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

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Date:	Thu, 24 Mar 2016 16:08:18 +0100
From:	Petr Tesarik <ptesarik@...e.com>
To:	David Sterba <dsterba@...e.cz>
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, 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.

Just my 2 cents (I haven't tried it),
Petr T