Re: [PATCH v2 3/3] nfsd: start non-blocking writeback after adding nfsd_file to the LRU

NeilBrown
2022-10-27T22:25:38Z

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.
>
> 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(-)
>
> 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, unsigned int may)
> }
>
> static void
> -nfsd_file_flush(struct nfsd_file *nf)
> +nfsd_file_fsync(struct nfsd_file *nf)
> {
> struct file *file = nf->nf_file;
>
> @@ -327,6 +327,22 @@ nfsd_file_flush(struct nfsd_file *nf)
> nfsd_reset_write_verifier(net_generic(nf->nf_net, nfsd_net_id));
> }
>
> +static void
> +nfsd_file_flush(struct nfsd_file *nf)
> +{
> + struct file *file = nf->nf_file;
> + unsigned long nrpages;
> +
> + if (!file || !(file->f_mode & FMODE_WRITE))
> + return;
> +
> + nrpages = 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);
>
> - nfsd_file_flush(nf);
> + nfsd_file_fsync(nf);
>
> if (nf->nf_mark)
> nfsd_file_mark_put(nf->nf_mark);
> @@ -500,12 +516,21 @@ nfsd_file_put(struct nfsd_file *nf)
>
> if (test_bit(NFSD_FILE_GC, &nf->nf_flags)) {
> /*
> - * If this is the last reference (nf_ref == 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 == 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);
> }
> --
> 2.37.3
>
>