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nfs_path() returns an ERR_PTR(), it doesn't return null.
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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implicit slab.h inclusion from percpu.h
percpu.h is included by sched.h and module.h and thus ends up being
included when building most .c files. percpu.h includes slab.h which
in turn includes gfp.h making everything defined by the two files
universally available and complicating inclusion dependencies.
percpu.h -> slab.h dependency is about to be removed. Prepare for
this change by updating users of gfp and slab facilities include those
headers directly instead of assuming availability. As this conversion
needs to touch large number of source files, the following script is
used as the basis of conversion.
http://userweb.kernel.org/~tj/misc/slabh-sweep.py
The script does the followings.
* Scan files for gfp and slab usages and update includes such that
only the necessary includes are there. ie. if only gfp is used,
gfp.h, if slab is used, slab.h.
* When the script inserts a new include, it looks at the include
blocks and try to put the new include such that its order conforms
to its surrounding. It's put in the include block which contains
core kernel includes, in the same order that the rest are ordered -
alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
doesn't seem to be any matching order.
* If the script can't find a place to put a new include (mostly
because the file doesn't have fitting include block), it prints out
an error message indicating which .h file needs to be added to the
file.
The conversion was done in the following steps.
1. The initial automatic conversion of all .c files updated slightly
over 4000 files, deleting around 700 includes and adding ~480 gfp.h
and ~3000 slab.h inclusions. The script emitted errors for ~400
files.
2. Each error was manually checked. Some didn't need the inclusion,
some needed manual addition while adding it to implementation .h or
embedding .c file was more appropriate for others. This step added
inclusions to around 150 files.
3. The script was run again and the output was compared to the edits
from #2 to make sure no file was left behind.
4. Several build tests were done and a couple of problems were fixed.
e.g. lib/decompress_*.c used malloc/free() wrappers around slab
APIs requiring slab.h to be added manually.
5. The script was run on all .h files but without automatically
editing them as sprinkling gfp.h and slab.h inclusions around .h
files could easily lead to inclusion dependency hell. Most gfp.h
inclusion directives were ignored as stuff from gfp.h was usually
wildly available and often used in preprocessor macros. Each
slab.h inclusion directive was examined and added manually as
necessary.
6. percpu.h was updated not to include slab.h.
7. Build test were done on the following configurations and failures
were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my
distributed build env didn't work with gcov compiles) and a few
more options had to be turned off depending on archs to make things
build (like ipr on powerpc/64 which failed due to missing writeq).
* x86 and x86_64 UP and SMP allmodconfig and a custom test config.
* powerpc and powerpc64 SMP allmodconfig
* sparc and sparc64 SMP allmodconfig
* ia64 SMP allmodconfig
* s390 SMP allmodconfig
* alpha SMP allmodconfig
* um on x86_64 SMP allmodconfig
8. percpu.h modifications were reverted so that it could be applied as
a separate patch and serve as bisection point.
Given the fact that I had only a couple of failures from tests on step
6, I'm fairly confident about the coverage of this conversion patch.
If there is a breakage, it's likely to be something in one of the arch
headers which should be easily discoverable easily on most builds of
the specific arch.
Signed-off-by: Tejun Heo <tj@kernel.org>
Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
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bdi_unregister is called by nfs_put_super which is only called by
generic_shutdown_super if ->s_root is not NULL. So if we error out
in a circumstance where we called nfs_bdi_register (i.e. server !=
NULL) but have not set s_root, then we need to call bdi_unregister
explicitly in nfs_get_sb and various other *_get_sb() functions.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Ensure that we unregister the bdi before kill_anon_super() calls
ida_remove() on our device name.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@kernel.org
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This reverts commit e9496ff46a20a8592fdc7bdaaf41b45eb808d310. Quoth Al:
"it's dependent on a lot of other stuff not currently in mainline
and badly broken with current fs/namespace.c. Sorry, badly
out-of-order cherry-pick from old queue.
PS: there's a large pending series reworking the refcounting and
lifetime rules for vfsmounts that will, among other things, allow to
rip a subtree away _without_ dissolving connections in it, to be
garbage-collected when all active references are gone. It's
considerably saner wrt "is the subtree busy" logics, but it's nowhere
near being ready for merge at the moment; this changeset is one of the
things becoming possible with that sucker, but it certainly shouldn't
have been picked during this cycle. My apologies..."
Noticed-by: Eric Paris <eparis@redhat.com>
Requested-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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When the "rsize=" or "wsize=" mount options are not specified,
text-based mounts have slightly different behavior than legacy binary
mounts. Text-based mounts use the smaller of the server's maximum
and the client's maximum, but binary mounts use the smaller of the
server's _preferred_ size and the client's maximum.
This difference is actually pretty subtle. Most servers advertise
the same value as their maximum and their preferred transfer size, so
the end result is the same in most cases.
The reason for this difference is that for text-based mounts, if
r/wsize are not specified, they are set to the largest value supported
by the client. For legacy mounts, the values are set to zero if these
options are not specified.
nfs_server_set_fsinfo() can negotiate the transfer size defaults
correctly in any case. There's no need to specify any particular
value as default in the text-based option parsing logic.
Note that nfs4 doesn't use nfs_server_set_fsinfo(), but the mount.nfs4
command does set rsize and wsize to 0 if the user didn't specify these
options. So, make the same change for text-based NFSv4 mounts.
Thanks to James Pearson <james-p@moving-picture.com> for reporting and
diagnosing the problem.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Recent changes to snprintf() introduced the %pI6c formatter, which can
display an IPv6 address with standard shorthanding. Use this new
formatter when displaying IPv6 server addresses in /proc/mounts.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Solaris uses netids as values for the proto= option, so that when
someone specifies "tcp6" they get traffic over TCP + IPv6. Until
recently, this has never really been an issue for Linux since it didn't
support NFS over IPv6. The netid and the protocol name were generally
always the same (modulo any strange configuration in /etc/netconfig).
The solaris manpage documents their proto= option as:
proto= _netid_ | rdma
This patch is intended to bring Linux closer to how the Solaris proto=
option works, by declaring a static netid mapping in the kernel and
converting the proto= and mountproto= options to follow it and display
the proper values in /proc/mounts.
Much of this functionality will need to be provided by a userspace
mount.nfs patch. Chuck Lever has a patch to change mount.nfs in
the same way. In principle, we could do *all* of this in userspace but
that would mean that the options in /proc/mounts may not match the
options used by userspace.
The alternative to the static mapping here is to add a mechanism to
upcall to userspace for netid's. I'm not opposed to that option, but
it'll probably mean more overhead (and quite a bit more code). Rather
than shoot for that at first, I figured it was probably better to
start simply.
Comments welcome.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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None of the code in nfs_umount_begin() or nfs_remount() has any BKL
dependency.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Fix a (small) memory leak in one of the error paths of the NFS mount
options parsing code.
Regression introduced in 2.6.30 by commit a67d18f (NFS: load the
rpc/rdma transport module automatically).
Reported-by: Yinghai Lu <yinghai@kernel.org>
Reported-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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struct sockaddr_storage * can safely be used as struct sockaddr *.
Suppress an "incompatible pointer type" warning.
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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The NFSv4 renew daemon is shared between all active super blocks that refer
to a particular NFS server, so it is wrong to be shutting it down in
nfs4_kill_super every time a super block is destroyed.
This patch therefore kills nfs4_renewd_prepare_shutdown altogether, and
leaves it up to nfs4_shutdown_client() to also shut down the renew daemon
by means of the existing call to nfs4_kill_renewd().
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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The recent changeset 53a0b9c4c99ab0085a06421f71592722e5b3fd5f (NFS: Replace
nfs_parse_ip_address() with rpc_pton()) broke nfs_remount, since the call
to rpc_pton() will zero out the port number in data->nfs_server.address.
This is actually due to a bug in nfs_remount: it should be looking at the
port number in nfs_server.port instead...
This fixes bug
http://bugzilla.kernel.org/show_bug.cgi?id=14276
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Currently, the port and mount port will both display as 65535 if you do not
specify a port number. That would be wrong...
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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With the recent spate of changes, the nfs protocol version will now default
to 2 instead of 3, while the mount protocol version defaults to 3.
The following patch should ensure the defaults are consistent with the
previous defaults of vers=3,proto=tcp,mountvers=3,mountproto=tcp.
This fixes the bug
http://bugzilla.kernel.org/show_bug.cgi?id=14259
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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We forget to set nfs_server.protocol in tcp case when old-style binary
options are passed to mount. The thing remains zero and never validated
afterwards. As the result, we hit BUG in fs/nfs/client.c:588.
Breakage has been introduced in NFS: Add nfs_alloc_parsed_mount_data
merged yesterday...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Propagate the NFS 'fsc' mount option through NFS automounts of various types.
This is now required as commit:
commit c02d7adf8c5429727a98bad1d039bccad4c61c50
Author: Trond Myklebust <Trond.Myklebust@netapp.com>
Date: Mon Jun 22 15:09:14 2009 -0400
NFSv4: Replace nfs4_path_walk() with VFS path lookup in a private namespace
uses VFS-driven automounting to reach all submounts barring the root, thus
preventing fscaching from being enabled on any submount other than the root.
This patch gets around that by propagating the NFS_OPTION_FSCACHE flag across
automounts. If a uniquifier is supplied to a mount then this is propagated to
all automounts of that mount too.
Signed-off-by: David Howells <dhowells@redhat.com>
[Trond: Fixed up the definition of nfs_fscache_get_super_cookie for the
case of #undef CONFIG_NFS_FSCACHE]
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Allocating nfs_parsed_mount_data and setting up the defaults is nearly
the same for both nfs and nfs4 mounts.
Both paths seem to use nfs_validate_transport_protocol(), so setting a
default value for nfs_server.protocol ought to be unnecessary.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Keep it in the case of the legacy binary mount interface, but purge it from
the nfs_server structure.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Otherwise we could be attempting to flush data for a writeback
thread and bdi that have already disappeared.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
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We do this automatically in get_sb_bdev() from the set_bdev_super()
callback. Filesystems that have their own private backing_dev_info
must assign that in ->fill_super().
Note that ->s_bdi assignment is required for proper writeback!
Acked-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
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Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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When mounting an "nfs" type file system, recognize "v4," "vers=4," or
"nfsvers=4" mount options, and convert the file system to "nfs4" under
the covers.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
[trondmy: fixed up binary mount code so it sets the 'version' field too]
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Clean up: Refactor nfs4_get_sb() to allow its guts to be invoked by
nfs_get_sb().
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Clean up: Refactor the part of nfs4_validate_mount_options() that
handles text-based options, so we can call it from the NFSv2/v3
option validation function.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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The meaning of not specifying the "port=" mount option is different
for "-t nfs" and "-t nfs4" mounts. The default port value for
NFSv2/v3 mounts is 0, but the default for NFSv4 mounts is 2049.
To support "-t nfs -o vers=4", the mount option parser must detect
when "port=" is missing so that the correct default port value can be
set depending on which NFS version is requested.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Some releases of Linux rpc.mountd (nfs-utils 1.1.4 and later) return an
empty auth flavor list if no sec= was specified for the export. This is
notably broken server behavior.
The new auth flavor list checking added in a recent commit rejects this
case. The OpenSolaris client does too.
The broken mountd implementation is already widely deployed. To avoid
a behavioral regression, the kernel's mount client skips flavor checking
(ie reverts to the pre-2.6.32 behavior) if mountd returns an empty
flavor list.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Clean up.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Clean up: Use the common routine now provided in sunrpc.ko for parsing mount
addresses.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Commit a14017db added support in the kernel's NFS mount client to
decode the authentication flavor list returned by mountd.
The NFS client can now use this list to determine whether the
authentication flavor requested by the user is actually supported
by the server.
Note we don't actually negotiate the security flavor if none was
specified by the user. Instead, we try to use AUTH_SYS, and fail if
the server does not support it. This prevents us from negotiating
an inappropriate security flavor (some servers list AUTH_NULL first).
If the server does not support AUTH_SYS, the user must provide an
appropriate security flavor by specifying the "sec=" mount option.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Previous logic in the NFS mount parsing code path assumed
auth_flavor_len was set to zero for simple authentication flavors
(like AUTH_UNIX), and 1 for compound flavors (like AUTH_GSS).
At some earlier point (maybe even before the option parsers were
merged?) specific checks for auth_flavor_len being zero were removed
from the functions that validate the mount option that sets the mount
point's authentication flavor.
Since we are populating an array for authentication flavors, the
auth_flavor_len should always be set to the number of flavors. Let's
eliminate some cleverness here, and prepare for new logic that needs
to know the number of flavors in the auth_flavors[] array.
(auth_flavors[] is an array because at some point we want to allow a
list of acceptable authentication flavors to be specified via the sec=
mount option. For now it remains a single element array).
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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The new minorversion= mount option (commit 3fd5be9e) was merged at
the same time as the recent sloppy parser fixes (commit a5a16bae),
so minorversion= still uses the old value parsing logic.
If the minorversion= option specifies a bogus value, it should fail
with "bad value" not "bad option."
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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As noted in the previous patch, the NFSv4 client mount code currently
has several limitations. If the mount path contains symlinks, or
referrals, or even if it just contains a '..', then the client code in
nfs4_path_walk() will fail with an error.
This patch replaces the nfs4_path_walk()-based lookup with a helper
function that sets up a private namespace to represent the namespace on the
server, then uses the ordinary VFS and NFS path lookup code to walk down the
mount path in that namespace.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Conflicts:
fs/nfs/client.c
fs/nfs/super.c
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Specifying "port=-5" with the kernel's current mount option parser
generates "unrecognized mount option". If "sloppy" is set, this
causes the mount to succeed and use the default values; the desired
behavior is that, since this is a valid option with an invalid value,
the mount should fail, even with "sloppy."
To properly handle "sloppy" parsing, we need to distinguish between
correct options with invalid values, and incorrect options. We will
need to parse integer values by hand, therefore, and not rely on
match_token().
For instance, these must all fail with "invalid value":
port=12345678
port=-5
port=samuel
and not with "unrecognized option," as they do currently.
Thus, for the sake of match_token() we need to treat the values for
these options as strings, and do the conversion to integers using
strict_strtol().
This is basically the same solution we used for the earlier "retry="
fix (commit ecbb3845), except in this case the kernel actually has to
parse the value, rather than ignore it.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Ian Kent reports:
"I've noticed a couple of other regressions with the options vers
and proto option of mount.nfs(8).
The commands:
mount -t nfs -o vers=<invalid version> <server>:/<path> /<mountpoint>
mount -t nfs -o proto=<invalid proto> <server>:/<path> /<mountpoint>
both immediately fail.
But if the "-s" option is also used they both succeed with the
mount falling back to defaults (by the look of it).
In the past these failed even when the sloppy option was given, as
I think they should. I believe the sloppy option is meant to allow
the mount command to still function for mount options (for example
in shared autofs maps) that exist on other Unix implementations but
aren't present in the Linux mount.nfs(8). So, an invalid value
specified for a known mount option is different to an unknown mount
option and should fail appropriately."
See RH bugzilla 486266.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Solder xdr_stream-based XDR decoding functions into the in-kernel mountd
client that are more careful about checking data types and watching for
buffer overflows. The new MNT3 decoder includes support for auth-flavor
list decoding.
The "_sz" macro for MNT3 replies was missing the size of the file handle.
I've added this back, and included the size of the auth flavor array.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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The "intr" mount option has been deprecated for a while, but
/proc/mounts continues to display "nointr" whether "intr" or "nointr"
has been specified for a mount point.
Since these options do not have any effect, simply do not display
them.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Frees the preallocated backchannel resources that are associated with
this session when the session is destroyed.
A backchannel is currently created once per session. Destroy the backchannel
only when the session is destroyed.
Signed-off-by: Ricardo Labiaga <ricardo.labiaga@netapp.com>
Signed-off-by: Andy Adamson<andros@netapp.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
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NFSv4 should just ignore the 'nolock' option. It is an NFSv2/v3 thing...
This fixes the Oops in http://bugzilla.kernel.org/show_bug.cgi?id=13330
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Implement the destroy_session operation conforming to
http://tools.ietf.org/html/draft-ietf-nfsv4-minorversion1-26
Signed-off-by: Ricardo Labiaga <ricardo.labiaga@netapp.com>
Signed-off-by: Andy Adamson<andros@umich.edu>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
[nfs41: remove extraneous rpc_clnt pointer]
Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
[nfs41; NFS_CS_READY required for DESTROY_SESSION]
Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
[nfs41: pass *session in seq_args and seq_res]
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
[nfs41: fix encode_destroy_session's xdr Xcoding pointer type]
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
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mount -t nfs4 -o minorversion=[0|1] specifies whether to use 4.0 or 4.1.
By default, the minorversion is set to 0.
Signed-off-by: Mike Sager <sager@netapp.com>
[set default minorversion to 0 as per Trond and SteveD's request]
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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[xfs, btrfs, capifs, shmem don't need BKL, exempt]
Signed-off-by: Alessio Igor Bogani <abogani@texware.it>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Push BKL down into ->umount_begin()
Signed-off-by: Alessio Igor Bogani <abogani@texware.it>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Due to an apparent typo, commit a67d18f89f5782806135aad4ee012ff78d45aae7
(NFS: load the rpc/rdma transport module automatically) lead to the
'proto=' mount option doing a double free, while Opt_mountproto leaks a
string.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Add NFS mount options to allow the local caching support to be enabled.
The attached patch makes it possible for the NFS filesystem to be told to make
use of the network filesystem local caching service (FS-Cache).
To be able to use this, a recent nfsutils package is required.
There are three variant NFS mount options that can be added to a mount command
to control caching for a mount. Only the last one specified takes effect:
(*) Adding "fsc" will request caching.
(*) Adding "fsc=<string>" will request caching and also specify a uniquifier.
(*) Adding "nofsc" will disable caching.
For example:
mount warthog:/ /a -o fsc
The cache of a particular superblock (NFS FSID) will be shared between all
mounts of that volume, provided they have the same connection parameters and
are not marked 'nosharecache'.
Where it is otherwise impossible to distinguish superblocks because all the
parameters are identical, but the 'nosharecache' option is supplied, a
uniquifying string must be supplied, else only the first mount will be
permitted to use the cache.
If there's a key collision, then the second mount will disable caching and give
a warning into the kernel log.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Steve Dickson <steved@redhat.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Daire Byrne <Daire.Byrne@framestore.com>
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