[RFC PATCH 03/10] ftrfs: add inode operations

[Aurelien DESBRIERES <aurelien@hackers.camp>]

From: Aurélien DESBRIERES <aurelien@hackers.camp>

Implement ftrfs_iget() to read inodes from the on-disk inode table:

- Locate inode block from s_inode_table_blk and inode number
- Read raw ftrfs_inode via sb_bread()
- Verify per-inode CRC32 checksum
- Populate VFS inode fields (mode, uid, gid, size, timestamps)
- Copy direct/indirect block pointers to ftrfs_inode_info
- Assign inode_operations and file_operations based on file type
- Use inode_state_read_once() for I_NEW test (kernel 7.0 API)

Signed-off-by: Aurélien DESBRIERES <aurelien@hackers.camp>
---
 fs/ftrfs/inode.c | 103 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 103 insertions(+)
 create mode 100644 fs/ftrfs/inode.c

diff --git a/fs/ftrfs/inode.c b/fs/ftrfs/inode.c
new file mode 100644
index 000000000..e1279c796
--- /dev/null
+++ b/fs/ftrfs/inode.c
@@ -0,0 +1,103 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * FTRFS — Inode operations
+ * Author: roastercode - Aurelien DESBRIERES <aurelien@hackers.camp>
+ */
+
+#include <linux/fs.h>
+#include <linux/buffer_head.h>
+#include <linux/slab.h>
+#include <linux/time.h>
+#include "ftrfs.h"
+
+/*
+ * ftrfs_iget — read inode from disk into VFS
+ * @sb:  superblock
+ * @ino: inode number (1-based)
+ *
+ * Inode table starts at s_inode_table_blk.
+ * Each block holds FTRFS_BLOCK_SIZE / sizeof(ftrfs_inode) inodes.
+ */
+struct inode *ftrfs_iget(struct super_block *sb, unsigned long ino)
+{
+	struct ftrfs_sb_info    *sbi = FTRFS_SB(sb);
+	struct ftrfs_inode_info *fi;
+	struct ftrfs_inode      *raw;
+	struct buffer_head      *bh;
+	struct inode            *inode;
+	unsigned long            inodes_per_block;
+	unsigned long            block, offset;
+	__u32                    crc;
+
+	inode = iget_locked(sb, ino);
+	if (!inode)
+		return ERR_PTR(-ENOMEM);
+
+	/* Already in cache */
+	if (!(inode_state_read_once(inode) & I_NEW))
+		return inode;
+
+	inodes_per_block = FTRFS_BLOCK_SIZE / sizeof(struct ftrfs_inode);
+	block  = le64_to_cpu(sbi->s_ftrfs_sb->s_inode_table_blk)
+		 + (ino - 1) / inodes_per_block;
+	offset = (ino - 1) % inodes_per_block;
+
+	bh = sb_bread(sb, block);
+	if (!bh) {
+		pr_err("ftrfs: unable to read inode block %lu\n", block);
+		iget_failed(inode);
+		return ERR_PTR(-EIO);
+	}
+
+	raw = (struct ftrfs_inode *)bh->b_data + offset;
+	/* Verify inode CRC32 */
+	crc = ftrfs_crc32(raw, offsetof(struct ftrfs_inode, i_crc32));
+	if (crc != le32_to_cpu(raw->i_crc32)) {
+		pr_err("ftrfs: inode %lu CRC32 mismatch\n", ino);
+		brelse(bh);
+		iget_failed(inode);
+		return ERR_PTR(-EIO);
+	}
+
+	fi = FTRFS_I(inode);
+
+	/* Populate VFS inode */
+	inode->i_mode  = le16_to_cpu(raw->i_mode);
+	inode->i_uid   = make_kuid(sb->s_user_ns, le16_to_cpu(raw->i_uid));
+	inode->i_gid   = make_kgid(sb->s_user_ns, le16_to_cpu(raw->i_gid));
+	set_nlink(inode, le16_to_cpu(raw->i_nlink));
+	inode->i_size  = le64_to_cpu(raw->i_size);
+	inode->i_blocks = le32_to_cpu(raw->i_blocks);
+
+	inode_set_atime(inode,
+		le64_to_cpu(raw->i_atime) / NSEC_PER_SEC,
+		le64_to_cpu(raw->i_atime) % NSEC_PER_SEC);
+	inode_set_mtime(inode,
+		le64_to_cpu(raw->i_mtime) / NSEC_PER_SEC,
+		le64_to_cpu(raw->i_mtime) % NSEC_PER_SEC);
+	inode_set_ctime(inode,
+		le64_to_cpu(raw->i_ctime) / NSEC_PER_SEC,
+		le64_to_cpu(raw->i_ctime) % NSEC_PER_SEC);
+
+	/* Copy block pointers to in-memory inode */
+	memcpy(fi->i_direct, raw->i_direct, sizeof(fi->i_direct));
+	fi->i_indirect  = raw->i_indirect;
+	fi->i_dindirect = raw->i_dindirect;
+	fi->i_flags     = le32_to_cpu(raw->i_flags);
+
+	/* Set ops based on file type */
+	if (S_ISDIR(inode->i_mode)) {
+		inode->i_op  = &ftrfs_dir_inode_operations;
+		inode->i_fop = &ftrfs_dir_operations;
+	} else if (S_ISREG(inode->i_mode)) {
+		inode->i_op  = &ftrfs_file_inode_operations;
+		inode->i_fop = &ftrfs_file_operations;
+	} else {
+		/* Special files: use generic */
+		init_special_inode(inode, inode->i_mode, 0);
+	}
+
+	brelse(bh);
+	unlock_new_inode(inode);
+	return inode;
+}
-- 
2.52.0