Commit graph

14904 commits

Author SHA1 Message Date
Chuck Lever
7630c852e1 NFS: Refactor NFSv4 text-based mount option validation
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>
2009-09-08 19:49:57 -04:00
Chuck Lever
4cfd74fc99 NFS: Mount option parser should detect missing "port="
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>
2009-09-08 19:49:47 -04:00
Harshula Jayasuriya
dbab8360ed NFS: out of date comment regarding O_EXCL above nfs3_proc_create()
Hi Trond,

Recently we were observing the behaviour difference between a 2.4.x and
2.6.x kernel with respect to O_EXCL. A comment from 2.4.x era, "For now,
we don't implement O_EXCL." seems inaccurate in TOT.

If so, here's a patch to remove the comment.

This patch is against:
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6

Signed-off-by: Harshula Jayasuriya <harshula@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-09-08 19:49:33 -04:00
Chuck Lever
5eecfde615 NFS: Handle a zero-length auth flavor list
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>
2009-08-23 23:43:57 -04:00
Jan Kara
e1af88a1ad nfs: Remove reference to generic_osync_inode from a comment
generic_file_direct_write() no longer calls generic_osync_inode() so remove the
comment.

CC: linux-nfs@vger.kernel.org
CC: Neil Brown <neilb@suse.de>
CC: "J. Bruce Fields" <bfields@fieldses.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-08-19 19:48:08 -04:00
Trond Myklebust
7d7ea88289 NFS: Use the DNS resolver in the mount code.
In the referral code, use it to look up the new server's ip address if the
fs_locations attribute contains a hostname.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-08-19 18:22:15 -04:00
Trond Myklebust
e571cbf1a4 NFS: Add a dns resolver for use with NFSv4 referrals and migration
The NFSv4 and NFSv4.1 protocols both allow for the redirection of a client
from one server to another in order to support filesystem migration and
replication. For full protocol support, we need to add the ability to
convert a DNS host name into an IP address that we can feed to the RPC
client.

We'll reuse the sunrpc cache, now that it has been converted to work with
rpc_pipefs.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-08-19 18:22:15 -04:00
Trond Myklebust
6a396f67d2 Merge branch 'nfsv4_xdr_cleanups-for-2.6.32' into nfs-for-2.6.32
Conflicts:
	fs/nfs/nfs4xdr.c
2009-08-19 18:21:52 -04:00
Benny Halevy
cccddf4f55 nfs: nfs4xdr: optimize low level decoding
do not increment decoding ptr if not needed.

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-08-14 14:02:26 -04:00
Benny Halevy
c0eae66ece nfs: nfs4xdr: get rid of READ_BUF
Use xdr_inline_decode instead.
Open code debug printout and error return.

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-08-14 14:02:23 -04:00
Benny Halevy
2460ba57c4 nfs: nfs4xdr: simplify decode_exchange_id by reusing decode_opaque_inline
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-08-14 14:02:20 -04:00
Benny Halevy
99398d0655 nfs: nfs4xdr: get rid of COPYMEM
Just directly call memcpy.

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-08-14 14:02:17 -04:00
Benny Halevy
e78291e4e0 nfs: nfs4xdr: introduce decode_sessionid helper
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-08-14 14:02:14 -04:00
Benny Halevy
db942bbd09 nfs: nfs4xdr: introduce decode_verifier helper
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
[Trond: Fixed up an 'uninitialised variable' issue in decode_readdir]
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-08-14 13:57:58 -04:00
Benny Halevy
07d30434cf nfs: nfs4xdr: introduce decode_opaque_fixed and decode_stateid helpers
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-08-14 13:26:27 -04:00
Benny Halevy
686841b3cc nfs: nfs4xdr: introduce print_overflow_msg
Part fo the nfs4xdr cleanup.  READ_BUF will go away.

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-08-14 13:24:38 -04:00
Benny Halevy
c816fd3406 nfs: nfs4xdr: get rid of READTIME
It has no users.

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-08-14 13:24:32 -04:00
Benny Halevy
3ceb4dbb99 nfs: nfs4xdr: get rid of READ64
s/READ64\(\*(.*)\)/p = xdr_decode_hyper(p, \1)/
s/READ64\((.*)\)/p = xdr_decode_hyper(p, &\1)/

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-08-14 13:24:13 -04:00
Benny Halevy
6f723f7710 nfs: nfs4xdr: get rid of READ32
s/READ32\((.*)\)/\1 = be32_to_cpup(p++)/

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-08-14 13:23:58 -04:00
Benny Halevy
811652bd6e nfs: nfs4xdr: merge xdr_encode_int+xdr_encode_opaque_fixed into xdr_encode_opaque
use encode_string where appropriate.

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-08-14 13:19:24 -04:00
Benny Halevy
345585132a nfs: nfs4xdr: optimize low level encoding
do not increment encoding ptr if not needed.

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-08-14 13:18:03 -04:00
Benny Halevy
13c65ce900 nfs: nfs4xdr: change RESERVE_SPACE macro into a static helper
In order to open code and expose the result pointer assignment.

Alternatively, we can open code the call to xdr_reserve_space
and do the BUG_ON an the error case at the call site.

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-08-14 13:17:17 -04:00
Benny Halevy
2220f13a8b nfs: nfs4xdr: encode_compound_hdr does not have to round up reserved bytes
This is already done by xdr_reserve_space and since encode_compound_hdr
is adding a byte count to "12" which is already word aligned, the xdr
level rounding will work just as well.

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-08-14 13:16:00 -04:00
Benny Halevy
42edd69812 nfs: nfs4xdr: optimize RESERVE_SPACE in encode_create_session and encode_sequence
Coalesce multilpe constant RESERVE_SPACEs into one

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-08-14 13:15:20 -04:00
Benny Halevy
93f0cf2594 nfs: nfs4xdr: get rid of WRITEMEM
s/WRITEMEM(/p = xdr_encode_opaque_fixed(p, /

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-08-14 13:13:58 -04:00
Benny Halevy
b95be5a976 nfs: nfs4xdr: get rid of WRITE64
s/WRITE64/p = xdr_encode_hyper(p, /

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-08-14 13:13:15 -04:00
Benny Halevy
e75bc1c89e nfs: nfs4xdr: get rid of WRITE32
s/WRITE32/*p++ = cpu_to_be32/

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-08-14 13:12:55 -04:00
Linus Torvalds
bc7af9ba15 Merge branch 'upstream-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jlbec/ocfs2
* 'upstream-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jlbec/ocfs2: (22 commits)
  ocfs2: Fix possible deadlock when extending quota file
  ocfs2: keep index within status_map[]
  ocfs2: Initialize the cluster we're writing to in a non-sparse extend
  ocfs2: Remove redundant BUG_ON in __dlm_queue_ast()
  ocfs2/quota: Release lock for error in ocfs2_quota_write.
  ocfs2: Define credit counts for quota operations
  ocfs2: Remove syncjiff field from quota info
  ocfs2: Fix initialization of blockcheck stats
  ocfs2: Zero out padding of on disk dquot structure
  ocfs2: Initialize blocks allocated to local quota file
  ocfs2: Mark buffer uptodate before calling ocfs2_journal_access_dq()
  ocfs2: Make global quota files blocksize aligned
  ocfs2: Use ocfs2_rec_clusters in ocfs2_adjust_adjacent_records.
  ocfs2: Fix deadlock on umount
  ocfs2: Add extra credits and access the modified bh in update_edge_lengths.
  ocfs2: Fail ocfs2_get_block() immediately when a block needs allocation
  ocfs2: Fix error return in ocfs2_write_cluster()
  ocfs2: Fix compilation warning for fs/ocfs2/xattr.c
  ocfs2: Initialize count in aio_write before generic_write_checks
  ocfs2: log the actual return value of ocfs2_file_aio_write()
  ...
2009-08-13 11:17:40 -07:00
Linus Torvalds
78efd1ddd9 Merge branch 'for-linus' of git://oss.sgi.com/xfs/xfs
* 'for-linus' of git://oss.sgi.com/xfs/xfs:
  xfs: fix spin_is_locked assert on uni-processor builds
  xfs: check for dinode realtime flag corruption
  use XFS_CORRUPTION_ERROR in xfs_btree_check_sblock
  xfs: switch to NOFS allocation under i_lock in xfs_attr_rmtval_get
  xfs: switch to NOFS allocation under i_lock in xfs_readlink_bmap
  xfs: switch to NOFS allocation under i_lock in xfs_attr_rmtval_set
  xfs: switch to NOFS allocation under i_lock in xfs_buf_associate_memory
  xfs: switch to NOFS allocation under i_lock in xfs_dir_cilookup_result
  xfs: switch to NOFS allocation under i_lock in xfs_da_buf_make
  xfs: switch to NOFS allocation under i_lock in xfs_da_state_alloc
  xfs: switch to NOFS allocation under i_lock in xfs_getbmap
  xfs: avoid memory allocation under m_peraglock in growfs code
2009-08-12 08:49:35 -07:00
Trond Myklebust
1ae88b2e44 NFS: Fix an O_DIRECT Oops...
We can't call nfs_readdata_release()/nfs_writedata_release() without
first initialising and referencing args.context. Doing so inside
nfs_direct_read_schedule_segment()/nfs_direct_write_schedule_segment()
causes an Oops.

We should rather be calling nfs_readdata_free()/nfs_writedata_free() in
those cases.

Looking at the O_DIRECT code, the "struct nfs_direct_req" is already
referencing the nfs_open_context for us. Since the readdata and writedata
structures carry a reference to that, we can simplify things by getting rid
of the extra nfs_open_context references, so that we can replace all
instances of nfs_readdata_release()/nfs_writedata_release().

Reported-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Tested-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-08-12 08:21:39 -07:00
Christoph Hellwig
a8914f3a6d xfs: fix spin_is_locked assert on uni-processor builds
Without SMP or preemption spin_is_locked always returns false,
so we can't do an assert with it.  Instead use assert_spin_locked,
which does the right thing on all builds.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Eric Sandeen <sandeen@sandeen.net>
Reported-by: Johannes Engel <jcnengel@googlemail.com>
Tested-by: Johannes Engel <jcnengel@googlemail.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>
2009-08-12 01:08:27 -05:00
Christoph Hellwig
b89d4208de xfs: check for dinode realtime flag corruption
Ramon tested XFS with a modified version of fsfuzzer and hit a NULL
pointer dereference in __xfs_get_blocks due to the RT device target
pointer being NULL.

To fix this reject inode with the realtime bit set on a a filesystem
without an RT subvolume during inode read.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Eric Sandeen <sandeen@sandeen.net>
Reviewed-by: Felix Blyakher <felixb@sgi.com>
Reported-by: Ramon de Carvalho Valle <ramon@risesecurity.org>
Tested-by: Ramon de Carvalho Valle <ramon@risesecurity.org>
Signed-off-by: Felix Blyakher <felixb@sgi.com>
2009-08-12 01:08:21 -05:00
Eric Sandeen
e0c222c411 use XFS_CORRUPTION_ERROR in xfs_btree_check_sblock
In Red Hat Bug 512552
 - Can't write to XFS mount during raid5 resync

a user ran into corruption while resyncing a raid, and we failed
a consistency test, but didn't get much more info; it'd be nice
to call XFS_CORRUPTION_ERROR here so we can see the buffer
contents.

Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Felix Blyakher <felixb@sgi.com>
2009-08-12 01:08:10 -05:00
Christoph Hellwig
ddd3a14e0f xfs: switch to NOFS allocation under i_lock in xfs_attr_rmtval_get
xfs_attr_rmtval_get is always called with i_lock held, but i_lock is taken
in reclaim context so all allocations under it must avoid recursions into
the filesystem.

Reported by the new reclaim context tracing in lockdep.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Felix Blyakher <felixb@sgi.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>
2009-08-12 01:08:01 -05:00
Christoph Hellwig
7b02ecb303 xfs: switch to NOFS allocation under i_lock in xfs_readlink_bmap
xfs_readlink_bmap is called with i_lock held, but i_lock is taken in
reclaim context so all allocations under it must avoid recursions into
the filesystem.

Reported by the new reclaim context tracing in lockdep.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Felix Blyakher <felixb@sgi.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>
2009-08-12 01:07:53 -05:00
Christoph Hellwig
10746e47e7 xfs: switch to NOFS allocation under i_lock in xfs_attr_rmtval_set
xfs_attr_rmtval_set is always called with i_lock held, and i_lock is taken
in reclaim context so all allocations under it must avoid recursions into
the filesystem.

Reported by the new reclaim context tracing in lockdep.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Felix Blyakher <felixb@sgi.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>
2009-08-12 01:07:44 -05:00
Christoph Hellwig
36fae17a64 xfs: switch to NOFS allocation under i_lock in xfs_buf_associate_memory
xfs_buf_associate_memory is used for setting up the spare buffer for the
log wrap case in xlog_sync which can happen under i_lock when called from
xfs_fsync. The i_lock mutex is taken in reclaim context so all allocations
under it must avoid recursions into the filesystem.  There are a couple
more uses of xfs_buf_associate_memory in the log recovery code that are
also affected by this, but I'd rather keep the code simple than passing on
a gfp_mask argument.  Longer term we should just stop requiring the memoery
allocation in xlog_sync by some smaller rework of the buffer layer.

Reported by the new reclaim context tracing in lockdep.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Felix Blyakher <felixb@sgi.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>
2009-08-12 01:07:38 -05:00
Christoph Hellwig
3f52c2f0a0 xfs: switch to NOFS allocation under i_lock in xfs_dir_cilookup_result
xfs_dir_cilookup_result is always called with i_lock held, but i_lock is taken
in reclaim context so all allocations under it must avoid recursions into the
filesystem.

Reported by the new reclaim context tracing in lockdep.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Felix Blyakher <felixb@sgi.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>
2009-08-12 01:07:23 -05:00
Christoph Hellwig
73195ed786 xfs: switch to NOFS allocation under i_lock in xfs_da_buf_make
i_lock is taken in the reclaim context so all allocations under it
must avoid recursions into the filesystem.

Reported by the new reclaim context tracing in lockdep.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Felix Blyakher <felixb@sgi.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>
2009-08-12 01:07:14 -05:00
Christoph Hellwig
f41d7fb9da xfs: switch to NOFS allocation under i_lock in xfs_da_state_alloc
xfs_da_state_alloc is always called with i_lock held, but i_lock is taken in
reclaim context so all allocations under it must avoid recursions into the
filesystem.

Reported by the new reclaim context tracing in lockdep.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Felix Blyakher <felixb@sgi.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>
2009-08-12 01:07:07 -05:00
Christoph Hellwig
ca35dcd6ca xfs: switch to NOFS allocation under i_lock in xfs_getbmap
xfs_getbmap allocates memory with i_lock held, but i_lock is taken in
reclaim context so all allocations under it must avoid recursions into
the filesystem.

Reported by the new reclaim context tracing in lockdep.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Felix Blyakher <felixb@sgi.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>
2009-08-12 01:06:59 -05:00
Christoph Hellwig
0cc6eee130 xfs: avoid memory allocation under m_peraglock in growfs code
Allocate the memory for the larger m_perag array before taking the
per-AG lock as the per-AG lock can be taken under the i_lock which
can be taken from reclaim context.

Reported by the new reclaim context tracing in lockdep.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Felix Blyakher <felixb@sgi.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>
2009-08-12 01:06:51 -05:00
Trond Myklebust
f884dcaead Merge branch 'sunrpc_cache-for-2.6.32' into nfs-for-2.6.32 2009-08-10 17:45:58 -04:00
Trond Myklebust
976a6f921c Merge branch 'patches_cel-for-2.6.32' into nfs-for-2.6.32 2009-08-10 17:45:50 -04:00
Jan Kara
b409d7a0ab ocfs2: Fix possible deadlock when extending quota file
In OCFS2, allocator locks rank above transaction start. Thus we
cannot extend quota file from inside a transaction less we could
deadlock.

We solve the problem by starting transaction not already in
ocfs2_acquire_dquot() but only in ocfs2_local_read_dquot() and
ocfs2_global_read_dquot() and we allocate blocks to quota files before starting
the transaction.  In case we crash, quota files will just have a few blocks
more but that's no problem since we just use them next time we extend the
quota file.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
2009-08-10 12:20:22 -07:00
Bartlomiej Zolnierkiewicz
e576e05a73 nfs: remove superfluous BUG_ON()s
Subject: [PATCH] nfs: remove superfluous BUG_ON()s

Remove duplicated BUG_ON()s from nfs[4]_create_server()
(we make the same checks earlier in both functions).

This takes care of the following entries from Dan's list:

fs/nfs/client.c +1078 nfs_create_server(47) warning: variable derefenced before check 'server->nfs_client'
fs/nfs/client.c +1079 nfs_create_server(48) warning: variable derefenced before check 'server->nfs_client->rpc_ops'
fs/nfs/client.c +1363 nfs4_create_server(43) warning: variable derefenced before check 'server->nfs_client'
fs/nfs/client.c +1364 nfs4_create_server(44) warning: variable derefenced before check 'server->nfs_

Reported-by: Dan Carpenter <error27@gmail.com>
Cc: corbet@lwn.net
Cc: eteo@redhat.com
Cc: Julia Lawall <julia@diku.dk>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-08-10 08:54:16 -04:00
Peter Staubach
38c73044f5 NFS: read-modify-write page updating
Hi.

I have a proposal for possibly resolving this issue.

I believe that this situation occurs due to the way that the
Linux NFS client handles writes which modify partial pages.

The Linux NFS client handles partial page modifications by
allocating a page from the page cache, copying the data from
the user level into the page, and then keeping track of the
offset and length of the modified portions of the page.  The
page is not marked as up to date because there are portions
of the page which do not contain valid file contents.

When a read call comes in for a portion of the page, the
contents of the page must be read in the from the server.
However, since the page may already contain some modified
data, that modified data must be written to the server
before the file contents can be read back in the from server.
And, since the writing and reading can not be done atomically,
the data must be written and committed to stable storage on
the server for safety purposes.  This means either a
FILE_SYNC WRITE or a UNSTABLE WRITE followed by a COMMIT.
This has been discussed at length previously.

This algorithm could be described as modify-write-read.  It
is most efficient when the application only updates pages
and does not read them.

My proposed solution is to add a heuristic to decide whether
to do this modify-write-read algorithm or switch to a read-
modify-write algorithm when initially allocating the page
in the write system call path.  The heuristic uses the modes
that the file was opened with, the offset in the page to
read from, and the size of the region to read.

If the file was opened for reading in addition to writing
and the page would not be filled completely with data from
the user level, then read in the old contents of the page
and mark it as Uptodate before copying in the new data.  If
the page would be completely filled with data from the user
level, then there would be no reason to read in the old
contents because they would just be copied over.

This would optimize for applications which randomly access
and update portions of files.  The linkage editor for the
C compiler is an example of such a thing.

I tested the attached patch by using rpmbuild to build the
current Fedora rawhide kernel.  The kernel without the
patch generated about 269,500 WRITE requests.  The modified
kernel containing the patch generated about 261,000 WRITE
requests.  Thus, about 8,500 fewer WRITE requests were
generated.  I suspect that many of these additional
WRITE requests were probably FILE_SYNC requests to WRITE
a single page, but I didn't test this theory.

The difference between this patch and the previous one was
to remove the unneeded PageDirty() test.  I then retested to
ensure that the resulting system continued to behave as
desired.

	Thanx...

		ps

Signed-off-by: Peter Staubach <staubach@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-08-10 08:54:16 -04:00
Trond Myklebust
074cc1deec NFS: Add a ->migratepage() aop for NFS
Make NFS a bit more friendly to NUMA and memory hot removal...

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2009-08-10 08:54:13 -04:00
Oleg Nesterov
704b836cbf mm_for_maps: take ->cred_guard_mutex to fix the race with exec
The problem is minor, but without ->cred_guard_mutex held we can race
with exec() and get the new ->mm but check old creds.

Now we do not need to re-check task->mm after ptrace_may_access(), it
can't be changed to the new mm under us.

Strictly speaking, this also fixes another very minor problem. Unless
security check fails or the task exits mm_for_maps() should never
return NULL, the caller should get either old or new ->mm.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
2009-08-10 20:49:26 +10:00
Oleg Nesterov
00f89d2185 mm_for_maps: shift down_read(mmap_sem) to the caller
mm_for_maps() takes ->mmap_sem after security checks, this looks
strange and obfuscates the locking rules. Move this lock to its
single caller, m_start().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
2009-08-10 20:48:32 +10:00