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bcachefs: dirent_format.h

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Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2024-01-20 23:57:10 -05:00
parent b36425da71
commit 7ffc4daa5f
2 changed files with 43 additions and 39 deletions
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40
fs/bcachefs/bcachefs_format.h
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@ -710,45 +710,6 @@ struct bch_reservation {
#define BKEY_BTREE_PTR_U64s_MAX \
(BKEY_U64s + BKEY_BTREE_PTR_VAL_U64s_MAX)
/* Dirents */
/*
* 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
/* Xattrs */
#define KEY_TYPE_XATTR_INDEX_USER 0
@ -1045,6 +1006,7 @@ struct bch_sb_field {
x(ext, 13) \
x(downgrade, 14)
#include "dirent_format.h"
#include "inode_format.h"
#include "quota_format.h"
#include "sb-counters_format.h"

42
fs/bcachefs/dirent_format.h Normal file
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@ -0,0 +1,42 @@
/* 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 */