ocfs2: store cookie in private data

Store the cookie to detect concurrent seeks on directories in
file->private_data.

Link: https://lore.kernel.org/r/20240830-vfs-file-f_version-v1-13-6d3e4816aa7b@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/ocfs2/dir.c

@@ -1932,6 +1932,7 @@ int ocfs2_readdir(struct file *file, struct dir_context *ctx)
 {
 	int error = 0;
 	struct inode *inode = file_inode(file);
+	struct ocfs2_file_private *fp = file->private_data;
 	int lock_level = 0;
 
 	trace_ocfs2_readdir((unsigned long long)OCFS2_I(inode)->ip_blkno);
@@ -1952,7 +1953,7 @@ int ocfs2_readdir(struct file *file, struct dir_context *ctx)
 		goto bail_nolock;
 	}
 
-	error = ocfs2_dir_foreach_blk(inode, &file->f_version, ctx, false);
+	error = ocfs2_dir_foreach_blk(inode, &fp->cookie, ctx, false);
 
 	ocfs2_inode_unlock(inode, lock_level);
 	if (error)

fs/ocfs2/file.c

@@ -2750,6 +2750,13 @@ static loff_t ocfs2_remap_file_range(struct file *file_in, loff_t pos_in,
 	return remapped > 0 ? remapped : ret;
 }
 
+static loff_t ocfs2_dir_llseek(struct file *file, loff_t offset, int whence)
+{
+	struct ocfs2_file_private *fp = file->private_data;
+
+	return generic_llseek_cookie(file, offset, whence, &fp->cookie);
+}
+
 const struct inode_operations ocfs2_file_iops = {
 	.setattr	= ocfs2_setattr,
 	.getattr	= ocfs2_getattr,
@@ -2797,7 +2804,7 @@ const struct file_operations ocfs2_fops = {
 
 WRAP_DIR_ITER(ocfs2_readdir) // FIXME!
 const struct file_operations ocfs2_dops = {
-	.llseek		= generic_file_llseek,
+	.llseek		= ocfs2_dir_llseek,
 	.read		= generic_read_dir,
 	.iterate_shared	= shared_ocfs2_readdir,
 	.fsync		= ocfs2_sync_file,
@@ -2843,7 +2850,7 @@ const struct file_operations ocfs2_fops_no_plocks = {
 };
 
 const struct file_operations ocfs2_dops_no_plocks = {
-	.llseek		= generic_file_llseek,
+	.llseek		= ocfs2_dir_llseek,
 	.read		= generic_read_dir,
 	.iterate_shared	= shared_ocfs2_readdir,
 	.fsync		= ocfs2_sync_file,

fs/ocfs2/file.h

@@ -20,6 +20,7 @@ struct ocfs2_alloc_context;
 enum ocfs2_alloc_restarted;
 
 struct ocfs2_file_private {
+	u64			cookie;
 	struct file		*fp_file;
 	struct mutex		fp_mutex;
 	struct ocfs2_lock_res	fp_flock;