Add a tracepoint to log the cell refcount and active user count and pass in
a reason code through various functions that manipulate these counters.
Additionally, a helper function, afs_see_cell(), is provided to log
interesting places that deal with a cell without actually doing any
accounting directly.
Signed-off-by: David Howells <dhowells@redhat.com>
Management of the lifetime of afs_cell struct has some problems due to the
usage counter being used to determine whether objects of that type are in
use in addition to whether anyone might be interested in the structure.
This is made trickier by cell objects being cached for a period of time in
case they're quickly reused as they hold the result of a setup process that
may be slow (DNS lookups, AFS RPC ops).
Problems include the cached root volume from alias resolution pinning its
parent cell record, rmmod occasionally hanging and occasionally producing
assertion failures.
Fix this by splitting the count of active users from the struct reference
count. Things then work as follows:
(1) The cell cache keeps +1 on the cell's activity count and this has to
be dropped before the cell can be removed. afs_manage_cell() tries to
exchange the 1 to a 0 with the cells_lock write-locked, and if
successful, the record is removed from the net->cells.
(2) One struct ref is 'owned' by the activity count. That is put when the
active count is reduced to 0 (final_destruction label).
(3) A ref can be held on a cell whilst it is queued for management on a
work queue without confusing the active count. afs_queue_cell() is
added to wrap this.
(4) The queue's ref is dropped at the end of the management. This is
split out into a separate function, afs_manage_cell_work().
(5) The root volume record is put after a cell is removed (at the
final_destruction label) rather then in the RCU destruction routine.
(6) Volumes hold struct refs, but aren't active users.
(7) Both counts are displayed in /proc/net/afs/cells.
There are some management function changes:
(*) afs_put_cell() now just decrements the refcount and triggers the RCU
destruction if it becomes 0. It no longer sets a timer to have the
manager do this.
(*) afs_use_cell() and afs_unuse_cell() are added to increase and decrease
the active count. afs_unuse_cell() sets the management timer.
(*) afs_queue_cell() is added to queue a cell with approprate refs.
There are also some other fixes:
(*) Don't let /proc/net/afs/cells access a cell's vllist if it's NULL.
(*) Make sure that candidate cells in lookups are properly destroyed
rather than being simply kfree'd. This ensures the bits it points to
are destroyed also.
(*) afs_dec_cells_outstanding() is now called in cell destruction rather
than at "final_destruction". This ensures that cell->net is still
valid to the end of the destructor.
(*) As a consequence of the previous two changes, move the increment of
net->cells_outstanding that was at the point of insertion into the
tree to the allocation routine to correctly balance things.
Fixes: 989782dcdc ("afs: Overhaul cell database management")
Signed-off-by: David Howells <dhowells@redhat.com>
The error handling in the VL server rotation in the case of there being no
contactable servers is not correct. In such a case, the records of all the
servers in the list are scanned and the errors and abort codes are mapped
and prioritised and one error is chosen. This is then forgotten and the
default error is used (EDESTADDRREQ).
Fix this by using the calculated error.
Also we need to note whether a server responded on one of its endpoints so
that we can priorise an error from an abort message over local and network
errors.
Fixes: 4584ae96ae ("afs: Fix missing net error handling")
Signed-off-by: David Howells <dhowells@redhat.com>
Don't use the running state for VL server probes to make decisions about
which server to use as the state is cleared at the start of a probe and
intermediate values might also be misleading.
Instead, add a separate 'latest known' rtt in the afs_vlserver struct and a
flag to indicate if the server is known to be responding and update these
as and when we know what to change them to.
Fixes: 3bf0fb6f33 ("afs: Probe multiple fileservers simultaneously")
Signed-off-by: David Howells <dhowells@redhat.com>
Convert various bitfields in afs_vlserver::probe to a mask and then expose
this and some other bits of information through /proc/net/afs/<cell>/vlservers
to make it easier to debug VL server communication issues.
Signed-off-by: David Howells <dhowells@redhat.com>
YFS Volume Location servers have an operation by which the cell name may be
queried. Use this to find out what a YFS server thinks the canonical cell
name should be.
Signed-off-by: David Howells <dhowells@redhat.com>
Remove three bits:
(1) afs_server::no_epoch is neither set nor used.
(2) afs_server::have_result is set and a wakeup is applied to it, but
nothing looks at it or waits on it.
(3) afs_vl_dump_edestaddrreq() prints afs_addr_list::probed, but nothing
sets it for VL servers.
Signed-off-by: David Howells <dhowells@redhat.com>
Based on 1 normalized pattern(s):
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public licence as published by
the free software foundation either version 2 of the licence or at
your option any later version
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-or-later
has been chosen to replace the boilerplate/reference in 114 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190520170857.552531963@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Currently, once configured, AFS cells are looked up in the DNS at regular
intervals - which is a waste of resources if those cells aren't being
used. It also leads to a problem where cells preloaded, but not
configured, before the network is brought up end up effectively statically
configured with no VL servers and are unable to get any.
Fix this by not doing the DNS lookup until the first time a cell is
touched. It is waited for if we don't have any cached records yet,
otherwise the DNS lookup to maintain the record is done in the background.
This has the downside that the first time you touch a cell, you now have to
wait for the upcall to do the required DNS lookups rather than them already
being cached.
Further, the record is not replaced if the old record has at least one
server in it and the new record doesn't have any.
Fixes: 0a5143f2f8 ("afs: Implement VL server rotation")
Signed-off-by: David Howells <dhowells@redhat.com>
Fix it such that afs_cell records always have a VL server list record
attached, even if it's a dummy one, so that various checks can be removed.
Signed-off-by: David Howells <dhowells@redhat.com>
kAFS can be given certain network errors (EADDRNOTAVAIL, EHOSTDOWN and
ERFKILL) that it doesn't handle in its server/address rotation algorithms.
They cause the probing and rotation to abort immediately rather than
rotating.
Fix this by:
(1) Abstracting out the error prioritisation from the VL and FS rotation
algorithms into a common function and expand usage into the server
probing code.
When multiple errors are available, this code selects the one we'd
prefer to return.
(2) Add handling for EADDRNOTAVAIL, EHOSTDOWN and ERFKILL.
Fixes: 0fafdc9f88 ("afs: Fix file locking")
Fixes: 0338747d8454 ("afs: Probe multiple fileservers simultaneously")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Send probes to all the unprobed fileservers in a fileserver list on all
addresses simultaneously in an attempt to find out the fastest route whilst
not getting stuck for 20s on any server or address that we don't get a
reply from.
This alleviates the problem whereby attempting to access a new server can
take a long time because the rotation algorithm ends up rotating through
all servers and addresses until it finds one that responds.
Signed-off-by: David Howells <dhowells@redhat.com>
Eliminate the address pointer from the address list cursor as it's
redundant (ac->addrs[ac->index] can be used to find the same address) and
address lists must be replaced rather than being rearranged, so is of
limited value.
Signed-off-by: David Howells <dhowells@redhat.com>
Provide an option to allow the file or volume location server cursor to be
dumped if the rotation routine falls off the end without managing to
contact a server.
Signed-off-by: David Howells <dhowells@redhat.com>
Track VL servers as independent entities rather than lumping all their
addresses together into one set and implement server-level rotation by:
(1) Add the concept of a VL server list, where each server has its own
separate address list. This code is similar to the FS server list.
(2) Use the DNS resolver to retrieve a set of servers and their associated
addresses, ports, preference and weight ratings.
(3) In the case of a legacy DNS resolver or an address list given directly
through /proc/net/afs/cells, create a list containing just a dummy
server record and attach all the addresses to that.
(4) Implement a simple rotation policy, for the moment ignoring the
priorities and weights assigned to the servers.
(5) Show the address list through /proc/net/afs/<cell>/vlservers. This
also displays the source and status of the data as indicated by the
upcall.
Signed-off-by: David Howells <dhowells@redhat.com>
David Howells