FS-Cache: Assertion failed: FS-Cache: 6 == 5 is false
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
linux (Ubuntu) |
Fix Released
|
Undecided
|
Daniel Axtens | ||
Trusty |
Fix Released
|
Undecided
|
Unassigned | ||
Xenial |
Fix Released
|
Undecided
|
Unassigned | ||
Artful |
Fix Released
|
Undecided
|
Unassigned | ||
Bionic |
Fix Released
|
Undecided
|
Unassigned |
Bug Description
== SRU Justification ==
[Impact]
Oops during heavy NFS + FSCache use:
[81738.886634] FS-Cache:
[81738.888281] FS-Cache: Assertion failed
[81738.889461] FS-Cache: 6 == 5 is false
[81738.890625] ------------[ cut here ]------------
[81738.891706] kernel BUG at /build/
6 == 5 represents an operation being DEAD when it was not expected to be.
[Cause]
There is a race in fscache and cachefiles.
One thread is in cachefiles_
1) object->work_lock is taken.
2) the operation is added to the to_do list.
3) the work lock is dropped.
4) fscache_
Another thread is in cachefiles_
1) object->work_lock is taken
2) an item is popped off the to_do list.
3) object->work_lock is dropped.
4) some processing is done on the item, and fscache_
Now if the this process in cachefiles_
(This is simplified and clarified from the original upstream analysis for this patch at https:/
[Fix]
(Old sauce patch being reverted) Move fscache_
(New upstream patch) Explicitly take a reference to the object while it is being enqueued. Adjust another part of the code to deal with the greater range of object states this exposes.
[Testcase]
A user has run ~100 hours of NFS stress tests and not seen this bug recur.
[Regression Potential]
- Limited to fscache/cachefiles.
- The change makes things more conservative (taking more references) so that's reassuring.
- There may be performance impacts but none have been observed so far.
Changed in linux (Ubuntu): | |
status: | New → Confirmed |
assignee: | nobody → Daniel Axtens (daxtens) |
Changed in linux (Ubuntu Trusty): | |
status: | New → Fix Committed |
Changed in linux (Ubuntu Xenial): | |
status: | New → Fix Committed |
Changed in linux (Ubuntu Artful): | |
status: | New → Fix Committed |
Changed in linux (Ubuntu Bionic): | |
status: | New → Fix Committed |
description: | updated |
tags: |
added: kernel-fixup-verification-needed-bionic removed: verification-needed-bionic |
tags: | added: verification-done-bionic |
tags: | added: cscc |
This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification- needed- artful' to 'verification- done-artful' . If the problem still exists, change the tag 'verification- needed- artful' to 'verification- failed- artful' .
If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.
See https:/ /wiki.ubuntu. com/Testing/ EnableProposed for documentation how to enable and use -proposed. Thank you!