exportfs: split out the ops for layout-based block device access

The support to grant layouts for direct block device access works
at a very different layer than the rest of exports.  Split the methods
for it into a separate struct, and move that into a separate header
to better split things out.  The pointer to the new operation vector
is kept in export_operations to avoid bloating the super_block.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Link: https://patch.msgid.link/20260423181854.743150-3-cel@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

MAINTAINERS

@@ -9903,7 +9903,7 @@ S:	Supported
 F:	Documentation/filesystems/nfs/exporting.rst
 F:	fs/exportfs/
 F:	fs/fhandle.c
-F:	include/linux/exportfs.h
+F:	include/linux/exportfs*.h
 
 FILESYSTEMS [IDMAPPED MOUNTS]
 M:	Christian Brauner <brauner@kernel.org>

fs/nfsd/blocklayout.c

@@ -2,7 +2,7 @@
 /*
  * Copyright (c) 2014-2016 Christoph Hellwig.
  */
-#include <linux/exportfs.h>
+#include <linux/exportfs_block.h>
 #include <linux/iomap.h>
 #include <linux/slab.h>
 #include <linux/pr.h>
@@ -32,8 +32,8 @@ nfsd4_block_map_extent(struct inode *inode, const struct svc_fh *fhp,
 	u32 device_generation = 0;
 	int error;
 
-	error = sb->s_export_op->map_blocks(inode, offset, length, &iomap,
-			iomode != IOMODE_READ, &device_generation);
+	error = sb->s_export_op->block_ops->map_blocks(inode, offset, length,
+			&iomap, iomode != IOMODE_READ, &device_generation);
 	if (error) {
 		if (error == -ENXIO)
 			return nfserr_layoutunavailable;
@@ -199,8 +199,8 @@ nfsd4_block_commit_blocks(struct inode *inode, struct nfsd4_layoutcommit *lcp,
 		iattr.ia_size = lcp->lc_newsize;
 	}
 
-	error = inode->i_sb->s_export_op->commit_blocks(inode, iomaps,
-			nr_iomaps, &iattr);
+	error = inode->i_sb->s_export_op->block_ops->commit_blocks(inode,
+			iomaps, nr_iomaps, &iattr);
 	kfree(iomaps);
 	return nfserrno(error);
 }
@@ -223,8 +223,8 @@ nfsd4_block_get_device_info_simple(struct super_block *sb,
 
 	b->type = PNFS_BLOCK_VOLUME_SIMPLE;
 	b->simple.sig_len = PNFS_BLOCK_UUID_LEN;
-	return sb->s_export_op->get_uuid(sb, b->simple.sig, &b->simple.sig_len,
-			&b->simple.offset);
+	return sb->s_export_op->block_ops->get_uuid(sb, b->simple.sig,
+			&b->simple.sig_len, &b->simple.offset);
 }
 
 static __be32

fs/nfsd/nfs4layouts.c

@@ -3,6 +3,7 @@
  * Copyright (c) 2014 Christoph Hellwig.
  */
 #include <linux/blkdev.h>
+#include <linux/exportfs_block.h>
 #include <linux/kmod.h>
 #include <linux/file.h>
 #include <linux/jhash.h>
@@ -129,6 +130,7 @@ void nfsd4_setup_layout_type(struct svc_export *exp)
 {
 #if defined(CONFIG_NFSD_BLOCKLAYOUT) || defined(CONFIG_NFSD_SCSILAYOUT)
 	struct super_block *sb = exp->ex_path.mnt->mnt_sb;
+	const struct exportfs_block_ops *bops = sb->s_export_op->block_ops;
 #endif
 
 	if (!(exp->ex_flags & NFSEXP_PNFS))
@@ -138,14 +140,11 @@ void nfsd4_setup_layout_type(struct svc_export *exp)
 	exp->ex_layout_types |= 1 << LAYOUT_FLEX_FILES;
 #endif
 #ifdef CONFIG_NFSD_BLOCKLAYOUT
-	if (sb->s_export_op->get_uuid &&
-	    sb->s_export_op->map_blocks &&
-	    sb->s_export_op->commit_blocks)
+	if (bops && bops->get_uuid && bops->map_blocks && bops->commit_blocks)
 		exp->ex_layout_types |= 1 << LAYOUT_BLOCK_VOLUME;
 #endif
 #ifdef CONFIG_NFSD_SCSILAYOUT
-	if (sb->s_export_op->map_blocks &&
-	    sb->s_export_op->commit_blocks &&
+	if (bops && bops->map_blocks && bops->commit_blocks &&
 	    sb->s_bdev &&
 	    sb->s_bdev->bd_disk->fops->pr_ops &&
 	    sb->s_bdev->bd_disk->fops->get_unique_id)

fs/xfs/xfs_export.c

@@ -244,8 +244,6 @@ const struct export_operations xfs_export_operations = {
 	.get_parent		= xfs_fs_get_parent,
 	.commit_metadata	= xfs_fs_nfs_commit_metadata,
 #ifdef CONFIG_EXPORTFS_BLOCK_OPS
-	.get_uuid		= xfs_fs_get_uuid,
-	.map_blocks		= xfs_fs_map_blocks,
-	.commit_blocks		= xfs_fs_commit_blocks,
+	.block_ops		= &xfs_export_block_ops,
 #endif
 };

fs/xfs/xfs_pnfs.c

@@ -49,7 +49,7 @@ xfs_break_leased_layouts(
  * Get a unique ID including its location so that the client can identify
  * the exported device.
  */
-int
+static int
 xfs_fs_get_uuid(
 	struct super_block	*sb,
 	u8			*buf,
@@ -104,7 +104,7 @@ xfs_fs_map_update_inode(
 /*
  * Get a layout for the pNFS client.
  */
-int
+static int
 xfs_fs_map_blocks(
 	struct inode		*inode,
 	loff_t			offset,
@@ -252,7 +252,7 @@ xfs_pnfs_validate_isize(
  * to manually flush the cache here similar to what the fsync code path does
  * for datasyncs on files that have no dirty metadata.
  */
-int
+static int
 xfs_fs_commit_blocks(
 	struct inode		*inode,
 	struct iomap		*maps,
@@ -332,3 +332,9 @@ xfs_fs_commit_blocks(
 	xfs_iunlock(ip, XFS_IOLOCK_EXCL);
 	return error;
 }
+
+const struct exportfs_block_ops xfs_export_block_ops = {
+	.get_uuid		= xfs_fs_get_uuid,
+	.map_blocks		= xfs_fs_map_blocks,
+	.commit_blocks		= xfs_fs_commit_blocks,
+};

fs/xfs/xfs_pnfs.h

@@ -2,13 +2,9 @@
 #ifndef _XFS_PNFS_H
 #define _XFS_PNFS_H 1
 
-#ifdef CONFIG_EXPORTFS_BLOCK_OPS
-int xfs_fs_get_uuid(struct super_block *sb, u8 *buf, u32 *len, u64 *offset);
-int xfs_fs_map_blocks(struct inode *inode, loff_t offset, u64 length,
-		struct iomap *iomap, bool write, u32 *device_generation);
-int xfs_fs_commit_blocks(struct inode *inode, struct iomap *maps, int nr_maps,
-		struct iattr *iattr);
+#include <linux/exportfs_block.h>
 
+#ifdef CONFIG_EXPORTFS_BLOCK_OPS
 int xfs_break_leased_layouts(struct inode *inode, uint *iolock,
 		bool *did_unlock);
 #else
@@ -18,4 +14,7 @@ xfs_break_leased_layouts(struct inode *inode, uint *iolock, bool *did_unlock)
 	return 0;
 }
 #endif /* CONFIG_EXPORTFS_BLOCK_OPS */
+
+extern const struct exportfs_block_ops xfs_export_block_ops;
+
 #endif /* _XFS_PNFS_H */

include/linux/exportfs.h

@@ -6,9 +6,8 @@
 #include <linux/path.h>
 
 struct dentry;
-struct iattr;
+struct exportfs_block_ops;
 struct inode;
-struct iomap;
 struct super_block;
 struct vfsmount;
 
@@ -260,19 +259,13 @@ struct handle_to_path_ctx {
  * @commit_metadata:
  *    @commit_metadata should commit metadata changes to stable storage.
  *
- * @get_uuid:
- *    Get a filesystem unique signature exposed to clients.
- *
- * @map_blocks:
- *    Map and, if necessary, allocate blocks for a layout.
- *
- * @commit_blocks:
- *    Commit blocks in a layout once the client is done with them.
- *
  * @flags:
  *    Allows the filesystem to communicate to nfsd that it may want to do things
  *    differently when dealing with it.
  *
+ * @block_ops:
+ *    Operations for layout grants to block on the underlying device.
+ *
  * Locking rules:
  *    get_parent is called with child->d_inode->i_rwsem down
  *    get_name is not (which is possibly inconsistent)
@@ -290,12 +283,6 @@ struct export_operations {
 	struct dentry * (*get_parent)(struct dentry *child);
 	int (*commit_metadata)(struct inode *inode);
 
-	int (*get_uuid)(struct super_block *sb, u8 *buf, u32 *len, u64 *offset);
-	int (*map_blocks)(struct inode *inode, loff_t offset,
-			  u64 len, struct iomap *iomap,
-			  bool write, u32 *device_generation);
-	int (*commit_blocks)(struct inode *inode, struct iomap *iomaps,
-			     int nr_iomaps, struct iattr *iattr);
 	int (*permission)(struct handle_to_path_ctx *ctx, unsigned int oflags);
 	struct file * (*open)(const struct path *path, unsigned int oflags);
 #define	EXPORT_OP_NOWCC			(0x1) /* don't collect v3 wcc data */
@@ -308,6 +295,10 @@ struct export_operations {
 #define EXPORT_OP_FLUSH_ON_CLOSE	(0x20) /* fs flushes file data on close */
 #define EXPORT_OP_NOLOCKS		(0x40) /* no file locking support */
 	unsigned long	flags;
+
+#ifdef CONFIG_EXPORTFS_BLOCK_OPS
+	const struct exportfs_block_ops *block_ops;
+#endif
 };
 
 /**

include/linux/exportfs_block.h

@@ -0,0 +1,39 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2014-2026 Christoph Hellwig.
+ *
+ * Support for exportfs-based layout grants for direct block device access.
+ */
+#ifndef LINUX_EXPORTFS_BLOCK_H
+#define LINUX_EXPORTFS_BLOCK_H 1
+
+#include <linux/types.h>
+
+struct iattr;
+struct inode;
+struct iomap;
+struct super_block;
+
+struct exportfs_block_ops {
+	/*
+	 * Get the in-band device unique signature exposed to clients.
+	 */
+	int (*get_uuid)(struct super_block *sb, u8 *buf, u32 *len, u64 *offset);
+
+	/*
+	 * Map blocks for direct block access.
+	 * If @write is %true, also allocate the blocks for the range if needed.
+	 */
+	int (*map_blocks)(struct inode *inode, loff_t offset, u64 len,
+			struct iomap *iomap, bool write,
+			u32 *device_generation);
+
+	/*
+	 * Commit blocks previously handed out by ->map_blocks and written to by
+	 * the client.
+	 */
+	int (*commit_blocks)(struct inode *inode, struct iomap *iomaps,
+			int nr_iomaps, struct iattr *iattr);
+};
+
+#endif /* LINUX_EXPORTFS_BLOCK_H */