exportfs: make ->encode_fh() a mandatory method for NFS export

Rename the default helper for encoding FILEID_INO32_GEN* file handles to
generic_encode_ino32_fh() and convert the filesystems that used the
default implementation to use the generic helper explicitly.

After this change, exportfs_encode_inode_fh() no longer has a default
implementation to encode FILEID_INO32_GEN* file handles.

This is a step towards allowing filesystems to encode non-decodeable
file handles for fanotify without having to implement any
export_operations.

Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Link: https://lore.kernel.org/r/20231023180801.2953446-3-amir73il@gmail.com
Acked-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>

19 files changed, 47 insertions, 19 deletions

diff --git a/Documentation/filesystems/nfs/exporting.rst b/Documentation/filesystems/nfs/exporting.rst
index 4b30daee399a..de64d2d002a2 100644
--- a/Documentation/filesystems/nfs/exporting.rst
+++ b/Documentation/filesystems/nfs/exporting.rst
@@ -122,12 +122,9 @@ 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)
+  encode_fh (mandatory)
     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
-    same information for the parent.
+    to find or create a dentry for the same object.
 
   fh_to_dentry (mandatory)
     Given a filehandle fragment, this should find the implied object and
diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst
index 4d05b9862451..9cc6cb27c4d5 100644
--- a/Documentation/filesystems/porting.rst
+++ b/Documentation/filesystems/porting.rst
@@ -1045,3 +1045,12 @@ filesystem type is now moved to a later point when the devices are closed:
 As this is a VFS level change it has no practical consequences for filesystems
 other than that all of them must use one of the provided kill_litter_super(),
 kill_anon_super(), or kill_block_super() helpers.
+
+---
+
+**mandatory**
+
+export_operations ->encode_fh() no longer has a default implementation to
+encode FILEID_INO32_GEN* file handles.
+Filesystems that used the default implementation may use the generic helper
+generic_encode_ino32_fh() explicitly.
diff --git a/fs/affs/namei.c b/fs/affs/namei.c
index 2fe4a5832fcf..d6b9758ee23d 100644
--- a/fs/affs/namei.c
+++ b/fs/affs/namei.c
@@ -568,6 +568,7 @@ static struct dentry *affs_fh_to_parent(struct super_block *sb, struct fid *fid,
 }
 
 const struct export_operations affs_export_ops = {
+	.encode_fh = generic_encode_ino32_fh,
 	.fh_to_dentry = affs_fh_to_dentry,
 	.fh_to_parent = affs_fh_to_parent,
 	.get_parent = affs_get_parent,
diff --git a/fs/befs/linuxvfs.c b/fs/befs/linuxvfs.c
index 9a16a51fbb88..410dcaffd5ab 100644
--- a/fs/befs/linuxvfs.c
+++ b/fs/befs/linuxvfs.c
@@ -96,6 +96,7 @@ static const struct address_space_operations befs_symlink_aops = {
 };
 
 static const struct export_operations befs_export_operations = {
+	.encode_fh	= generic_encode_ino32_fh,
 	.fh_to_dentry	= befs_fh_to_dentry,
 	.fh_to_parent	= befs_fh_to_parent,
 	.get_parent	= befs_get_parent,
diff --git a/fs/efs/super.c b/fs/efs/super.c
index b287f47c165b..f17fdac76b2e 100644
--- a/fs/efs/super.c
+++ b/fs/efs/super.c
@@ -123,6 +123,7 @@ static const struct super_operations efs_superblock_operations = {
 };
 
 static const struct export_operations efs_export_ops = {
+	.encode_fh	= generic_encode_ino32_fh,
 	.fh_to_dentry	= efs_fh_to_dentry,
 	.fh_to_parent	= efs_fh_to_parent,
 	.get_parent	= efs_get_parent,
diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index 3700af9ee173..edbe07a24156 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -626,6 +626,7 @@ static struct dentry *erofs_get_parent(struct dentry *child)
 }
 
 static const struct export_operations erofs_export_ops = {
+	.encode_fh = generic_encode_ino32_fh,
 	.fh_to_dentry = erofs_fh_to_dentry,
 	.fh_to_parent = erofs_fh_to_parent,
 	.get_parent = erofs_get_parent,
diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index 9ee205df8fa7..8f883c4758f5 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -343,20 +343,21 @@ out:
 }
 
 /**
- * export_encode_fh - default export_operations->encode_fh function
+ * generic_encode_ino32_fh - generic export_operations->encode_fh function
  * @inode:   the object to encode
- * @fid:     where to store the file handle fragment
- * @max_len: maximum length to store there
+ * @fh:      where to store the file handle fragment
+ * @max_len: maximum length to store there (in 4 byte units)
  * @parent:  parent directory inode, if wanted
  *
- * This default encode_fh function assumes that the 32 inode number
+ * This generic encode_fh function assumes that the 32 inode number
  * is suitable for locating an inode, and that the generation number
  * can be used to check that it is still valid.  It places them in the
  * filehandle fragment where export_decode_fh expects to find them.
  */
-static int export_encode_fh(struct inode *inode, struct fid *fid,
-		int *max_len, struct inode *parent)
+int generic_encode_ino32_fh(struct inode *inode, __u32 *fh, int *max_len,
+			    struct inode *parent)
 {
+	struct fid *fid = (void *)fh;
 	int len = *max_len;
 	int type = FILEID_INO32_GEN;
 
@@ -380,6 +381,7 @@ static int export_encode_fh(struct inode *inode, struct fid *fid,
 	*max_len = len;
 	return type;
 }
+EXPORT_SYMBOL_GPL(generic_encode_ino32_fh);
 
 /**
  * exportfs_encode_inode_fh - encode a file handle from inode
@@ -402,7 +404,7 @@ int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid,
 	if (nop && nop->encode_fh)
 		return nop->encode_fh(inode, fid->raw, max_len, parent);
 
-	return export_encode_fh(inode, fid, max_len, parent);
+	return -EOPNOTSUPP;
 }
 EXPORT_SYMBOL_GPL(exportfs_encode_inode_fh);
 
diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index aaf3e3e88cb2..b9f158a34997 100644
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -397,6 +397,7 @@ static struct dentry *ext2_fh_to_parent(struct super_block *sb, struct fid *fid,
 }
 
 static const struct export_operations ext2_export_ops = {
+	.encode_fh = generic_encode_ino32_fh,
 	.fh_to_dentry = ext2_fh_to_dentry,
 	.fh_to_parent = ext2_fh_to_parent,
 	.get_parent = ext2_get_parent,
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index dbebd8b3127e..c44db1915437 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1646,6 +1646,7 @@ static const struct super_operations ext4_sops = {
 };
 
 static const struct export_operations ext4_export_ops = {
+	.encode_fh = generic_encode_ino32_fh,
 	.fh_to_dentry = ext4_fh_to_dentry,
 	.fh_to_parent = ext4_fh_to_parent,
 	.get_parent = ext4_get_parent,
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index a8c8232852bb..60cfa11f65bf 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -3282,6 +3282,7 @@ static struct dentry *f2fs_fh_to_parent(struct super_block *sb, struct fid *fid,
 }
 
 static const struct export_operations f2fs_export_ops = {
+	.encode_fh = generic_encode_ino32_fh,
 	.fh_to_dentry = f2fs_fh_to_dentry,
 	.fh_to_parent = f2fs_fh_to_parent,
 	.get_parent = f2fs_get_parent,
diff --git a/fs/fat/nfs.c b/fs/fat/nfs.c
index 3626eb585a98..c52e63e10d35 100644
--- a/fs/fat/nfs.c
+++ b/fs/fat/nfs.c
@@ -279,6 +279,7 @@ static struct dentry *fat_get_parent(struct dentry *child_dir)
 }
 
 const struct export_operations fat_export_ops = {
+	.encode_fh	= generic_encode_ino32_fh,
 	.fh_to_dentry   = fat_fh_to_dentry,
 	.fh_to_parent   = fat_fh_to_parent,
 	.get_parent     = fat_get_parent,
diff --git a/fs/jffs2/super.c b/fs/jffs2/super.c
index 7ea37f49f1e1..f99591a634b4 100644
--- a/fs/jffs2/super.c
+++ b/fs/jffs2/super.c
@@ -150,6 +150,7 @@ static struct dentry *jffs2_get_parent(struct dentry *child)
 }
 
 static const struct export_operations jffs2_export_ops = {
+	.encode_fh = generic_encode_ino32_fh,
 	.get_parent = jffs2_get_parent,
 	.fh_to_dentry = jffs2_fh_to_dentry,
 	.fh_to_parent = jffs2_fh_to_parent,
diff --git a/fs/jfs/super.c b/fs/jfs/super.c
index 2e2f7f6d36a0..2cc2632f3c47 100644
--- a/fs/jfs/super.c
+++ b/fs/jfs/super.c
@@ -896,6 +896,7 @@ static const struct super_operations jfs_super_operations = {
 };
 
 static const struct export_operations jfs_export_operations = {
+	.encode_fh	= generic_encode_ino32_fh,
 	.fh_to_dentry	= jfs_fh_to_dentry,
 	.fh_to_parent	= jfs_fh_to_parent,
 	.get_parent	= jfs_get_parent,
diff --git a/fs/ntfs/namei.c b/fs/ntfs/namei.c
index ab44f2db533b..d7498ddc4a72 100644
--- a/fs/ntfs/namei.c
+++ b/fs/ntfs/namei.c
@@ -384,6 +384,7 @@ static struct dentry *ntfs_fh_to_parent(struct super_block *sb, struct fid *fid,
  * and due to using iget() whereas NTFS needs ntfs_iget().
  */
 const struct export_operations ntfs_export_ops = {
+	.encode_fh	= generic_encode_ino32_fh,
 	.get_parent	= ntfs_get_parent,	/* Find the parent of a given
 						   directory. */
 	.fh_to_dentry	= ntfs_fh_to_dentry,
diff --git a/fs/ntfs3/super.c b/fs/ntfs3/super.c
index f763e3256ccc..9153dffde950 100644
--- a/fs/ntfs3/super.c
+++ b/fs/ntfs3/super.c
@@ -811,6 +811,7 @@ static int ntfs_nfs_commit_metadata(struct inode *inode)
 }
 
 static const struct export_operations ntfs_export_ops = {
+	.encode_fh = generic_encode_ino32_fh,
 	.fh_to_dentry = ntfs_fh_to_dentry,
 	.fh_to_parent = ntfs_fh_to_parent,
 	.get_parent = ntfs3_get_parent,
diff --git a/fs/smb/client/export.c b/fs/smb/client/export.c
index 37c28415df1e..d606e8cbcb7d 100644
--- a/fs/smb/client/export.c
+++ b/fs/smb/client/export.c
@@ -41,13 +41,12 @@ static struct dentry *cifs_get_parent(struct dentry *dentry)
 }
 
 const struct export_operations cifs_export_ops = {
+	.encode_fh = generic_encode_ino32_fh,
 	.get_parent = cifs_get_parent,
-/*	Following five export operations are unneeded so far and can default:
-	.get_dentry =
-	.get_name =
-	.find_exported_dentry =
-	.decode_fh =
-	.encode_fs =  */
+/*
+ * Following export operations are mandatory for NFS export support:
+ *	.fh_to_dentry =
+ */
 };
 
 #endif /* CONFIG_CIFS_NFSD_EXPORT */
diff --git a/fs/squashfs/export.c b/fs/squashfs/export.c
index 723763746238..62972f0ff868 100644
--- a/fs/squashfs/export.c
+++ b/fs/squashfs/export.c
@@ -173,6 +173,7 @@ __le64 *squashfs_read_inode_lookup_table(struct super_block *sb,
 
 
 const struct export_operations squashfs_export_ops = {
+	.encode_fh = generic_encode_ino32_fh,
 	.fh_to_dentry = squashfs_fh_to_dentry,
 	.fh_to_parent = squashfs_fh_to_parent,
 	.get_parent = squashfs_get_parent
diff --git a/fs/ufs/super.c b/fs/ufs/super.c
index 23377c1baed9..a480810cd4e3 100644
--- a/fs/ufs/super.c
+++ b/fs/ufs/super.c
@@ -137,6 +137,7 @@ static struct dentry *ufs_get_parent(struct dentry *child)
 }
 
 static const struct export_operations ufs_export_ops = {
+	.encode_fh = generic_encode_ino32_fh,
 	.fh_to_dentry	= ufs_fh_to_dentry,
 	.fh_to_parent	= ufs_fh_to_parent,
 	.get_parent	= ufs_get_parent,
diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
index 5b3c9f30b422..85bd027494e5 100644
--- a/include/linux/exportfs.h
+++ b/include/linux/exportfs.h
@@ -235,7 +235,7 @@ extern int exportfs_encode_fh(struct dentry *dentry, struct fid *fid,
 
 static inline bool exportfs_can_encode_fid(const struct export_operations *nop)
 {
-	return nop;
+	return nop && nop->encode_fh;
 }
 
 static inline bool exportfs_can_decode_fh(const struct export_operations *nop)
@@ -279,6 +279,13 @@ extern struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
 /*
  * Generic helpers for filesystems.
  */
+#ifdef CONFIG_EXPORTFS
+int generic_encode_ino32_fh(struct inode *inode, __u32 *fh, int *max_len,
+			    struct inode *parent);
+#else
+#define generic_encode_ino32_fh NULL
+#endif
+
 extern struct dentry *generic_fh_to_dentry(struct super_block *sb,
 	struct fid *fid, int fh_len, int fh_type,
 	struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen));