linux-kernel - Re: [PATCH 2/2] floppy: error handling fixes on do_floppy

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Date:	Wed, 8 Aug 2012 15:57:30 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Herton Ronaldo Krzesinski <herton.krzesinski@...onical.com>
Cc:	Jiri Kosina <jkosina@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jens Axboe <axboe@...nel.dk>, Tejun Heo <tj@...nel.org>,
	linux-kernel@...r.kernel.org, Ben Hutchings <ben@...adent.org.uk>
Subject: Re: [PATCH 2/2] floppy: error handling fixes on do_floppy_init

On Wed, Aug 08, 2012 at 03:24:53PM -0300, Herton Ronaldo Krzesinski wrote:
> While looking at commit 3f9a5aa ("floppy: Cleanup disk->queue before
> caling put_disk() if add_disk() was never called") I noticed some
> problems with the error handling and cleanup:
> 
> * missing cleanup (put_disk) if blk_init_queue fails, dr is decremented
>   first in the error handling loop
> * if something fails in the add_disk loop, there is no cleanup of
>   previous iterations in the error handling.
> * "if (disks[dr]->queue)" check is bogus, when reaching there for each
>   dr should exist an queue allocated, and it doesn't take into account
>   iterations where add_disk wasn't done, if failure happens in add_disk
>   loop.
> * floppy_module_exit doesn't reset queue pointer if add_disk wasn't
>   done.

Hey, these seem to be multiple cleanups. Can you break these down into
individual patches. Review becomes easy.

[..]
> +		blk_cleanup_queue(disks[dr]->queue);
> +		/*
> +		 * put_disk() may not be paired with add_disk() and
> +		 * will put queue reference one extra time. fix it.
> +		 */
> +		if (dr > registered || !(allowed_drive_mask & (1 << dr)) ||
> +		    fdc_state[FDC(dr)].version == FDC_NONE)
>  			disks[dr]->queue = NULL;

I think checking for FDC_NONE and allowed_drive_mask() in multiple places
is becoming unreadable now. Can we just maintain a separate array to keep
track of disks on which we have called add_disk() and do the cleanup 
accordingly.

static unsigned short disk_registered[N_DRIVE];

/* do add_disk */
disk_registered[drive] = 1;


out_put_disk:
	while(dr--) {
		if (disks[dr]->queue && !disk_registered[dr]) {
			blk_cleanup_queue()
			disks[dr]->queue = NULL;
		}
	}

Same disk_registered[] can be used for your other loop of remove drives.
Also it can be used in cleaning up code in floppy_module_exit().

I think this will make code much more readable. Right now this error 
handling loop is just getting too complicated.

Thanks
Vivek
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