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Merge pull request #4255 from greatroar/fuse-hash

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fuse: Mix inode hashes in a non-symmetric way
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Michael Eischer 2023-04-07 12:56:57 +02:00 committed by GitHub
commit 26a3c47c5c
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3 changed files with 33 additions and 2 deletions
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18
changelog/unreleased/issue-4253 Normal file
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@ -0,0 +1,18 @@
Bugfix: Mount command should no longer create spurious filesystem loops
When a backup contains a directory that has the same name as its parent,
say, a/b/b, and the GNU find command were run on this backup in a restic
mount, find command would refuse to traverse the lowest "b" directory,
instead printing "File system loop detected". This is due to the way the
restic mount command generates inode numbers for directories in the mount
point.
The rule for generating these inode numbers was changed in 0.15.0. It has
now been changed again to avoid this issue. A perfect rule does not exist,
but the probability of this behavior occurring is now extremely small.
When it does occur, the mount point is not broken, and scripts that traverse
the mount point should work as long as they don't rely on inode numbers for
detecting filesystem loops.
https://github.com/restic/restic/issues/4253
https://github.com/restic/restic/pull/4255

11
internal/fuse/fuse_test.go
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@ -258,6 +258,17 @@ func TestInodeFromNode(t *testing.T) {
ino1 = inodeFromNode(1, node)
ino2 = inodeFromNode(2, node)
rtest.Assert(t, ino1 != ino2, "same inode %d but different parent", ino1)
// Regression test: in a path a/b/b, the grandchild should not get the
// same inode as the grandparent.
a := &restic.Node{Name: "a", Type: "dir", Links: 2}
ab := &restic.Node{Name: "b", Type: "dir", Links: 2}
abb := &restic.Node{Name: "b", Type: "dir", Links: 2}
inoA := inodeFromNode(1, a)
inoAb := inodeFromNode(inoA, ab)
inoAbb := inodeFromNode(inoAb, abb)
rtest.Assert(t, inoA != inoAb, "inode(a/b) = inode(a)")
rtest.Assert(t, inoA != inoAbb, "inode(a/b/b) = inode(a)")
}
var sink uint64

6
internal/fuse/inode.go
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@ -10,9 +10,11 @@ import (
"github.com/restic/restic/internal/restic"
)
const prime = 11400714785074694791 // prime1 from xxhash.
// inodeFromName generates an inode number for a file in a meta dir.
func inodeFromName(parent uint64, name string) uint64 {
inode := parent ^ xxhash.Sum64String(cleanupNodeName(name))
inode := prime*parent ^ xxhash.Sum64String(cleanupNodeName(name))
// Inode 0 is invalid and 1 is the root. Remap those.
if inode < 2 {
@ -33,7 +35,7 @@ func inodeFromNode(parent uint64, node *restic.Node) (inode uint64) {
} else {
// Else, use the name and the parent inode.
// node.{DeviceID,Inode} may not even be reliable.
inode = parent ^ xxhash.Sum64String(cleanupNodeName(node.Name))
inode = prime*parent ^ xxhash.Sum64String(cleanupNodeName(node.Name))
}
// Inode 0 is invalid and 1 is the root. Remap those.