linux-kernel - Re: [PATCH] add procfs tunable to enable immediate panic when there are busy inodes after umount

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Date:	Tue, 29 May 2007 23:38:13 +0400
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	Jeff Layton <jlayton@...hat.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] add procfs tunable to enable immediate panic when there are busy inodes after umount

On Tue, May 29, 2007 at 11:40:42AM -0400, Jeff Layton wrote:
> After spending quite a bit of time tracking down a "VFS: busy inodes
> after unmount" problem, it occurs to me that it would be nice to be
> able to force a panic when that occurs. While an oops message alone is
> not generally helpful for tracking down this sort of problem,
> collecting and analyzing a coredump when this occurs can be.
>
> The following patch adds a procfs tunable that allows you to force a
> core when a "busy inodes after umount" problem occurs. It also changes
> the classic error message to be something a bit less cryptic to users.

> @@ -303,10 +305,15 @@ void generic_shutdown_super(struct super_block *sb)
>  			sop->put_super(sb);
>
>  		/* Forget any remaining inodes */
> -		if (invalidate_inodes(sb)) {
> -			printk("VFS: Busy inodes after unmount of %s. "
> -			   "Self-destruct in 5 seconds.  Have a nice day...\n",
> -			   sb->s_id);
> +		if (busy = invalidate_inodes(sb)) {
> +			printk("VFS: %d busy inodes after unmount of %s. ",
> +				 busy, sb->s_id);
> +			if (umount_debug != 0) {
> +				printk("Crashing host on request.\n");
> +				BUG();
> +			} else {
> +				printk("This machine will likely crash eventually. Consider a reboot.\n");
> +			}

You can add just BUG_ON here and do

	echo 1 >/proc/sys/kernel/panic_on_oops

-
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