afs: Fix afs_server_list to be cleaned up with RCU

[ Upstream commit e6bace7313d61e31f2b16fa3d774fd8cb3cb869e ]

afs_server_list is accessed with the rcu_read_lock() held from
volume->servers, so it

afs: Fix afs_server_list to be cleaned up with RCU

[ Upstream commit e6bace7313d61e31f2b16fa3d774fd8cb3cb869e ]

afs_server_list is accessed with the rcu_read_lock() held from
volume->servers, so it needs to be cleaned up correctly.

Fix this by using kfree_rcu() instead of kfree().

Fixes: 8a070a964877 ("afs: Detect cell aliases 1 - Cells with root volumes")
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Signed-off-by: Sasha Levin <sashal@kernel.org>

show more ...

afs: Reorganise volume and server trees to be rooted on the cell

Reorganise afs_volume objects such that they're in a tree keyed on volume
ID, rooted at on an afs_cell object rather than being in mu

afs: Reorganise volume and server trees to be rooted on the cell

Reorganise afs_volume objects such that they're in a tree keyed on volume
ID, rooted at on an afs_cell object rather than being in multiple trees,
each of which is rooted on an afs_server object.

afs_server structs become per-cell and acquire a pointer to the cell.

The process of breaking a callback then starts with finding the server by
its network address, following that to the cell and then looking up each
volume ID in the volume tree.

This is simpler than the afs_vol_interest/afs_cb_interest N:M mapping web
and allows those structs and the code for maintaining them to be simplified
or removed.

It does make a couple of things a bit more tricky, though:

(1) Operations now start with a volume, not a server, so there can be more
than one answer as to whether or not the server we'll end up using
supports the FS.InlineBulkStatus RPC.

(2) CB RPC operations that specify the server UUID. There's still a tree
of servers by UUID on the afs_net struct, but the UUIDs in it aren't
guaranteed unique.

Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

afs: Retain more of the VLDB record for alias detection

Save more bits from the volume location database record obtained for a
server so that we can use this information in cell alias detection.

Si

afs: Retain more of the VLDB record for alias detection

Save more bits from the volume location database record obtained for a
server so that we can use this information in cell alias detection.

Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

afs: Split the usage count on struct afs_server

Split the usage count on the afs_server struct to have an active count that
registers who's actually using it separately from the reference count on
t

afs: Split the usage count on struct afs_server

Split the usage count on the afs_server struct to have an active count that
registers who's actually using it separately from the reference count on
the object.

This allows a future patch to dispatch polling probes without advancing the
"unuse" time into the future each time we emit a probe, which would
otherwise prevent unused server records from expiring.

Included in this:

(1) The latter part of afs_destroy_server() in which the RCU destruction
of afs_server objects is invoked and the outstanding server count is
decremented is split out into __afs_put_server().

(2) afs_put_server() now calls __afs_put_server() rather then setting the
management timer.

(3) The calls begun by afs_fs_give_up_all_callbacks() and
afs_fs_get_capabilities() can now take a ref on the server record, so
afs_destroy_server() can just drop its ref and needn't wait for the
completion of these calls. They'll put the ref when they're done.

(4) Because of (3), afs_fs_probe_done() no longer needs to wake up
afs_destroy_server() with server->probe_outstanding.

(5) afs_gc_servers can be simplified. It only needs to check if
server->active is 0 rather than playing games with the refcount.

(6) afs_manage_servers() can propose a server for gc if usage == 0 rather
than if ref == 1. The gc is effected by (5).

Signed-off-by: David Howells <dhowells@redhat.com>

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afs: Use the serverUnique field in the UVLDB record to reduce rpc ops

The U-version VLDB volume record retrieved by the VL.GetEntryByNameU rpc op
carries a change counter (the serverUnique field) fo

afs: Use the serverUnique field in the UVLDB record to reduce rpc ops

The U-version VLDB volume record retrieved by the VL.GetEntryByNameU rpc op
carries a change counter (the serverUnique field) for each fileserver
listed in the record as backing that volume. This is incremented whenever
the registration details for a fileserver change (such as its address
list). Note that the same value will be seen in all UVLDB records that
refer to that fileserver.

This should be checked before calling the VL server to re-query the address
list for a fileserver. If it's the same, there's no point doing the query.

Reported-by: Jeffrey Altman <jaltman@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

afs: Trace afs_server usage

Add a tracepoint (afs_server) to track the afs_server object usage count.

Signed-off-by: David Howells <dhowells@redhat.com>

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152

Based on 1 normalized pattern(s):

this program is free software you can redistribute it and or modify
it under the terms of th

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152

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 license as published by
the free software foundation either version 2 of the license 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 3029 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070032.746973796@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

afs: Use struct_size() in kzalloc()

One of the more common cases of allocation size calculations is finding the
size of a structure that has a zero-sized array at the end, along with
memory for some

afs: Use struct_size() in kzalloc()

One of the more common cases of allocation size calculations is finding the
size of a structure that has a zero-sized array at the end, along with
memory for some number of elements for that array. For example:

struct foo {
int stuff;
void *entry[];
};

instance = kzalloc(sizeof(struct foo) + sizeof(void *) * count, GFP_KERNEL);

Instead of leaving these open-coded and prone to type mistakes, we can now
use the new struct_size() helper:

instance = kzalloc(struct_size(instance, entry, count), GFP_KERNEL);

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

afs: Probe multiple fileservers simultaneously

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

afs: Probe multiple fileservers simultaneously

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>

show more ...

afs: Fix refcounting in callback registration

The refcounting on afs_cb_interest struct objects in
afs_register_server_cb_interest() is wrong as it uses the server list
entry's call back interest po

afs: Fix refcounting in callback registration

The refcounting on afs_cb_interest struct objects in
afs_register_server_cb_interest() is wrong as it uses the server list
entry's call back interest pointer without regard for the fact that it
might be replaced at any time and the object thrown away.

Fix this by:

(1) Put a lock on the afs_server_list struct that can be used to
mediate access to the callback interest pointers in the servers array.

(2) Keep a ref on the callback interest that we get from the entry.

(3) Dropping the old reference held by vnode->cb_interest if we replace
the pointer.

Fixes: c435ee34551e ("afs: Overhaul the callback handling")
Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

afs: Fix server list handling

Fix server list handling in the following ways:

(1) In afs_alloc_volume(), remove duplicate server list build code. This
was already done by afs_alloc_server_li

afs: Fix server list handling

Fix server list handling in the following ways:

(1) In afs_alloc_volume(), remove duplicate server list build code. This
was already done by afs_alloc_server_list() which afs_alloc_volume()
previously called. This just results in twice as many VL RPCs.

(2) In afs_deliver_vl_get_entry_by_name_u(), use the number of server
records indicated by ->nServers in the UVLDB record returned by the
VL.GetEntryByNameU RPC call rather than scanning all NMAXNSERVERS
slots. Unused slots may contain garbage.

(3) In afs_alloc_server_list(), don't stop converting a UVLDB record into
a server list just because we can't look up one of the servers. Just
skip that server and go on to the next. If we can't look up any of
the servers then we'll fail at the end.

Without this patch, an attempt to view the umich.edu root cell using
something like "ls /afs/umich.edu" on a dynamic root (future patch) mount
or an autocell mount will result in ENOMEDIUM. The failure is due to kafs
not stopping after nServers'worth of records have been read, but then
trying to access a server with a garbage UUID and getting an error, which
aborts the server list build.

Fixes: d2ddc776a458 ("afs: Overhaul volume and server record caching and fileserver rotation")
Reported-by: Jonathan Billings <jsbillings@jsbillings.org>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: stable@vger.kernel.org

show more ...

afs: Fix file locking

Fix the AFS file locking whereby the use of the big kernel lock (which
could be slept with) was replaced by a spinlock (which couldn't). The
problem is that the AFS code was d

afs: Fix file locking

Fix the AFS file locking whereby the use of the big kernel lock (which
could be slept with) was replaced by a spinlock (which couldn't). The
problem is that the AFS code was doing stuff inside the critical section
that might call schedule(), so this is a broken transformation.

Fix this by the following means:

(1) Use a state machine with a proper state that can only be changed under
the spinlock rather than using a collection of bit flags.

(2) Cache the key used for the lock and the lock type in the afs_vnode
struct so that the manager work function doesn't have to refer to a
file_lock struct that's been dequeued. This makes signal handling
safer.

(4) Move the unlock from afs_do_unlk() to afs_fl_release_private() which
means that unlock is achieved in other circumstances too.

(5) Unlock the file on the server before taking the next conflicting lock.

Also change:

(1) Check the permits on a file before actually trying the lock.

(2) fsync the file before effecting an explicit unlock operation. We
don't fsync if the lock is erased otherwise as we might not be in a
context where we can actually do that.

Further fixes:

(1) Fixed-fileserver address rotation is made to work. It's only used by
the locking functions, so couldn't be tested before.

Fixes: 72f98e72551f ("locks: turn lock_flocks into a spinlock")
Signed-off-by: David Howells <dhowells@redhat.com>
cc: jlayton@redhat.com

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afs: Overhaul volume and server record caching and fileserver rotation

The current code assumes that volumes and servers are per-cell and are
never shared, but this is not enforced, and, indeed, pub

afs: Overhaul volume and server record caching and fileserver rotation

The current code assumes that volumes and servers are per-cell and are
never shared, but this is not enforced, and, indeed, public cells do exist
that are aliases of each other. Further, an organisation can, say, set up
a public cell and a private cell with overlapping, but not identical, sets
of servers. The difference is purely in the database attached to the VL
servers.

The current code will malfunction if it sees a server in two cells as it
assumes global address -> server record mappings and that each server is in
just one cell.

Further, each server may have multiple addresses - and may have addresses
of different families (IPv4 and IPv6, say).

To this end, the following structural changes are made:

(1) Server record management is overhauled:

(a) Server records are made independent of cell. The namespace keeps
track of them, volume records have lists of them and each vnode
has a server on which its callback interest currently resides.

(b) The cell record no longer keeps a list of servers known to be in
that cell.

(c) The server records are now kept in a flat list because there's no
single address to sort on.

(d) Server records are now keyed by their UUID within the namespace.

(e) The addresses for a server are obtained with the VL.GetAddrsU
rather than with VL.GetEntryByName, using the server's UUID as a
parameter.

(f) Cached server records are garbage collected after a period of
non-use and are counted out of existence before purging is allowed
to complete. This protects the work functions against rmmod.

(g) The servers list is now in /proc/fs/afs/servers.

(2) Volume record management is overhauled:

(a) An RCU-replaceable server list is introduced. This tracks both
servers and their coresponding callback interests.

(b) The superblock is now keyed on cell record and numeric volume ID.

(c) The volume record is now tied to the superblock which mounts it,
and is activated when mounted and deactivated when unmounted.
This makes it easier to handle the cache cookie without causing a
double-use in fscache.

(d) The volume record is loaded from the VLDB using VL.GetEntryByNameU
to get the server UUID list.

(e) The volume name is updated if it is seen to have changed when the
volume is updated (the update is keyed on the volume ID).

(3) The vlocation record is got rid of and VLDB records are no longer
cached. Sufficient information is stored in the volume record, though
an update to a volume record is now no longer shared between related
volumes (volumes come in bundles of three: R/W, R/O and backup).

and the following procedural changes are made:

(1) The fileserver cursor introduced previously is now fleshed out and
used to iterate over fileservers and their addresses.

(2) Volume status is checked during iteration, and the server list is
replaced if a change is detected.

(3) Server status is checked during iteration, and the address list is
replaced if a change is detected.

(4) The abort code is saved into the address list cursor and -ECONNABORTED
returned in afs_make_call() if a remote abort happened rather than
translating the abort into an error message. This allows actions to
be taken depending on the abort code more easily.

(a) If a VMOVED abort is seen then this is handled by rechecking the
volume and restarting the iteration.

(b) If a VBUSY, VRESTARTING or VSALVAGING abort is seen then this is
handled by sleeping for a short period and retrying and/or trying
other servers that might serve that volume. A message is also
displayed once until the condition has cleared.

(c) If a VOFFLINE abort is seen, then this is handled as VBUSY for the
moment.

(d) If a VNOVOL abort is seen, the volume is rechecked in the VLDB to
see if it has been deleted; if not, the fileserver is probably
indicating that the volume couldn't be attached and needs
salvaging.

(e) If statfs() sees one of these aborts, it does not sleep, but
rather returns an error, so as not to block the umount program.

(5) The fileserver iteration functions in vnode.c are now merged into
their callers and more heavily macroised around the cursor. vnode.c
is removed.

(6) Operations on a particular vnode are serialised on that vnode because
the server will lock that vnode whilst it operates on it, so a second
op sent will just have to wait.

(7) Fileservers are probed with FS.GetCapabilities before being used.
This is where service upgrade will be done.

(8) A callback interest on a fileserver is set up before an FS operation
is performed and passed through to afs_make_call() so that it can be
set on the vnode if the operation returns a callback. The callback
interest is passed through to afs_iget() also so that it can be set
there too.

In general, record updating is done on an as-needed basis when we try to
access servers, volumes or vnodes rather than offloading it to work items
and special threads.

Notes:

(1) Pre AFS-3.4 servers are no longer supported, though this can be added
back if necessary (AFS-3.4 was released in 1998).

(2) VBUSY is retried forever for the moment at intervals of 1s.

(3) /proc/fs/afs/<cell>/servers no longer exists.

Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

afs: Reorganise volume and server trees to be rooted on the cell

Reorganise afs_volume objects such that they're in a tree keyed on volume
ID, rooted at on an afs_cell object rather than

afs: Reorganise volume and server trees to be rooted on the cell

Reorganise afs_volume objects such that they're in a tree keyed on volume
ID, rooted at on an afs_cell object rather than being in multiple trees,
each of which is rooted on an afs_server object.

afs_server structs become per-cell and acquire a pointer to the cell.

The process of breaking a callback then starts with finding the server by
its network address, following that to the cell and then looking up each
volume ID in the volume tree.

This is simpler than the afs_vol_interest/afs_cb_interest N:M mapping web
and allows those structs and the code for maintaining them to be simplified
or removed.

It does make a couple of things a bit more tricky, though:

(1) Operations now start with a volume, not a server, so there can be more
than one answer as to whether or not the server we'll end up using
supports the FS.InlineBulkStatus RPC.

(2) CB RPC operations that specify the server UUID. There's still a tree
of servers by UUID on the afs_net struct, but the UUIDs in it aren't
guaranteed unique.

Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

afs: Retain more of the VLDB record for alias detection

Save more bits from the volume location database record obtained for a
server so that we can use this information in cell alias de

afs: Retain more of the VLDB record for alias detection

Save more bits from the volume location database record obtained for a
server so that we can use this information in cell alias detection.

Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

afs: Split the usage count on struct afs_server

Split the usage count on the afs_server struct to have an active count that
registers who's actually using it separately from the referenc

afs: Split the usage count on struct afs_server

Split the usage count on the afs_server struct to have an active count that
registers who's actually using it separately from the reference count on
the object.

This allows a future patch to dispatch polling probes without advancing the
"unuse" time into the future each time we emit a probe, which would
otherwise prevent unused server records from expiring.

Included in this:

(1) The latter part of afs_destroy_server() in which the RCU destruction
of afs_server objects is invoked and the outstanding server count is
decremented is split out into __afs_put_server().

(2) afs_put_server() now calls __afs_put_server() rather then setting the
management timer.

(3) The calls begun by afs_fs_give_up_all_callbacks() and
afs_fs_get_capabilities() can now take a ref on the server record, so
afs_destroy_server() can just drop its ref and needn't wait for the
completion of these calls. They'll put the ref when they're done.

(4) Because of (3), afs_fs_probe_done() no longer needs to wake up
afs_destroy_server() with server->probe_outstanding.

(5) afs_gc_servers can be simplified. It only needs to check if
server->active is 0 rather than playing games with the refcount.

(6) afs_manage_servers() can propose a server for gc if usage == 0 rather
than if ref == 1. The gc is effected by (5).

Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

afs: Use the serverUnique field in the UVLDB record to reduce rpc ops

The U-version VLDB volume record retrieved by the VL.GetEntryByNameU rpc op
carries a change counter (the serverUniq

afs: Use the serverUnique field in the UVLDB record to reduce rpc ops

The U-version VLDB volume record retrieved by the VL.GetEntryByNameU rpc op
carries a change counter (the serverUnique field) for each fileserver
listed in the record as backing that volume. This is incremented whenever
the registration details for a fileserver change (such as its address
list). Note that the same value will be seen in all UVLDB records that
refer to that fileserver.

This should be checked before calling the VL server to re-query the address
list for a fileserver. If it's the same, there's no point doing the query.

Reported-by: Jeffrey Altman <jaltman@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

Merge tag 'afs-next-20190628' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

Pull afs updates from David Howells:
"A set of minor changes for AFS:

- Remo

Merge tag 'afs-next-20190628' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

Pull afs updates from David Howells:
"A set of minor changes for AFS:

- Remove an unnecessary check in afs_unlink()

- Add a tracepoint for tracking callback management

- Add a tracepoint for afs_server object usage

- Use struct_size()

- Add mappings for AFS UAE abort codes to Linux error codes, using
symbolic names rather than hex numbers in the .c file"

* tag 'afs-next-20190628' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
afs: Add support for the UAE error table
fs/afs: use struct_size() in kzalloc()
afs: Trace afs_server usage
afs: Add some callback management tracepoints
afs: afs_unlink() doesn't need to check dentry->d_inode

show more ...

afs: Trace afs_server usage

Add a tracepoint (afs_server) to track the afs_server object usage count.

Signed-off-by: David Howells <dhowells@redhat.com>

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152

Based on 1 normalized pattern(s):

this program is free software you can redistribute it and or modify
it u

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152

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 license as published by
the free software foundation either version 2 of the license 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 3029 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070032.746973796@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

afs: Use struct_size() in kzalloc()

One of the more common cases of allocation size calculations is finding the
size of a structure that has a zero-sized array at the end, along with

afs: Use struct_size() in kzalloc()

One of the more common cases of allocation size calculations is finding the
size of a structure that has a zero-sized array at the end, along with
memory for some number of elements for that array. For example:

struct foo {
int stuff;
void *entry[];
};

instance = kzalloc(sizeof(struct foo) + sizeof(void *) * count, GFP_KERNEL);

Instead of leaving these open-coded and prone to type mistakes, we can now
use the new struct_size() helper:

instance = kzalloc(struct_size(instance, entry, count), GFP_KERNEL);

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

afs: Probe multiple fileservers simultaneously

Send probes to all the unprobed fileservers in a fileserver list on all
addresses simultaneously in an attempt to find out the fastest rout

afs: Probe multiple fileservers simultaneously

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>

show more ...

afs: Fix refcounting in callback registration

The refcounting on afs_cb_interest struct objects in
afs_register_server_cb_interest() is wrong as it uses the server list
entry's call

afs: Fix refcounting in callback registration

The refcounting on afs_cb_interest struct objects in
afs_register_server_cb_interest() is wrong as it uses the server list
entry's call back interest pointer without regard for the fact that it
might be replaced at any time and the object thrown away.

Fix this by:

(1) Put a lock on the afs_server_list struct that can be used to
mediate access to the callback interest pointers in the servers array.

(2) Keep a ref on the callback interest that we get from the entry.

(3) Dropping the old reference held by vnode->cb_interest if we replace
the pointer.

Fixes: c435ee34551e ("afs: Overhaul the callback handling")
Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

afs: Fix server list handling

Fix server list handling in the following ways:

(1) In afs_alloc_volume(), remove duplicate server list build code. This
was already done by

afs: Fix server list handling

Fix server list handling in the following ways:

(1) In afs_alloc_volume(), remove duplicate server list build code. This
was already done by afs_alloc_server_list() which afs_alloc_volume()
previously called. This just results in twice as many VL RPCs.

(2) In afs_deliver_vl_get_entry_by_name_u(), use the number of server
records indicated by ->nServers in the UVLDB record returned by the
VL.GetEntryByNameU RPC call rather than scanning all NMAXNSERVERS
slots. Unused slots may contain garbage.

(3) In afs_alloc_server_list(), don't stop converting a UVLDB record into
a server list just because we can't look up one of the servers. Just
skip that server and go on to the next. If we can't look up any of
the servers then we'll fail at the end.

Without this patch, an attempt to view the umich.edu root cell using
something like "ls /afs/umich.edu" on a dynamic root (future patch) mount
or an autocell mount will result in ENOMEDIUM. The failure is due to kafs
not stopping after nServers'worth of records have been read, but then
trying to access a server with a garbage UUID and getting an error, which
aborts the server list build.

Fixes: d2ddc776a458 ("afs: Overhaul volume and server record caching and fileserver rotation")
Reported-by: Jonathan Billings <jsbillings@jsbillings.org>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: stable@vger.kernel.org

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afs: Fix file locking

Fix the AFS file locking whereby the use of the big kernel lock (which
could be slept with) was replaced by a spinlock (which couldn't). The
problem is that th

afs: Fix file locking

Fix the AFS file locking whereby the use of the big kernel lock (which
could be slept with) was replaced by a spinlock (which couldn't). The
problem is that the AFS code was doing stuff inside the critical section
that might call schedule(), so this is a broken transformation.

Fix this by the following means:

(1) Use a state machine with a proper state that can only be changed under
the spinlock rather than using a collection of bit flags.

(2) Cache the key used for the lock and the lock type in the afs_vnode
struct so that the manager work function doesn't have to refer to a
file_lock struct that's been dequeued. This makes signal handling
safer.

(4) Move the unlock from afs_do_unlk() to afs_fl_release_private() which
means that unlock is achieved in other circumstances too.

(5) Unlock the file on the server before taking the next conflicting lock.

Also change:

(1) Check the permits on a file before actually trying the lock.

(2) fsync the file before effecting an explicit unlock operation. We
don't fsync if the lock is erased otherwise as we might not be in a
context where we can actually do that.

Further fixes:

(1) Fixed-fileserver address rotation is made to work. It's only used by
the locking functions, so couldn't be tested before.

Fixes: 72f98e72551f ("locks: turn lock_flocks into a spinlock")
Signed-off-by: David Howells <dhowells@redhat.com>
cc: jlayton@redhat.com

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