On Mon, Aug 19, 2024 at 11:40 PM Chuck Lever <chuck.lever@xxxxxxxxxx> wrote:
>
> On Mon, Aug 19, 2024 at 11:21:05PM +0900, Namjae Jeon wrote:
> > >
> > > [ ... 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.
>
> Fair enough. I don't see a reference to fs/fat/nfs.c, so may I
> request that this added context be included in the patch description
> before this patch is merged?
Sure, I haven't decided yet whether to accept this patch.
I'll look into it more and decide.
>
> Out of curiosity, is any CI testing done on fat exported via NFS? At
> the moment I don't happen to include it in NFSD's CI matrix.
I don't maintain fat-fs, so I'm not sure if it's been verified with
some CI test.
However, if exfat support NFS export, I'll verify it with that test.
>
>
> > > 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
>
> --
> Chuck Lever
