Start building up from the famfs module operations. This commit
includes the following:
* Register as a file system
* Parse mount parameters
* Allocate or find (and initialize) a superblock via famfs_get_tree()
* Lookup the host dax device, and bail if it's in use (or not dax)
* Register as the holder of the dax device if it's available
* Add Kconfig and Makefile misc to build famfs
* Add FAMFS_SUPER_MAGIC to include/uapi/linux/magic.h
* Add export of fs/namei.c:may_open_dev(), which famfs needs to call
* Update MAINTAINERS file for the fs/famfs/ path
The following exports had to happen to enable famfs:
* This uses the new fs/super.c:kill_char_super() - the other kill*super
helpers were not quite right.
* This uses the dev_dax_iomap export of dax_dev_get()
This commit builds but is otherwise too incomplete to run
Signed-off-by: John Groves <j...@groves.net>
---
MAINTAINERS | 1 +
fs/Kconfig | 2 +
fs/Makefile | 1 +
fs/famfs/Kconfig | 10 ++
fs/famfs/Makefile | 5 +
fs/famfs/famfs_inode.c | 345 +++++++++++++++++++++++++++++++++++++
fs/famfs/famfs_internal.h | 36 ++++
fs/namei.c | 1 +
include/uapi/linux/magic.h | 1 +
9 files changed, 402 insertions(+)
create mode 100644 fs/famfs/Kconfig
create mode 100644 fs/famfs/Makefile
create mode 100644 fs/famfs/famfs_inode.c
create mode 100644 fs/famfs/famfs_internal.h
diff --git a/MAINTAINERS b/MAINTAINERS
index 3f2d847dcf01..365d678e2f40 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8188,6 +8188,7 @@ L: linux-...@vger.kernel.org
L: linux-fsde...@vger.kernel.org
S: Supported
F: Documentation/filesystems/famfs.rst
+F: fs/famfs
FANOTIFY
M: Jan Kara <j...@suse.cz>
diff --git a/fs/Kconfig b/fs/Kconfig
index a46b0cbc4d8f..53b4629e92a0 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -140,6 +140,8 @@ source "fs/autofs/Kconfig"
source "fs/fuse/Kconfig"
source "fs/overlayfs/Kconfig"
+source "fs/famfs/Kconfig"
+
menu "Caches"
source "fs/netfs/Kconfig"
diff --git a/fs/Makefile b/fs/Makefile
index 6ecc9b0a53f2..3393f399a9e9 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -129,3 +129,4 @@ obj-$(CONFIG_EFIVAR_FS) += efivarfs/
obj-$(CONFIG_EROFS_FS) += erofs/
obj-$(CONFIG_VBOXSF_FS) += vboxsf/
obj-$(CONFIG_ZONEFS_FS) += zonefs/
+obj-$(CONFIG_FAMFS) += famfs/
diff --git a/fs/famfs/Kconfig b/fs/famfs/Kconfig
new file mode 100644
index 000000000000..edb8980820f7
--- /dev/null
+++ b/fs/famfs/Kconfig
@@ -0,0 +1,10 @@
+
+
+config FAMFS
+ tristate "famfs: shared memory file system"
+ depends on DEV_DAX && FS_DAX && DEV_DAX_IOMAP
+ help
+ Support for the famfs file system. Famfs is a dax file system that
+ can support scale-out shared access to fabric-attached memory
+ (e.g. CXL shared memory). Famfs is not a general purpose file system;
+ it is an enabler for data sets in shared memory.
diff --git a/fs/famfs/Makefile b/fs/famfs/Makefile
new file mode 100644
index 000000000000..62230bcd6793
--- /dev/null
+++ b/fs/famfs/Makefile
@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_FAMFS) += famfs.o
+
+famfs-y := famfs_inode.o
diff --git a/fs/famfs/famfs_inode.c b/fs/famfs/famfs_inode.c
new file mode 100644
index 000000000000..61306240fc0b
--- /dev/null
+++ b/fs/famfs/famfs_inode.c
@@ -0,0 +1,345 @@
+// 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/time.h>
+#include <linux/init.h>
+#include <linux/string.h>
+#include <linux/parser.h>
+#include <linux/magic.h>
+#include <linux/slab.h>
+#include <linux/fs_context.h>
+#include <linux/fs_parser.h>
+#include <linux/dax.h>
+#include <linux/hugetlb.h>
+#include <linux/iomap.h>
+#include <linux/path.h>
+#include <linux/namei.h>
+
+#include "famfs_internal.h"
+
+#define FAMFS_DEFAULT_MODE 0755
+
+static struct inode *famfs_get_inode(struct super_block *sb,
+ const struct inode *dir,
+ umode_t mode, dev_t dev)
+{
+ struct inode *inode = new_inode(sb);
+ struct timespec64 tv;
+
+ if (!inode)
+ return NULL;
+
+ inode->i_ino = get_next_ino();
+ inode_init_owner(&nop_mnt_idmap, inode, dir, mode);
+ inode->i_mapping->a_ops = &ram_aops;
+ mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
+ mapping_set_unevictable(inode->i_mapping);
+ tv = inode_set_ctime_current(inode);
+ inode_set_mtime_to_ts(inode, tv);
+ inode_set_atime_to_ts(inode, tv);
+
+ switch (mode & S_IFMT) {
+ default:
+ init_special_inode(inode, mode, dev);
+ break;
+ case S_IFREG:
+ inode->i_op = NULL /* famfs_file_inode_operations */;
+ inode->i_fop = NULL /* &famfs_file_operations */;
+ break;
+ case S_IFDIR:
+ inode->i_op = NULL /* famfs_dir_inode_operations */;
+ inode->i_fop = &simple_dir_operations;
+
+ /* Directory inodes start off with i_nlink == 2 (for ".") */
+ inc_nlink(inode);
+ break;
+ case S_IFLNK:
+ inode->i_op = &page_symlink_inode_operations;
+ inode_nohighmem(inode);
+ break;
+ }
+ return inode;
+}
+
+/*
+ * famfs dax_operations (for char dax)
+ */
+static int
+famfs_dax_notify_failure(struct dax_device *dax_dev, u64 offset,
+ u64 len, int mf_flags)
+{
+ struct super_block *sb = dax_holder(dax_dev);
+ struct famfs_fs_info *fsi = sb->s_fs_info;
+
+ pr_err("%s: rootdev=%s offset=%lld len=%llu flags=%x\n", __func__,
+ fsi->rootdev, offset, len, mf_flags);
+
+ return 0;
+}
+
+static const struct dax_holder_operations famfs_dax_holder_ops = {
+ .notify_failure = famfs_dax_notify_failure,
+};
+
+/*****************************************************************************
+ * fs_context_operations
+ */
+
+static int
+famfs_fill_super(struct super_block *sb, struct fs_context *fc)
+{
+ int rc = 0;
+
+ sb->s_maxbytes = MAX_LFS_FILESIZE;
+ sb->s_blocksize = PAGE_SIZE;
+ sb->s_blocksize_bits = PAGE_SHIFT;
+ sb->s_magic = FAMFS_SUPER_MAGIC;
+ sb->s_op = NULL /* famfs_super_ops */;
+ sb->s_time_gran = 1;
+
+ return rc;
+}
+
+static int
+lookup_daxdev(const char *pathname, dev_t *devno)
+{
+ struct inode *inode;
+ struct path path;
+ int err;
+
+ if (!pathname || !*pathname)
+ return -EINVAL;
+
+ err = kern_path(pathname, LOOKUP_FOLLOW, &path);
+ if (err)
+ return err;
+
+ inode = d_backing_inode(path.dentry);
+ if (!S_ISCHR(inode->i_mode)) {
+ err = -EINVAL;
+ goto out_path_put;
+ }
+
+ if (!may_open_dev(&path)) { /* had to export this */
+ err = -EACCES;
+ goto out_path_put;
+ }
+
+ /* if it's dax, i_rdev is struct dax_device */
+ *devno = inode->i_rdev;
+
+out_path_put:
+ path_put(&path);
+ return err;
+}
+
+static int
+famfs_get_tree(struct fs_context *fc)
+{
+ struct famfs_fs_info *fsi = fc->s_fs_info;
+ struct dax_device *dax_devp;
+ struct super_block *sb;
+ struct inode *inode;
+ dev_t daxdevno;
+ int err;
+
+ /* TODO: clean up chatty messages */
+
+ err = lookup_daxdev(fc->source, &daxdevno);
+ if (err)
+ return err;
+
+ fsi->daxdevno = daxdevno;
+
+ /* This will set sb->s_dev=daxdevno */
+ sb = sget_dev(fc, daxdevno);
+ if (IS_ERR(sb)) {
+ pr_err("%s: sget_dev error\n", __func__);
+ return PTR_ERR(sb);
+ }
+
+ if (sb->s_root) {
+ pr_info("%s: found a matching suerblock for %s\n",
+ __func__, fc->source);
+
+ /* We don't expect to find a match by dev_t; if we do, it must
+ * already be mounted, so we bail
+ */
+ err = -EBUSY;
+ goto deactivate_out;
+ } else {
+ pr_info("%s: initializing new superblock for %s\n",
+ __func__, fc->source);
+ err = famfs_fill_super(sb, fc);
+ if (err)
+ goto deactivate_out;
+ }
+
+ /* This will fail if it's not a dax device */
+ dax_devp = dax_dev_get(daxdevno);
+ if (!dax_devp) {
+ pr_warn("%s: device %s not found or not dax\n",
+ __func__, fc->source);
+ err = -ENODEV;
+ goto deactivate_out;
+ }
+
+ err = fs_dax_get(dax_devp, sb, &famfs_dax_holder_ops);
+ if (err) {
+ pr_err("%s: fs_dax_get(%lld) failed\n", __func__,
(u64)daxdevno);
+ err = -EBUSY;
+ goto deactivate_out;
+ }
+ fsi->dax_devp = dax_devp;
+
+ inode = famfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
+ sb->s_root = d_make_root(inode);
+ if (!sb->s_root) {
+ pr_err("%s: d_make_root() failed\n", __func__);
+ err = -ENOMEM;
+ fs_put_dax(fsi->dax_devp, sb);
+ goto deactivate_out;
+ }
+
+ sb->s_flags |= SB_ACTIVE;
+
+ WARN_ON(fc->root);
+ fc->root = dget(sb->s_root);
+ return err;
+
+deactivate_out:
+ pr_debug("%s: deactivating sb=%llx\n", __func__, (u64)sb);
+ deactivate_locked_super(sb);
+ return err;
+}
+
+/*****************************************************************************/
+
+enum famfs_param {
+ Opt_mode,
+ Opt_dax,
+};
+
+const struct fs_parameter_spec famfs_fs_parameters[] = {
+ fsparam_u32oct("mode", Opt_mode),
+ fsparam_string("dax", Opt_dax),
+ {}
+};
+
+static int famfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
+{
+ struct famfs_fs_info *fsi = fc->s_fs_info;
+ struct fs_parse_result result;
+ int opt;
+
+ opt = fs_parse(fc, famfs_fs_parameters, param, &result);
+ if (opt == -ENOPARAM) {
+ opt = vfs_parse_fs_param_source(fc, param);
+ if (opt != -ENOPARAM)
+ return opt;
+
+ return 0;
+ }
+ if (opt < 0)
+ return opt;
+
+ switch (opt) {
+ case Opt_mode:
+ fsi->mount_opts.mode = result.uint_32 & S_IALLUGO;
+ break;
+ case Opt_dax:
+ if (strcmp(param->string, "always"))
+ pr_notice("%s: invalid dax mode %s\n",
+ __func__, param->string);
+ break;
+ }
+
+ return 0;
+}
+
+static void famfs_free_fc(struct fs_context *fc)
+{
+ struct famfs_fs_info *fsi = fc->s_fs_info;
+
+ if (fsi && fsi->rootdev)
+ kfree(fsi->rootdev);
+
+ kfree(fsi);
+}
+
+static const struct fs_context_operations famfs_context_ops = {
+ .free = famfs_free_fc,
+ .parse_param = famfs_parse_param,
+ .get_tree = famfs_get_tree,
+};
+
+static int famfs_init_fs_context(struct fs_context *fc)
+{
+ struct famfs_fs_info *fsi;
+
+ fsi = kzalloc(sizeof(*fsi), GFP_KERNEL);
+ if (!fsi)
+ return -ENOMEM;
+
+ fsi->mount_opts.mode = FAMFS_DEFAULT_MODE;
+ fc->s_fs_info = fsi;
+ fc->ops = &famfs_context_ops;
+ return 0;
+}
+
+static void famfs_kill_sb(struct super_block *sb)
+{
+ struct famfs_fs_info *fsi = sb->s_fs_info;
+
+ if (fsi->dax_devp)
+ fs_put_dax(fsi->dax_devp, sb);
+ if (fsi && fsi->rootdev)
+ kfree(fsi->rootdev);
+ kfree(fsi);
+ sb->s_fs_info = NULL;
+
+ kill_char_super(sb); /* new */
+}
+
+#define MODULE_NAME "famfs"
+static struct file_system_type famfs_fs_type = {
+ .name = MODULE_NAME,
+ .init_fs_context = famfs_init_fs_context,
+ .parameters = famfs_fs_parameters,
+ .kill_sb = famfs_kill_sb,
+ .fs_flags = FS_USERNS_MOUNT,
+};
+
+/******************************************************************************
+ * Module stuff
+ */
+static int __init init_famfs_fs(void)
+{
+ int rc;
+
+ rc = register_filesystem(&famfs_fs_type);
+
+ return rc;
+}
+
+static void
+__exit famfs_exit(void)
+{
+ unregister_filesystem(&famfs_fs_type);
+ pr_info("%s: unregistered\n", __func__);
+}
+
+fs_initcall(init_famfs_fs);
+module_exit(famfs_exit);
+
+MODULE_AUTHOR("John Groves, Micron Technology");
+MODULE_LICENSE("GPL");
diff --git a/fs/famfs/famfs_internal.h b/fs/famfs/famfs_internal.h
new file mode 100644
index 000000000000..951b32ec4fbd
--- /dev/null
+++ b/fs/famfs/famfs_internal.h
@@ -0,0 +1,36 @@
+/* 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.
+ */
+#ifndef FAMFS_INTERNAL_H
+#define FAMFS_INTERNAL_H
+
+struct famfs_mount_opts {
+ umode_t mode;
+};
+
+/**
+ * @famfs_fs_info
+ *
+ * @mount_opts: the mount options
+ * @dax_devp: The underlying character devdax device
+ * @rootdev: Dax device path used in mount
+ * @daxdevno: Dax device dev_t
+ * @deverror: True if the dax device has called our notify_failure entry
+ * point, or if other "shutdown" conditions exist
+ */
+struct famfs_fs_info {
+ struct famfs_mount_opts mount_opts;
+ struct dax_device *dax_devp;
+ char *rootdev;
+ dev_t daxdevno;
+ bool deverror;
+};
+
+#endif /* FAMFS_INTERNAL_H */
diff --git a/fs/namei.c b/fs/namei.c
index c5b2a25be7d0..f24b268473cd 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3229,6 +3229,7 @@ bool may_open_dev(const struct path *path)
return !(path->mnt->mnt_flags & MNT_NODEV) &&
!(path->mnt->mnt_sb->s_iflags & SB_I_NODEV);
}
+EXPORT_SYMBOL(may_open_dev);
static int may_open(struct mnt_idmap *idmap, const struct path *path,
int acc_mode, int flag)
diff --git a/include/uapi/linux/magic.h b/include/uapi/linux/magic.h
index 1b40a968ba91..e9bdd6a415e2 100644
--- a/include/uapi/linux/magic.h
+++ b/include/uapi/linux/magic.h
@@ -37,6 +37,7 @@
#define HOSTFS_SUPER_MAGIC 0x00c0ffee
#define OVERLAYFS_SUPER_MAGIC 0x794c7630
#define FUSE_SUPER_MAGIC 0x65735546
+#define FAMFS_SUPER_MAGIC 0x87b282ff
#define MINIX_SUPER_MAGIC 0x137F /* minix v1 fs, 14 char names */
#define MINIX_SUPER_MAGIC2 0x138F /* minix v1 fs, 30 char names */
--
2.43.0
