xfs: don't call xfs_da_shrink_inode with NULL bp

xfs_attr3_leaf_create may have errored out before instantiating a buffer,
for example if the blkno is out of range.  In that case there is no work
to do to remove it, and in fact xfs_da_shrink_inode will lead to an oops
if we try.

This also seems to fix a flaw where the original error from
xfs_attr3_leaf_create gets overwritten in the cleanup case, and it
removes a pointless assignment to bp which isn't used after this.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=199969
Reported-by: Xu, Wen <wen.xu@gatech.edu>
Tested-by: Xu, Wen <wen.xu@gatech.edu>
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
xfs_attr3_leaf_hdr_to_disk(
	struct xfs_da_geometry		*geo,
	struct xfs_attr_leafblock	*to,
	struct xfs_attr3_icleaf_hdr	*from)
{
	int				i;

	ASSERT(from->magic == XFS_ATTR_LEAF_MAGIC ||
	       from->magic == XFS_ATTR3_LEAF_MAGIC);

	if (from->magic == XFS_ATTR3_LEAF_MAGIC) {
		struct xfs_attr3_leaf_hdr *hdr3 = (struct xfs_attr3_leaf_hdr *)to;

		hdr3->info.hdr.forw = cpu_to_be32(from->forw);
		hdr3->info.hdr.back = cpu_to_be32(from->back);
		hdr3->info.hdr.magic = cpu_to_be16(from->magic);
		hdr3->count = cpu_to_be16(from->count);
		hdr3->usedbytes = cpu_to_be16(from->usedbytes);
		xfs_attr3_leaf_firstused_to_disk(geo, to, from);
		hdr3->holes = from->holes;
		hdr3->pad1 = 0;

		for (i = 0; i < XFS_ATTR_LEAF_MAPSIZE; i++) {
			hdr3->freemap[i].base = cpu_to_be16(from->freemap[i].base);
			hdr3->freemap[i].size = cpu_to_be16(from->freemap[i].size);
		}
		return;
	}
	to->hdr.info.forw = cpu_to_be32(from->forw);
	to->hdr.info.back = cpu_to_be32(from->back);
	to->hdr.info.magic = cpu_to_be16(from->magic);
	to->hdr.count = cpu_to_be16(from->count);
	to->hdr.usedbytes = cpu_to_be16(from->usedbytes);
	xfs_attr3_leaf_firstused_to_disk(geo, to, from);
	to->hdr.holes = from->holes;
	to->hdr.pad1 = 0;

	for (i = 0; i < XFS_ATTR_LEAF_MAPSIZE; i++) {
		to->hdr.freemap[i].base = cpu_to_be16(from->freemap[i].base);
		to->hdr.freemap[i].size = cpu_to_be16(from->freemap[i].size);
	}
}

xfs_attr3_leaf_hdr_to_disk(
	struct xfs_da_geometry		*geo,
	struct xfs_attr_leafblock	*to,
	struct xfs_attr3_icleaf_hdr	*from)
{
	int				i;

	ASSERT(from->magic == XFS_ATTR_LEAF_MAGIC ||
	       from->magic == XFS_ATTR3_LEAF_MAGIC);

	if (from->magic == XFS_ATTR3_LEAF_MAGIC) {
		struct xfs_attr3_leaf_hdr *hdr3 = (struct xfs_attr3_leaf_hdr *)to;

		hdr3->info.hdr.forw = cpu_to_be32(from->forw);
		hdr3->info.hdr.back = cpu_to_be32(from->back);
		hdr3->info.hdr.magic = cpu_to_be16(from->magic);
		hdr3->count = cpu_to_be16(from->count);
		hdr3->usedbytes = cpu_to_be16(from->usedbytes);
		xfs_attr3_leaf_firstused_to_disk(geo, to, from);
		hdr3->holes = from->holes;
		hdr3->pad1 = 0;

		for (i = 0; i < XFS_ATTR_LEAF_MAPSIZE; i++) {
			hdr3->freemap[i].base = cpu_to_be16(from->freemap[i].base);
			hdr3->freemap[i].size = cpu_to_be16(from->freemap[i].size);
		}
		return;
	}
	to->hdr.info.forw = cpu_to_be32(from->forw);
	to->hdr.info.back = cpu_to_be32(from->back);
	to->hdr.info.magic = cpu_to_be16(from->magic);
	to->hdr.count = cpu_to_be16(from->count);
	to->hdr.usedbytes = cpu_to_be16(from->usedbytes);
	xfs_attr3_leaf_firstused_to_disk(geo, to, from);
	to->hdr.holes = from->holes;
	to->hdr.pad1 = 0;

	for (i = 0; i < XFS_ATTR_LEAF_MAPSIZE; i++) {
		to->hdr.freemap[i].base = cpu_to_be16(from->freemap[i].base);
		to->hdr.freemap[i].size = cpu_to_be16(from->freemap[i].size);
	}
}
