Re: Patch For Making Readdir_plus configurable

[Steve Dickson <SteveD@redhat.com>]

Hello,

On 25/07/14 12:19, Rishi Agrawal wrote:
> Hi,
>    One of our customer's application only needs file names not
> file attributes. With directories having 10K+ inodes (assuming buffer
> cache has directory blocks cached having file names, but inode
> cache is limited and hence need eviction of older cached inodes),
> older inodes are evicted periodically. So if they keep on doing
> readdir(2) from NSF client on multiple directories, some directory's
> files are periodically removed from inode cache and hence new
> readdir(2) on same directory requires disk access to bring back
> inodes again to inode cache.
> 
> As READDIRPLUS request fetches attributes also, doing getattr on
> each file on server, it causes unnecessary disk accesses. If
> READDIRPLUS on NFS client is returned with -ENOTSUPP, NFS
> client uses READDIR request which just gets the names of the files
> in a directory, not attributes, hence avoiding disk accesses on server.
> 
> Can this be per-export tunable so that different application can
> use it in different ways, some supporting readdirplus and others
> not supporting readdirplus?
> 
> I have worked on a patch against 3.15.6 for this. Also I am
> adding a patch against latest nfs-utils to have an export option
> for this. Can someone let me know if these patches are adequate
> or if any other changes are required. Patches attached, although
> with minimal testing. I would like to know if something like this
> can be added and if the patch can be reworked if I am missing
> something for NFSv4.

I just notice that the nfs-utils patch does not update
the exports(5) man page. In that update please note
this is a v3 only thing.... Not clear what we are going
to do in the v4 case.

Finally, please inline your patch posting in the your
email as its is explained there
   https://www.kernel.org/doc/Documentation/SubmittingPatches

It just makes it easier for everyone to do the review... 

tia,

steved.