Re: [PATCH 5.10] nfsd: Replace use of rwsem with errseq_t

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, Jun 07, 2022 at 01:10:36PM -0700, Leah Rumancik wrote:
> From: Trond Myklebust <trond.myklebust@hammerspace.com>
> 
> [ Upstream commit 555dbf1a9aac6d3150c8b52fa35f768a692f4eeb ]
> 
> The nfsd_file nf_rwsem is currently being used to separate file write
> and commit instances to ensure that we catch errors and apply them to
> the correct write/commit.
> We can improve scalability at the expense of a little accuracy (some
> extra false positives) by replacing the nf_rwsem with more careful
> use of the errseq_t mechanism to track errors across the different
> operations.
> 
> [Leah: This patch is for 5.10. 5011af4c698a ("nfsd: Fix stable writes")
> introduced a 75% performance regression on parallel random write
> workloads. With this commit, the performance is restored to 90% of what
> it was prior to 5011af4c698a. The changes to the fsync for asynchronous
> copies were not included in this backport version as the fsync was not
> added until 5.14 (eac0b17a77fb).]
> 
> Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> Signed-off-by: Leah Rumancik <leah.rumancik@gmail.com>
> [ cel: rebased on zero-verifier fix ]
> ---
>  fs/nfsd/filecache.c |  1 -
>  fs/nfsd/filecache.h |  1 -
>  fs/nfsd/nfs4proc.c  |  7 ++++---
>  fs/nfsd/vfs.c       | 40 +++++++++++++++-------------------------
>  4 files changed, 19 insertions(+), 30 deletions(-)

What about 5.15?  We can't take this patch for 5.10 only as if you
upgrade to 5.15 you would have a regression.  Can you provide a version
for that tree so that I can then apply this one too?

thanks,

greg k-h