Re: [RFC PATCH v3 04/12] btrfs: get rid of trivial __btrfs_lookup_bio_sums() wrappers

[Omar Sandoval <osandov@osandov.com>]

On Tue, Nov 26, 2019 at 03:56:31PM +0200, Nikolay Borisov wrote:
> 
> 
> On 20.11.19 г. 20:24 ч., Omar Sandoval wrote:
> > From: Omar Sandoval <osandov@fb.com>
> > 
> > Currently, we have two wrappers for __btrfs_lookup_bio_sums():
> > btrfs_lookup_bio_sums_dio(), which is used for direct I/O, and
> > btrfs_lookup_bio_sums(), which is used everywhere else. The only
> > difference is that the _dio variant looks up csums starting at the given
> > offset instead of using the page index, which isn't actually direct
> > I/O-specific. Let's clean up the signature and return value of
> > __btrfs_lookup_bio_sums(), rename it to btrfs_lookup_bio_sums(), and get
> > rid of the trivial helpers.
> > 
> > Signed-off-by: Omar Sandoval <osandov@fb.com>
> 
> Overall looks good but 2 nits, see below.
> 
> In any case:
> 
> Reviewed-by: Nikolay Borisov <nborisov@suse.com>

Thanks!

> > ---
> >  fs/btrfs/compression.c |  4 ++--
> >  fs/btrfs/ctree.h       |  4 +---
> >  fs/btrfs/file-item.c   | 35 +++++++++++++++++------------------
> >  fs/btrfs/inode.c       |  6 +++---
> >  4 files changed, 23 insertions(+), 26 deletions(-)
> > 
> > diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
> > index b05b361e2062..4df6f0c58dc9 100644
> > --- a/fs/btrfs/compression.c
> > +++ b/fs/btrfs/compression.c
> > @@ -660,7 +660,7 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
> >  
> >  			if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
> >  				ret = btrfs_lookup_bio_sums(inode, comp_bio,
> > -							    sums);
> > +							    false, 0, sums);
> >  				BUG_ON(ret); /* -ENOMEM */
> >  			}
> >  
> > @@ -689,7 +689,7 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
> >  	BUG_ON(ret); /* -ENOMEM */
> >  
> >  	if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
> > -		ret = btrfs_lookup_bio_sums(inode, comp_bio, sums);
> > +		ret = btrfs_lookup_bio_sums(inode, comp_bio, false, 0, sums);
> >  		BUG_ON(ret); /* -ENOMEM */
> >  	}
> >  
> > diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> > index fe2b8765d9e6..4bc40bf49b0e 100644
> > --- a/fs/btrfs/ctree.h
> > +++ b/fs/btrfs/ctree.h
> > @@ -2787,9 +2787,7 @@ struct btrfs_dio_private;
> >  int btrfs_del_csums(struct btrfs_trans_handle *trans,
> >  		    struct btrfs_fs_info *fs_info, u64 bytenr, u64 len);
> >  blk_status_t btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio,
> > -				   u8 *dst);
> > -blk_status_t btrfs_lookup_bio_sums_dio(struct inode *inode, struct bio *bio,
> > -			      u64 logical_offset);
> > +				   bool at_offset, u64 offset, u8 *dst);
> >  int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,
> >  			     struct btrfs_root *root,
> >  			     u64 objectid, u64 pos,
> > diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
> > index 1a599f50837b..a87c40502267 100644
> > --- a/fs/btrfs/file-item.c
> > +++ b/fs/btrfs/file-item.c
> > @@ -148,8 +148,21 @@ int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
> >  	return ret;
> >  }
> >  
> > -static blk_status_t __btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio,
> > -				   u64 logical_offset, u8 *dst, int dio)
> > +/**
> > + * btrfs_lookup_bio_sums - Look up checksums for a bio.
> > + * @inode: inode that the bio is for.
> > + * @bio: bio embedded in btrfs_io_bio.
> > + * @at_offset: If true, look up checksums for the extent at @c offset.
> 
> nit: that @c is an editing artifact?

Oops, I mixed up kernel-doc with Doxygen. Fixed, thanks.

> On the other hand rather than
> having an explicit bool signifying whether we want a specific offset
> can't we simply check if offset is != 0 ?

Zero is a perfectly valid offset to have an extent at, but we could do
(u64)-1 instead. I'm not sure what's cleaner.