Commit graph

4904 commits

Author SHA1 Message Date
NeilBrown 237f8306c3 NFS: don't expect errors from mempool_alloc().
Commit fbe77c30e9 ("NFS: move rw_mode to nfs_pageio_header")
reintroduced some pointless code that commit 518662e0fc ("NFS: fix
usage of mempools.") had recently removed.

Remove it again.

Cc: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-09-06 12:31:15 -04:00
Trond Myklebust 7af7a5963c Merge branch 'bugfixes' 2017-08-20 13:04:12 -04:00
Chuck Lever 53a75f22e7 NFS: Fix NFSv2 security settings
For a while now any NFSv2 mount where sec= is specified uses
AUTH_NULL. If sec= is not specified, the mount uses AUTH_UNIX.
Commit e68fd7c807 ("mount: use sec= that was specified on the
command line") attempted to address a very similar problem with
NFSv3, and should have fixed this too, but it has a bug.

The MNTv1 MNT procedure does not return a list of security flavors,
so our client makes up a list containing just AUTH_NULL. This should
enable nfs_verify_authflavors() to assign the sec= specified flavor,
but instead, it incorrectly sets it to AUTH_NULL.

I expect this would also be a problem for any NFSv3 server whose
MNTv3 MNT procedure returned a security flavor list containing only
AUTH_NULL.

Fixes: e68fd7c807 ("mount: use sec= that was specified on ... ")
BugLink: https://bugzilla.linux-nfs.org/show_bug.cgi?id=310
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-20 12:43:34 -04:00
NeilBrown b79e87e070 NFSv4.1: don't use machine credentials for CLOSE when using 'sec=sys'
An NFSv4.1 client might close a file after the user who opened it has
logged off.  In this case the user's credentials may no longer be
valid, if they are e.g. kerberos credentials that have expired.

NFSv4.1 has a mechanism to allow the client to use machine credentials
to close a file.  However due to a short-coming in the RFC, a CLOSE
with those credentials may not be possible if the file in question
isn't exported to the same security flavor - the required PUTFH must
be rejected when this is the case.

Specifically if a server and client support kerberos in general and
have used it to form a machine credential, but the file is only
exported to "sec=sys", a PUTFH with the machine credentials will fail,
so CLOSE is not possible.

As RPC_AUTH_UNIX (used by sec=sys) credentials can never expire, there
is no value in using the machine credential in place of them.
So in that case, just use the users credentials for CLOSE etc, as you would
in NFSv4.0

Signed-off-by: Neil Brown <neilb@suse.com>
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-20 12:43:17 -04:00
Trond Myklebust 3bde7afdab NFS: Remove unused parameter gfp_flags from nfs_pageio_init()
Now that the mirror allocation has been moved, the parameter can go.
Also remove the redundant symbol export.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-20 11:35:33 -04:00
Trond Myklebust 14abcb0bf5 NFSv4: Fix up mirror allocation
There are a number of callers of nfs_pageio_complete() that want to
continue using the nfs_pageio_descriptor without needing to call
nfs_pageio_init() again. Examples include nfs_pageio_resend() and
nfs_pageio_cond_complete().

The problem is that nfs_pageio_complete() also calls
nfs_pageio_cleanup_mirroring(), which frees up the array of mirrors.
This can lead to writeback errors, in the next call to
nfs_pageio_setup_mirroring().

Fix by simply moving the allocation of the mirrors to
nfs_pageio_setup_mirroring().

Link: https://bugzilla.kernel.org/show_bug.cgi?id=196709
Reported-by: JianhongYin <yin-jianhong@163.com>
Cc: stable@vger.kernel.org # 4.0+
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-20 10:36:35 -04:00
Trond Myklebust b7561e5186 Merge branch 'writeback' 2017-08-18 14:51:10 -04:00
Trond Myklebust 2ce209c42c NFS: Wait for requests that are locked on the commit list
If a request is on the commit list, but is locked, we will currently skip
it, which can lead to livelocking when the commit count doesn't reduce
to zero.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:48 -04:00
Trond Myklebust 8205b9ce03 NFSv4/pnfs: Replace pnfs_put_lseg_locked() with pnfs_put_lseg()
Now that we no longer hold the inode->i_lock when manipulating the
commit lists, it is safe to call pnfs_put_lseg() again.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:48 -04:00
Trond Myklebust 4b9bb25b36 NFS: Switch to using mapping->private_lock for page writeback lookups.
Switch from using the inode->i_lock for this to avoid contention with
other metadata manipulation.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:48 -04:00
Trond Myklebust 5cb953d4b1 NFS: Use an atomic_long_t to count the number of commits
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:48 -04:00
Trond Myklebust a6b6d5b85a NFS: Use an atomic_long_t to count the number of requests
Rather than forcing us to take the inode->i_lock just in order to bump
the number.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:47 -04:00
Trond Myklebust e824f99ada NFSv4: Use a mutex to protect the per-inode commit lists
The commit lists can get very large, so using the inode->i_lock can
end up affecting general metadata performance.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:47 -04:00
Trond Myklebust b30d2f04c3 NFS: Refactor nfs_page_find_head_request()
Split out the 2 cases so that we can treat the locking differently.
The issue is that the locking in the pageswapcache cache is highly
linked to the commit list locking.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:47 -04:00
Trond Myklebust bd37d6fce1 NFSv4: Convert nfs_lock_and_join_requests() to use nfs_page_find_head_request()
Hide the locking from nfs_lock_and_join_requests() so that we can
separate out the requirements for swapcache pages.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:47 -04:00
Trond Myklebust 7e8a30f8b4 NFS: Fix up nfs_page_group_covers_page()
Fix up the test in nfs_page_group_covers_page(). The simplest implementation
is to check that we have a set of intersecting or contiguous subrequests
that connect page offset 0 to nfs_page_length(req->wb_page).

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:47 -04:00
Trond Myklebust 1344b7ea17 NFS: Remove unused parameter from nfs_page_group_lock()
nfs_page_group_lock() is now always called with the 'nonblock'
parameter set to 'false'.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:47 -04:00
Trond Myklebust dee83046e7 NFS: Remove unuse function nfs_page_group_lock_wait()
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:47 -04:00
Trond Myklebust 902a4c0046 NFS: Remove nfs_page_group_clear_bits()
At this point, we only expect ever to potentially see PG_REMOVE and
PG_TEARDOWN being set on the subrequests.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:47 -04:00
Trond Myklebust 5b2b5187fa NFS: Fix nfs_page_group_destroy() and nfs_lock_and_join_requests() race cases
Since nfs_page_group_destroy() does not take any locks on the requests
to be freed, we need to ensure that we don't inadvertently free the
request in nfs_destroy_unlinked_subrequests() while the last reference
is being released elsewhere.

Do this by:

1) Taking a reference to the request unless it is already being freed
2) Checking (under the page group lock) if PG_TEARDOWN is already set before
   freeing an unreferenced request in nfs_destroy_unlinked_subrequests()

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:47 -04:00
Trond Myklebust 74a6d4b5ae NFS: Further optimise nfs_lock_and_join_requests()
When locking the entire group in order to remove subrequests,
the locks are always taken in order, and with the page group
lock being taken after the page head is locked. The intention
is that:

1) The lock on the group head guarantees that requests may not
   be removed from the group (although new entries could be appended
   if we're not holding the group lock).
2) It is safe to drop and retake the page group lock while iterating
   through the list, in particular when waiting for a subrequest lock.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:47 -04:00
Trond Myklebust b5bab9bf91 NFS: Reduce inode->i_lock contention in nfs_lock_and_join_requests()
We should no longer need the inode->i_lock, now that we've
straightened out the request locking. The locking schema is now:

1) Lock page head request
2) Lock the page group
3) Lock the subrequests one by one

Note that there is a subtle race with nfs_inode_remove_request() due
to the fact that the latter does not lock the page head, when removing
it from the struct page. Only the last subrequest is locked, hence
we need to re-check that the PagePrivate(page) is still set after
we've locked all the subrequests.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:47 -04:00
Trond Myklebust 7e6cca6caf NFS: Remove page group limit in nfs_flush_incompatible()
nfs_try_to_update_request() should be able to cope now.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:47 -04:00
Trond Myklebust f6032f216f NFS: Teach nfs_try_to_update_request() to deal with request page_groups
Simplify the code, and avoid some flushes to disk.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:47 -04:00
Trond Myklebust b66aaa8dfe NFS: Fix the inode request accounting when pages have subrequests
Both nfs_destroy_unlinked_subrequests() and nfs_lock_and_join_requests()
manipulate the inode flags adjusting the NFS_I(inode)->nrequests.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:47 -04:00
Trond Myklebust 31a01f093e NFS: Don't unlock writebacks before declaring PG_WB_END
We don't want nfs_lock_and_join_requests() to start fiddling with
the request before the call to nfs_page_group_sync_on_bit().

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:46 -04:00
Trond Myklebust e14bebf6de NFS: Don't check request offset and size without holding a lock
Request offsets and sizes are not guaranteed to be stable unless you
are holding the request locked.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:46 -04:00
Trond Myklebust a0e265bc78 NFS: Fix an ABBA issue in nfs_lock_and_join_requests()
All other callers of nfs_page_group_lock() appear to already hold the
page lock on the head page, so doing it in the opposite order here
is inefficient, although not deadlock prone since we roll back all
locks on contention.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:46 -04:00
Trond Myklebust 7cb9cd9aa2 NFS: Fix a reference and lock leak in nfs_lock_and_join_requests()
Yes, this is a situation that should never happen (hence the WARN_ON)
but we should still ensure that we free up the locks and references to
the faulty pages.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:46 -04:00
Trond Myklebust 08fead2ae5 NFS: Ensure we always dereference the page head last
This fixes a race with nfs_page_group_sync_on_bit() whereby the
call to wake_up_bit() in nfs_page_group_unlock() could occur after
the page header had been freed.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:46 -04:00
Trond Myklebust 1403390d83 NFS: Reduce lock contention in nfs_try_to_update_request()
Micro-optimisation to move the lockless check into the for(;;) loop.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:46 -04:00
Trond Myklebust 82749dd4ef NFS: Reduce lock contention in nfs_page_find_head_request()
Add a lockless check for whether or not the page might be carrying
an existing writeback before we grab the inode->i_lock.

Reported-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:46 -04:00
Trond Myklebust 6d17d653c9 NFS: Simplify page writeback
We don't expect the page header lock to ever be held across I/O, so
it should always be safe to wait for it, even if we're doing nonblocking
writebacks.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-15 11:54:46 -04:00
Trond Myklebust 55cfcd1211 Merge branch 'open_state' 2017-08-15 11:54:13 -04:00
Trond Myklebust 75e8c48b9e NFSv4: Use the nfs4_state being recovered in _nfs4_opendata_to_nfs4_state()
If we're recovering a nfs4_state, then we should try to use that instead
of looking up a new stateid. Only do that if the inodes match, though.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-13 20:36:15 -04:00
Trond Myklebust 4e2fcac773 NFSv4: Use correct inode in _nfs4_opendata_to_nfs4_state()
When doing open by filehandle we don't really want to lookup a new inode,
but rather update the one we've got. Add a helper which does this for us.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-13 20:36:15 -04:00
Linus Torvalds 216e4a1def Some more NFS client bugfixes for 4.13
Stable fix:
 - Fix leaking nfs4_ff_ds_version array
 
 Other fixes:
 - Improve TEST_STATEID OLD_STATEID handling to prevent recovery loop
 - Require 64-bit sector_t for pNFS blocklayout to prevent 32-bit compile
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Merge tag 'nfs-for-4.13-5' of git://git.linux-nfs.org/projects/anna/linux-nfs

Pull NFS client fixes from Anna Schumaker:
 "A few more NFS client bugfixes from me for rc5.

  Dros has a stable fix for flexfiles to prevent leaking the
  nfs4_ff_ds_version arrays when freeing a layout, Trond fixed a
  potential recovery loop situation with the TEST_STATEID operation, and
  Christoph fixed up the pNFS blocklayout Kconfig options to prevent
  unsafe use with kernels that don't have large block device support.
  Summary:

  Stable fix:
   - fix leaking nfs4_ff_ds_version array

  Other fixes:
   - improve TEST_STATEID OLD_STATEID handling to prevent recovery loop

   - require 64-bit sector_t for pNFS blocklayout to prevent 32-bit
     compile errors"

* tag 'nfs-for-4.13-5' of git://git.linux-nfs.org/projects/anna/linux-nfs:
  pnfs/blocklayout: require 64-bit sector_t
  NFSv4: Ignore NFS4ERR_OLD_STATEID in nfs41_check_open_stateid()
  nfs/flexfiles: fix leak of nfs4_ff_ds_version arrays
2017-08-11 13:54:09 -07:00
Christoph Hellwig 8a9d6e964d pnfs/blocklayout: require 64-bit sector_t
The blocklayout code does not compile cleanly for a 32-bit sector_t,
and also has no reliable checks for devices sizes, which makes it
unsafe to use with a kernel that doesn't support large block devices.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 5c83746a0c ("pnfs/blocklayout: in-kernel GETDEVICEINFO XDR parsing")
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2017-08-11 14:10:13 -04:00
Trond Myklebust c0ca0e5934 NFSv4: Ignore NFS4ERR_OLD_STATEID in nfs41_check_open_stateid()
If the call to TEST_STATEID returns NFS4ERR_OLD_STATEID, then it just
means we raced with other calls to OPEN.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2017-08-09 13:36:56 -04:00
Weston Andros Adamson 1feb26162b nfs/flexfiles: fix leak of nfs4_ff_ds_version arrays
The client was freeing the nfs4_ff_layout_ds, but not the contained
nfs4_ff_ds_version array.

Signed-off-by: Weston Andros Adamson <dros@primarydata.com>
Cc: stable@vger.kernel.org # v4.0+
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2017-08-08 17:18:10 -04:00
Trond Myklebust bfab281721 NFSv4: Cleanup setting of the migration flags.
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-07 09:32:55 -04:00
Trond Myklebust 937e3133cd NFSv4.1: Ensure we clear the SP4_MACH_CRED flags in nfs4_sp4_select_mode()
If the server changes, so that it no longer supports SP4_MACH_CRED, or
that it doesn't support the same set of SP4_MACH_CRED functionality,
then we want to ensure that we clear the unsupported flags.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-07 09:32:55 -04:00
Trond Myklebust 9c760d1fd5 NFSv4: Refactor _nfs4_proc_exchange_id()
Tease apart the functionality in nfs4_exchange_id_done() so that
it is easier to debug exchange id vs trunking issues by moving
all the processing out of nfs4_exchange_id_done() and into the
callers.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2017-08-07 09:32:55 -04:00
Linus Torvalds 19ec50a438 Two more NFS client bugfixes for 4.13
Stable fix:
 - Fix EXCHANGE_ID corrupt verifier issue
 
 Other fix:
 - Fix double frees in nfs4_test_session_trunk()
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Merge tag 'nfs-for-4.13-4' of git://git.linux-nfs.org/projects/anna/linux-nfs

Pull NFS client fixes from Anna Schumaker:
 "Two fixes from Trond this time, now that he's back from his vacation.
  The first is a stable fix for the EXCHANGE_ID issue on the mailing
  list, and the other fixes a double-free situation that he found at the
  same time.

  Stable fix:
   - Fix EXCHANGE_ID corrupt verifier issue

  Other fix:
   - Fix double frees in nfs4_test_session_trunk()"

* tag 'nfs-for-4.13-4' of git://git.linux-nfs.org/projects/anna/linux-nfs:
  NFSv4: Fix double frees in nfs4_test_session_trunk()
  NFSv4: Fix EXCHANGE_ID corrupt verifier issue
2017-08-02 20:56:44 -07:00
Trond Myklebust d9cb73300a NFSv4: Fix double frees in nfs4_test_session_trunk()
rpc_clnt_add_xprt() expects the callback function to be synchronous, and
expects to release the transport and switch references itself.

Fixes: 04fa2c6bb5 ("NFS pnfs data server multipath session trunking")
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2017-08-02 09:45:55 -04:00
Trond Myklebust fd40559c86 NFSv4: Fix EXCHANGE_ID corrupt verifier issue
The verifier is allocated on the stack, but the EXCHANGE_ID RPC call was
changed to be asynchronous by commit 8d89bd70bc. If we interrrupt
the call to rpc_wait_for_completion_task(), we can therefore end up
transmitting random stack contents in lieu of the verifier.

Fixes: 8d89bd70bc ("NFS setup async exchange_id")
Cc: stable@vger.kernel.org # v4.9+
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2017-08-01 16:28:55 -04:00
Linus Torvalds 286ba844c5 More NFS client bugfixes for 4.13
Stable fixes:
 - Fix a race where CB_NOTIFY_LOCK fails to wake a waiter
 - Invalidate file size when taking a lock to prevent corruption
 
 Other fixes:
 - Don't excessively generate tiny writes with fallocate
 - Use the raw NFS access mask in nfs4_opendata_access()
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Merge tag 'nfs-for-4.13-3' of git://git.linux-nfs.org/projects/anna/linux-nfs

Pull NFS client fixes from Anna Schumaker:
 "More NFS client bugfixes for 4.13.

  Most of these fix locking bugs that Ben and Neil noticed, but I also
  have a patch to fix one more access bug that was reported after last
  week.

  Stable fixes:
   - Fix a race where CB_NOTIFY_LOCK fails to wake a waiter
   - Invalidate file size when taking a lock to prevent corruption

  Other fixes:
   - Don't excessively generate tiny writes with fallocate
   - Use the raw NFS access mask in nfs4_opendata_access()"

* tag 'nfs-for-4.13-3' of git://git.linux-nfs.org/projects/anna/linux-nfs:
  NFSv4.1: Fix a race where CB_NOTIFY_LOCK fails to wake a waiter
  NFS: Optimize fallocate by refreshing mapping when needed.
  NFS: invalidate file size when taking a lock.
  NFS: Use raw NFS access mask in nfs4_opendata_access()
2017-07-28 14:44:56 -07:00
Benjamin Coddington b7dbcc0e43 NFSv4.1: Fix a race where CB_NOTIFY_LOCK fails to wake a waiter
nfs4_retry_setlk() sets the task's state to TASK_INTERRUPTIBLE within the
same region protected by the wait_queue's lock after checking for a
notification from CB_NOTIFY_LOCK callback.  However, after releasing that
lock, a wakeup for that task may race in before the call to
freezable_schedule_timeout_interruptible() and set TASK_WAKING, then
freezable_schedule_timeout_interruptible() will set the state back to
TASK_INTERRUPTIBLE before the task will sleep.  The result is that the task
will sleep for the entire duration of the timeout.

Since we've already set TASK_INTERRUPTIBLE in the locked section, just use
freezable_schedule_timout() instead.

Fixes: a1d617d8f1 ("nfs: allow blocking locks to be awoken by lock callbacks")
Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Cc: stable@vger.kernel.org # v4.9+
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2017-07-28 15:35:30 -04:00
NeilBrown 6ba80d4348 NFS: Optimize fallocate by refreshing mapping when needed.
posix_fallocate() will allocate space in an NFS file by considering
the last byte of every 4K block.  If it is before EOF, it will read
the byte and if it is zero, a zero is written out.  If it is after EOF,
the zero is unconditionally written.

For the blocks beyond EOF, if NFS believes its cache is valid, it will
expand these writes to write full pages, and then will merge the pages.
This results if (typically) 1MB writes.  If NFS believes its cache is
not valid (particularly if NFS_INO_INVALID_DATA or
NFS_INO_REVAL_PAGECACHE are set - see nfs_write_pageuptodate()), it will
send the individual 1-byte writes. This results in (typically) 256 times
as many RPC requests, and can be substantially slower.

Currently nfs_revalidate_mapping() is only used when reading a file or
mmapping a file, as these are times when the content needs to be
up-to-date.  Writes don't generally need the cache to be up-to-date, but
writes beyond EOF can benefit, particularly in the posix_fallocate()
case.

So this patch calls nfs_revalidate_mapping() when writing beyond EOF -
i.e. when there is a gap between the end of the file and the start of
the write.  If the cache is thought to be out of date (as happens after
taking a file lock), this will cause a GETATTR, and the two flags
mentioned above will be cleared.  With this, posix_fallocate() on a
newly locked file does not generate excessive tiny writes.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2017-07-27 11:22:42 -04:00
NeilBrown 442ce0499c NFS: invalidate file size when taking a lock.
Prior to commit ca0daa277a ("NFS: Cache aggressively when file is open
for writing"), NFS would revalidate, or invalidate, the file size when
taking a lock.  Since that commit it only invalidates the file content.

If the file size is changed on the server while wait for the lock, the
client will have an incorrect understanding of the file size and could
corrupt data.  This particularly happens when writing beyond the
(supposed) end of file and can be easily be demonstrated with
posix_fallocate().

If an application opens an empty file, waits for a write lock, and then
calls posix_fallocate(), glibc will determine that the underlying
filesystem doesn't support fallocate (assuming version 4.1 or earlier)
and will write out a '0' byte at the end of each 4K page in the region
being fallocated that is after the end of the file.
NFS will (usually) detect that these writes are beyond EOF and will
expand them to cover the whole page, and then will merge the pages.
Consequently, NFS will write out large blocks of zeroes beyond where it
thought EOF was.  If EOF had moved, the pre-existing part of the file
will be over-written.  Locking should have protected against this,
but it doesn't.

This patch restores the use of nfs_zap_caches() which invalidated the
cached attributes.  When posix_fallocate() asks for the file size, the
request will go to the server and get a correct answer.

cc: stable@vger.kernel.org (v4.8+)
Fixes: ca0daa277a ("NFS: Cache aggressively when file is open for writing")
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2017-07-27 11:22:42 -04:00