Re: [PATCH v3 14/26] xfs: parent pointer attribute creation

["Darrick J. Wong" <djwong@kernel.org>]

On Wed, Sep 21, 2022 at 10:44:46PM -0700, allison.henderson@oracle.com wrote:
> From: Allison Henderson <allison.henderson@oracle.com>
> 
> Add parent pointer attribute during xfs_create, and subroutines to
> initialize attributes
> 
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> Signed-off-by: Allison Henderson <allison.henderson@oracle.com>
> ---
>  fs/xfs/Makefile            |   1 +
>  fs/xfs/libxfs/xfs_attr.c   |   4 +-
>  fs/xfs/libxfs/xfs_attr.h   |   4 +-
>  fs/xfs/libxfs/xfs_parent.c | 135 +++++++++++++++++++++++++++++++++++++
>  fs/xfs/libxfs/xfs_parent.h |  32 +++++++++
>  fs/xfs/xfs_inode.c         |  37 ++++++++--
>  fs/xfs/xfs_xattr.c         |   2 +-
>  fs/xfs/xfs_xattr.h         |   1 +
>  8 files changed, 207 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/xfs/Makefile b/fs/xfs/Makefile
> index 03135a1c31b6..e2b2cf50ffcf 100644
> --- a/fs/xfs/Makefile
> +++ b/fs/xfs/Makefile
> @@ -40,6 +40,7 @@ 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_attr.c b/fs/xfs/libxfs/xfs_attr.c
> index 0c9589261990..805aaa5639d2 100644
> --- a/fs/xfs/libxfs/xfs_attr.c
> +++ b/fs/xfs/libxfs/xfs_attr.c
> @@ -886,7 +886,7 @@ xfs_attr_lookup(
>  	return error;
>  }
>  
> -static int
> +int
>  xfs_attr_intent_init(
>  	struct xfs_da_args	*args,
>  	unsigned int		op_flags,	/* op flag (set or remove) */
> @@ -904,7 +904,7 @@ xfs_attr_intent_init(
>  }
>  
>  /* Sets an attribute for an inode as a deferred operation */
> -static int
> +int
>  xfs_attr_defer_add(
>  	struct xfs_da_args	*args)
>  {
> diff --git a/fs/xfs/libxfs/xfs_attr.h b/fs/xfs/libxfs/xfs_attr.h
> index b79dae788cfb..0cf23f5117ad 100644
> --- a/fs/xfs/libxfs/xfs_attr.h
> +++ b/fs/xfs/libxfs/xfs_attr.h
> @@ -544,6 +544,7 @@ int xfs_inode_hasattr(struct xfs_inode *ip);
>  bool xfs_attr_is_leaf(struct xfs_inode *ip);
>  int xfs_attr_get_ilocked(struct xfs_da_args *args);
>  int xfs_attr_get(struct xfs_da_args *args);
> +int xfs_attr_defer_add(struct xfs_da_args *args);
>  int xfs_attr_set(struct xfs_da_args *args);
>  int xfs_attr_set_iter(struct xfs_attr_intent *attr);
>  int xfs_attr_remove_iter(struct xfs_attr_intent *attr);
> @@ -552,7 +553,8 @@ bool xfs_attr_namecheck(struct xfs_mount *mp, const void *name, size_t length,
>  int xfs_attr_calc_size(struct xfs_da_args *args, int *local);
>  void xfs_init_attr_trans(struct xfs_da_args *args, struct xfs_trans_res *tres,
>  			 unsigned int *total);
> -
> +int xfs_attr_intent_init(struct xfs_da_args *args, unsigned int op_flags,
> +			 struct xfs_attr_intent  **attr);
>  /*
>   * Check to see if the attr should be upgraded from non-existent or shortform to
>   * single-leaf-block attribute list.
> diff --git a/fs/xfs/libxfs/xfs_parent.c b/fs/xfs/libxfs/xfs_parent.c
> new file mode 100644
> index 000000000000..dddbf096a4b5
> --- /dev/null
> +++ b/fs/xfs/libxfs/xfs_parent.c
> @@ -0,0 +1,135 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2022 Oracle, Inc.
> + * All rights reserved.
> + */
> +#include "xfs.h"
> +#include "xfs_fs.h"
> +#include "xfs_format.h"
> +#include "xfs_da_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_da_btree.h"
> +#include "xfs_attr.h"
> +#include "xfs_da_btree.h"
> +#include "xfs_attr_sf.h"
> +#include "xfs_bmap.h"
> +#include "xfs_defer.h"
> +#include "xfs_log.h"
> +#include "xfs_xattr.h"
> +#include "xfs_parent.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 behavior 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.

Hoisting a discussion (that I never replied to; sorry... :( ) from last
time around:

>> Shouldn't we increase XFS_LINK_SPACE_RES to avoid this?  The reserve
>> pool isn't terribly large (8192 blocks) and was really only supposed
>> to save us from an ENOSPC shutdown if an unwritten extent conversion
>> in the writeback endio handler needs a few more blocks.
>>
>Did you maybe mean XFS_IALLOC_SPACE_RES?  That looks like the macro
>that's getting used below in xfs_create

I meant modifying XFS_MKDIR_SPACE_RES and XFS_CREATE_SPACE_RES:

unsigned int
xfs_pptr_calc_space_res(
	struct xfs_mount	*mp,
	unsigned int		namelen)
{
	/*
	 * Code lifted from xfs_attr_calc_size, check this for
	 * correctness since I assumed that a pptr never requires rmt
	 * blocks...
	 */
	return XFS_DAENTER_SPACE_RES(mp, XFS_ATTR_FORK) +
	       XFS_NEXTENTADD_SPACE_RES(mp, namelen, XFS_ATTR_FORK);
}

unsigned int
xfs_create_space_res(
	struct xfs_mount	*mp,
	unsigned int		namelen)
{
	unsigned int		ret;

	ret = XFS_IALLOC_SPACE_RES(mp) + XFS_DIRENTER_SPACE_RES(mp, namelen);
	if (xfs_has_parent(mp))
		ret += xfs_pptr_calc_space_res(mp, namelen);

	return ret;
}

unsigned int
xfs_mkdir_space_res(
	struct xfs_mount	*mp,
	unsigned int		namelen)
{
	return xfs_create_space_res(mp, namelen);
}

(and then change the function case names as necessary)

>> IOWs, we really ought to ENOSPC at transaction reservation time
>> instead of draining the reserve pool.
>It looks like we do that in most cases.  I dont actually see rsvd
>getting set, other than in xfs_attr_set.  Which isnt used in parent
>pointer updating, and should probably be removed.  I suspect it's a
>relic of the pre-larp version of the set. So perhaps the comment is
>stale and should be removed as well.

The block reservations for create/mkdir/link/unlink all need to be
adjusted upwards, which will eliminate the need for the comment.

> + */
> +
> +
> +/* 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,
> +	struct xfs_inode		*ip,
> +	uint32_t			p_diroffset)
> +{
> +	xfs_ino_t			p_ino = ip->i_ino;
> +	uint32_t			p_gen = VFS_I(ip)->i_generation;
> +
> +	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);
> +}
> +
> +int
> +xfs_parent_init(
> +	xfs_mount_t                     *mp,

Nit: typedef usage.

Everything else below here looks good though. :)

--D

> +	struct xfs_parent_defer		**parentp)
> +{
> +	struct xfs_parent_defer		*parent;
> +	int				error;
> +
> +	if (!xfs_has_parent(mp))
> +		return 0;
> +
> +	error = xfs_attr_grab_log_assist(mp);
> +	if (error)
> +		return error;
> +
> +	parent = kzalloc(sizeof(*parent), GFP_KERNEL);
> +	if (!parent)
> +		return -ENOMEM;
> +
> +	/* init parent da_args */
> +	parent->args.geo = mp->m_attr_geo;
> +	parent->args.whichfork = XFS_ATTR_FORK;
> +	parent->args.attr_filter = XFS_ATTR_PARENT;
> +	parent->args.op_flags = XFS_DA_OP_OKNOENT | XFS_DA_OP_LOGGED;
> +	parent->args.name = (const uint8_t *)&parent->rec;
> +	parent->args.namelen = sizeof(struct xfs_parent_name_rec);
> +
> +	*parentp = parent;
> +	return 0;
> +}
> +
> +int
> +xfs_parent_defer_add(
> +	struct xfs_trans	*tp,
> +	struct xfs_parent_defer	*parent,
> +	struct xfs_inode	*dp,
> +	struct xfs_name		*parent_name,
> +	xfs_dir2_dataptr_t	diroffset,
> +	struct xfs_inode	*child)
> +{
> +	struct xfs_da_args	*args = &parent->args;
> +
> +	xfs_init_parent_name_rec(&parent->rec, dp, diroffset);
> +	args->hashval = xfs_da_hashname(args->name, args->namelen);
> +
> +	args->trans = tp;
> +	args->dp = child;
> +	if (parent_name) {
> +		parent->args.value = (void *)parent_name->name;
> +		parent->args.valuelen = parent_name->len;
> +	}
> +
> +	return xfs_attr_defer_add(args);
> +}
> +
> +void
> +xfs_parent_cancel(
> +	xfs_mount_t		*mp,
> +	struct xfs_parent_defer *parent)
> +{
> +	xlog_drop_incompat_feat(mp->m_log);
> +	kfree(parent);
> +}
> +
> diff --git a/fs/xfs/libxfs/xfs_parent.h b/fs/xfs/libxfs/xfs_parent.h
> new file mode 100644
> index 000000000000..971044458f8a
> --- /dev/null
> +++ b/fs/xfs/libxfs/xfs_parent.h
> @@ -0,0 +1,32 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2022 Oracle, Inc.
> + * All Rights Reserved.
> + */
> +#ifndef	__XFS_PARENT_H__
> +#define	__XFS_PARENT_H__
> +
> +/*
> + * Dynamically allocd structure used to wrap the needed data to pass around
> + * the defer ops machinery
> + */
> +struct xfs_parent_defer {
> +	struct xfs_parent_name_rec	rec;
> +	struct xfs_da_args		args;
> +};
> +
> +/*
> + * Parent pointer attribute prototypes
> + */
> +void xfs_init_parent_name_rec(struct xfs_parent_name_rec *rec,
> +			      struct xfs_inode *ip,
> +			      uint32_t p_diroffset);
> +void xfs_init_parent_name_irec(struct xfs_parent_name_irec *irec,
> +			       struct xfs_parent_name_rec *rec);
> +int xfs_parent_init(xfs_mount_t *mp, struct xfs_parent_defer **parentp);
> +int xfs_parent_defer_add(struct xfs_trans *tp, struct xfs_parent_defer *parent,
> +			 struct xfs_inode *dp, struct xfs_name *parent_name,
> +			 xfs_dir2_dataptr_t diroffset, struct xfs_inode *child);
> +void xfs_parent_cancel(xfs_mount_t *mp, struct xfs_parent_defer *parent);
> +
> +#endif	/* __XFS_PARENT_H__ */
> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> index 6eb264598517..181d6417412e 100644
> --- a/fs/xfs/xfs_inode.c
> +++ b/fs/xfs/xfs_inode.c
> @@ -37,6 +37,8 @@
>  #include "xfs_reflink.h"
>  #include "xfs_ag.h"
>  #include "xfs_log_priv.h"
> +#include "xfs_parent.h"
> +#include "xfs_xattr.h"
>  
>  struct kmem_cache *xfs_inode_cache;
>  
> @@ -949,7 +951,7 @@ xfs_bumplink(
>  int
>  xfs_create(
>  	struct user_namespace	*mnt_userns,
> -	xfs_inode_t		*dp,
> +	struct xfs_inode	*dp,
>  	struct xfs_name		*name,
>  	umode_t			mode,
>  	dev_t			rdev,
> @@ -961,7 +963,7 @@ xfs_create(
>  	struct xfs_inode	*ip = NULL;
>  	struct xfs_trans	*tp = NULL;
>  	int			error;
> -	bool                    unlock_dp_on_error = false;
> +	bool			unlock_dp_on_error = false;
>  	prid_t			prid;
>  	struct xfs_dquot	*udqp = NULL;
>  	struct xfs_dquot	*gdqp = NULL;
> @@ -969,6 +971,8 @@ xfs_create(
>  	struct xfs_trans_res	*tres;
>  	uint			resblks;
>  	xfs_ino_t		ino;
> +	xfs_dir2_dataptr_t	diroffset;
> +	struct xfs_parent_defer	*parent = NULL;
>  
>  	trace_xfs_create(dp, name);
>  
> @@ -995,6 +999,12 @@ xfs_create(
>  		tres = &M_RES(mp)->tr_create;
>  	}
>  
> +	if (xfs_has_parent(mp)) {
> +		error = xfs_parent_init(mp, &parent);
> +		if (error)
> +			goto out_release_dquots;
> +	}
> +
>  	/*
>  	 * Initially assume that the file does not exist and
>  	 * reserve the resources for that case.  If that is not
> @@ -1010,7 +1020,7 @@ xfs_create(
>  				resblks, &tp);
>  	}
>  	if (error)
> -		goto out_release_dquots;
> +		goto drop_incompat;
>  
>  	xfs_ilock(dp, XFS_ILOCK_EXCL | XFS_ILOCK_PARENT);
>  	unlock_dp_on_error = true;
> @@ -1020,6 +1030,7 @@ xfs_create(
>  	 * entry pointing to them, but a directory also the "." entry
>  	 * pointing to itself.
>  	 */
> +	init_xattrs = init_xattrs || xfs_has_parent(mp);
>  	error = xfs_dialloc(&tp, dp->i_ino, mode, &ino);
>  	if (!error)
>  		error = xfs_init_new_inode(mnt_userns, tp, dp, ino, mode,
> @@ -1034,11 +1045,12 @@ xfs_create(
>  	 * the transaction cancel unlocking dp so don't do it explicitly in the
>  	 * error path.
>  	 */
> -	xfs_trans_ijoin(tp, dp, XFS_ILOCK_EXCL);
> +	xfs_trans_ijoin(tp, dp, 0);
>  	unlock_dp_on_error = false;
>  
>  	error = xfs_dir_createname(tp, dp, name, ip->i_ino,
> -				   resblks - XFS_IALLOC_SPACE_RES(mp), NULL);
> +				   resblks - XFS_IALLOC_SPACE_RES(mp),
> +				   &diroffset);
>  	if (error) {
>  		ASSERT(error != -ENOSPC);
>  		goto out_trans_cancel;
> @@ -1054,6 +1066,17 @@ xfs_create(
>  		xfs_bumplink(tp, dp);
>  	}
>  
> +	/*
> +	 * If we have parent pointers, we need to add the attribute containing
> +	 * the parent information now.
> +	 */
> +	if (parent) {
> +		error = xfs_parent_defer_add(tp, parent, dp, name, diroffset,
> +					     ip);
> +		if (error)
> +			goto out_trans_cancel;
> +	}
> +
>  	/*
>  	 * If this is a synchronous mount, make sure that the
>  	 * create transaction goes to disk before returning to
> @@ -1079,6 +1102,7 @@ xfs_create(
>  
>  	*ipp = ip;
>  	xfs_iunlock(ip, XFS_ILOCK_EXCL);
> +	xfs_iunlock(dp, XFS_ILOCK_EXCL | XFS_ILOCK_PARENT);
>  	return 0;
>  
>   out_trans_cancel:
> @@ -1093,6 +1117,9 @@ xfs_create(
>  		xfs_finish_inode_setup(ip);
>  		xfs_irele(ip);
>  	}
> + drop_incompat:
> +	if (parent)
> +		xfs_parent_cancel(mp, parent);
>   out_release_dquots:
>  	xfs_qm_dqrele(udqp);
>  	xfs_qm_dqrele(gdqp);
> diff --git a/fs/xfs/xfs_xattr.c b/fs/xfs/xfs_xattr.c
> index c325a28b89a8..d9067c5f6bd6 100644
> --- a/fs/xfs/xfs_xattr.c
> +++ b/fs/xfs/xfs_xattr.c
> @@ -27,7 +27,7 @@
>   * they must release the permission by calling xlog_drop_incompat_feat
>   * when they're done.
>   */
> -static inline int
> +int
>  xfs_attr_grab_log_assist(
>  	struct xfs_mount	*mp)
>  {
> diff --git a/fs/xfs/xfs_xattr.h b/fs/xfs/xfs_xattr.h
> index 2b09133b1b9b..3fd6520a4d69 100644
> --- a/fs/xfs/xfs_xattr.h
> +++ b/fs/xfs/xfs_xattr.h
> @@ -7,6 +7,7 @@
>  #define __XFS_XATTR_H__
>  
>  int xfs_attr_change(struct xfs_da_args *args);
> +int xfs_attr_grab_log_assist(struct xfs_mount *mp);
>  
>  extern const struct xattr_handler *xfs_xattr_handlers[];
>  
> -- 
> 2.25.1
>