[LU-6137] Update timestamps arbitrarily on MDS

• Status: Resolved
• Project: Lustre
• Affects Version/s: Lustre 2.7.0
• Fix Version/s: Lustre 2.8.0
• Type: Bug
• Priority: Critical
• Reporter: Niu Yawei (Inactive)
• Assignee: Niu Yawei (Inactive)
• Resolution: Fixed
• Severity: 3

Description

There was a timestamps update policy on MDS: ctime is increasing
only, which means if the ctime to be updated is behind of current
inode->i_ctime, then this timestamps update will be rejected.

This policy sounds not reasonable and it could lead to following
problems:

1. If time isn't synced on clients, the file created by the client
having advanced clock will have advanced ctime, so any operations
from the client with lagging clock won't be able to update file
timestamps.

2. If the client clock is adjusted to a past time, then this client
won't be able to change timestamps to the already create files.

3. Server time could be used on inode->i_ctime if the client time
isn't provided for certain operation from some old version
client, and if the server time is ahead of client time, we'll
run into the same problem.

4. Sometime ldiskfs API may set server time on inode->i_ctime (
ext4 nomctime patch doesn't cover all cases), and it should be
overwritten by client time in upper layer (see
mdt_reint_setxattr()), however, because of the timestamps update
policy, the overwrite operation could fail if the server time
is ahead of client time.

Issue Links

• is related to: LU-6087 sanity test_300b: mtime not change af...
• is related to: LU-7310 sanityn test_39a fails with 'mtime is...

Comments

[Niu Yawei (Inactive)]

http://review.whamcloud.com/#/c/13396

[Gerrit Updater]

Niu Yawei ([e-mail]) uploaded a new patch: http://review.whamcloud.com/13705
Subject: LU-6137 ldiskfs: simplify nocmtime patch
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: fe5d5a9e3a65dd5ae4f777332c2804d5200d4d3d

[Niu Yawei (Inactive)]

The patch above is split: http://review.whamcloud.com/13705 (fix ldiskfs nocmtime only).

[Gerrit Updater]

Oleg Drokin ([e-mail]) merged in patch http://review.whamcloud.com/13705/
Subject: LU-6137 ldiskfs: simplify nocmtime patch
Project: fs/lustre-release
Branch: master
Current Patch Set:
Commit: d2c828a32a3b019194051ee24607eafee517cc43

[James A Simmons]

Patch has landed to master. Ticket can be closed.

[Niu Yawei (Inactive)]

There are two patches tracked in this ticket, one is landed, another is still being reviewed, please keep it open.

[Gerrit Updater]

Niu Yawei ([e-mail]) uploaded a new patch: http://review.whamcloud.com/13994
Subject: LU-6137 ldiskfs: simplify nocmtime patch
Project: fs/lustre-release
Branch: b2_5
Current Patch Set: 1
Commit: 86b16e3251db5aa655edbce6f8b9a97651d79bb8

[Andreas Dilger]

Could you please work on a conf-sanity test that changes the clocks on the MDS and OSS nodes, as described in LU-6087, so that we can find and fix this kind of problem more easily. They should try both setting either the MDS clock or OSS clock ahead of the client, and also behind the client clock.

[Gerrit Updater]

Niu Yawei ([e-mail]) uploaded a new patch: http://review.whamcloud.com/14122
Subject: LU-6137 test: Server time should not be used
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: 3d2f13ab9fd49590934bb178d7dc7fb0bbc5b22c

[Niu Yawei (Inactive)]

Add sanity test to verify that server time isn't used: http://review.whamcloud.com/14122

[Niu Yawei (Inactive)]

The patch fixing ldiskfs is landed, which can fix customer's problem. The other two patches were abandoned.