NFS: Add linux/nfs_fh.h

Plenty of spots around the kernel need the full definition of struct
nfs_fh but not the cred, sunrpc, and uapi dependencies that
linux/nfs.h pulls in along with it.

Relocate struct nfs_fh to its own header, and include that header in
linux/nfs.h so existing consumers keep building. Over time, consumers
can then replace

  #include <linux/nfs.h>

with

  #include <linux/nfs_fh.h>

While relocating the code, add kernel-doc comments for the FH
operations and convert nfs_compare_fh() to return bool.

Link: https://patch.msgid.link/20260720141442.783935-2-cel@kernel.org
Signed-off-by: Chuck Lever <cel@kernel.org>

2 files changed, 65 insertions, 37 deletions

diff --git a/include/linux/nfs.h b/include/linux/nfs.h
index 0906a0b40c6a..0e2a0b1e3061 100644
--- a/include/linux/nfs.h
+++ b/include/linux/nfs.h
@@ -11,8 +11,8 @@
 #include <linux/cred.h>
 #include <linux/sunrpc/auth.h>
 #include <linux/sunrpc/msg_prot.h>
-#include <linux/string.h>
-#include <linux/crc32.h>
+#include <linux/nfs_fh.h>
+
 #include <uapi/linux/nfs.h>
 
 /* The LOCALIO program is entirely private to Linux and is
@@ -22,30 +22,6 @@
 #define LOCALIOPROC_NULL		0
 #define LOCALIOPROC_UUID_IS_LOCAL	1
 
-/*
- * This is the kernel NFS client file handle representation
- */
-#define NFS_MAXFHSIZE		128
-struct nfs_fh {
-	unsigned short		size;
-	unsigned char		data[NFS_MAXFHSIZE];
-};
-
-/*
- * Returns a zero iff the size and data fields match.
- * Checks only "size" bytes in the data field.
- */
-static inline int nfs_compare_fh(const struct nfs_fh *a, const struct nfs_fh *b)
-{
-	return a->size != b->size || memcmp(a->data, b->data, a->size) != 0;
-}
-
-static inline void nfs_copy_fh(struct nfs_fh *target, const struct nfs_fh *source)
-{
-	target->size = source->size;
-	memcpy(target->data, source->data, source->size);
-}
-
 enum nfs3_stable_how {
 	NFS_UNSTABLE = 0,
 	NFS_DATA_SYNC = 1,
@@ -55,15 +31,4 @@ enum nfs3_stable_how {
 	NFS_INVALID_STABLE_HOW = -1
 };
 
-/**
- * nfs_fhandle_hash - calculate the crc32 hash for the filehandle
- * @fh - pointer to filehandle
- *
- * returns a crc32 hash for the filehandle that is compatible with
- * the one displayed by "wireshark".
- */
-static inline u32 nfs_fhandle_hash(const struct nfs_fh *fh)
-{
-	return ~crc32_le(0xFFFFFFFF, &fh->data[0], fh->size);
-}
 #endif /* _LINUX_NFS_H */
diff --git a/include/linux/nfs_fh.h b/include/linux/nfs_fh.h
new file mode 100644
index 000000000000..49dfc5ec60fe
--- /dev/null
+++ b/include/linux/nfs_fh.h
@@ -0,0 +1,63 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * struct nfs_fh is an NFS version-agnostic data structure that
+ * stores an NFS file handle. It is also commonly used in NFS
+ * related APIs.
+ */
+#ifndef _LINUX_NFS_FH_H
+#define _LINUX_NFS_FH_H
+
+#include <linux/types.h>
+#include <linux/string.h>
+#include <linux/crc32.h>
+
+/*
+ * The largest file handle size today is an NFSv4 file handle,
+ * which can be up to 128 octets long.
+ */
+#define NFS_MAXFHSIZE		128
+struct nfs_fh {
+	unsigned short		size;
+	unsigned char		data[NFS_MAXFHSIZE];
+};
+
+/**
+ * nfs_compare_fh - Compare two NFS file handles
+ * @a: An NFS file handle to be compared
+ * @b: An NFS file handle to be compared
+ *
+ * Checks only "size" bytes in each data field.
+ *
+ * Return: %false if the two file handles are equal, otherwise %true
+ */
+static inline bool nfs_compare_fh(const struct nfs_fh *a, const struct nfs_fh *b)
+{
+	return a->size != b->size || memcmp(a->data, b->data, a->size) != 0;
+}
+
+/**
+ * nfs_copy_fh - Copy an NFS file handle
+ * @target: Destination file handle
+ * @source: Source file handle
+ *
+ * Copies source->size bytes of file handle data into target.
+ */
+static inline void nfs_copy_fh(struct nfs_fh *target, const struct nfs_fh *source)
+{
+	target->size = source->size;
+	memcpy(target->data, source->data, source->size);
+}
+
+/**
+ * nfs_fhandle_hash - Calculate the crc32 hash for the filehandle
+ * @fh: An NFS file handle to hash
+ *
+ * Return: a crc32 hash for the filehandle that is compatible with
+ * the one displayed by "wireshark"
+ */
+static inline u32 nfs_fhandle_hash(const struct nfs_fh *fh)
+{
+	return ~crc32_le(0xFFFFFFFF, &fh->data[0], fh->size);
+}
+
+#endif /* _LINUX_NFS_FH_H */