Re: [PATCH 1/3] btrfs: Initialize btrfs_io_ctl instead of memsetting it

[Goldwyn Rodrigues <rgoldwyn@suse.de>]

On 16:47 27/02, David Sterba wrote:
> On Mon, Feb 25, 2019 at 01:07:42PM -0600, Goldwyn Rodrigues wrote:
> > From: Goldwyn Rodrigues <rgoldwyn@suse.com>
> > 
> > io_ctl_init() memsets it to zero anyways. However, I presume the
> > memset was added to avoid the WARN_ON in io_ctl_init().
> 
> I don't see any WARN_ON in io_ctl_init, you probably mean
> __btrfs_write_out_cache.

Yes, __btrfs_write_out_cache.

> > 
> > Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
> > ---
> >  fs/btrfs/free-space-cache.c | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> > 
> > diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
> > index 74aa552f4793..c813378ebf08 100644
> > --- a/fs/btrfs/free-space-cache.c
> > +++ b/fs/btrfs/free-space-cache.c
> > @@ -3544,13 +3544,12 @@ int btrfs_write_out_ino_cache(struct btrfs_root *root,
> >  	struct btrfs_fs_info *fs_info = root->fs_info;
> >  	struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
> >  	int ret;
> > -	struct btrfs_io_ctl io_ctl;
> > +	struct btrfs_io_ctl io_ctl = {0};
> 
> Doesn't this zero the bytes unconditionally? The memset below happens
> only when the inode cache is on.

Yes, but does it matter. I assumed assignment is faster than memset, but
a google search says gcc optimization is smart enough now. So, this patch
seems irrelevant.


-- 
Goldwyn