Re: [patch v4 1/1] md: Software Raid autodetect dev list not array

[Michael J. Evans]

From: Michael J. Evans <mjevans1983@xxxxxxxxx>

In current release kernels the md module (Software RAID) uses a static array
 (dev_t[128]) to store partition/device info temporarily for autostart.

This patch replaces that static array with a list.

Signed-off-by: Michael J. Evans <mjevans1983@xxxxxxxxx>
--- 
Version 4:
Minor formatting cleanup for kzAlloc error message.
Should I remove the first patch section in version 5?

Version 3:
md_autodetect_dev failure message is now more usefully verbose.
removed unused i_found that was leftover from initial verification.
Thank you Randy Dunlap for pointing where INT_MAX was, fixme fixed.

Version 2:
using list_add_tail, and corrected missing i_passed++;.
removed sections of code that would never be reached.

Version 1:
The data/structures are only used within md.c, and very close together.
However I wonder if the structural information shouldn't go in to...
../../include/linux/raid/md_k.h instead.


I discovered this (and that the devices are added as disks/partitions are
discovered at boot) while I was debugging why only one of my MD arrays would
come up whole, while all the others were short a disk.

I eventually discovered that it was enumerating through all of 9 of my 11 hds
(2 had only 4 partitions apiece) while the other 9 have 15 partitions
(I wanted 64 per drive...). The last partition of the 8th drive in my 9 drive
raid 5 sets wasn't added, thus making the final md array short both a parity
and data disk, and it was started later, elsewhere.

Subject: [patch 1/1] md: Software Raid autodetect dev list not array

SOFTWARE RAID (Multiple Disks) SUPPORT
P:	Ingo Molnar
M:	mingo@xxxxxxxxxx
P:	Neil Brown
M:	neilb@xxxxxxx
L:	linux-raid@xxxxxxxxxxxxxxx
S:	Supported
Unless you have a reason NOT to do so, CC linux-kernel@xxxxxxxxxxxxxxxx

12: Has been tested with CONFIG_PREEMPT, CONFIG_DEBUG_PREEMPT,
    CONFIG_DEBUG_SLAB, CONFIG_DEBUG_PAGEALLOC, CONFIG_DEBUG_MUTEXES,
    CONFIG_DEBUG_SPINLOCK, CONFIG_DEBUG_SPINLOCK_SLEEP all simultaneously
    enabled.

It has been tested with CONFIG_SMP set and unset (Different x86_64 systems).
It has been tested with CONFIG_PREEMPT set and unset (same system).
CONFIG_LBD isn't even an option in my .config file.

Note: between 2.6.22 and 2.6.23-rc3-git5
                rdev = md_import_device(dev,0, 0);
became
                rdev = md_import_device(dev,0, 90);
So the patch has been edited to patch around that line.

Signed-off-by: Michael J. Evans <mjevans1983@xxxxxxxxx>
=============================================================
--- linux/drivers/md/md.c.orig	2007-08-21 03:19:42.511576248 -0700
+++ linux/drivers/md/md.c	2007-08-21 04:30:09.775525710 -0700
@@ -24,4 +24,6 @@

+   - autodetect dev list not array: Michael J. Evans <mjevans1983@xxxxxxxxx>
+
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2, or (at your option)
@@ -5752,13 +5754,26 @@ void md_autodetect_dev(dev_t dev)
  * Searches all registered partitions for autorun RAID arrays
  * at boot time.
  */
-static dev_t detected_devices[128];
-static int dev_cnt;
+
+static LIST_HEAD(all_detected_devices);
+struct detected_devices_node {
+	struct list_head list;
+	dev_t dev;
+};
 
 void md_autodetect_dev(dev_t dev)
 {
-	if (dev_cnt >= 0 && dev_cnt < 127)
-		detected_devices[dev_cnt++] = dev;
+	struct detected_devices_node *node_detected_dev;
+	char strbuf[BDEVNAME_SIZE];
+
+	node_detected_dev = kzalloc(sizeof(*node_detected_dev), GFP_KERNEL);
+	if (node_detected_dev) {
+		node_detected_dev->dev = dev;
+		list_add_tail(&node_detected_dev->list, &all_detected_devices);
+	} else {
+		printk(KERN_CRIT "md: md_autodetect_dev: kzAlloc node failed"
+			", skipping dev(%d,%d)\n", MAJOR(dev), MINOR(dev));
+	}
 }
 
 
@@ -5765,7 +5760,12 @@ static void autostart_arrays(int part)
 static void autostart_arrays(int part)
 {
 	mdk_rdev_t *rdev;
-	int i;
+	struct detected_devices_node *node_detected_dev;
+	dev_t dev;
+	int i_scanned, i_passed;
+
+	i_scanned = 0;
+	i_passed = 0;
 
 	printk(KERN_INFO "md: Autodetecting RAID arrays.\n");
 
@@ -5772,3 +5792,7 @@ static void autostart_arrays(int part)
-	for (i = 0; i < dev_cnt; i++) {
-		dev_t dev = detected_devices[i];
-
+	while (!list_empty(&all_detected_devices) && i_scanned < INT_MAX) {
+		i_scanned++;
+		node_detected_dev = list_entry(all_detected_devices.next,
+					struct detected_devices_node, list);
+		list_del(&node_detected_dev->list);
+		dev = node_detected_dev->dev;
+		kfree(node_detected_dev);
@@ -5781,8 +5807,11 @@ static void autostart_arrays(int part)
 			continue;
 		}
 		list_add(&rdev->same_set, &pending_raid_disks);
+		i_passed++;
 	}
-	dev_cnt = 0;
+
+	printk(KERN_INFO "md: Scanned %d and added %d devices.\n",
+						i_scanned, i_passed);
 
 	autorun_devices(part);
 }
-
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