Lock shared storage rebase2#1019
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Multiple host writing to the same empty file at the same time could have overwritten each other's newly created file header, leading to data corruption. Fix the race by placing a byte-range lock on the file when creating the file header.
This exercises the byte-range locks we just added.
This fails right now:
1 jakob@brikett:~/go/src/github.com/rfjakob/gocryptfs/tests/cluster$ go test -run TestOpenTruncate -v
=== RUN TestOpenTruncate
cluster_test.go:235: POSIX compliance issue: non-exlusive create failed with err=file exists
doWrite 2898550: corrupt header: ParseHeader: header is all-zero. Header hexdump: 000000000000000000000000000000000000
cluster_test.go:240: iteration 1: WriteAt: write /var/tmp/gocryptfs-test-parent-1026/1896094179/TestOpenTruncate.4202105280.mnt2/foo: input/output error
--- FAIL: TestOpenTruncate (0.10s)
FAIL
exit status 1
FAIL github.com/rfjakob/gocryptfs/v2/tests/cluster 0.099s
1 jakob@brikett:~/go/src/github.com/rfjakob/gocryptfs/tests/cluster$ go test -run TestOpenTruncate -v
=== RUN TestOpenTruncate
cluster_test.go:235: POSIX compliance issue: non-exlusive create failed with err=file exists
doRead 2898565: corrupt block #0: cipher: message authentication failed
ino2898565 fh9: RMW read failed: errno=5
cluster_test.go:240: iteration 8: WriteAt: write /var/tmp/gocryptfs-test-parent-1026/652691834/TestOpenTruncate.281532388.mnt1/foo: input/output error
--- FAIL: TestOpenTruncate (0.09s)
FAIL
exit status 1
FAIL github.com/rfjakob/gocryptfs/v2/tests/cluster 0.095s
With -sharedstorage, we keep the on-disk file header. Other mounts may have the file ID cached so we cannot mess with it. This makes TestOpenTruncate pass.
Scary. But explains why TestConcurrentCreate fails.
gocryptfs/tests/cluster$ go test -run TestPoCTornWrite
--- FAIL: TestPoCTornWrite (0.00s)
poc_test.go:210: iteration 214: inconsistent block: d6d6d6d6d6d6d6d6d1d1d1d1d1d1d1d1d1d1d1d1d1d1d1d1d1d1d1d1d1d1d1d1d1d1d1d1d1d1d1d1d1d1
FAIL
As we must write complete ciphertext blocks (except at EOF), non-overlapping plaintext writes can overlap in the ciphertext. And because overlapping writes can turn the data into data soup (see TestPoCTornWrite) we serialize them using fcntl locking.
Add the -sharedstorage flag to the mounts and make it more
severe by adjusting the I/O and file sizes to arbitrary unaligned
values.
It passes *most of the time*.
If it fails, it's like this, and the reason is that there is no
fcntl locks in the READ path yet.
gocryptfs/tests/cluster$ go test -run TestClusterConcurrentRW -v
=== RUN TestClusterConcurrentRW
doRead 2895433: corrupt block #0: cipher: message authentication failed
doRead 2895433: corrupt block #0: cipher: message authentication failed
doRead 2895433: corrupt block #0: cipher: message authentication failed
cluster_test.go:98: readThread iteration 9165: ReadAt failed: read /var/tmp/gocryptfs-test-parent-1026/3021427391/TestClusterConcurrentRW.366469887.mnt1/foo: input/output error
--- FAIL: TestClusterConcurrentRW (0.40s)
FAIL
exit status 1
FAIL github.com/rfjakob/gocryptfs/v2/tests/cluster 0.406s
With -sharedstorage, when we get a decryption error, we lock the byte range and try again. This makes concurrent R/W safe agains torn writes. #754
Complain loudly when the underlying storage does not support byte-range locks. #754
Prevent reads and writes concurrent with the truncate operation. It's racy on tmpfs and ext4 ( https://lore.kernel.org/all/18e9fa0f-ec31-9107-459c-ae1694503f87@gmail.com/t/ ) as evident by TestOpenTruncate test failures: === RUN TestOpenTruncate cluster_test.go:209: POSIX compliance issue: non-exlusive create failed with err=file exists doRead 16384215: corrupt block #0: cipher: message authentication failed ino16384215 fh8: RMW read failed: errno=5 cluster_test.go:214: iteration 1: WriteAt: write /tmp/gocryptfs-test-parent-1026/1358464214/TestOpenTruncate.1788296708.mnt2/foo: input/output error --- FAIL: TestOpenTruncate (0.06s) FAIL exit status 1 FAIL github.com/rfjakob/gocryptfs/v2/tests/cluster 7.880s Relates-to: #56
...and one typo.
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