tree 50a1d7f2e8791c3af949391359fb1279b1073244
parent 5c965db86e6b0e90a3112228820598e824920278
author Trond Myklebust <trondmy@gmail.com> 1578343177 -0500
committer Anna Schumaker <Anna.Schumaker@Netapp.com> 1579103673 -0500

NFS: Add mount option 'softreval'

Add a mount option 'softreval' that allows attribute revalidation 'getattr'
calls to time out, and causes them to fall back to using the cached
attributes.
The use case for this option is for ensuring that we can still (slowly)
traverse paths and use cached information even when the server is down.
Once the server comes back up again, the getattr calls start succeeding,
and the caches will revalidate as usual.

The 'softreval' mount option is automatically enabled if you have
specified 'softerr'.  It can be turned off using the options
'nosoftreval', or 'hard'.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>