| 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
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| 2 | #ifndef _BCACHEFS_DIRENT_FORMAT_H |
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| 3 | #define _BCACHEFS_DIRENT_FORMAT_H |
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| 4 | |
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| 5 | /* |
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| 6 | * Dirents (and xattrs) have to implement string lookups; since our b-tree |
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| 7 | * doesn't support arbitrary length strings for the key, we instead index by a |
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| 8 | * 64 bit hash (currently truncated sha1) of the string, stored in the offset |
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| 9 | * field of the key - using linear probing to resolve hash collisions. This also |
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| 10 | * provides us with the readdir cookie posix requires. |
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| 11 | * |
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| 12 | * Linear probing requires us to use whiteouts for deletions, in the event of a |
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| 13 | * collision: |
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| 14 | */ |
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| 15 | |
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| 16 | struct bch_dirent { |
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| 17 | struct bch_val v; |
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| 18 | |
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| 19 | /* Target inode number: */ |
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| 20 | union { |
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| 21 | __le64 d_inum; |
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| 22 | struct { /* DT_SUBVOL */ |
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| 23 | __le32 d_child_subvol; |
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| 24 | __le32 d_parent_subvol; |
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| 25 | }; |
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| 26 | }; |
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| 27 | |
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| 28 | /* |
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| 29 | * Copy of mode bits 12-15 from the target inode - so userspace can get |
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| 30 | * the filetype without having to do a stat() |
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| 31 | */ |
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| 32 | __u8 d_type; |
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| 33 | |
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| 34 | __u8 d_name[]; |
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| 35 | } __packed __aligned(8); |
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| 36 | |
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| 37 | #define DT_SUBVOL 16 |
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| 38 | #define BCH_DT_MAX 17 |
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| 39 | |
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| 40 | #define BCH_NAME_MAX 512 |
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| 41 | |
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| 42 | #endif /* _BCACHEFS_DIRENT_FORMAT_H */ |
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| 43 | |
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