>
> [ ... adding linux-nfs@xxxxxxxxxxxxxxx ]
>
> On Mon, Aug 19, 2024 at 03:15:28PM +0300, andrii.polianytsia@xxxxxxxxxxxxxxx wrote:
> > Add NFS export support to the exFAT filesystem by implementing
> > the necessary export operations in fs/exfat/super.c. Enable
> > exFAT filesystems to be exported and accessed over NFS, enhancing
> > their utility in networked environments.
> >
> > Introduce the exfat_export_ops structure, which includes
> > functions to handle file handles and inode lookups necessary for NFS
> > operations.
>
> My memory is dim, but I think the reason that exporting exfat isn't
> supported already is because it's file handles aren't persistent.
Yes, and fat is the same but it supports nfs.
They seem to want to support it even considering the -ESTALE result by eviction.
This patch seems to refer to /fs/fat/nfs.c code which has the same issue.
>
> NFS requires that file handles remain the same across server
> restarts or umount/mount cycles of the exported file system.
>
>
> > Signed-off-by: Sergii Boryshchenko <sergii.boryshchenko@xxxxxxxxxxxxxxx>
> > Signed-off-by: Andrii Polianytsia <andrii.polianytsia@xxxxxxxxxxxxxxx>
> > ---
> > fs/exfat/super.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 65 insertions(+)
> >
> > diff --git a/fs/exfat/super.c b/fs/exfat/super.c
> > index 323ecebe6f0e..cb6dcafc3007 100644
> > --- a/fs/exfat/super.c
> > +++ b/fs/exfat/super.c
> > @@ -18,6 +18,7 @@
> > #include <linux/nls.h>
> > #include <linux/buffer_head.h>
> > #include <linux/magic.h>
> > +#include <linux/exportfs.h>
> >
> > #include "exfat_raw.h"
> > #include "exfat_fs.h"
> > @@ -195,6 +196,69 @@ static const struct super_operations exfat_sops = {
> > .show_options = exfat_show_options,
> > };
> >
> > +/**
> > + * exfat_export_get_inode - Get inode for export operations
> > + * @sb: Superblock pointer
> > + * @ino: Inode number
> > + * @generation: Generation number
> > + *
> > + * Returns pointer to inode or error pointer in case of an error.
> > + */
> > +static struct inode *exfat_export_get_inode(struct super_block *sb, u64 ino,
> > + u32 generation)
> > +{
> > + struct inode *inode = NULL;
> > +
> > + if (ino == 0)
> > + return ERR_PTR(-ESTALE);
> > +
> > + inode = ilookup(sb, ino);
> > + if (inode && generation && inode->i_generation != generation) {
> > + iput(inode);
> > + return ERR_PTR(-ESTALE);
> > + }
> > +
> > + return inode;
> > +}
> > +
> > +/**
> > + * exfat_fh_to_dentry - Convert file handle to dentry
> > + * @sb: Superblock pointer
> > + * @fid: File identifier
> > + * @fh_len: Length of the file handle
> > + * @fh_type: Type of the file handle
> > + *
> > + * Returns dentry corresponding to the file handle.
> > + */
> > +static struct dentry *exfat_fh_to_dentry(struct super_block *sb,
> > + struct fid *fid, int fh_len, int fh_type)
> > +{
> > + return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
> > + exfat_export_get_inode);
> > +}
> > +
> > +/**
> > + * exfat_fh_to_parent - Convert file handle to parent dentry
> > + * @sb: Superblock pointer
> > + * @fid: File identifier
> > + * @fh_len: Length of the file handle
> > + * @fh_type: Type of the file handle
> > + *
> > + * Returns parent dentry corresponding to the file handle.
> > + */
> > +static struct dentry *exfat_fh_to_parent(struct super_block *sb,
> > + struct fid *fid, int fh_len, int fh_type)
> > +{
> > + return generic_fh_to_parent(sb, fid, fh_len, fh_type,
> > + exfat_export_get_inode);
> > +}
> > +
> > +static const struct export_operations exfat_export_ops = {
> > + .encode_fh = generic_encode_ino32_fh,
> > + .fh_to_dentry = exfat_fh_to_dentry,
> > + .fh_to_parent = exfat_fh_to_parent,
> > +};
> > +
> > enum {
> > Opt_uid,
> > Opt_gid,
> > @@ -633,6 +697,7 @@ static int exfat_fill_super(struct super_block *sb, struct fs_context *fc)
> > sb->s_flags |= SB_NODIRATIME;
> > sb->s_magic = EXFAT_SUPER_MAGIC;
> > sb->s_op = &exfat_sops;
> > + sb->s_export_op = &exfat_export_ops;
> >
> > sb->s_time_gran = 10 * NSEC_PER_MSEC;
> > sb->s_time_min = EXFAT_MIN_TIMESTAMP_SECS;
> > --
> > 2.25.1
> >
> >
>
> --
> Chuck Lever
