Re: [PATCH 2/2] Btrfs: don't iterate mod seq list when putting a tree mod seq

[David Sterba <dsterba@suse.cz>]

On Wed, Jan 22, 2020 at 03:32:16PM -0500, Josef Bacik wrote:
> On 1/22/20 7:23 AM, fdmanana@kernel.org wrote:
> > From: Filipe Manana <fdmanana@suse.com>
> > 
> > Each new element added to the mod seq list is always appended to the list,
> > and each one gets a sequence number coming from a counter which gets
> > incremented everytime a new element is added to the list (or a new node
> > is added to the tree mod log rbtree). Therefore the element with the
> > lowest sequence number is always the first element in the list.
> > 
> > So just remove the list iteration at btrfs_put_tree_mod_seq() that
> > computes the minimum sequence number in the list and replace it with
> > a check for the first element's sequence number.
> > 
> > Signed-off-by: Filipe Manana <fdmanana@suse.com>
> 
> This looks like a prime place for list_first_entry_or_null, but I'm not married 
> to it

The if (!list_empty()) looks more readable to me as it's explicit, only implied
by list_first_entry_or_null.