On Thu, 2025-07-31 at 15:44 -0400, Mike Snitzer wrote:
> NFS doesn't have any DIO alignment constraints but it doesn't support
> STATX_DIOALIGN, so update NFSD such that it doesn't disable the use of
> NFSD_IO_DIRECT if it is reexporting NFS.
>
> Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
> ---
> fs/nfs/export.c | 3 ++-
> fs/nfsd/filecache.c | 11 +++++++++++
> include/linux/exportfs.h | 13 +++++++++++++
> 3 files changed, 26 insertions(+), 1 deletion(-)
>
> diff --git a/fs/nfs/export.c b/fs/nfs/export.c
> index e9c233b6fd209..2cae75ba6b35d 100644
> --- a/fs/nfs/export.c
> +++ b/fs/nfs/export.c
> @@ -155,5 +155,6 @@ const struct export_operations nfs_export_ops = {
> EXPORT_OP_REMOTE_FS |
> EXPORT_OP_NOATOMIC_ATTR |
> EXPORT_OP_FLUSH_ON_CLOSE |
> - EXPORT_OP_NOLOCKS,
> + EXPORT_OP_NOLOCKS |
> + EXPORT_OP_NO_DIOALIGN_NEEDED,
> };
> diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
> index 5601e839a72da..ea489dd44fd9a 100644
> --- a/fs/nfsd/filecache.c
> +++ b/fs/nfsd/filecache.c
> @@ -1066,6 +1066,17 @@ nfsd_file_getattr(const struct svc_fh *fhp, struct nfsd_file *nf)
> nfsd_io_cache_write != NFSD_IO_DIRECT))
> return nfs_ok;
>
> + if (exportfs_handles_unaligned_dio(nf->nf_file->f_path.mnt->mnt_sb->s_export_op)) {
> + /* Underlying filesystem doesn't support STATX_DIOALIGN
> + * but it can handle all unaligned DIO, so establish
> + * DIO alignment that is accommodating.
> + */
> + nf->nf_dio_mem_align = 4;
> + nf->nf_dio_offset_align = PAGE_SIZE;
> + nf->nf_dio_read_offset_align = nf->nf_dio_offset_align;
> + return nfs_ok;
> + }
> +
> status = fh_getattr(fhp, &stat);
> if (status != nfs_ok)
> return status;
> diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
> index 9369a607224c1..626b8486dd985 100644
> --- a/include/linux/exportfs.h
> +++ b/include/linux/exportfs.h
> @@ -247,6 +247,7 @@ struct export_operations {
> */
> #define EXPORT_OP_FLUSH_ON_CLOSE (0x20) /* fs flushes file data on close */
> #define EXPORT_OP_NOLOCKS (0x40) /* no file locking support */
> +#define EXPORT_OP_NO_DIOALIGN_NEEDED (0x80) /* fs can handle unaligned DIO */
> unsigned long flags;
> };
>
> @@ -262,6 +263,18 @@ exportfs_cannot_lock(const struct export_operations *export_ops)
> return export_ops->flags & EXPORT_OP_NOLOCKS;
> }
>
> +/**
> + * exportfs_handles_unaligned_dio() - check if export can handle unaligned DIO
> + * @export_ops: the nfs export operations to check
> + *
> + * Returns true if the export can handle unaligned DIO.
> + */
> +static inline bool
> +exportfs_handles_unaligned_dio(const struct export_operations *export_ops)
> +{
> + return export_ops->flags & EXPORT_OP_NO_DIOALIGN_NEEDED;
> +}
> +
> extern int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid,
> int *max_len, struct inode *parent,
> int flags);
Would it not be simpler (better?) to add support for STATX_DIOALIGN to
NFS, and just have it report '1' for both values?
--
Jeff Layton <jlayton@xxxxxxxxxx>
