Re: [Nbd] [PATCH 1/7] block: export blkdev_reread_part() and __blkdev_reread_part()
- To: Peter Zijlstra <peterz@...1270...>
- Cc: Jens Axboe <axboe@...161...>, Stefan Weinhuber <wein@...1296...>, "nbd-general@lists.sourceforge.net" <nbd-general@lists.sourceforge.net>, linux-s390@...25..., Mike Galbraith <bitbucket@...1990...>, Ming Lei <ming.lei@...1301...>, Stefan Haberland <stefan.haberland@...1296...>, Sebastian Ott <sebott@...1294...>, Linux Kernel Mailing List <linux-kernel@...25...>, Christoph Hellwig <hch@...1270...>, Fabian Frederick <fabf@...1980...>, Alexander Viro <viro@...1300...>, David Herrmann <dh.herrmann@...17...>, Tejun Heo <tj@...1285...>, Andrew Morton <akpm@...133...>
- Subject: Re: [Nbd] [PATCH 1/7] block: export blkdev_reread_part() and __blkdev_reread_part()
- From: Jarod Wilson <jarod@...696...>
- Date: Wed, 8 Apr 2015 11:27:48 -0400
- Message-id: <20150408152748.GJ14217@...696...>
- In-reply-to: <20150408150325.GJ5029@...1991...>
- References: <1428218688-4092-1-git-send-email-ming.lei@...1301...> <1428474226-27386-1-git-send-email-jarod@...696...> <1428474226-27386-2-git-send-email-jarod@...696...> <CACVXFVOQH_tNdBtgNH8UhLan304cSacRTzqvvRhndLauexTvaw@...18...> <20150408150325.GJ5029@...1991...>
On Wed, Apr 08, 2015 at 05:03:25PM +0200, Peter Zijlstra wrote:
> On Wed, Apr 08, 2015 at 10:50:56PM +0800, Ming Lei wrote:
> > > +/*
> > > + * This is an exported API for the block driver, and will not
> > > + * acquire bd_mutex, leaving it up to the caller to handle
> > > + * any necessary locking.
> >
> > Actually, the function is introduced and should be used in case
> > that bd_mutex has been held already, such as clearing fd in
> > loop release().
> >
> > > + */
> > > +int __blkdev_reread_part(struct block_device *bdev)
> > > {
> > > struct gendisk *disk = bdev->bd_disk;
> > >
>
> lockdep_assert_held(&bdev->bd_mutex);
>
> is an excellent means of avoiding that comment and verifying its
> actually true :-)
Ah, yes, that was actually suggested by Christoph as well, I was too hasty
shoving something back out the door on multiple counts.
> > > + */
> > > +int blkdev_reread_part(struct block_device *bdev)
> > > +{
> > > + int res;
> > > +
> > > if (!mutex_trylock(&bdev->bd_mutex))
> > > return -EBUSY;
>
> Is that really needed? It seems rather poor form.
It goes away later in the series and gets converted to a straight
mutex_lock().
--
Jarod Wilson
jarod@...696...
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