Messages in this thread | | | Date | Mon, 6 Apr 2015 00:40:12 +0800 | Subject | Re: [PATCH 1/6] block: export blkdev_reread_part() | From | Ming Lei <> |
| |
On Mon, Apr 6, 2015 at 12:12 AM, Christoph Hellwig <hch@infradead.org> wrote: >> +/* >> + * This is exported as API for block driver, can be called >> + * with requiring bd_mutex or not. >> + */ >> +int __blkdev_reread_part(struct block_device *bdev, bool lock) >> { >> struct gendisk *disk = bdev->bd_disk; >> int res; >> @@ -159,12 +163,14 @@ static int blkdev_reread_part(struct block_device *bdev) >> return -EINVAL; >> if (!capable(CAP_SYS_ADMIN)) >> return -EACCES; >> - if (!mutex_trylock(&bdev->bd_mutex)) >> + if (lock && !mutex_trylock(&bdev->bd_mutex)) >> return -EBUSY; > > Please don't add funtions that do conditional locking, instead move > all the code into blkdev_reread_part_nolock, and then wrap it: > > int blkdev_reread_part(struct block_device *bdev) > { > if (!mutex_trylock(&bdev->bd_mutex)) > return -EBUSY; > blkdev_reread_part_nolock(bdev); > mutex_unlock(&bdev->bd_mutex); > }
Yes, it is more clean, but with extra acquiring lock cost for the failure cases, especially when we replace trylock with mutex_lock().
> > Please also add a lockdep_assert_held to blkdev_reread_part_nolock to > ensure callers actually do hold the lock.
Good point!
Thanks, Ming Lei
| |