1 files changed, 88 insertions, 0 deletions
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 */