6.1-stable review patch. If anyone has any objections, please let me know.
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From: Dennis Marttinen twelho@welho.tech
commit 72386d5245b249f5a0a8fabb881df7ad947b8ea4 upstream.
The CephFS kernel driver forgets to set the filesystem magic signature in its superblock. As a result, IMA policy rules based on fsmagic matching do not apply as intended. This causes a major performance regression in Talos Linux [1] when mounting CephFS volumes, such as when deploying Rook Ceph [2]. Talos Linux ships a hardened kernel with the following IMA policy (irrelevant lines omitted):
[...] dont_measure fsmagic=0xc36400 # CEPH_SUPER_MAGIC [...] measure func=FILE_CHECK mask=^MAY_READ euid=0 measure func=FILE_CHECK mask=^MAY_READ uid=0 [...]
Currently, IMA compares 0xc36400 == 0x0 for CephFS files, resulting in all files opened with O_RDONLY or O_RDWR getting measured with SHA512 on every open(2):
10 69990c87e8af323d47e2d6ae4... ima-ng sha512:<hash> /data/cephfs/test-file
Since O_WRONLY is rare, this results in an order of magnitude lower performance than expected for practically all file operations. Properly setting CEPH_SUPER_MAGIC in the CephFS superblock resolves the regression.
Tests performed on a 3x replicated Ceph v19.3.0 cluster across three i5-7200U nodes each equipped with one Micron 7400 MAX M.2 disk (BlueStore) and Gigabit ethernet, on Talos Linux v1.10.2:
FS-Mark 3.3 Test: 500 Files, Empty Files/s > Higher Is Better 6.12.27-talos . 16.6 |==== +twelho patch . 208.4 |====================================================
FS-Mark 3.3 Test: 500 Files, 1KB Size Files/s > Higher Is Better 6.12.27-talos . 15.6 |======= +twelho patch . 118.6 |====================================================
FS-Mark 3.3 Test: 500 Files, 32 Sub Dirs, 1MB Size Files/s > Higher Is Better 6.12.27-talos . 12.7 |=============== +twelho patch . 44.7 |=====================================================
IO500 [3] 2fcd6d6 results (benchmarks within variance omitted):
| IO500 benchmark | 6.12.27-talos | +twelho patch | Speedup | |-------------------|----------------|----------------|-----------| | mdtest-easy-write | 0.018524 kIOPS | 1.135027 kIOPS | 6027.33 % | | mdtest-hard-write | 0.018498 kIOPS | 0.973312 kIOPS | 5161.71 % | | ior-easy-read | 0.064727 GiB/s | 0.155324 GiB/s | 139.97 % | | mdtest-hard-read | 0.018246 kIOPS | 0.780800 kIOPS | 4179.29 % |
This applies outside of synthetic benchmarks as well, for example, the time to rsync a 55 MiB directory with ~12k of mostly small files drops from an unusable 10m5s to a reasonable 26s (23x the throughput).
[1]: https://www.talos.dev/ [2]: https://www.talos.dev/v1.10/kubernetes-guides/configuration/ceph-with-rook/ [3]: https://github.com/IO500/io500
Cc: stable@vger.kernel.org Signed-off-by: Dennis Marttinen twelho@welho.tech Reviewed-by: Viacheslav Dubeyko Slava.Dubeyko@ibm.com Signed-off-by: Ilya Dryomov idryomov@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/ceph/super.c | 1 + 1 file changed, 1 insertion(+)
--- a/fs/ceph/super.c +++ b/fs/ceph/super.c @@ -1136,6 +1136,7 @@ static int ceph_set_super(struct super_b s->s_time_min = 0; s->s_time_max = U32_MAX; s->s_flags |= SB_NODIRATIME | SB_NOATIME; + s->s_magic = CEPH_SUPER_MAGIC;
ret = set_anon_super_fc(s, fc); if (ret != 0)