fs/bcachefs/dirent_format.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _BCACHEFS_DIRENT_FORMAT_H
#define _BCACHEFS_DIRENT_FORMAT_H

/*
 * Dirents (and xattrs) have to implement string lookups; since our b-tree
 * doesn't support arbitrary length strings for the key, we instead index by a
 * 64 bit hash (currently truncated sha1) of the string, stored in the offset
 * field of the key - using linear probing to resolve hash collisions. This also
 * provides us with the readdir cookie posix requires.
 *
 * Linear probing requires us to use whiteouts for deletions, in the event of a
 * collision:
 */

struct bch_dirent {
	struct bch_val		v;

	/* Target inode number: */
	union {
	__le64			d_inum;
	struct {		/* DT_SUBVOL */
	__le32			d_child_subvol;
	__le32			d_parent_subvol;
	};
	};

	/*
	 * Copy of mode bits 12-15 from the target inode - so userspace can get
	 * the filetype without having to do a stat()
	 */
	__u8			d_type;

	__u8			d_name[];
} __packed __aligned(8);

#define DT_SUBVOL	16
#define BCH_DT_MAX	17

#define BCH_NAME_MAX	512

#endif /* _BCACHEFS_DIRENT_FORMAT_H */