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a0885d5d69
Since 0.15 (#4020), inodes are generated as hashes of names, xor'd with the parent inode. That means that the inode of a/b/b is h(a/b/b) = h(a) ^ h(b) ^ h(b) = h(a). I.e., the grandchild has the same inode as the grandparent. GNU find trips over this because it thinks it has encountered a loop in the filesystem, and fails to search a/b/b. This happens more generally when the same name occurs an even number of times. Fix this by multiplying the parent by a large prime, so the combining operation is not longer symmetric in its arguments. This is what the FNV hash does, which we used prior to 0.15. The hash is now h(a/b/b) = h(b) ^ p*(h(b) ^ p*h(a)) Note that we already ensure that h(x) is never zero. Collisions can still occur, but they should be much less likely to occur within a single path. Fixes #4253.
46 lines
1.2 KiB
Go
46 lines
1.2 KiB
Go
//go:build darwin || freebsd || linux
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// +build darwin freebsd linux
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package fuse
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import (
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"encoding/binary"
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"github.com/cespare/xxhash/v2"
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"github.com/restic/restic/internal/restic"
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)
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const prime = 11400714785074694791 // prime1 from xxhash.
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// inodeFromName generates an inode number for a file in a meta dir.
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func inodeFromName(parent uint64, name string) uint64 {
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inode := prime*parent ^ xxhash.Sum64String(cleanupNodeName(name))
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// Inode 0 is invalid and 1 is the root. Remap those.
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if inode < 2 {
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inode += 2
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}
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return inode
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}
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// inodeFromNode generates an inode number for a file within a snapshot.
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func inodeFromNode(parent uint64, node *restic.Node) (inode uint64) {
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if node.Links > 1 && node.Type != "dir" {
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// If node has hard links, give them all the same inode,
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// irrespective of the parent.
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var buf [16]byte
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binary.LittleEndian.PutUint64(buf[:8], node.DeviceID)
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binary.LittleEndian.PutUint64(buf[8:], node.Inode)
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inode = xxhash.Sum64(buf[:])
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} else {
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// Else, use the name and the parent inode.
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// node.{DeviceID,Inode} may not even be reliable.
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inode = prime*parent ^ xxhash.Sum64String(cleanupNodeName(node.Name))
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}
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// Inode 0 is invalid and 1 is the root. Remap those.
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if inode < 2 {
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inode += 2
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}
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return inode
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}
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