Messages in this thread Patch in this message | | | From | Nikanth Karthikesan <> | Subject | Re: [PATCH] Fix error handling in add_disk | Date | Wed, 24 Jun 2009 12:18:13 +0530 |
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On Wednesday 24 June 2009 02:53:57 Andrew Morton wrote: > On Wed, 17 Jun 2009 12:31:10 +0530 > > Nikanth Karthikesan <knikanth@suse.de> 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, which this patch changes. So no caller check for it's return value! And hence errors are ignored, and nothing breaks.
> > 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.
Signed-off-by: Nikanth Karthikesan <knikanth@suse.de>
---
diff --git a/block/genhd.c b/block/genhd.c index fe7ccc0..ae48a89 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); @@ -511,9 +511,9 @@ static int exact_lock(dev_t devt, void *data) * This function registers the partitioning information in @disk * with the kernel. * - * FIXME: error handling + * TODO: Remove WARN_ON()'s when all the callers handle the error. */ -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)) + goto err_out; + disk_to_dev(disk)->devt = devt; /* ->major and ->first_minor aren't supposed to be @@ -541,16 +540,34 @@ 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); + if (WARN_ON(retval)) + goto err_free_devt; + register_disk(disk); - blk_register_queue(disk); + + retval = blk_register_queue(disk); + if (WARN_ON(retval)) + goto err_free_region; 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); + if (WARN_ON(retval)) + goto err_free_queue; + + return 0; + +err_free_queue: + blk_unregister_queue(disk); +err_free_region: + blk_unregister_region(disk_devt(disk), disk->minors); +err_free_devt: + blk_free_devt(disk_devt(disk)); +err_out: + return retval; } 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 *),
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