This commit introduces fs/famfs/famfs_file.c and the famfs
file_operations for read/write.
This is not usable yet because:
* It calls dax_iomap_rw() with NULL iomap_ops (which will be
introduced in a subsequent commit).
* famfs_ioctl() is coming in a later commit, and it is necessary
to map a file to a memory allocation.
Signed-off-by: John Groves <john@xxxxxxxxxx>
---
fs/famfs/Makefile | 2 +-
fs/famfs/famfs_file.c | 122 ++++++++++++++++++++++++++++++++++++++
fs/famfs/famfs_inode.c | 2 +-
fs/famfs/famfs_internal.h | 2 +
4 files changed, 126 insertions(+), 2 deletions(-)
create mode 100644 fs/famfs/famfs_file.c
diff --git a/fs/famfs/Makefile b/fs/famfs/Makefile
index 62230bcd6793..8cac90c090a4 100644
--- a/fs/famfs/Makefile
+++ b/fs/famfs/Makefile
@@ -2,4 +2,4 @@
obj-$(CONFIG_FAMFS) += famfs.o
-famfs-y := famfs_inode.o
+famfs-y := famfs_inode.o famfs_file.o
diff --git a/fs/famfs/famfs_file.c b/fs/famfs/famfs_file.c
new file mode 100644
index 000000000000..48036c71d4ed
--- /dev/null
+++ b/fs/famfs/famfs_file.c
@@ -0,0 +1,122 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * famfs - dax file system for shared fabric-attached memory
+ *
+ * Copyright 2023-2024 Micron Technology, Inc.
+ *
+ * This file system, originally based on ramfs the dax support from xfs,
+ * is intended to allow multiple host systems to mount a common file system
+ * view of dax files that map to shared memory.
+ */
+
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/dax.h>
+#include <linux/iomap.h>
+
+#include "famfs_internal.h"
+
+/*********************************************************************
+ * file_operations
+ */
+
+/* Reject I/O to files that aren't in a valid state */
+static ssize_t
+famfs_file_invalid(struct inode *inode)
+{
+ if (!IS_DAX(inode)) {
+ pr_debug("%s: inode %llx IS_DAX is false\n", __func__, (u64)inode);
+ return -ENXIO;
+ }
+ return 0;
+}
+
+static ssize_t
+famfs_rw_prep(struct kiocb *iocb, struct iov_iter *ubuf)
+{
+ struct inode *inode = iocb->ki_filp->f_mapping->host;
+ struct super_block *sb = inode->i_sb;
+ struct famfs_fs_info *fsi = sb->s_fs_info;
+ size_t i_size = i_size_read(inode);
+ size_t count = iov_iter_count(ubuf);
+ size_t max_count;
+ ssize_t rc;
+
+ if (fsi->deverror)
+ return -ENODEV;
+
+ rc = famfs_file_invalid(inode);
+ if (rc)
+ return rc;
+
+ max_count = max_t(size_t, 0, i_size - iocb->ki_pos);
+
+ if (count > max_count)
+ iov_iter_truncate(ubuf, max_count);
+
+ if (!iov_iter_count(ubuf))
+ return 0;
+
+ return rc;
+}
+
+static ssize_t
+famfs_dax_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+ ssize_t rc;
+
+ rc = famfs_rw_prep(iocb, to);
+ if (rc)
+ return rc;
+
+ if (!iov_iter_count(to))
+ return 0;
+
+ rc = dax_iomap_rw(iocb, to, NULL /*&famfs_iomap_ops */);
+
+ file_accessed(iocb->ki_filp);
+ return rc;
+}
+
+/**
+ * famfs_dax_write_iter()
+ *
+ * We need our own write-iter in order to prevent append
+ *
+ * @iocb:
+ * @from: iterator describing the user memory source for the write
+ */
+static ssize_t
+famfs_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+ ssize_t rc;
+
+ rc = famfs_rw_prep(iocb, from);
+ if (rc)
+ return rc;
+
+ if (!iov_iter_count(from))
+ return 0;
+
+ return dax_iomap_rw(iocb, from, NULL /*&famfs_iomap_ops*/);
+}
+
+const struct file_operations famfs_file_operations = {
+ .owner = THIS_MODULE,
+
+ /* Custom famfs operations */
+ .write_iter = famfs_dax_write_iter,
+ .read_iter = famfs_dax_read_iter,
+ .unlocked_ioctl = NULL /*famfs_file_ioctl*/,
+ .mmap = NULL /* famfs_file_mmap */,
+
+ /* Force PMD alignment for mmap */
+ .get_unmapped_area = thp_get_unmapped_area,
+
+ /* Generic Operations */
+ .fsync = noop_fsync,
+ .splice_read = filemap_splice_read,
+ .splice_write = iter_file_splice_write,
+ .llseek = generic_file_llseek,
+};
+
diff --git a/fs/famfs/famfs_inode.c b/fs/famfs/famfs_inode.c
index e00e9cdecadf..490a2c0fd326 100644
--- a/fs/famfs/famfs_inode.c
+++ b/fs/famfs/famfs_inode.c
@@ -56,7 +56,7 @@ static struct inode *famfs_get_inode(struct super_block *sb,
break;
case S_IFREG:
inode->i_op = &famfs_file_inode_operations;
- inode->i_fop = NULL /* &famfs_file_operations */;
+ inode->i_fop = &famfs_file_operations;
break;
case S_IFDIR:
inode->i_op = &famfs_dir_inode_operations;
diff --git a/fs/famfs/famfs_internal.h b/fs/famfs/famfs_internal.h
index 951b32ec4fbd..36efaef425e7 100644
--- a/fs/famfs/famfs_internal.h
+++ b/fs/famfs/famfs_internal.h
@@ -11,6 +11,8 @@
#ifndef FAMFS_INTERNAL_H
#define FAMFS_INTERNAL_H
+extern const struct file_operations famfs_file_operations;
+
struct famfs_mount_opts {
umode_t mode;
};
--
2.43.0
