[PATCH 00/27] afs: Improvements

David Howells
2020-05-29T22:00:15Z

Here's a set of patches to make a number of improvements to the AFS driver:

(1) Improve callback (ie. third party change notification) processing by:

(a) Relying more on the fact we're doing this under RCU and by using
fewer locks.

This involves making the inode hash table RCU safe and providing
some RCU-safe accessor functions. The search can then be done
without taking the inode_hash_lock. Care must be taken because
the object may be being deleted and no wait is made.

This is also used to improve Ext4's time updating. Konstantin
Khlebnikov said "For now, I've plugged this issue with try-lock in
ext4 lazy time update. This solution is much better."

(b) Moving to keeping volumes in a tree indexed by volume ID rather
than a flat list.

(c) Making the server and volume records logically part of the cell.
This means that a server record now points directly at the cell
and the tree of volumes is there. This removes an N:M mapping
table, simplifying things.

(2) Improve keeping NAT or firewall channels open for the server callbacks
to reach the client by actively polling the fileserver on a timed
basis, instead of only doing it when we have an operation to process.

(3) Improving detection of delayed or lost callbacks by including the
parent directory in the list of file IDs to be queried when doing a
bulk status fetch from lookup. We can then check to see if our copy
of the directory has changed under us without us getting notified.

(4) Determine aliasing of cells (such as a cell that is pointed to be a
DNS alias). This allows us to avoid having ambiguity due to
apparently different cells using the same volume and file servers.

(5) Improve the fileserver rotation to do more probing when it detects
that all of the addresses to a server are listed as non-responsive.
It's possible that an address that previously stopped responding has
become responsive again.

Beyond that, lay some foundations for making some calls asynchronous:

(1) Turn the fileserver cursor struct into a general operation struct and
hang the parameters off of that rather than keeping them in local
variables and hang results off of that rather than the call struct.

(2) Implement some general operation handling code and simplify the
callers of operations that affect a volume or a volume component (such
as a file). Most of the operation is now done by core code.

(3) Operations are supplied with a table of operations to issue different
variants of RPCs and to manage the completion, where all the required
data is held in the operation object, thereby allowing these to be
called from a workqueue.

(4) Put the standard "if (begin), while(select), call op, end" sequence
into a canned function that just emulates the current behaviour for
now.

There are also some fixes interspersed:

(1) Don't let the EACCES from ICMP6 mapping reach the user as such, since
it's confusing as to whether it's a filesystem error. Convert it to
EHOSTUNREACH.

(2) Don't use the epoch value acquired through probing a server. If we
have two servers with the same UUID but in different cells, it's hard
to draw conclusions from them having different epoch values.

(3) Don't interpret the argument to the CB.ProbeUuid RPC as a fileserver
UUID and look up a fileserver from it.

(4) Deal with servers in different cells having the same UUIDs. In the
event that a CB.InitCallBackState3 RPC is received, we have to break
the callback promises for every server record matching that UUID.

(5) Don't let afs_statfs return values that go below 0.

(6) Don't use running fileserver probe state to make server selection and
address selection decisions on. Only make decisions on final state as
the running state is cleared at the start of probing.

The patches are here:

http://git.kernel.org/cgit/linux/kernel/git/dhowells/linux-fs.git/log/?h=afs-next

David
---
David Howells (1):
afs: Adjust the fileserver rotation algorithm to reprobe/retry more quickly

fs/afs/Makefile | 2 +
fs/afs/afs.h | 3 +-
fs/afs/afs_vl.h | 1 +
fs/afs/callback.c | 345 ++++--------
fs/afs/cell.c | 10 +-
fs/afs/cmservice.c | 67 +--
fs/afs/dir.c | 1253 ++++++++++++++++++++----------------------
fs/afs/dir_silly.c | 190 +++----
fs/afs/dynroot.c | 93 ++++
fs/afs/file.c | 62 ++-
fs/afs/flock.c | 114 ++--
fs/afs/fs_operation.c | 239 ++++++++
fs/afs/fs_probe.c | 339 +++++++++---
fs/afs/fsclient.c | 1295 +++++++++++++++++---------------------------
fs/afs/inode.c | 491 ++++++++---------
fs/afs/internal.h | 523 ++++++++++--------
fs/afs/main.c | 6 +-
fs/afs/proc.c | 42 +-
fs/afs/protocol_yfs.h | 2 +-
fs/afs/rotate.c | 443 ++++++---------
fs/afs/rxrpc.c | 45 +-
fs/afs/security.c | 8 +-
fs/afs/server.c | 299 ++++++----
fs/afs/server_list.c | 40 +-
fs/afs/super.c | 107 ++--
fs/afs/vl_alias.c | 384 +++++++++++++
fs/afs/vl_rotate.c | 4 +
fs/afs/vlclient.c | 146 ++++-
fs/afs/volume.c | 152 ++++--
fs/afs/write.c | 148 +++--
fs/afs/xattr.c | 300 +++++-----
fs/afs/yfsclient.c | 914 +++++++++++++------------------
fs/ext4/inode.c | 44 +-
fs/inode.c | 173 +++++-
include/linux/fs.h | 3 +
include/trace/events/afs.h | 111 +++-
net/rxrpc/peer_event.c | 3 +
net/rxrpc/proc.c | 6 +-
38 files changed, 4484 insertions(+), 3923 deletions(-)
create mode 100644 fs/afs/fs_operation.c
create mode 100644 fs/afs/vl_alias.c