[RFC PATCH 05/10] ftrfs: add file operations

[Aurelien DESBRIERES <aurelien@hackers.camp>]

From: Aurélien DESBRIERES <aurelien@hackers.camp>

Implement basic file read/write using generic VFS helpers:

- ftrfs_file_operations: generic_file_read_iter, generic_file_write_iter
- ftrfs_file_inode_operations: getattr via simple_getattr
- ftrfs_address_space_operations: readpage via block_read_full_folio,
  writepage via block_write_full_folio, bmap via generic_block_bmap

Read path delegates to the page cache via generic helpers.
Write path is wired but depends on the block allocator (alloc.c)
and write_inode (namei.c) for persistence.

Signed-off-by: Aurélien DESBRIERES <aurelien@hackers.camp>
---
 fs/ftrfs/file.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)
 create mode 100644 fs/ftrfs/file.c

diff --git a/fs/ftrfs/file.c b/fs/ftrfs/file.c
new file mode 100644
index 000000000..ef121359b
--- /dev/null
+++ b/fs/ftrfs/file.c
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * FTRFS — File operations (skeleton)
+ * Author: roastercode - Aurelien DESBRIERES <aurelien@hackers.camp>
+ *
+ * NOTE: read/write use generic_file_* for now.
+ * The EDAC/RS layer will intercept at the block I/O level (next iteration).
+ */
+
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include "ftrfs.h"
+
+const struct file_operations ftrfs_file_operations = {
+	.llseek         = generic_file_llseek,
+	.read_iter      = generic_file_read_iter,
+	.write_iter     = generic_file_write_iter,
+	.mmap           = generic_file_mmap,
+	.fsync          = generic_file_fsync,
+	.splice_read    = filemap_splice_read,
+};
+
+const struct inode_operations ftrfs_file_inode_operations = {
+	.getattr        = simple_getattr,
+};
-- 
2.52.0