linux-kernel - Re: [patch v2 1/1] md: Software Raid autodetect dev list not array

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Date:	Sun, 26 Aug 2007 09:56:51 -0700
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	"Michael J. Evans" <mjevans1983@...cast.net>
Cc:	Neil Brown <neilb@...e.de>, Ingo Molnar <mingo@...hat.com>,
	linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
	Michael J "." Evans <mjevans1983@...il.com>
Subject: Re: [patch v2 1/1] md: Software Raid autodetect dev list not array

On Sun, 26 Aug 2007 04:51:24 -0700 Michael J. Evans wrote:

> From: Michael J. Evans <mjevans1983@...il.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@...il.com>
> --- 
> Version 2: Following Neil Brown's requests...
> using list_add_tail, and corrected missing i_passed++;.
> removed sections of code that would never be reached.
> - -
> 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@...hat.com
> P:	Neil Brown
> M:	neilb@...e.de
> L:	linux-raid@...r.kernel.org
> S:	Supported
> Unless you have a reason NOT to do so, CC linux-kernel@...r.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.

It's not an option 64_BIT builds.

> 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. (might be fuzzy)
> 
> Signed-off-by: Michael J. Evans <mjevans1983@...il.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
> @@ -5752,13 +5754,24 @@ 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;
> +	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: kzAlloc node failed, skipping device."
> +				 " : 0x%p.\n", node_detected_dev);

Is there any way to tell the user what device (or partition?) is
bein skipped?  This printk should just print (confirm) that
node_detected_dev is NULL.  Shouldn't it just print <dev> in
major:minor format?

> +	}
>  }
>  
>  
> @@ -5765,7 +5778,12 @@ 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;
> +	signed int i_found;

Drop "signed", like the surrounding code.
Leave a blank line between data declarations and beginning of code.

> +	i_scanned = 0;
> +	i_passed = 0;
>  
>  	printk(KERN_INFO "md: Autodetecting RAID arrays.\n");
>  
> @@ -5772,3 +5790,8 @@ static void autostart_arrays(int part)
> -	for (i = 0; i < dev_cnt; i++) {
> -		dev_t dev = detected_devices[i];
> -
> +		/* FIXME: max 'int' #DEFINEd somewhere?  not   0x7FFFFFFF ? */

include/linux/kernel.h has INT_MAX, UINT_MAX, LONG_MAX, ULONG_MAX,
LLONG_MAX, ULLONG_MAX.

> +	while (!list_empty(&all_detected_devices) && i_scanned < 0x7FFFFFFF) {
> +		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);


---
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***
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