Re: [PATCH v4 1/5] NFSD: filecache: add STATX_DIOALIGN and STATX_DIO_READ_ALIGN support

Jeff Layton
2025-07-23T18:58:20Z

On Wed, 2025-07-23 at 11:43 -0400, Mike Snitzer wrote:
> Use STATX_DIOALIGN and STATX_DIO_READ_ALIGN to get and store DIO
> alignment attributes from underlying filesystem in associated
> nfsd_file. This is done when the nfsd_file is first opened for
> a regular file.
>
> Signed-off-by: Mike Snitzer <snitzer@kernel.org>
> ---
> fs/nfsd/filecache.c | 32 ++++++++++++++++++++++++++++++++
> fs/nfsd/filecache.h | 4 ++++
> fs/nfsd/nfsfh.c | 4 ++++
> 3 files changed, 40 insertions(+)
>
> diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
> index 8581c131338b..5447dba6c5da 100644
> --- a/fs/nfsd/filecache.c
> +++ b/fs/nfsd/filecache.c
> @@ -231,6 +231,9 @@ nfsd_file_alloc(struct net *net, struct inode *inode, unsigned char need,
> refcount_set(&nf->nf_ref, 1);
> nf->nf_may = need;
> nf->nf_mark = NULL;
> + nf->nf_dio_mem_align = 0;
> + nf->nf_dio_offset_align = 0;
> + nf->nf_dio_read_offset_align = 0;
> return nf;
> }
>
> @@ -1048,6 +1051,33 @@ nfsd_file_is_cached(struct inode *inode)
> return ret;
> }
>
> +static __be32
> +nfsd_file_getattr(const struct svc_fh *fhp, struct nfsd_file *nf)
> +{
> + struct inode *inode = file_inode(nf->nf_file);
> + struct kstat stat;
> + __be32 status;
> +
> + /* Currently only need to get DIO alignment info for regular files */
> + if (!S_ISREG(inode->i_mode))
> + return nfs_ok;
> +
> + status = fh_getattr(fhp, &stat);
> + if (status != nfs_ok)
> + return status;
> +
> + if (stat.result_mask & STATX_DIOALIGN) {
> + nf->nf_dio_mem_align = stat.dio_mem_align;
> + nf->nf_dio_offset_align = stat.dio_offset_align;
> + }
> + if (stat.result_mask & STATX_DIO_READ_ALIGN)
> + nf->nf_dio_read_offset_align = stat.dio_read_offset_align;
> + else
> + nf->nf_dio_read_offset_align = nf->nf_dio_offset_align;
> +
> + return status;
> +}
> +
> static __be32
> nfsd_file_do_acquire(struct svc_rqst *rqstp, struct net *net,
> struct svc_cred *cred,
> @@ -1166,6 +1196,8 @@ nfsd_file_do_acquire(struct svc_rqst *rqstp, struct net *net,
> }
> status = nfserrno(ret);
> trace_nfsd_file_open(nf, status);
> + if (status == nfs_ok)
> + status = nfsd_file_getattr(fhp, nf);

Doing a getattr alongside every open could be expensive in some
configurations (like reexported NFS). We may want to skip doing this
getattr this if O_DIRECT isn't is use. Is that possible?

> }
> } else
> status = nfserr_jukebox;
> diff --git a/fs/nfsd/filecache.h b/fs/nfsd/filecache.h
> index 24ddf60e8434..e3d6ca2b6030 100644
> --- a/fs/nfsd/filecache.h
> +++ b/fs/nfsd/filecache.h
> @@ -54,6 +54,10 @@ struct nfsd_file {
> struct list_head nf_gc;
> struct rcu_head nf_rcu;
> ktime_t nf_birthtime;
> +
> + u32 nf_dio_mem_align;
> + u32 nf_dio_offset_align;
> + u32 nf_dio_read_offset_align;
> };
>
> int nfsd_file_cache_init(void);
> diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c
> index f4a3cc9e31e0..bdba2ba828a6 100644
> --- a/fs/nfsd/nfsfh.c
> +++ b/fs/nfsd/nfsfh.c
> @@ -677,8 +677,12 @@ __be32 fh_getattr(const struct svc_fh *fhp, struct kstat *stat)
> .mnt = fhp->fh_export->ex_path.mnt,
> .dentry = fhp->fh_dentry,
> };
> + struct inode *inode = d_inode(p.dentry);
> u32 request_mask = STATX_BASIC_STATS;
>
> + if (S_ISREG(inode->i_mode))
> + request_mask |= (STATX_DIOALIGN | STATX_DIO_READ_ALIGN);
> +
> if (fhp->fh_maxsize == NFS4_FHSIZE)
> request_mask |= (STATX_BTIME | STATX_CHANGE_COOKIE);
>

--
Jeff Layton <jlayton@kernel.org>