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Sparse reports that the synopsis of nfsd_open_local_fh() does not
match its kdoc comment. Introduced by commit e6f7e1487ab5
("nfs_localio: simplify interface to nfsd for getting nfsd_file").
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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The nfsd_localio_operations structure contains nfsd_file_get() to get a
reference to an nfsd_file. This is only used in one place, where
nfsd_open_local_fh() is also used.
This patch combines the two, calling nfsd_open_local_fh() passing a
pointer to where the nfsd_file pointer might be stored. If there is a
pointer there an nfsd_file_get() can get a reference, that reference is
returned. If not a new nfsd_file is acquired, stored at the pointer,
and returned. When we store a reference we also increase the refcount
on the net, as that refcount is decrements when we clear the stored
pointer.
We now get an extra reference *before* storing the new nfsd_file at the
given location. This avoids possible races with the nfsd_file being
freed before the final reference can be taken.
This patch moves the rcu_dereference() needed after fetching from
ro_file or rw_file into the nfsd code where the 'struct nfs_file' is
fully defined. This avoids an error reported by older versions of gcc
such as gcc-8 which complain about rcu_dereference() use in contexts
where the structure (which will supposedly be accessed) is not fully
defined.
Reported-by: Pali Rohár <pali@kernel.org>
Reported-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Fixes: 86e00412254a ("nfs: cache all open LOCALIO nfsd_file(s) in client")
Signed-off-by: NeilBrown <neil@brown.name>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
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Having separate nfsd_file_put and nfsd_file_put_local in struct
nfsd_localio_operations doesn't make much sense. The difference is that
nfsd_file_put doesn't drop a reference to the nfs_net which is what
keeps nfsd from shutting down.
Currently, if nfsd tries to shutdown it will invalidate the files stored
in the list from the nfs_uuid and this will drop all references to the
nfsd net that the client holds. But the client could still hold some
references to nfsd_files for active IO. So nfsd might think is has
completely shut down local IO, but hasn't and has no way to wait for
those active IO requests to complete.
So this patch changes nfsd_file_get to nfsd_file_get_local and has it
increase the ref count on the nfsd net and it replaces all calls to
->nfsd_put_file to ->nfsd_put_file_local.
It also changes ->nfsd_open_local_fh to return with the refcount on the
net elevated precisely when a valid nfsd_file is returned.
This means that whenever the client holds a valid nfsd_file, there will
be an associated count on the nfsd net, and so the count can only reach
zero when all nfsd_files have been returned.
nfs_local_file_put() is changed to call nfs_to_nfsd_file_put_local()
instead of replacing calls to one with calls to the other because this
will help a later patch which changes nfs_to_nfsd_file_put_local() to
take an __rcu pointer while nfs_local_file_put() doesn't.
Fixes: 86e00412254a ("nfs: cache all open LOCALIO nfsd_file(s) in client")
Signed-off-by: NeilBrown <neil@brown.name>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
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This tracking enables __nfsd_file_cache_purge() to call
nfs_localio_invalidate_clients(), upon shutdown or export change, to
nfs_close_local_fh() all open nfsd_files that are still cached by the
LOCALIO nfs clients associated with nfsd_net that is being shutdown.
Now that the client must track all open nfsd_files there was more work
than necessary being done with the global nfs_uuids_lock contended.
This manifested in various RCU issues, e.g.:
hrtimer: interrupt took 47969440 ns
rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
Use nfs_uuid->lock to protect all nfs_uuid_t members, instead of
nfs_uuids_lock, once nfs_uuid_is_local() adds the client to
nn->local_clients.
Also add 'local_clients_lock' to 'struct nfsd_net' to protect
nn->local_clients. And store a pointer to spinlock in the 'list_lock'
member of nfs_uuid_t so nfs_localio_disable_client() can use it to
avoid taking the global nfs_uuids_lock.
In combination, these split out locks eliminate the use of the single
nfslocalio.c global nfs_uuids_lock in the IO paths (open and close).
Also refactored associated fs/nfs_common/nfslocalio.c methods' locking
to reduce work performed with spinlocks held in general.
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
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This global spinlock protects all nfs_uuid_t relative to the global
nfs_uuids list. A later commit will split this global spinlock so
prepare by renaming this lock to reflect its intended narrow scope.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
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Also update Documentation/filesystems/nfs/localio.rst accordingly
and reduce the technical documentation debt that was previously
captured in that document.
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
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In later a commit LOCALIO must call both nfsd_file_get and
nfsd_file_put to manage extra nfsd_file references.
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
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Add nfs_to_nfsd_file_put_local() interface to fix race with nfsd
module unload. Similarly, use RCU around nfs_open_local_fh()'s error
path call to nfs_to->nfsd_serv_put(). Holding RCU ensures that NFS
will safely _call and return_ from its nfs_to calls into the NFSD
functions nfsd_file_put_local() and nfsd_serv_put().
Otherwise, if RCU isn't used then there is a narrow window when NFS's
reference for the nfsd_file and nfsd_serv are dropped and the NFSD
module could be unloaded, which could result in a crash from the
return instruction for either nfs_to->nfsd_file_put_local() or
nfs_to->nfsd_serv_put().
Reported-by: NeilBrown <neilb@suse.de>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
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The LOCALIO auxiliary RPC protocol consists of a single "UUID_IS_LOCAL"
RPC method that allows the Linux NFS client to verify the local Linux
NFS server can see the nonce (single-use UUID) the client generated and
made available in nfs_common. The server expects this protocol to use
the same transport as NFS and NFSACL for its RPCs. This protocol
isn't part of an IETF standard, nor does it need to be considering it
is Linux-to-Linux auxiliary RPC protocol that amounts to an
implementation detail.
The UUID_IS_LOCAL method encodes the client generated uuid_t in terms of
the fixed UUID_SIZE (16 bytes). The fixed size opaque encode and decode
XDR methods are used instead of the less efficient variable sized
methods.
The RPC program number for the NFS_LOCALIO_PROGRAM is 400122 (as assigned
by IANA, see https://www.iana.org/assignments/rpc-program-numbers/ ):
Linux Kernel Organization 400122 nfslocalio
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
[neilb: factored out and simplified single localio protocol]
Co-developed-by: NeilBrown <neilb@suse.de>
Signed-off-by: NeilBrown <neilb@suse.de>
Acked-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
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Add server support for bypassing NFS for localhost reads, writes, and
commits. This is only useful when both the client and server are
running on the same host.
If nfsd_open_local_fh() fails then the NFS client will both retry and
fallback to normal network-based read, write and commit operations if
localio is no longer supported.
Care is taken to ensure the same NFS security mechanisms are used
(authentication, etc) regardless of whether localio or regular NFS
access is used. The auth_domain established as part of the traditional
NFS client access to the NFS server is also used for localio. Store
auth_domain for localio in nfsd_uuid_t and transfer it to the client
if it is local to the server.
Relative to containers, localio gives the client access to the network
namespace the server has. This is required to allow the client to
access the server's per-namespace nfsd_net struct.
This commit also introduces the use of NFSD's percpu_ref to interlock
nfsd_destroy_serv and nfsd_open_local_fh, to ensure nn->nfsd_serv is
not destroyed while in use by nfsd_open_local_fh and other LOCALIO
client code.
CONFIG_NFS_LOCALIO enables NFS server support for LOCALIO.
Signed-off-by: Weston Andros Adamson <dros@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Co-developed-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Co-developed-by: NeilBrown <neilb@suse.de>
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
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