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SubjectRe: [PATCH] block: add_disk: fix error handling
On Sun,  5 Dec 2010 16:15:27 +0100 Richard Weinberger <richard@nod.at> wrote:

> This patch brings better error handling to the
> add_disk function.
> Now it reports success or failure.

So does that mean that all callers of add_disk should now check the return
status and possible error-out ??? Sounds a bit painful.

Could you summaries the real-life situations in which add_disk can fail?
And what the consequences of failure are?

Thanks,
NeilBrown



>
> Signed-off-by: Richard Weinberger <richard@nod.at>
> ---
> block/genhd.c | 34 +++++++++++++++++++++++++++-------
> include/linux/genhd.h | 2 +-
> 2 files changed, 28 insertions(+), 8 deletions(-)
>
> diff --git a/block/genhd.c b/block/genhd.c
> index 5fa2b44..075e630 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -508,10 +508,8 @@ static int exact_lock(dev_t devt, void *data)
> *
> * This function registers the partitioning information in @disk
> * with the kernel.
> - *
> - * FIXME: error handling
> */
> -void add_disk(struct gendisk *disk)
> +int add_disk(struct gendisk *disk)
> {
> struct backing_dev_info *bdi;
> dev_t devt;
> @@ -529,7 +527,7 @@ void add_disk(struct gendisk *disk)
> retval = blk_alloc_devt(&disk->part0, &devt);
> if (retval) {
> WARN_ON(1);
> - return;
> + goto out;
> }
> disk_to_dev(disk)->devt = devt;
>
> @@ -541,16 +539,38 @@ void add_disk(struct gendisk *disk)
>
> /* Register BDI before referencing it from bdev */
> bdi = &disk->queue->backing_dev_info;
> - bdi_register_dev(bdi, disk_devt(disk));
> + retval = bdi_register_dev(bdi, disk_devt(disk));
> + if (retval) {
> + WARN_ON(1);
> + goto out_free_devt;
> + }
>
> blk_register_region(disk_devt(disk), disk->minors, NULL,
> exact_match, exact_lock, disk);
> register_disk(disk);
> - blk_register_queue(disk);
> + retval = blk_register_queue(disk);
> + if (retval) {
> + WARN_ON(1);
> + goto out_unregister_bdi;
> + }
>
> retval = sysfs_create_link(&disk_to_dev(disk)->kobj, &bdi->dev->kobj,
> "bdi");
> - WARN_ON(retval);
> + if (retval) {
> + WARN_ON(1);
> + goto out_unregister_queue;
> + }
> +
> + return 0;
> +
> +out_unregister_queue:
> + blk_unregister_queue(disk);
> +out_unregister_bdi:
> + bdi_unregister(bdi);
> +out_free_devt:
> + blk_free_devt(devt);
> +out:
> + return -1;
> }
>
> EXPORT_SYMBOL(add_disk);
> diff --git a/include/linux/genhd.h b/include/linux/genhd.h
> index 7a7b9c1..4e7ab8e 100644
> --- a/include/linux/genhd.h
> +++ b/include/linux/genhd.h
> @@ -393,7 +393,7 @@ static inline void free_part_info(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);



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