> On Jan 10, 2020, at 5:43 PM, Schumaker, Anna <Anna.Schumaker@xxxxxxxxxx> wrote:
>
> Hi Chuck,
>
> On Fri, 2020-01-10 at 17:41 -0500, Chuck Lever wrote:
>> NetApp Security WARNING: This is an external email. Do not click links or open
>> attachments unless you recognize the sender and know the content is safe.
>>
>>
>>
>>
>> Hi Anna-
>>
>>> On Jan 10, 2020, at 5:34 PM, schumaker.anna@xxxxxxxxx wrote:
>>>
>>> From: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
>>>
>>> There are some workloads where READ_PLUS might end up hurting
>>> performance,
>>
>> Can you say more about this? Have you seen workloads that are
>> hurt by READ_PLUS? Nothing jumps out at me from the tables in
>> the cover letter.
>
> It's mostly something I've seen when using btrfs in a virtual machine (so
> probably not a wide use case, and it's possible I need to change something in my
> setup to get it working better).
>
>>
>>
>>> so let's be nice to users and provide a way to disable this
>>> operation similar to how READDIR_PLUS can be disabled.
>>
>> Does it make sense to hold off on a mount option until there
>> is evidence that there is no other way to work around such a
>> performance regression?
>>
>> - Attempt to address the regression directly
>> - Improve the heuristics about when READ_PLUS is used
>> - Document that dropping back to vers=4.1 will disable it
>
> Yeah, we could hold off on the patch for now and see if anybody has any issues
> first.
>
>>
>> Any experience with NFS/RDMA?
>
> Not yet, but I can try to test that next week.
Thanks for your response!
> Anna
>
>>
>>
>>> Signed-off-by: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
>>> ---
>>> fs/nfs/fs_context.c | 14 ++++++++++++++
>>> fs/nfs/nfs4client.c | 3 +++
>>> include/linux/nfs_fs_sb.h | 1 +
>>> 3 files changed, 18 insertions(+)
>>>
>>> diff --git a/fs/nfs/fs_context.c b/fs/nfs/fs_context.c
>>> index 0247dcb7b316..82ba07c7c1ce 100644
>>> --- a/fs/nfs/fs_context.c
>>> +++ b/fs/nfs/fs_context.c
>>> @@ -64,6 +64,7 @@ enum nfs_param {
>>> Opt_proto,
>>> Opt_rdirplus,
>>> Opt_rdma,
>>> + Opt_readplus,
>>> Opt_resvport,
>>> Opt_retrans,
>>> Opt_retry,
>>> @@ -120,6 +121,7 @@ static const struct fs_parameter_spec nfs_param_specs[]
>>> = {
>>> fsparam_string("proto", Opt_proto),
>>> fsparam_flag_no("rdirplus", Opt_rdirplus),
>>> fsparam_flag ("rdma", Opt_rdma),
>>> + fsparam_flag_no("readplus", Opt_readplus),
>>> fsparam_flag_no("resvport", Opt_resvport),
>>> fsparam_u32 ("retrans", Opt_retrans),
>>> fsparam_string("retry", Opt_retry),
>>> @@ -555,6 +557,12 @@ static int nfs_fs_context_parse_param(struct fs_context
>>> *fc,
>>> else
>>> ctx->options |= NFS_OPTION_MIGRATION;
>>> break;
>>> + case Opt_readplus:
>>> + if (result.negated)
>>> + ctx->options |= NFS_OPTION_NO_READ_PLUS;
>>> + else
>>> + ctx->options &= ~NFS_OPTION_NO_READ_PLUS;
>>> + break;
>>>
>>> /*
>>> * options that take numeric values
>>> @@ -1176,6 +1184,10 @@ static int nfs_fs_context_validate(struct fs_context
>>> *fc)
>>> (ctx->version != 4 || ctx->minorversion != 0))
>>> goto out_migration_misuse;
>>>
>>> + if (ctx->options & NFS_OPTION_NO_READ_PLUS &&
>>> + (ctx->version != 4 || ctx->minorversion < 2))
>>> + goto out_noreadplus_misuse;
>>> +
>>> /* Verify that any proto=/mountproto= options match the address
>>> * families in the addr=/mountaddr= options.
>>> */
>>> @@ -1254,6 +1266,8 @@ static int nfs_fs_context_validate(struct fs_context
>>> *fc)
>>> ctx->version, ctx->minorversion);
>>> out_migration_misuse:
>>> return nfs_invalf(fc, "NFS: 'Migration' not supported for this NFS
>>> version");
>>> +out_noreadplus_misuse:
>>> + return nfs_invalf(fc, "NFS: 'noreadplus' not supported for this NFS
>>> version\n");
>>> out_version_unavailable:
>>> nfs_errorf(fc, "NFS: Version unavailable");
>>> return ret;
>>> diff --git a/fs/nfs/nfs4client.c b/fs/nfs/nfs4client.c
>>> index 0cd767e5c977..868dc3c36ba1 100644
>>> --- a/fs/nfs/nfs4client.c
>>> +++ b/fs/nfs/nfs4client.c
>>> @@ -1016,6 +1016,9 @@ static int nfs4_server_common_setup(struct nfs_server
>>> *server,
>>> server->caps |= server->nfs_client->cl_mvops->init_caps;
>>> if (server->flags & NFS_MOUNT_NORDIRPLUS)
>>> server->caps &= ~NFS_CAP_READDIRPLUS;
>>> + if (server->options & NFS_OPTION_NO_READ_PLUS)
>>> + server->caps &= ~NFS_CAP_READ_PLUS;
>>> +
>>> /*
>>> * Don't use NFS uid/gid mapping if we're using AUTH_SYS or lower
>>> * authentication.
>>> diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
>>> index 11248c5a7b24..360e70c7bbb6 100644
>>> --- a/include/linux/nfs_fs_sb.h
>>> +++ b/include/linux/nfs_fs_sb.h
>>> @@ -172,6 +172,7 @@ struct nfs_server {
>>> unsigned int clone_blksize; /* granularity of a CLONE
>>> operation */
>>> #define NFS_OPTION_FSCACHE 0x00000001 /* - local caching enabled */
>>> #define NFS_OPTION_MIGRATION 0x00000002 /* - NFSv4 migration enabled
>>> */
>>> +#define NFS_OPTION_NO_READ_PLUS 0x00000004 /* - NFSv4.2 READ_PLUS
>>> enabled */
>>>
>>> struct nfs_fsid fsid;
>>> __u64 maxfilesize; /* maximum file size */
>>> --
>>> 2.24.1
>>>
>>
>> --
>> Chuck Lever
>>
>>
>>
--
Chuck Lever
