Brian Behlendorf writes:

The root cause of the NFS hang we were observing appears to be a rare
deadlock between the kernel provided usermodehelper API and the linux NFS
client.  The deadlock can arise because both of these services use the
generic linux work queues.  The usermodehelper API run the specified user
application in the context of the work queue.  And NFS submits both cleanup
and reconnect work to the generic work queue for handling.  Normally this
is fine but a deadlock can result in the following situation.

  - NFS client is in a disconnected state
  - [events/0] runs a usermodehelper app with an NFS dependent operation,
    this triggers an NFS reconnect.
  - NFS reconnect happens to be submitted to [events/0] work queue.
  - Deadlock, the [events/0] work queue will never process the
    reconnect because it is blocked on the previous NFS dependent
    operation which will not complete.`

The solution is simply to run reconnect requests on rpciod.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Ensures that an rpc_client always has the possibility to send asynchronous
RPC calls.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Instead of taking the mutex every time we just need to increment/decrement
rpciod_users, we can optmise by using atomic_inc_not_zero and
atomic_dec_and_test.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

The kref now does most of what cl_count + cl_user used to do. The only
remaining role for cl_count is to tell us if we are in a 'shutdown'
phase. We can provide that information using a single bit field instead
of a full atomic counter.

Also rename rpc_destroy_client() to rpc_close_client(), which reflects
better what its role is these days.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Replace it with explicit calls to rpc_shutdown_client() or
rpc_destroy_client() (for the case of asynchronous calls).
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Its use is at best racy, and there is only one user (lockd), which has
additional locking that makes the whole thing redundant.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Use that to protect the rpc_clnt->cl_tasks list instead of using a global
lock.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Also ensure that nfs_inode ncommit and npages are large enough to represent
all possible values for the number of pages.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Add a tag for requests that are waiting for a COMMIT
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

The nfs_access_cache_shrinker may race with nfs_access_zap_cache().
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Also get rid of a redundant call to nfs_setattr_update_inode(). The call to
nfs3_proc_setattr() already takes care of that.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

The Linux NFS4 client simply skips over the bitmask in an O_EXCL open
call and so it doesn't bother to reset any fields that may be holding
the verifier. This patch has us save the first two words of the bitmask
(which is all the current client has #defines for). The client then
later checks this bitmask and turns on the appropriate flags in the
sattr->ia_verify field for the following SETATTR call.

This patch only currently checks to see if the server used the atime
and mtime slots for the verifier (which is what the Linux server uses
for this). I'm not sure of what other fields the server could
reasonably use, but adding checks for others should be trivial.
Signed-off-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

They disappeared some time around 2.6.18.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

nfs_symlink() allocates a GFP_KERNEL page for the pagecache. Most
pagecache pages are allocated using GFP_HIGHUSER, and there's no reason
not to do that in nfs_symlink() as well.
Signed-off-by: NJeff Layton <jlayton@redhat.com>

We don't need to revalidate the fsid on the root directory. It suffices to
revalidate it on the current directory.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Use rpc_run_task() instead of doing it ourselves.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

nfs4_do_close() does not currently have any way to ensure that the user
won't attempt to unmount the partition while the asynchronous RPC call
is completing. This again may cause Oopses in nfs_update_inode().

Add a vfsmount argument to nfs4_close_state to ensure that the partition
remains mounted while we're closing the file.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

A number of race conditions may currently ensue if the user presses ^C
and then unmounts the partition while an asynchronous open() is in
progress.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Since PG_uptodate may now end up getting set during the call to
nfs_wb_page(), we can avoid putting a read request on the wire in those
situations.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

The write may fail, so we should not mark the page as uptodate until we are
certain that the data has been accepted and written to disk by the server.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

There is no need to fail the entire O_DIRECT read/write just because
get_user_pages() returned fewer pages than we requested.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Add the termios2 structure ready for enabling on most platforms.  One or
two like Sparc are plain weird so have been left alone.  Most can use the
same structure as ktermios for termios2 (ie the newer ioctl uses the
structure matching the current kernel structure)
Signed-off-by: NAlan Cox <alan@redhat.com>
Cc: Bryan Wu <bryan.wu@analog.com>
Cc: Ian Molton <spyro@f2s.com>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Mikael Starvik <starvik@axis.com>
Cc: David Howells <dhowells@redhat.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Hirokazu Takata <takata@linux-m32r.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Cc: Matthew Wilcox <willy@debian.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Kazumoto Kojima <kkojima@rr.iij4u.or.jp>
Cc: Richard Curnow <rc@rc0.org.uk>
Cc: Miles Bader <uclinux-v850@lsi.nec.co.jp>
Cc: Chris Zankel <chris@zankel.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Many places in kernel use seq_file API to iterate over a regular list_head.
The code for such iteration is identical in all the places, so it's worth
introducing a common helpers.

This makes code about 300 lines smaller:

The first version of this patch made the helper functions static inline
in the seq_file.h header. This patch moves them to the fs/seq_file.c as
Andrew proposed. The vmlinux .text section sizes are as follows:

2.6.22-rc1-mm1:              0x001794d5
with the previous version:   0x00179505
with this patch:             0x00179135

The config file used was make allnoconfig with the "y" inclusion of all
the possible options to make the files modified by the patch compile plus
drivers I have on the test node.

This patch:

Many places in kernel use seq_file API to iterate over a regular list_head.
The code for such iteration is identical in all the places, so it's worth
introducing a common helpers.
Signed-off-by: NPavel Emelianov <xemul@openvz.org>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>