa_scsi_dev_t *added[], int *nadded,
+	struct hpsa_scsi_dev_t *removed[], int *nremoved)
+{
+	/* assumes h->devlock is held */
+	BUG_ON(entry < 0 || entry >= HPSA_MAX_SCSI_DEVS_PER_HBA);
+	removed[*nremoved] = h->dev[entry];
+	(*nremoved)++;
+	h->dev[entry] = new_entry;
+	added[*nadded] = new_entry;
+	(*nadded)++;
+	dev_info(&h->pdev->dev, "%s device c%db%dt%dl%d changed.\n",
+		scsi_device_type(new_entry->devtype), hostno, new_entry->bus,
+			new_entry->target, new_entry->lun);
+}
+
 /* Remove an entry from h->dev[] array. */
 static void hpsa_scsi_remove_entry(struct ctlr_info *h, int hostno, int entry,
 	struct hpsa_scsi_dev_t *removed[], int *nremoved)
@@ -835,12 +853,8 @@ static void adjust_hpsa_scsi_table(struct ctlr_info *h, int hostno,
 			continue; /* remove ^^^, hence i not incremented */
 		} else if (device_change == DEVICE_CHANGED) {
 			changes++;
-			hpsa_scsi_remove_entry(h, hostno, i,
-				removed, &nremoved);
-			(void) hpsa_scsi_add_entry(h, hostno, sd[entry],
-				added, &nadded);
-			/* add can't fail, we just removed one. */
-
+			hpsa_scsi_replace_entry(h, hostno, i, sd[entry],
+				added, &nadded, removed, &nremoved);
 			/* Set it to NULL to prevent it from being freed
 			 * at the bottom of hpsa_update_scsi_devices()
 			 */

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