linux-kernel - Re: [PATCH 1/1] Btrfs: Code Cleanup

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Message-ID: <20160324160905.GS29764@suse.cz>
Date:	Thu, 24 Mar 2016 17:09:06 +0100
From:	David Sterba <dsterba@...e.cz>
To:	Petr Tesarik <ptesarik@...e.com>
Cc:	Flex Liu <fliu@...ell.com>, David Sterba <dsterba@...e.com>,
	linux-btrfs@...r.kernel.org, Chris Mason <clm@...com>,
	Josef Bacik <jbacik@...com>, linux-kernel@...r.kernel.org,
	Flex Liu <fliu@...e.com>
Subject: Re: [PATCH 1/1] Btrfs: Code Cleanup

On Thu, Mar 24, 2016 at 04:08:18PM +0100, Petr Tesarik wrote:
> On Thu, 24 Mar 2016 16:03:07 +0100
> David Sterba <dsterba@...e.cz> wrote:
> 
> > On Sun, Mar 20, 2016 at 03:11:11PM +0800, Flex Liu wrote:
> >[...]
> > > --- a/fs/btrfs/volumes.c
> > > +++ b/fs/btrfs/volumes.c
> > > @@ -2325,7 +2325,10 @@ int btrfs_init_new_device(struct btrfs_root *root, char *device_path)
> > >  	if (seeding_dev) {
> > >  		sb->s_flags &= ~MS_RDONLY;
> > >  		ret = btrfs_prepare_sprout(root);
> > > -		BUG_ON(ret); /* -ENOMEM */
> > > +		if (ret) {
> > > +			btrfs_abort_transaction(trans, root, ret);
> > 
> > The transaction abort seems a bit heavy as it will take down the whole
> > filesystem. It's called from the device add ioctl, this is a restartable
> > operation.
> > 
> > Unfortunatelly btrfs_prepare_sprout is called after the transaction
> > start so btrfs_abort_transaction must be called. To avoid it, the code
> > would need to be reorganized, so the memory allocations happen in
> > advance.
> 
> On the other hand, an abort is still better than a BUG_ON(), and it may
> be easier to make incremental improvements.

That's acceptable, if there are going to be incremental improvements.