Commit fb102fe7 authored by Darrick J. Wong's avatar Darrick J. Wong
Browse files

xfs: create a hashname function for parent pointers 



Although directory entry and parent pointer recordsets look very similar
(name -> ino), there's one major difference between them: a file can be
hardlinked from multiple parent directories with the same filename.
This is common in shared container environments where a base directory
tree might be hardlink-copied multiple times.  IOWs the same 'ls'
program might be hardlinked to multiple /srv/*/bin/ls paths.

We don't want parent pointer operations to bog down on hash collisions
between the same dirent name, so create a special hash function that
mixes in the parent directory inode number.

Signed-off-by: default avatarDarrick J. Wong <djwong@kernel.org>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
parent 7dba4a5f

fs/xfs/libxfs/xfs_attr.c

+3 −0
Original line number Diff line number Diff line
@@ -437,6 +437,9 @@ xfs_attr_hashval( 
{

	ASSERT(xfs_attr_check_namespace(attr_flags));



	if (attr_flags & XFS_ATTR_PARENT)

		return xfs_parent_hashattr(mp, name, namelen, value, valuelen);



	return xfs_attr_hashname(name, namelen);

}

fs/xfs/libxfs/xfs_parent.c

+47 −0
Original line number Diff line number Diff line
@@ -90,3 +90,50 @@ xfs_parent_valuecheck( 


	return true;

}



/* Compute the attribute name hash for a parent pointer. */

xfs_dahash_t

xfs_parent_hashval(

	struct xfs_mount		*mp,

	const uint8_t			*name,

	int				namelen,

	xfs_ino_t			parent_ino)

{

	struct xfs_name			xname = {

		.name			= name,

		.len			= namelen,

	};



	/*

	 * Use the same dirent name hash as would be used on the directory, but

	 * mix in the parent inode number to avoid collisions on hardlinked

	 * files with identical names but different parents.

	 */

	return xfs_dir2_hashname(mp, &xname) ^

		upper_32_bits(parent_ino) ^ lower_32_bits(parent_ino);

}



/* Compute the attribute name hash from the xattr components. */

xfs_dahash_t

xfs_parent_hashattr(

	struct xfs_mount		*mp,

	const uint8_t			*name,

	int				namelen,

	const void			*value,

	int				valuelen)

{

	const struct xfs_parent_rec	*rec = value;



	/* Requires a local attr value in xfs_parent_rec format */

	if (valuelen != sizeof(struct xfs_parent_rec)) {

		ASSERT(valuelen == sizeof(struct xfs_parent_rec));

		return 0;

	}



	if (!value) {

		ASSERT(value != NULL);

		return 0;

	}



	return xfs_parent_hashval(mp, name, namelen, be64_to_cpu(rec->p_ino));

}

fs/xfs/libxfs/xfs_parent.h

+5 −0
Original line number Diff line number Diff line
@@ -12,4 +12,9 @@ bool xfs_parent_namecheck(unsigned int attr_flags, const void *name, 
bool xfs_parent_valuecheck(struct xfs_mount *mp, const void *value,

		size_t valuelen);



xfs_dahash_t xfs_parent_hashval(struct xfs_mount *mp, const uint8_t *name,

		int namelen, xfs_ino_t parent_ino);

xfs_dahash_t xfs_parent_hashattr(struct xfs_mount *mp, const uint8_t *name,

		int namelen, const void *value, int valuelen);



#endif /* __XFS_PARENT_H__ */

fs/xfs/scrub/attr.c

+4 −0
Original line number Diff line number Diff line
@@ -536,6 +536,10 @@ xchk_xattr_rec( 
			xchk_da_set_corrupt(ds, level);

			goto out;

		}

		if (ent->flags & XFS_ATTR_PARENT) {

			xchk_da_set_corrupt(ds, level);

			goto out;

		}

		calc_hash = xfs_attr_hashval(mp, ent->flags, rentry->name,

					     rentry->namelen, NULL,

					     be32_to_cpu(rentry->valuelen));