[ ... 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.
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
