linux-kernel - Re: Issue with qla2xxx_probe

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Date:	Tue, 29 Apr 2008 16:12:51 -0400
From:	"Alan D. Brunelle" <Alan.Brunelle@...com>
To:	Andrew Vasquez <andrew.vasquez@...gic.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jens Axboe <jens.axboe@...cle.com>, linux-driver@...gic.com,
	linux-scsi@...r.kernel.org, James.Bottomley@...eleye.com
Subject: Re: Issue with qla2xxx_probe_one

Andrew Vasquez wrote:
> On Tue, 29 Apr 2008, Alan D. Brunelle wrote:
>
>> I /think/ that there is an issue with this routine /if/ the firmware
>> images are not loaded properly - on a 16-way ia64 box I am starting to
>> see this with an up-stream kernel (Jens Axboe's origin/io-cpu-affinity
>> branch). In any event, it looks to me that :
>>
>>         if (qla2x00_initialize_adapter(ha)) {
>>                 qla_printk(KERN_WARNING, ha,
>>                     "Failed to initialize adapter\n");
>>
>>                 DEBUG2(printk("scsi(%ld): Failed to initialize
adapter - "
>>                     "Adapter flags %x.\n",
>>                     ha->host_no, ha->device_flags));
>>
>>                 ret = -ENODEV;
>>                 goto probe_failed;
>>         }
>>
>> skips around:
>>
>>         ret = scsi_add_host(host, &pdev->dev);
>>
>> which is needed to properly initialize the freelist (via:
>> scsi_setup_command_freelist).
>
> Wasn't something like this posted recently to linux-scsi:
>
> http://lkml.org/lkml/2008/4/27/333
>
> this is sitting in scsi-misc-2.6.git:
>
> [SCSI] bug fix for free list handling
>
http://git.kernel.org/?p=linux/kernel/git/jejb/scsi-misc-2.6.git;a=commitdiff;h=a79cbe1aa5dd695f0ee012ecde1ff88b1192e326
>
> which I gather will be pushed soon...

My apologies for not having seeing that.

But after looking at it, doesn't it still have a hole?

o  scsi_setup_command_freelist initializes the free_list list.

o  It then invokes scsi_get_host_cmd_pool, if this fails there is no
need to invoke scsi_put_host_cmd_pool (it wasn't gotten).

o  If scsi_get_host_cmd_pool succeeds but scsi_pool_alloc_command fails,
it will (correctly) invoke scsi_put_host_cmd_pool.

However, if either of scsi_get_host_cmd_pool or scsi_put_host_cmd_pool
happens to fail, we'll end up in scsi_destroy_command_freelist - and
since the free_list was initialized, the while loop will be bypassed,
but scsi_put_host_cmd_pool will be invoked an extra time. And this is
badness, right?

Wouldn't the attached patch [boot tested on my previously failing
system] be correct (and perhaps cleaner - you're not looking at the
innards of the list data structure to determine things)?

Alan

View attachment "0001-Ensure-proper-handling-of-the-scsi-free_list-handlin.patch" of type "text/x-diff" (1285 bytes)