On Tue, 2023-04-25 at 16:01 +0300, Amir Goldstein wrote:
> So far, all callers of exportfs_encode_inode_fh(), except for fsnotify's
> show_mark_fhandle(), check that filesystem can decode file handles, but
> we would like to add more callers that do not require a file handle that
> can be decoded.
>
> Introduce a flag to explicitly request a file handle that may not to be
> decoded later and a wrapper exportfs_encode_fid() that sets this flag
> and convert show_mark_fhandle() to use the new wrapper.
>
> This will be used to allow adding fanotify support to filesystems that
> do not support NFS export.
>
> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
> Documentation/filesystems/nfs/exporting.rst | 4 ++--
> fs/exportfs/expfs.c | 18 ++++++++++++++++--
> fs/notify/fanotify/fanotify.c | 4 ++--
> fs/notify/fdinfo.c | 2 +-
> include/linux/exportfs.h | 12 +++++++++++-
> 5 files changed, 32 insertions(+), 8 deletions(-)
>
> diff --git a/Documentation/filesystems/nfs/exporting.rst b/Documentation/filesystems/nfs/exporting.rst
> index 0e98edd353b5..3d97b8d8f735 100644
> --- a/Documentation/filesystems/nfs/exporting.rst
> +++ b/Documentation/filesystems/nfs/exporting.rst
> @@ -122,8 +122,8 @@ are exportable by setting the s_export_op field in the struct
> super_block. This field must point to a "struct export_operations"
> struct which has the following members:
>
> - encode_fh (optional)
> - Takes a dentry and creates a filehandle fragment which can later be used
> + encode_fh (optional)
> + Takes a dentry and creates a filehandle fragment which may later be used
> to find or create a dentry for the same object. The default
> implementation creates a filehandle fragment that encodes a 32bit inode
> and generation number for the inode encoded, and if necessary the
> diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
> index bf1b4925fedd..1b35dda5bdda 100644
> --- a/fs/exportfs/expfs.c
> +++ b/fs/exportfs/expfs.c
> @@ -381,11 +381,25 @@ static int export_encode_fh(struct inode *inode, struct fid *fid,
> return type;
> }
>
> +/**
> + * exportfs_encode_inode_fh - encode a file handle from inode
> + * @inode: the object to encode
> + * @fid: where to store the file handle fragment
> + * @max_len: maximum length to store there
> + * @flags: properties of the requrested file handle
> + */
> int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid,
> - int *max_len, struct inode *parent)
> + int *max_len, struct inode *parent, int flags)
> {
> const struct export_operations *nop = inode->i_sb->s_export_op;
>
> + /*
> + * If a decodeable file handle was requested, we need to make sure that
> + * filesystem can decode file handles.
> + */
> + if (nop && !(flags & EXPORT_FH_FID) && !nop->fh_to_dentry)
> + return -EOPNOTSUPP;
> +
If you're moving this check into this function, then it might be good to
remove the same check from the callers that are doing this check now.
> if (nop && nop->encode_fh)
> return nop->encode_fh(inode, fid->raw, max_len, parent);
>
> @@ -416,7 +430,7 @@ int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len,
> parent = p->d_inode;
> }
>
> - error = exportfs_encode_inode_fh(inode, fid, max_len, parent);
> + error = exportfs_encode_inode_fh(inode, fid, max_len, parent, flags);
> dput(p);
>
> return error;
> diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
> index 29bdd99b29fa..d1a49f5b6e6d 100644
> --- a/fs/notify/fanotify/fanotify.c
> +++ b/fs/notify/fanotify/fanotify.c
> @@ -380,7 +380,7 @@ static int fanotify_encode_fh_len(struct inode *inode)
> if (!inode)
> return 0;
>
> - exportfs_encode_inode_fh(inode, NULL, &dwords, NULL);
> + exportfs_encode_inode_fh(inode, NULL, &dwords, NULL, 0);
> fh_len = dwords << 2;
>
> /*
> @@ -443,7 +443,7 @@ static int fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode,
> }
>
> dwords = fh_len >> 2;
> - type = exportfs_encode_inode_fh(inode, buf, &dwords, NULL);
> + type = exportfs_encode_inode_fh(inode, buf, &dwords, NULL, 0);
> err = -EINVAL;
> if (!type || type == FILEID_INVALID || fh_len != dwords << 2)
> goto out_err;
> diff --git a/fs/notify/fdinfo.c b/fs/notify/fdinfo.c
> index 55081ae3a6ec..5c430736ec12 100644
> --- a/fs/notify/fdinfo.c
> +++ b/fs/notify/fdinfo.c
> @@ -50,7 +50,7 @@ static void show_mark_fhandle(struct seq_file *m, struct inode *inode)
> f.handle.handle_bytes = sizeof(f.pad);
> size = f.handle.handle_bytes >> 2;
>
> - ret = exportfs_encode_inode_fh(inode, (struct fid *)f.handle.f_handle, &size, NULL);
> + ret = exportfs_encode_fid(inode, (struct fid *)f.handle.f_handle, &size);
> if ((ret == FILEID_INVALID) || (ret < 0)) {
> WARN_ONCE(1, "Can't encode file handler for inotify: %d\n", ret);
> return;
> diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
> index 2b1048238170..635e89e1dae7 100644
> --- a/include/linux/exportfs.h
> +++ b/include/linux/exportfs.h
> @@ -136,6 +136,7 @@ struct fid {
> };
>
> #define EXPORT_FH_CONNECTABLE 0x1
> +#define EXPORT_FH_FID 0x2
Please add comments about what these flags are intended to indicate.
>
> /**
> * struct export_operations - for nfsd to communicate with file systems
> @@ -226,9 +227,18 @@ struct export_operations {
> };
>
> extern int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid,
> - int *max_len, struct inode *parent);
> + int *max_len, struct inode *parent,
> + int flags);
> extern int exportfs_encode_fh(struct dentry *dentry, struct fid *fid,
> int *max_len, int flags);
> +
> +static inline int exportfs_encode_fid(struct inode *inode, struct fid *fid,
> + int *max_len)
> +{
> + return exportfs_encode_inode_fh(inode, fid, max_len, NULL,
> + EXPORT_FH_FID);
> +}
> +
> extern struct dentry *exportfs_decode_fh_raw(struct vfsmount *mnt,
> struct fid *fid, int fh_len,
> int fileid_type,
--
Jeff Layton <jlayton@xxxxxxxxxx>
