-----BEGIN PGP SIGNATURE-----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=0anM
-----END PGP SIGNATURE-----
Merge tag 'afs-fixes-20201016' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs
Pull afs updates from David Howells:
"A collection of fixes to fix afs_cell struct refcounting, thereby
fixing a slew of related syzbot bugs:
- Fix the cell tree in the netns to use an rwsem rather than RCU.
There seem to be some problems deriving from the use of RCU and a
seqlock to walk the rbtree, but it's not entirely clear what since
there are several different failures being seen.
Changing things to use an rwsem instead makes it more robust. The
extra performance derived from using RCU isn't necessary in this
case since the only time we're looking up a cell is during mount or
when cells are being manually added.
- Fix the refcounting by splitting the usage counter into a memory
refcount and an active users counter. The usage counter was doing
double duty, keeping track of whether a cell is still in use and
keeping track of when it needs to be destroyed - but this makes the
clean up tricky. Separating these out simplifies the logic.
- Fix purging a cell that has an alias. A cell alias pins the cell
it's an alias of, but the alias is always later in the list. Trying
to purge in a single pass causes rmmod to hang in such a case.
- Fix cell removal. If a cell's manager is requeued whilst it's
removing itself, the manager will run again and re-remove itself,
causing problems in various places. Follow Hillf Danton's
suggestion to insert a more terminal state that causes the manager
to do nothing post-removal.
In additional to the above, two other changes:
- Add a tracepoint for the cell refcount and active users count. This
helped with debugging the above and may be useful again in future.
- Downgrade an assertion to a print when a still-active server is
seen during purging. This was happening as a consequence of
incomplete cell removal before the servers were cleaned up"
* tag 'afs-fixes-20201016' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
afs: Don't assert on unpurgeable server records
afs: Add tracing for cell refcount and active user count
afs: Fix cell removal
afs: Fix cell purging with aliases
afs: Fix cell refcounting by splitting the usage counter
afs: Fix rapid cell addition/removal by not using RCU on cells tree
fad70111d5