[PATCH v3 2/4] exportfs: split out the ops for layout-based block device access

Chuck Lever
2026-04-23T18:19:02Z

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>
---
MAINTAINERS | 2 +-
fs/nfsd/blocklayout.c | 14 ++++++------
fs/nfsd/nfs4layouts.c | 9 ++++----
fs/xfs/xfs_export.c | 4 +---
fs/xfs/xfs_pnfs.c | 12 ++++++++---
fs/xfs/xfs_pnfs.h | 11 +++++-----
include/linux/exportfs.h | 25 +++++++---------------
include/linux/exportfs_block.h | 39 ++++++++++++++++++++++++++++++++++
8 files changed, 74 insertions(+), 42 deletions(-)
create mode 100644 include/linux/exportfs_block.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 4e4edad57d46..d2ff02cee0cb 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -9892,7 +9892,7 @@ 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>
diff --git a/fs/nfsd/blocklayout.c b/fs/nfsd/blocklayout.c
index 24cc5025f649..e612fcf8666a 100644
--- a/fs/nfsd/blocklayout.c
+++ b/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
diff --git a/fs/nfsd/nfs4layouts.c b/fs/nfsd/nfs4layouts.c
index 69e41105efdd..cf5b7eb417c5 100644
--- a/fs/nfsd/nfs4layouts.c
+++ b/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)
diff --git a/fs/xfs/xfs_export.c b/fs/xfs/xfs_export.c
index e3e3c3c89840..9b2ad3786b19 100644
--- a/fs/xfs/xfs_export.c
+++ b/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
};
diff --git a/fs/xfs/xfs_pnfs.c b/fs/xfs/xfs_pnfs.c
index 221e55887a2a..12e083f1b9ba 100644
--- a/fs/xfs/xfs_pnfs.c
+++ b/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,
+};
diff --git a/fs/xfs/xfs_pnfs.h b/fs/xfs/xfs_pnfs.h
index 940c6c2ad88c..bf43b2009e4c 100644
--- a/fs/xfs/xfs_pnfs.h
+++ b/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 */
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..1f52fea8e4dc
--- /dev/null
+++ b/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 */
--
2.53.0