Re: [patch v5 1/1] md: Software Raid autodetect dev list not array

Michael J. Evans
2007-08-28T13:28:42Z

From: Michael J. Evans <mjevans1983@gmail.com>

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@gmail.com>
---
Version 5:
patched modified to cleanly patch against 2.6.23-rc4 (Offsets only)
Removed credit from head of file since the changelogs are archived.

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@redhat.com
P: Neil Brown
M: neilb@suse.de
L: linux-raid@vger.kernel.org
S: Supported
Unless you have a reason NOT to do so, CC linux-kernel@vger.kernel.org.

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@gmail.com>
=============================================================
--- 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
@@ -5781,13 +5781,26 @@ 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));
+ }
}

@@ -5794,7 +5787,12 @@ 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");

@@ -5801,3 +5821,7 @@ 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);
@@ -5810,8 +5834,11 @@ 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);
}