Re: [PATCH v3 12/17] xfs: parent pointer attribute creation

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Tue, Nov 28, 2017 at 10:49:18AM -0800, Darrick J. Wong wrote:
> On Fri, Nov 17, 2017 at 11:21:40AM -0700, Allison Henderson wrote:
> > From: Dave Chinner <dchinner@redhat.com>
> > 
> > Add parent pointer attribute during xfs_create, and
> > subroutines to initialize attributes
> > 
> > [bfoster: rebase, use VFS inode generation]
> > [achender: rebased, changed __unint32_t to xfs_dir2_dataptr_t,
> > 	   fixed some null pointer bugs,
> > 	   merged error handling patch,
> > 	   added subroutines to handle attribute initialization]
> > 
> > Signed-off-by: Dave Chinner <dchinner@redhat.com>
> > Signed-off-by: Allison Henderson <allison.henderson@oracle.com>
> > ---
> > v2: remove unnecessary ENOSPC handling in xfs_attr_set_first_parent
> > 
> > Signed-off-by: Allison Henderson <allison.henderson@oracle.com>
> > ---
> >  fs/xfs/Makefile            |  1 +
> >  fs/xfs/libxfs/xfs_parent.c | 93 ++++++++++++++++++++++++++++++++++++++++++++++
> >  fs/xfs/xfs_attr.h          | 15 +++++++-
> >  fs/xfs/xfs_inode.c         | 16 +++++++-
> >  4 files changed, 123 insertions(+), 2 deletions(-)
> > 
> > diff --git a/fs/xfs/Makefile b/fs/xfs/Makefile
> > index ec6486b..3015bca 100644
> > --- a/fs/xfs/Makefile
> > +++ b/fs/xfs/Makefile
> > @@ -52,6 +52,7 @@ xfs-y				+= $(addprefix libxfs/, \
> >  				   xfs_inode_fork.o \
> >  				   xfs_inode_buf.o \
> >  				   xfs_log_rlimit.o \
> > +				   xfs_parent.o \
> >  				   xfs_ag_resv.o \
> >  				   xfs_rmap.o \
> >  				   xfs_rmap_btree.o \
> > diff --git a/fs/xfs/libxfs/xfs_parent.c b/fs/xfs/libxfs/xfs_parent.c
> > new file mode 100644
> > index 0000000..5eec0ab
> > --- /dev/null
> > +++ b/fs/xfs/libxfs/xfs_parent.c
> > @@ -0,0 +1,93 @@
> > +/*
> > + * Copyright (c) 2015 Red Hat, Inc.
> > + * All rights reserved.
> 
> /me sticks his hand in the hornet's nest: given how much Allison has
> reworked the original pptr code to use deferred ops, maybe it's more
> appropriate to have both the RH copyright for the original code and the
> oracle copyright for the pptr stuff at the top of this file?
> 
> (Not a lawyer, don't play one on tv.)
> 
> > + *
> > + * This program is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU General Public License as
> > + * published by the Free Software Foundation.
> > + *
> > + * This program is distributed in the hope that it would be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > + * GNU General Public License for more details.
> > + *
> > + * You should have received a copy of the GNU General Public License
> > + * along with this program; if not, write the Free Software Foundation
> > + */
> > +#include "xfs.h"
> > +#include "xfs_fs.h"
> > +#include "xfs_format.h"
> > +#include "xfs_log_format.h"
> > +#include "xfs_shared.h"
> > +#include "xfs_trans_resv.h"
> > +#include "xfs_mount.h"
> > +#include "xfs_bmap_btree.h"
> > +#include "xfs_inode.h"
> > +#include "xfs_error.h"
> > +#include "xfs_trace.h"
> > +#include "xfs_trans.h"
> > +#include "xfs_attr.h"
> > +
> > +/*
> > + * Parent pointer attribute handling.
> > + *
> > + * Because the attribute value is a filename component, it will never be longer
> > + * than 255 bytes. This means the attribute will always be a local format
> > + * attribute as it is xfs_attr_leaf_entsize_local_max() for v5 filesystems will
> > + * always be larger than this (max is 75% of block size).
> > + *
> > + * Creating a new parent attribute will always create a new attribute - there
> > + * should never, ever be an existing attribute in the tree for a new inode.
> > + * ENOSPC behaviour is problematic - creating the inode without the parent
> > + * pointer is effectively a corruption, so we allow parent attribute creation
> > + * to dip into the reserve block pool to avoid unexpected ENOSPC errors from
> > + * occurring.
> > + */
> > +
> > +
> > +/* Initializes a xfs_parent_name_rec to be stored as an attribute name */
> > +void
> > +xfs_init_parent_name_rec(
> > +			struct xfs_parent_name_rec	*rec,
> > +			unsigned long long int		p_ino,
> 
> xfs_ino_t ?
> 
> > +			unsigned int			p_gen,
> 
> uint32_t ?
> 
> > +			unsigned int			p_diroffset)
> > +{
> > +	rec->p_ino = cpu_to_be64(p_ino);
> > +	rec->p_gen = cpu_to_be32(p_gen);
> > +	rec->p_diroffset = cpu_to_be32(p_diroffset);
> > +}
> > +
> > +/* Initializes a xfs_parent_name_irec from an xfs_parent_name_rec */
> > +void
> > +xfs_init_parent_name_irec(
> > +			struct xfs_parent_name_irec	*irec,
> > +			struct xfs_parent_name_rec	*rec)
> > +{
> > +	irec->p_ino = be64_to_cpu(rec->p_ino);
> > +	irec->p_gen = be32_to_cpu(rec->p_gen);
> > +	irec->p_diroffset = be32_to_cpu(rec->p_diroffset);
> > +}
> > +
> > +/*
> > + * Add a parent record to an inode with existing parent records.
> > + */
> > +int
> > +xfs_parent_add(
> > +	struct xfs_trans        *tp,
> > +	struct xfs_inode        *parent,
> > +	struct xfs_inode        *child,
> > +	struct xfs_name         *child_name,
> > +	uint32_t                diroffset,
> > +	struct xfs_defer_ops    *dfops,
> > +	xfs_fsblock_t           *firstblock)
> 
> This function doesn't use tp or firstblock, so you can omit the parameters.
> 
> > +{
> > +	struct xfs_parent_name_rec rec;
> > +
> > +	xfs_init_parent_name_rec(&rec, parent->i_ino,
> > +		VFS_I(parent)->i_generation, diroffset);
> > +
> > +	return xfs_attr_set_deferred(child, dfops, &rec, sizeof(rec),
> > +		(void *)child_name->name, child_name->len, ATTR_PARENT);
> > +}
> 
> Do you think these functions will be useful for xfs_repair (and
> xfs_scrub) to rebuild the parent pointers?  These three functions seem
> like the sort of thing that could go into libxfs/xfs_parent.c to get
> shared around.
> 
> I guess I did babble last week about moving pretty much everything
> related to handling the pptr xattrs into libxfs so that the only code in
> fs/xfs/xfs_parent.c is the ioctl implementation.  Maybe also an enhanced
> "connect this file handle dentry to its parents" feature for file handle
> users, though the current system hasn't generated a ton of complaints so
> this might be unnecessary.

Bah, /me fails to notice that this was added to libxfs/xfs_parent.c.
Please substitute the previous two paragraphs with:

Why are the function prototypes for these functions in fs/xfs/xfs_attr.h?
They ought to be in libxfs/xfs_parent.h.

--D

> --D
> 
> > diff --git a/fs/xfs/xfs_attr.h b/fs/xfs/xfs_attr.h
> > index 1f5c711..09ef747 100644
> > --- a/fs/xfs/xfs_attr.h
> > +++ b/fs/xfs/xfs_attr.h
> > @@ -19,6 +19,8 @@
> >  #define	__XFS_ATTR_H__
> >  
> >  #include "libxfs/xfs_defer.h"
> > +#include "libxfs/xfs_da_format.h"
> > +#include "libxfs/xfs_format.h"
> >  
> >  struct xfs_inode;
> >  struct xfs_da_args;
> > @@ -184,5 +186,16 @@ int xfs_attr_set_deferred(struct xfs_inode *dp, struct xfs_defer_ops *dfops,
> >  			  unsigned int valuelen, int flags);
> >  int xfs_attr_remove_deferred(struct xfs_inode *dp, struct xfs_defer_ops *dfops,
> >  			    void *name, unsigned int namelen, int flags);
> > -
> > +/*
> > + * Parent pointer attribute prototypes
> > + */
> > +void xfs_init_parent_name_rec(struct xfs_parent_name_rec *rec,
> > +		unsigned long long int p_ino, unsigned int p_gen,
> > +		unsigned int  p_diroffset);
> > +void xfs_init_parent_name_irec(struct xfs_parent_name_irec *irec,
> > +			struct xfs_parent_name_rec *rec);
> > +int xfs_parent_add(struct xfs_trans *tp, struct xfs_inode *parent,
> > +		struct xfs_inode *child, struct xfs_name *child_name,
> > +		xfs_dir2_dataptr_t diroffset, struct xfs_defer_ops *dfops,
> > +		xfs_fsblock_t *firstblock);
> >  #endif	/* __XFS_ATTR_H__ */
> > diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> > index f7986d8..1c45c73 100644
> > --- a/fs/xfs/xfs_inode.c
> > +++ b/fs/xfs/xfs_inode.c
> > @@ -1164,6 +1164,7 @@ xfs_create(
> >  	struct xfs_dquot	*pdqp = NULL;
> >  	struct xfs_trans_res	*tres;
> >  	uint			resblks;
> > +	xfs_dir2_dataptr_t	diroffset;
> >  
> >  	trace_xfs_create(dp, name);
> >  
> > @@ -1253,7 +1254,7 @@ xfs_create(
> >  	error = xfs_dir_createname(tp, dp, name, ip->i_ino,
> >  					&first_block, &dfops, resblks ?
> >  					resblks - XFS_IALLOC_SPACE_RES(mp) : 0,
> > -					NULL);
> > +					&diroffset);
> >  	if (error) {
> >  		ASSERT(error != -ENOSPC);
> >  		goto out_trans_cancel;
> > @@ -1272,6 +1273,19 @@ xfs_create(
> >  	}
> >  
> >  	/*
> > +	 * If we have parent pointers, we need to add the attribute containing
> > +	 * the parent information now. This must be done within the same
> > +	 * transaction the directory entry is created, while the new inode
> > +	 * contains nothing in the inode literal area.
> > +	 */
> > +	if (xfs_sb_version_hasparent(&mp->m_sb)) {
> > +		error = xfs_parent_add(tp, dp, ip, name, diroffset,
> > +					  &dfops, &first_block);
> > +		if (error)
> > +			goto out_bmap_cancel;
> > +	}
> > +
> > +	/*
> >  	 * If this is a synchronous mount, make sure that the
> >  	 * create transaction goes to disk before returning to
> >  	 * the user.
> > -- 
> > 2.7.4
> > 
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