43 lines
1.0 KiB
C
43 lines
1.0 KiB
C
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/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _BCACHEFS_DIRENT_FORMAT_H
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#define _BCACHEFS_DIRENT_FORMAT_H
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/*
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* Dirents (and xattrs) have to implement string lookups; since our b-tree
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* doesn't support arbitrary length strings for the key, we instead index by a
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* 64 bit hash (currently truncated sha1) of the string, stored in the offset
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* field of the key - using linear probing to resolve hash collisions. This also
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* provides us with the readdir cookie posix requires.
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*
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* Linear probing requires us to use whiteouts for deletions, in the event of a
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* collision:
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*/
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struct bch_dirent {
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struct bch_val v;
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/* Target inode number: */
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union {
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__le64 d_inum;
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struct { /* DT_SUBVOL */
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__le32 d_child_subvol;
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__le32 d_parent_subvol;
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};
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};
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/*
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* Copy of mode bits 12-15 from the target inode - so userspace can get
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* the filetype without having to do a stat()
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*/
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__u8 d_type;
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__u8 d_name[];
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} __packed __aligned(8);
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#define DT_SUBVOL 16
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#define BCH_DT_MAX 17
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#define BCH_NAME_MAX 512
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#endif /* _BCACHEFS_DIRENT_FORMAT_H */
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