From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755876AbZFYKPu (ORCPT ); Thu, 25 Jun 2009 06:15:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752303AbZFYKPi (ORCPT ); Thu, 25 Jun 2009 06:15:38 -0400 Received: from cantor.suse.de ([195.135.220.2]:51245 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752234AbZFYKPh (ORCPT ); Thu, 25 Jun 2009 06:15:37 -0400 From: Nikanth Karthikesan Organization: suse.de To: Andrew Morton Subject: Re: [PATCH] Fix error handling in add_disk Date: Thu, 25 Jun 2009 15:47:01 +0530 User-Agent: KMail/1.11.1 (Linux/2.6.27.23-0.1-default; KDE/4.2.1; x86_64; ; ) Cc: axboe@kernel.dk, linux-kernel@vger.kernel.org References: <200906171231.10438.knikanth@suse.de> <200906241218.13538.knikanth@suse.de> <20090624201154.7e89cbee.akpm@linux-foundation.org> In-Reply-To: <20090624201154.7e89cbee.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200906251547.01349.knikanth@suse.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thursday 25 June 2009 08:41:54 Andrew Morton wrote: > On Wed, 24 Jun 2009 12:18:13 +0530 Nikanth Karthikesan wrote: > > On Wednesday 24 June 2009 02:53:57 Andrew Morton wrote: > > > On Wed, 17 Jun 2009 12:31:10 +0530 > > > > > > Nikanth Karthikesan wrote: > > > > Fix error handling in add_disk. Also add WARN_ON()'s in case > > > > of error, which can be removed once the callers handle the error. > > > > > > I have a vague ancestral memory that some of the unchecked errors which > > > you're now checking for actually do happen in practice, and that this > > > "fix" will end up breaking currently-working setups. > > > > > > Or maybe I'm thinking of a similar but different piece of code (maybe > > > it was the partition code?). > > > > > > Still, I think it would be prudent to initially make this patch > > > continue to ignore the errors. So add the warnings, but don't change > > > the response to errors. Then we can get the change distributed for a > > > bit of testing and if that all looks good then we can add the control > > > flow changes later. > > > > add_disk and blk_register_region are functions returning void masking the > > error > > ugh, we're bad. > > > which this patch changes. So no caller check for it's return value! And > > hence errors are ignored, and nothing breaks. > > It _does_ change behaviour. add_disk() can now bale out if, for > example, sysfs_create_link() failed. As it commonly does, due to > various screwups. > ah, yes. This patch does mofiy behaviour. :( > > > > retval = blk_alloc_devt(&disk->part0, &devt); > > > > if (retval) { > > > > WARN_ON(1); > > > > - return; > > > > + goto err_out; > > > > } > > > > ... > > > > + if (retval) { > > > > + WARN_ON(1); > > > > + goto err_free_devt; > > > > + } > > > > ... > > > > + if (retval) { > > > > + WARN_ON(1); > > > > + goto err_free_region; > > > > + } > > > > ... > > > > - WARN_ON(retval); > > > > + if (retval) { > > > > + WARN_ON(1); > > > > + goto err_free_queue; > > > > + } > > > > > > These all can be coded as > > > > > > if (WARN_ON(retval)) > > > goto foo; > > > > done. > > > > Thanks > > Nikanth > > > > > > Fix error handling in add_disk. Also add WARN_ON()'s in case > > of error, which can be removed once the callers handle the error. > > The changelog hasn't been updated to reflect this discussion. There's > information missing here. > > > Also, why was this patch written? Have you observed some behaviour > which this patch improved or corrected? > No. I am just trying to cleanup. > I applaud the effort, but it's obviously incomplete. Do you intend to > add further error checking and handling in this area? I was intending to fix the callers one by one. But it seems to be better to do it in one go. I would work on it and send complete patches. Till then could we add few more WARN_ON's and return error code for the case where add_disk fails completely? Thanks Nikanth Add WARN_ON's in case of errors during add_disk. Also return error code when add_disk fails completely. As akpm suggested, in case of partial failure, dont change the current behaviour and return success. Signed-off-by: Nikanth Karthikesan --- diff --git a/block/genhd.c b/block/genhd.c index fe7ccc0..077bf63 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -472,11 +472,11 @@ static char *bdevt_str(dev_t devt, char *buf) * range must be nonzero * The hash chain is sorted on range, so that subranges can override. */ -void blk_register_region(dev_t devt, unsigned long range, struct module *module, +int blk_register_region(dev_t devt, unsigned long range, struct module *module, struct kobject *(*probe)(dev_t, int *, void *), int (*lock)(dev_t, void *), void *data) { - kobj_map(bdev_map, devt, range, module, probe, lock, data); + return kobj_map(bdev_map, devt, range, module, probe, lock, data); } EXPORT_SYMBOL(blk_register_region); @@ -513,7 +513,7 @@ static int exact_lock(dev_t devt, void *data) * * FIXME: error handling */ -void add_disk(struct gendisk *disk) +int add_disk(struct gendisk *disk) { struct backing_dev_info *bdi; dev_t devt; @@ -529,10 +529,9 @@ void add_disk(struct gendisk *disk) disk->flags |= GENHD_FL_UP; retval = blk_alloc_devt(&disk->part0, &devt); - if (retval) { - WARN_ON(1); - return; - } + if (WARN_ON(retval)) + return retval; + disk_to_dev(disk)->devt = devt; /* ->major and ->first_minor aren't supposed to be @@ -541,16 +540,22 @@ void add_disk(struct gendisk *disk) disk->major = MAJOR(devt); disk->first_minor = MINOR(devt); - blk_register_region(disk_devt(disk), disk->minors, NULL, + retval = blk_register_region(disk_devt(disk), disk->minors, NULL, exact_match, exact_lock, disk); + WARN_ON(retval); + register_disk(disk); - blk_register_queue(disk); + + retval = blk_register_queue(disk); + WARN_ON(retval); bdi = &disk->queue->backing_dev_info; bdi_register_dev(bdi, disk_devt(disk)); retval = sysfs_create_link(&disk_to_dev(disk)->kobj, &bdi->dev->kobj, "bdi"); WARN_ON(retval); + + return 0; } EXPORT_SYMBOL(add_disk); diff --git a/include/linux/genhd.h b/include/linux/genhd.h index 149fda2..df3344a 100644 --- a/include/linux/genhd.h +++ b/include/linux/genhd.h @@ -339,7 +339,7 @@ static inline void part_dec_in_flight(struct hd_struct *part) extern void part_round_stats(int cpu, struct hd_struct *part); /* block/genhd.c */ -extern void add_disk(struct gendisk *disk); +extern int add_disk(struct gendisk *disk); extern void del_gendisk(struct gendisk *gp); extern void unlink_gendisk(struct gendisk *gp); extern struct gendisk *get_gendisk(dev_t dev, int *partno); @@ -534,7 +534,7 @@ extern struct gendisk *alloc_disk_node(int minors, int node_id); extern struct gendisk *alloc_disk(int minors); extern struct kobject *get_disk(struct gendisk *disk); extern void put_disk(struct gendisk *disk); -extern void blk_register_region(dev_t devt, unsigned long range, +extern int blk_register_region(dev_t devt, unsigned long range, struct module *module, struct kobject *(*probe)(dev_t, int *, void *), int (*lock)(dev_t, void *),