Re: [PATCH 03/18] btrfs: basic dax read

[Goldwyn Rodrigues <rgoldwyn@suse.de>]

On  8:14 21/05, Darrick J. Wong wrote:
> On Mon, Apr 29, 2019 at 12:26:34PM -0500, Goldwyn Rodrigues wrote:
> > From: Goldwyn Rodrigues <rgoldwyn@suse.com>
> > 
> > Perform a basic read using iomap support. The btrfs_iomap_begin()
> > finds the extent at the position and fills the iomap data
> > structure with the values.
> > 
> > Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
> > ---
> >  fs/btrfs/Makefile |  1 +
> >  fs/btrfs/ctree.h  |  5 +++++
> >  fs/btrfs/dax.c    | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
> >  fs/btrfs/file.c   | 11 ++++++++++-
> >  4 files changed, 65 insertions(+), 1 deletion(-)
> >  create mode 100644 fs/btrfs/dax.c
> > 
> > diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
> > index ca693dd554e9..1fa77b875ae9 100644
> > --- a/fs/btrfs/Makefile
> > +++ b/fs/btrfs/Makefile
> > @@ -12,6 +12,7 @@ btrfs-y += super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \
> >  	   reada.o backref.o ulist.o qgroup.o send.o dev-replace.o raid56.o \
> >  	   uuid-tree.o props.o free-space-tree.o tree-checker.o
> >  
> > +btrfs-$(CONFIG_FS_DAX) += dax.o
> >  btrfs-$(CONFIG_BTRFS_FS_POSIX_ACL) += acl.o
> >  btrfs-$(CONFIG_BTRFS_FS_CHECK_INTEGRITY) += check-integrity.o
> >  btrfs-$(CONFIG_BTRFS_FS_REF_VERIFY) += ref-verify.o
> > diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> > index 9512f49262dd..b7bbe5130a3b 100644
> > --- a/fs/btrfs/ctree.h
> > +++ b/fs/btrfs/ctree.h
> > @@ -3795,6 +3795,11 @@ int btrfs_reada_wait(void *handle);
> >  void btrfs_reada_detach(void *handle);
> >  int btree_readahead_hook(struct extent_buffer *eb, int err);
> >  
> > +#ifdef CONFIG_FS_DAX
> > +/* dax.c */
> > +ssize_t btrfs_file_dax_read(struct kiocb *iocb, struct iov_iter *to);
> > +#endif /* CONFIG_FS_DAX */
> > +
> >  static inline int is_fstree(u64 rootid)
> >  {
> >  	if (rootid == BTRFS_FS_TREE_OBJECTID ||
> > diff --git a/fs/btrfs/dax.c b/fs/btrfs/dax.c
> > new file mode 100644
> > index 000000000000..bf3d46b0acb6
> > --- /dev/null
> > +++ b/fs/btrfs/dax.c
> > @@ -0,0 +1,49 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * DAX support for BTRFS
> > + *
> > + * Copyright (c) 2019  SUSE Linux
> > + * Author: Goldwyn Rodrigues <rgoldwyn@suse.com>
> > + */
> > +
> > +#ifdef CONFIG_FS_DAX
> > +#include <linux/dax.h>
> > +#include <linux/iomap.h>
> > +#include "ctree.h"
> > +#include "btrfs_inode.h"
> > +
> > +static int btrfs_iomap_begin(struct inode *inode, loff_t pos,
> > +		loff_t length, unsigned flags, struct iomap *iomap)
> > +{
> > +	struct extent_map *em;
> > +	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
> > +	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, pos, length, 0);
> > +	if (em->block_start == EXTENT_MAP_HOLE) {
> > +		iomap->type = IOMAP_HOLE;
> > +		return 0;
> 
> I'm not doing a rigorous review of the btrfs-specific pieces, but you're
> required to fill out the other iomap fields for a read hole.

I fixed this in the patch adding write support. However, this
looks wrong as a patch. I will fix this.

-- 
Goldwyn