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  1. 01 6月, 2018 3 次提交
    • N
      NFS: Avoid quadratic search when freeing delegations. · e04bbf6b
      由 NeilBrown 提交于 
      There are three places that walk all delegation for an nfs_client and
restart whenever they find something interesting - potentially
resulting in a quadratic search:  If there are 10,000 uninteresting
delegations followed by 10,000 interesting one, then the code
skips over 100,000,000 delegations, which can take a noticeable amount
of time.

Of these nfs_delegation_reap_unclaimed() and
nfs_reap_expired_delegations() are only called during unusual events:
a server reboots or reports expired delegations, probably due to a
network partition.  Optimizing these is not particularly important.

The third, nfs_client_return_marked_delegations(), is called
periodically via nfs_expire_unreferenced_delegations().  It could
cause periodic problems on a busy server.

New delegations are added to the end of the list, so if there are
10,000 open files with delegations, and 10,000 more recently opened files
that received delegations but are now closed, then
nfs_client_return_marked_delegations() can take seconds to skip over
the 10,000 open files 10,000 times.  That is a waste of time.

The avoid this waste a place-holder (an inode) is kept when locks are
dropped, so that the place can usually be found again after taking
rcu_readlock().  This place holder ensure that we find the right
starting point in the list of nfs_servers, and makes is probable that
we find the right starting point in the list of delegations.
We might need to occasionally restart at the head of that list.

It might be possible that the place_holder inode could lose its
delegation separately, and then get a new one using the same (freed
and then reallocated) 'struct nfs_delegation'.  Were this to happen,
the new delegation would be at the end of the list and we would miss
returning some other delegations.  This would have the effect of
unnecessarily delaying the return of some unused delegations until the
next time this function is called - typically 90 seconds later.  As
this is not a correctness issue and is vanishingly unlikely to happen,
it does not seem worth addressing.
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>
      e04bbf6b
    • N
      NFS: use cond_resched() when restarting walk of delegation list. · 3ca951b6
      由 NeilBrown 提交于 
      In three places we walk the list of delegations for an nfs_client
until an interesting one is found, then we act of that delegation
and restart the walk.

New delegations are added to the end of a list and the interesting
delegations are usually old, so in many case we won't repeat
a long walk over and over again, but it is possible - particularly if
the first server in the list has a large number of uninteresting
delegations.

In each cache the work done on interesting delegations will often
complete without sleeping, so this could loop many times without
giving up the CPU.

So add a cond_resched() at an appropriate point to avoid hogging the
CPU for too long.
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>
      3ca951b6
    • N
      NFS: slight optimization for walking list for delegations · f3893491
      由 NeilBrown 提交于 
      There are 3 places where we walk the list of delegations
for an nfs_client.
In each case there are two nested loops, one for nfs_servers
and one for nfs_delegations.

When we find an interesting delegation we try to get an active
reference to the server.  If that fails, it is pointless to
continue to look at the other delegation for the server as
we will never be able to get an active reference.
So instead of continuing in the inner loop, break out
and continue in the outer loop.
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>
      f3893491
  3. 11 4月, 2018 2 次提交
  5. 29 1月, 2018 1 次提交
  7. 18 11月, 2017 1 次提交
  9. 15 8月, 2017 1 次提交
  11. 02 12月, 2016 1 次提交
  13. 28 9月, 2016 9 次提交
  15. 18 5月, 2016 1 次提交
  17. 08 10月, 2015 1 次提交
  19. 21 9月, 2015 1 次提交
    • T
      NFSv4: Recovery of recalled read delegations is broken · 24311f88
      由 Trond Myklebust 提交于 
      When a read delegation is being recalled, and we're reclaiming the
cached opens, we need to make sure that we only reclaim read-only
modes.
A previous attempt to do this, relied on retrieving the delegation
type from the nfs4_opendata structure. Unfortunately, as Kinglong
pointed out, this field can only be set when performing reboot recovery.

Furthermore, if we call nfs4_open_recover(), then we end up clobbering
the state->flags for all modes that we're not recovering...

The fix is to have the delegation recall code pass this information
to the recovery call, and then refactor the recovery code so that
nfs4_open_delegation_recall() does not need to call nfs4_open_recover().
Reported-by: NKinglong Mee <kinglongmee@gmail.com>
Fixes: 39f897fd ("NFSv4: When returning a delegation, don't...")
Tested-by: NKinglong Mee <kinglongmee@gmail.com>
Cc: NeilBrown <neilb@suse.com>
Cc: stable@vger.kernel.org # v4.2+
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>
      24311f88
  21. 08 9月, 2015 2 次提交
  23. 28 3月, 2015 1 次提交
  25. 13 3月, 2015 1 次提交
  27. 03 3月, 2015 4 次提交
  29. 02 3月, 2015 1 次提交
  31. 14 2月, 2015 1 次提交
  33. 25 1月, 2015 1 次提交
  35. 17 1月, 2015 3 次提交
  37. 13 11月, 2014 2 次提交
  39. 13 7月, 2014 1 次提交
  41. 03 3月, 2014 1 次提交
  43. 22 8月, 2013 1 次提交