2 files changed, 96 insertions, 17 deletions

diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
index 8bcdba28b406..c835bc64f4fa 100644
--- a/include/linux/exportfs.h
+++ b/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
 };
 
 /**
diff --git a/include/linux/exportfs_block.h b/include/linux/exportfs_block.h
new file mode 100644
index 000000000000..de519b7b599b
--- /dev/null
+++ b/include/linux/exportfs_block.h
@@ -0,0 +1,88 @@
+/* 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/blkdev.h>
+#include <linux/exportfs.h>
+#include <linux/fs.h>
+
+struct inode;
+struct iomap;
+struct super_block;
+
+/*
+ * There are the two types of block-style layout support:
+ *  - In-band implies a device identified by a unique cookie inside the actual
+ *    device address space checked by the ->get_uuid method as used by the pNFS
+ *    block layout.  This is a bit dangerous and deprecated.
+ *  - Out of band implies identification by out of band unique identifiers
+ *    specified by the storage protocol, which is much safer and used by the
+ *    pNFS SCSI/NVMe layouts.
+ */
+typedef unsigned int __bitwise expfs_block_layouts_t;
+#define EXPFS_BLOCK_FLAG(__bit) \
+	((__force expfs_block_layouts_t)(1u << __bit))
+#define EXPFS_BLOCK_IN_BAND_ID		EXPFS_BLOCK_FLAG(0)
+#define EXPFS_BLOCK_OUT_OF_BAND_ID	EXPFS_BLOCK_FLAG(1)
+
+struct exportfs_block_ops {
+	/*
+	 * Returns the EXPFS_BLOCK_* bitmap of supported layout types.
+	 */
+	expfs_block_layouts_t (*layouts_supported)(struct super_block *sb);
+
+	/*
+	 * 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, loff_t new_size);
+};
+
+static inline bool
+exportfs_bdev_supports_out_of_band_id(struct block_device *bdev)
+{
+	return bdev->bd_disk->fops->pr_ops &&
+		bdev->bd_disk->fops->get_unique_id;
+}
+
+#ifdef CONFIG_EXPORTFS_BLOCK_OPS
+static inline expfs_block_layouts_t
+exportfs_layouts_supported(struct super_block *sb)
+{
+	const struct exportfs_block_ops *bops = sb->s_export_op->block_ops;
+
+	if (!bops ||
+	    !bops->layouts_supported ||
+	    WARN_ON_ONCE(!bops->map_blocks) ||
+	    WARN_ON_ONCE(!bops->commit_blocks))
+		return 0;
+	return bops->layouts_supported(sb);
+}
+#else
+static inline expfs_block_layouts_t
+exportfs_layouts_supported(struct super_block *sb)
+{
+	return 0;
+}
+#endif /* CONFIG_EXPORTFS_BLOCK_OPS */
+
+#endif /* LINUX_EXPORTFS_BLOCK_H */