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Apply server breaks to mmap'd files that are being used from that server
from the call processor work function rather than punting it off to a
workqueue. The work item, afs_server_init_callback(), then bumps each
individual inode off to its own work item introducing a potentially lengthy
delay. This reduces that delay at the cost of extending the amount of time
we delay replying to the CB.InitCallBack3 notification RPC from the server.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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Move the code that does validity checking of vnodes and volumes with
respect to third-party changes into its own file.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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Defer volume record destruction to a workqueue so that afs_put_volume()
isn't going to run the destruction process in the callback workqueue whilst
the server is holding up other clients whilst waiting for us to reply to a
CB.CallBack notification RPC.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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Make it possible to find the afs_volume structs that are using an
afs_server struct to aid in breaking volume callbacks.
The way this is done is that each afs_volume already has an array of
afs_server_entry records that point to the servers where that volume might
be found. An afs_volume backpointer and a list node is added to each entry
and each entry is then added to an RCU-traversable list on the afs_server
to which it points.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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Combine the endpoint state bool-type members into a bitmask so that some of
them can be waited upon more easily.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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Keep a record of the current fileserver endpoint state, including the probe
state, and replace it when a new probe is started rather than just
squelching the old state and overwriting it. Clearance of the old state
can cause a race if there's another thread also currently trying to
communicate with that server.
It appears that this race might be the culprit for some occasions where
kafs complains about invalid data in the RPC reply because the rotation
algorithm fell all the way through without actually issuing an RPC call and
the error return got filled in from the probe state (which has a zero error
recorded). Whatever happens to be in the caller's reply buffer is then
taken as the response.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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When probing all the addresses for a volume location server, dispatch them
in order of descending priority to try and get back highest priority one
first.
Also add a tracepoint to show the transmission and completion of the
probes.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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When probing all the addresses for a fileserver, dispatch them in order of
descending priority to try and get back highest priority one first.
Also add a tracepoint to show the transmission and completion of the
probes.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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Add a field to each address in an address list (afs_addr_list struct) that
records the current priority for that address according to the address
preference table. We don't want to do this every time we use an address
list, so the version number of the address preference table is recorded in
the address list too and we only re-mark the list when we see the version
change.
These numbers are then displayed through /proc/net/afs/servers.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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AFS servers may have multiple addresses, but the client can't easily judge
between them as to which one is best. For instance, an address that has a
larger RTT might actually have a better bandwidth because it goes through a
switch rather than being directly connected - but we can't work this out
dynamically unless we push through sufficient data that we can measure it.
To allow the administrator to configure this, add a list of preference
weightings for server addresses by IPv4/IPv6 address or subnet and allow
this to be viewed through a procfile and altered by writing text commands
to that same file. Preference rules can be added/updated by:
echo "add <proto> <addr>[/<subnet>] <prior>" >/proc/fs/afs/addr_prefs
echo "add udp 1.2.3.4 1000" >/proc/fs/afs/addr_prefs
echo "add udp 192.168.0.0/16 3000" >/proc/fs/afs/addr_prefs
echo "add udp 1001:2002:0:6::/64 4000" >/proc/fs/afs/addr_prefs
and removed by:
echo "del <proto> <addr>[/<subnet>]" >/proc/fs/afs/addr_prefs
echo "del udp 1.2.3.4" >/proc/fs/afs/addr_prefs
where the priority is a number between 0 and 65535.
The list is split between IPv4 and IPv6 addresses and each sublist is kept
in numerical order, with rules that would otherwise match but have
different subnet masking being ordered with the most specific submatch
first.
A subsequent patch will apply these rules.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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Remove afs_cmp_addr_list() as it was never implemented.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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In /proc/net/afs/servers, show the cell name and the last error for each
address in the server's list.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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Make afs use the netfs write helpers.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
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Track the file position above which the server is not expected to have any
data (the "zero point") and preemptively assume that we can satisfy
requests by filling them with zeroes locally rather than attempting to
download them if they're over that line - even if we've written data back
to the server. Assume that any data that was written back above that
position is held in the local cache. Note that we have to split requests
that straddle the line.
Make use of this to optimise away some reads from the server. We need to
set the zero point in the following circumstances:
(1) When we see an extant remote inode and have no cache for it, we set
the zero_point to i_size.
(2) On local inode creation, we set zero_point to 0.
(3) On local truncation down, we reduce zero_point to the new i_size if
the new i_size is lower.
(4) On local truncation up, we don't change zero_point.
(5) On local modification, we don't change zero_point.
(6) On remote invalidation, we set zero_point to the new i_size.
(7) If stored data is discarded from the pagecache or culled from fscache,
we must set zero_point above that if the data also got written to the
server.
(8) If dirty data is written back to the server, but not fscache, we must
set zero_point above that.
(9) If a direct I/O write is made, set zero_point above that.
Assuming the above, any read from the server at or above the zero_point
position will return all zeroes.
The zero_point value can be stored in the cache, provided the above rules
are applied to it by any code that culls part of the local cache.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
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Implement support for unbuffered writes and direct I/O writes. If the
write is misaligned with respect to the fscrypt block size, then RMW cycles
are performed if necessary. DIO writes are a special case of unbuffered
writes with extra restriction imposed, such as block size alignment
requirements.
Also provide a field that can tell the code to add some extra space onto
the bounce buffer for use by the filesystem in the case of a
content-encrypted file.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
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Fold the afs_addr_cursor struct into the afs_operation struct and the
afs_vl_cursor struct and fold its operations into their callers also.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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Use the rxrpc_peer plus the service ID as the call address instead of
passing in a sockaddr_srx down to rxrpc. The peer record is obtained by
using rxrpc_kernel_get_peer(). This avoids the need to repeatedly look up
the peer and allows rxrpc to hold on to resources for it.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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Rename the ->index and ->untried fields of the afs_vl_cursor and
afs_operation struct to ->server_index and ->untried_servers to avoid
confusion with address iteration fields when those get folded in.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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Add a tracepoint to track the lifetime of the afs_addr_list struct.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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Simplify error handling a bit by moving it from the afs_addr_cursor struct
to the afs_operation and afs_vl_cursor structs and using the error
prioritisation function for accumulating errors from multiple sources (AFS
tries to rotate between multiple fileservers, some of which may be
inaccessible or in some state of offlinedness).
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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Don't put the afs_call struct in afs_wait_for_call_to_complete() but rather
have the caller do it. This will allow the caller to fish stuff out of the
afs_call struct rather than the afs_addr_cursor struct, thereby allowing a
subsequent patch to subsume it.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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Wrap most op->error accesses with inline funcs which will make it easier
for a subsequent patch to replace op->error with something else. Two
functions are added to this end:
(1) afs_op_error() - Get the error code.
(2) afs_op_set_error() - Set the error code.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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Set op->nr_iterations to -1 to indicate that we need to begin fileserver
iteration rather than setting error to SHRT_MAX. This makes it easier to
eliminate the address cursor.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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When processing the result of a call, handle the VIO and UAEIO abort
specifically rather than leaving it to a default case. Rather than
erroring out unconditionally, see if there's another server if the volume
has more than one server available, otherwise return -EREMOTEIO.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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Rename the failed member of struct addr_list to probe_failed as it's
specifically related to probe failures.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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In the rotation algorithms for iterating over volume location servers and
file servers, don't skip servers from which we got a valid response to a
probe (either a reply DATA packet or an ABORT) even if we didn't manage to
get an RTT reading.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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Change rxrpc's API such that:
(1) A new function, rxrpc_kernel_lookup_peer(), is provided to look up an
rxrpc_peer record for a remote address and a corresponding function,
rxrpc_kernel_put_peer(), is provided to dispose of it again.
(2) When setting up a call, the rxrpc_peer object used during a call is
now passed in rather than being set up by rxrpc_connect_call(). For
afs, this meenat passing it to rxrpc_kernel_begin_call() rather than
the full address (the service ID then has to be passed in as a
separate parameter).
(3) A new function, rxrpc_kernel_remote_addr(), is added so that afs can
get a pointer to the transport address for display purposed, and
another, rxrpc_kernel_remote_srx(), to gain a pointer to the full
rxrpc address.
(4) The function to retrieve the RTT from a call, rxrpc_kernel_get_srtt(),
is then altered to take a peer. This now returns the RTT or -1 if
there are insufficient samples.
(5) Rename rxrpc_kernel_get_peer() to rxrpc_kernel_call_get_peer().
(6) Provide a new function, rxrpc_kernel_get_peer(), to get a ref on a
peer the caller already has.
This allows the afs filesystem to pin the rxrpc_peer records that it is
using, allowing faster lookups and pointer comparisons rather than
comparing sockaddr_rxrpc contents. It also makes it easier to get hold of
the RTT. The following changes are made to afs:
(1) The addr_list struct's addrs[] elements now hold a peer struct pointer
and a service ID rather than a sockaddr_rxrpc.
(2) When displaying the transport address, rxrpc_kernel_remote_addr() is
used.
(3) The port arg is removed from afs_alloc_addrlist() since it's always
overridden.
(4) afs_merge_fs_addr4() and afs_merge_fs_addr6() do peer lookup and may
now return an error that must be handled.
(5) afs_find_server() now takes a peer pointer to specify the address.
(6) afs_find_server(), afs_compare_fs_alists() and afs_merge_fs_addr[46]{}
now do peer pointer comparison rather than address comparison.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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Turn the afs_addr_list address array into an array of structs, thereby
allowing per-address (such as RTT) info to be added.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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Add some comments on AFS abort code handling in the rotation algorithm and
adjust the errors produced to match.
Reported-by: Jeffrey E Altman <jaltman@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeffrey Altman <jaltman@auristor.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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David Howells says:
(3) afs_check_validity().
(4) afs_getattr().
These are both pretty short, so your solution is probably good for them.
That said, afs_vnode_commit_status() can spend a long time under the
write lock - and pretty much every file RPC op returns a status update.
Change these functions to use read_seqbegin(). This simplifies the code
and doesn't change the current behaviour, the "seq" counter is always even
so read_seqbegin_or_lock() can never take the lock.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/20231130115617.GA21584@redhat.com/
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David Howells says:
(5) afs_find_server().
There could be a lot of servers in the list and each server can have
multiple addresses, so I think this would be better with an exclusive
second pass.
The server list isn't likely to change all that often, but when it does
change, there's a good chance several servers are going to be
added/removed one after the other. Further, this is only going to be
used for incoming cache management/callback requests from the server,
which hopefully aren't going to happen too often - but it is remotely
drivable.
(6) afs_find_server_by_uuid().
Similarly to (5), there could be a lot of servers to search through, but
they are in a tree not a flat list, so it should be faster to process.
Again, it's not likely to change that often and, again, when it does
change it's likely to involve multiple changes. This can be driven
remotely by an incoming cache management request but is mostly going to
be driven by setting up or reconfiguring a volume's server list -
something that also isn't likely to happen often.
Make the "seq" counter odd on the 2nd pass, otherwise read_seqbegin_or_lock()
never takes the lock.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/20231130115614.GA21581@redhat.com/
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David Howells says:
(2) afs_lookup_volume_rcu().
There can be a lot of volumes known by a system. A thousand would
require a 10-step walk and this is drivable by remote operation, so I
think this should probably take a lock on the second pass too.
Make the "seq" counter odd on the 2nd pass, otherwise read_seqbegin_or_lock()
never takes the lock.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/20231130115606.GA21571@redhat.com/
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Add three iov_iter structs:
(1) Add an iov_iter (->iter) to the I/O request to describe the
unencrypted-side buffer.
(2) Add an iov_iter (->io_iter) to the I/O request to describe the
encrypted-side I/O buffer. This may be a different size to the buffer
in (1).
(3) Add an iov_iter (->io_iter) to the I/O subrequest to describe the part
of the I/O buffer for that subrequest.
This will allow future patches to point to a bounce buffer instead for
purposes of handling oversize writes, decryption (where we want to save the
encrypted data to the cache) and decompression.
These iov_iters persist for the lifetime of the (sub)request, and so can be
accessed multiple times without worrying about them being deallocated upon
return to the caller.
The network filesystem must appropriately advance the iterator before
terminating the request.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
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Provide default invalidate_folio and release_folio calls. These will need
to interact with invalidation correctly at some point. They will be needed
if netfslib is to make use of folio->private for its own purposes.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
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AFS currently uses folio->private to store the range of bytes within a
folio that have been modified - the idea being that if we have, say, a 2MiB
folio and someone writes a single byte, we only have to write back that
single page and not the whole 2MiB folio - thereby saving on network
bandwidth.
Remove this, at least for now, and accept the extra network load (which
doesn't matter in the common case of writing a whole file at a time from
beginning to end).
This makes folio->private available for netfslib to use.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
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Move the resource pinning-for-writeback from fscache code to netfslib code.
This is used to keep a cache backing object pinned whilst we have dirty
pages on the netfs inode in the pagecache such that VM writeback will be
able to reach it.
Whilst we're at it, switch the parameters of netfs_unpin_writeback() to
match ->write_inode() so that it can be used for that directly.
Note that this mechanism could be more generically useful than that for
network filesystems. Quite often they have to keep around other resources
(e.g. authentication tokens or network connections) until the writeback is
complete.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
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Remove ->begin_cache_operation() in favour of just calling fscache directly.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: Christian Brauner <christian@brauner.io>
cc: linux-fsdevel@vger.kernel.org
cc: linux-cachefs@redhat.com
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When an afs_volume struct is put, its refcount is reduced to 0 before
the cell->volume_lock is taken and the volume removed from the
cell->volumes tree.
Unfortunately, this means that the lookup code can race and see a volume
with a zero ref in the tree, resulting in a use-after-free:
refcount_t: addition on 0; use-after-free.
WARNING: CPU: 3 PID: 130782 at lib/refcount.c:25 refcount_warn_saturate+0x7a/0xda
...
RIP: 0010:refcount_warn_saturate+0x7a/0xda
...
Call Trace:
afs_get_volume+0x3d/0x55
afs_create_volume+0x126/0x1de
afs_validate_fc+0xfe/0x130
afs_get_tree+0x20/0x2e5
vfs_get_tree+0x1d/0xc9
do_new_mount+0x13b/0x22e
do_mount+0x5d/0x8a
__do_sys_mount+0x100/0x12a
do_syscall_64+0x3a/0x94
entry_SYSCALL_64_after_hwframe+0x62/0x6a
Fix this by:
(1) When putting, use a flag to indicate if the volume has been removed
from the tree and skip the rb_erase if it has.
(2) When looking up, use a conditional ref increment and if it fails
because the refcount is 0, replace the node in the tree and set the
removal flag.
Fixes: 20325960f875 ("afs: Reorganise volume and server trees to be rooted on the cell")
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeffrey Altman <jaltman@auristor.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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In afs_update_cell(), ret is the result of the DNS lookup and the errors
are to be handled by a switch - however, the value gets clobbered in
between by setting it to -ENOMEM in case afs_alloc_vlserver_list()
fails.
Fix this by moving the setting of -ENOMEM into the error handling for
OOM failure. Further, only do it if we don't have an alternative error
to return.
Found by Linux Verification Center (linuxtesting.org) with SVACE. Based
on a patch from Anastasia Belova [1].
Fixes: d5c32c89b208 ("afs: Fix cell DNS lookup")
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeffrey Altman <jaltman@auristor.com>
cc: Anastasia Belova <abelova@astralinux.ru>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
cc: lvc-project@linuxtesting.org
Link: https://lore.kernel.org/r/20231221085849.1463-1-abelova@astralinux.ru/ [1]
Link: https://lore.kernel.org/r/1700862.1703168632@warthog.procyon.org.uk/ # v1
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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In the afs dynamic root directory, the ->lookup() function does a DNS check
on the cell being asked for and if the DNS upcall reports an error it will
report an error back to userspace (typically ENOENT).
However, if a failed DNS upcall returns a new-style result, it will return
a valid result, with the status field set appropriately to indicate the
type of failure - and in that case, dns_query() doesn't return an error and
we let stat() complete with no error - which can cause confusion in
userspace as subsequent calls that trigger d_automount then fail with
ENOENT.
Fix this by checking the status result from a valid dns_query() and
returning an error if it indicates a failure.
Fixes: bbb4c4323a4d ("dns: Allow the dns resolver to retrieve a server set")
Reported-by: Markus Suvanto <markus.suvanto@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=216637
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Markus Suvanto <markus.suvanto@gmail.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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Fix the afs dynamic root's d_delete function to always delete unused
dentries rather than only deleting them if they're positive. With things
as they stand upstream, negative dentries stemming from failed DNS lookups
stick around preventing retries.
Fixes: 66c7e1d319a5 ("afs: Split the dynroot stuff out and give it its own ops tables")
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Markus Suvanto <markus.suvanto@gmail.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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If an AFS cell that has an unreachable (eg. ENETUNREACH) server listed (VL
server or fileserver), an asynchronous probe to one of its addresses may
fail immediately because sendmsg() returns an error. When this happens, a
refcount underflow can happen if certain events hit a very small window.
The way this occurs is:
(1) There are two levels of "call" object, the afs_call and the
rxrpc_call. Each of them can be transitioned to a "completed" state
in the event of success or failure.
(2) Asynchronous afs_calls are self-referential whilst they are active to
prevent them from evaporating when they're not being processed. This
reference is disposed of when the afs_call is completed.
Note that an afs_call may only be completed once; once completed
completing it again will do nothing.
(3) When a call transmission is made, the app-side rxrpc code queues a Tx
buffer for the rxrpc I/O thread to transmit. The I/O thread invokes
sendmsg() to transmit it - and in the case of failure, it transitions
the rxrpc_call to the completed state.
(4) When an rxrpc_call is completed, the app layer is notified. In this
case, the app is kafs and it schedules a work item to process events
pertaining to an afs_call.
(5) When the afs_call event processor is run, it goes down through the
RPC-specific handler to afs_extract_data() to retrieve data from rxrpc
- and, in this case, it picks up the error from the rxrpc_call and
returns it.
The error is then propagated to the afs_call and that is completed
too. At this point the self-reference is released.
(6) If the rxrpc I/O thread manages to complete the rxrpc_call within the
window between rxrpc_send_data() queuing the request packet and
checking for call completion on the way out, then
rxrpc_kernel_send_data() will return the error from sendmsg() to the
app.
(7) Then afs_make_call() will see an error and will jump to the error
handling path which will attempt to clean up the afs_call.
(8) The problem comes when the error handling path in afs_make_call()
tries to unconditionally drop an async afs_call's self-reference.
This self-reference, however, may already have been dropped by
afs_extract_data() completing the afs_call
(9) The refcount underflows when we return to afs_do_probe_vlserver() and
that tries to drop its reference on the afs_call.
Fix this by making afs_make_call() attempt to complete the afs_call rather
than unconditionally putting it. That way, if afs_extract_data() manages
to complete the call first, afs_make_call() won't do anything.
The bug can be forced by making do_udp_sendmsg() return -ENETUNREACH and
sticking an msleep() in rxrpc_send_data() after the 'success:' label to
widen the race window.
The error message looks something like:
refcount_t: underflow; use-after-free.
WARNING: CPU: 3 PID: 720 at lib/refcount.c:28 refcount_warn_saturate+0xba/0x110
...
RIP: 0010:refcount_warn_saturate+0xba/0x110
...
afs_put_call+0x1dc/0x1f0 [kafs]
afs_fs_get_capabilities+0x8b/0xe0 [kafs]
afs_fs_probe_fileserver+0x188/0x1e0 [kafs]
afs_lookup_server+0x3bf/0x3f0 [kafs]
afs_alloc_server_list+0x130/0x2e0 [kafs]
afs_create_volume+0x162/0x400 [kafs]
afs_get_tree+0x266/0x410 [kafs]
vfs_get_tree+0x25/0xc0
fc_mount+0xe/0x40
afs_d_automount+0x1b3/0x390 [kafs]
__traverse_mounts+0x8f/0x210
step_into+0x340/0x760
path_openat+0x13a/0x1260
do_filp_open+0xaf/0x160
do_sys_openat2+0xaf/0x170
or something like:
refcount_t: underflow; use-after-free.
...
RIP: 0010:refcount_warn_saturate+0x99/0xda
...
afs_put_call+0x4a/0x175
afs_send_vl_probes+0x108/0x172
afs_select_vlserver+0xd6/0x311
afs_do_cell_detect_alias+0x5e/0x1e9
afs_cell_detect_alias+0x44/0x92
afs_validate_fc+0x9d/0x134
afs_get_tree+0x20/0x2e6
vfs_get_tree+0x1d/0xc9
fc_mount+0xe/0x33
afs_d_automount+0x48/0x9d
__traverse_mounts+0xe0/0x166
step_into+0x140/0x274
open_last_lookups+0x1c1/0x1df
path_openat+0x138/0x1c3
do_filp_open+0x55/0xb4
do_sys_openat2+0x6c/0xb6
Fixes: 34fa47612bfe ("afs: Fix race in async call refcounting")
Reported-by: Bill MacAllister <bill@ca-zephyr.org>
Closes: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1052304
Suggested-by: Jeffrey E Altman <jaltman@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeffrey Altman <jaltman@auristor.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/2633992.1702073229@warthog.procyon.org.uk/ # v1
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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There were already assertions that we were not passing a tail page to
error_remove_page(), so make the compiler enforce that by converting
everything to pass and use a folio.
Link: https://lkml.kernel.org/r/20231117161447.2461643-7-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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In preparation for removing the return value entirely, stop testing it
in afs.
Link: https://lkml.kernel.org/r/20231108204605.745109-3-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Steve French <sfrench@samba.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time via CONFIG_UBSAN_BOUNDS (for
array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).
While there, use struct_size() helper, instead of the open-coded
version, to calculate the size for the allocation of the whole
flexible structure, including of course, the flexible-array member.
This code was found with the help of Coccinelle, and audited and
fixed manually.
Signed-off-by: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/ZSVKwBmxQ1amv47E@work
Signed-off-by: Kees Cook <keescook@chromium.org>
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Saves a pointer per struct dentry and actually makes the things less
clumsy. Cleaned the d_walk() and dcache_readdir() a bit by use
of hlist_for_... iterators.
A couple of new helpers - d_first_child() and d_next_sibling(),
to make the expressions less awful.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Mark a superblock that is for for an R/O or Backup volume as SB_RDONLY when
mounting it.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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AFS doesn't really do locking on R/O volumes as fileservers don't maintain
state with each other and thus a lock on a R/O volume file on one
fileserver will not be be visible to someone looking at the same file on
another fileserver.
Further, the server may return an error if you try it.
Fix this by doing what other AFS clients do and handle filelocking on R/O
volume files entirely within the client and don't touch the server.
Fixes: 6c6c1d63c243 ("afs: Provide mount-time configurable byte-range file locking emulation")
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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Make AFS return error ENOENT if no cell SRV or AFSDB DNS record (or
cellservdb config file record) can be found rather than returning
EDESTADDRREQ.
Also add cell name lookup info to the cursor dump.
Fixes: d5c32c89b208 ("afs: Fix cell DNS lookup")
Reported-by: Markus Suvanto <markus.suvanto@gmail.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216637
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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When kafs tries to look up a cell in the DNS or the local config, it will
translate a lookup failure into EDESTADDRREQ whereas OpenAFS translates it
into ENOENT. Applications such as West expect the latter behaviour and
fail if they see the former.
This can be seen by trying to mount an unknown cell:
# mount -t afs %example.com:cell.root /mnt
mount: /mnt: mount(2) system call failed: Destination address required.
Fixes: 4d673da14533 ("afs: Support the AFS dynamic root")
Reported-by: Markus Suvanto <markus.suvanto@gmail.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216637
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeffrey Altman <jaltman@auristor.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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