Re: [PATCH 3/5] exportfs: make ->encode_fh() a mandatory method for NFS export

[Dave Kleikamp <dave.kleikamp@oracle.com>]

On 10/18/23 9:16AM, Jeff Layton wrote:
> On Wed, 2023-10-18 at 12:59 +0300, Amir Goldstein wrote:
>> export_operations ->encode_fh() no longer has a default implementation to
>> encode FILEID_INO32_GEN* file handles.
>>
>> 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.

Isn't it possible for some of these filesystems to be compiled without 
CONFIG_EXPORTFS set? Should exportfs.h define an null 
generic_encode_ino32_fh() in that case?

Shaggy

>>
>> This is a step towards allowing filesystems to encode non-decodeable file
>> handles for fanotify without having to implement any export_operations.
>>
>> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
>> ---
>>   Documentation/filesystems/nfs/exporting.rst |  7 ++-----
>>   Documentation/filesystems/porting.rst       |  9 +++++++++
>>   fs/affs/namei.c                             |  1 +
>>   fs/befs/linuxvfs.c                          |  1 +
>>   fs/efs/super.c                              |  1 +
>>   fs/erofs/super.c                            |  1 +
>>   fs/exportfs/expfs.c                         | 14 ++++++++------
>>   fs/ext2/super.c                             |  1 +
>>   fs/ext4/super.c                             |  1 +
>>   fs/f2fs/super.c                             |  1 +
>>   fs/fat/nfs.c                                |  1 +
>>   fs/jffs2/super.c                            |  1 +
>>   fs/jfs/super.c                              |  1 +
>>   fs/ntfs/namei.c                             |  1 +
>>   fs/ntfs3/super.c                            |  1 +
>>   fs/smb/client/export.c                      |  9 +++------
>>   fs/squashfs/export.c                        |  1 +
>>   fs/ufs/super.c                              |  1 +
>>   include/linux/exportfs.h                    |  4 +++-
>>   19 files changed, 39 insertions(+), 18 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..197ef78a5014 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.
>> +Fillesystems 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..30da4539e257 100644
>> --- a/fs/exportfs/expfs.c
>> +++ b/fs/exportfs/expfs.c
>> @@ -343,20 +343,21 @@ static int get_name(const struct path *path, char *name, struct dentry *child)
>>   }
>>   
>>   /**
>> - * 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
>> + * @fh:      where to store the file handle fragment
>>    * @max_len: maximum length to store there
>>    * @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 5661a363005e..661ffb5aa1e0 100644
>> --- a/fs/ntfs3/super.c
>> +++ b/fs/ntfs3/super.c
>> @@ -789,6 +789,7 @@ 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..834e9c9197b4 100644
>> --- a/fs/smb/client/export.c
>> +++ b/fs/smb/client/export.c
>> @@ -41,13 +41,10 @@ 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..6b6e01321405 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 +279,8 @@ extern struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
>>   /*
>>    * Generic helpers for filesystems.
>>    */
>> +int generic_encode_ino32_fh(struct inode *inode, __u32 *fh, int *max_len,
>> +			    struct inode *parent);
>>   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));
> 
> Looks straightforward.
> 
> Reviewed-by: Jeff Layton <jlayton@kernel.org>