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From:   "NeilBrown" <neilb@suse.de>
To:     "Jeff Layton" <jlayton@kernel.org>
Cc:     chuck.lever@oracle.com, linux-nfs@vger.kernel.org
Subject: Re: [PATCH v2 3/3] nfsd: start non-blocking writeback after adding
 nfsd_file to the LRU
In-reply-to: <20221027215213.138304-4-jlayton@kernel.org>
References: <20221027215213.138304-1-jlayton@kernel.org>,
 <20221027215213.138304-4-jlayton@kernel.org>
Date:   Fri, 28 Oct 2022 09:25:26 +1100
Message-id: <166690952613.13915.11556395606559286695@noble.neil.brown.name>
Precedence: bulk

On Fri, 28 Oct 2022, Jeff Layton wrote:
> When a GC entry gets added to the LRU, kick off SYNC_NONE writeback
> so that we can be ready to close it out when the time comes.
>=20
> Signed-off-by: Jeff Layton <jlayton@kernel.org>

This looks sensible.
Reviewed-by: NeilBrown <neilb@suse.de>

Thanks,
NeilBrown


> ---
>  fs/nfsd/filecache.c | 37 +++++++++++++++++++++++++++++++------
>  1 file changed, 31 insertions(+), 6 deletions(-)
>=20
> diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
> index d2bbded805d4..491d3d9a1870 100644
> --- a/fs/nfsd/filecache.c
> +++ b/fs/nfsd/filecache.c
> @@ -316,7 +316,7 @@ nfsd_file_alloc(struct nfsd_file_lookup_key *key, unsig=
ned int may)
>  }
> =20
>  static void
> -nfsd_file_flush(struct nfsd_file *nf)
> +nfsd_file_fsync(struct nfsd_file *nf)
>  {
>  	struct file *file =3D nf->nf_file;
> =20
> @@ -327,6 +327,22 @@ nfsd_file_flush(struct nfsd_file *nf)
>  		nfsd_reset_write_verifier(net_generic(nf->nf_net, nfsd_net_id));
>  }
> =20
> +static void
> +nfsd_file_flush(struct nfsd_file *nf)
> +{
> +	struct file *file =3D nf->nf_file;
> +	unsigned long nrpages;
> +
> +	if (!file || !(file->f_mode & FMODE_WRITE))
> +		return;
> +
> +	nrpages =3D file->f_mapping->nrpages;
> +	if (nrpages) {
> +		this_cpu_add(nfsd_file_pages_flushed, nrpages);
> +		filemap_flush(file->f_mapping);
> +	}
> +}
> +
>  static void
>  nfsd_file_free(struct nfsd_file *nf)
>  {
> @@ -337,7 +353,7 @@ nfsd_file_free(struct nfsd_file *nf)
>  	this_cpu_inc(nfsd_file_releases);
>  	this_cpu_add(nfsd_file_total_age, age);
> =20
> -	nfsd_file_flush(nf);
> +	nfsd_file_fsync(nf);
> =20
>  	if (nf->nf_mark)
>  		nfsd_file_mark_put(nf->nf_mark);
> @@ -500,12 +516,21 @@ nfsd_file_put(struct nfsd_file *nf)
> =20
>  	if (test_bit(NFSD_FILE_GC, &nf->nf_flags)) {
>  		/*
> -		 * If this is the last reference (nf_ref =3D=3D 1), then transfer
> -		 * it to the LRU. If the add to the LRU fails, just put it as
> -		 * usual.
> +		 * If this is the last reference (nf_ref =3D=3D 1), then try
> +		 * to transfer it to the LRU.
> +		 */
> +		if (refcount_dec_not_one(&nf->nf_ref))
> +			return;
> +
> +		/*
> +		 * If the add to the list succeeds, try to kick off SYNC_NONE
> +		 * writeback. If the add fails, then just fall through to
> +		 * decrement as usual.
>  		 */
> -		if (refcount_dec_not_one(&nf->nf_ref) || nfsd_file_lru_add(nf))
> +		if (nfsd_file_lru_add(nf)) {
> +			nfsd_file_flush(nf);
>  			return;
> +		}
>  	}
>  	__nfsd_file_put(nf);
>  }
> --=20
> 2.37.3
>=20
>=20