[RFC PATCH 11/20] famfs: Add fs_context_operations

John Groves
2024-02-23T17:42:49Z

This commit introduces the famfs fs_context_operations and
famfs_get_inode() which is used by the context operations.

Signed-off-by: John Groves <john@groves.net>
---
fs/famfs/famfs_inode.c | 178 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 178 insertions(+)

diff --git a/fs/famfs/famfs_inode.c b/fs/famfs/famfs_inode.c
index 82c861998093..f98f82962d7b 100644
--- a/fs/famfs/famfs_inode.c
+++ b/fs/famfs/famfs_inode.c
@@ -41,6 +41,50 @@ static const struct super_operations famfs_ops;
static const struct inode_operations famfs_file_inode_operations;
static const struct inode_operations famfs_dir_inode_operations;

+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);
+
+ if (inode) {
+ struct timespec64 tv;
+
+ 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 = &famfs_file_inode_operations;
+ inode->i_fop = &famfs_file_operations;
+ break;
+ case S_IFDIR:
+ inode->i_op = &famfs_dir_inode_operations;
+ inode->i_fop = &simple_dir_operations;
+
+ /* Directory inodes start off with i_nlink == 2 (for "." entry) */
+ inc_nlink(inode);
+ break;
+ case S_IFLNK:
+ inode->i_op = &page_symlink_inode_operations;
+ inode_nohighmem(inode);
+ break;
+ }
+ }
+ return inode;
+}
+
/**********************************************************************************
* famfs super_operations
*
@@ -150,6 +194,140 @@ famfs_open_device(
return 0;
}

+/*****************************************************************************************
+ * fs_context_operations
+ */
+static int
+famfs_fill_super(
+ struct super_block *sb,
+ struct fs_context *fc)
+{
+ struct famfs_fs_info *fsi = sb->s_fs_info;
+ struct inode *inode;
+ int rc = 0;
+
+ sb->s_maxbytes = MAX_LFS_FILESIZE;
+ sb->s_blocksize = PAGE_SIZE;
+ sb->s_blocksize_bits = PAGE_SHIFT;
+ sb->s_magic = FAMFS_MAGIC;
+ sb->s_op = &famfs_ops;
+ sb->s_time_gran = 1;
+
+ rc = famfs_open_device(sb, fc);
+ if (rc)
+ goto out;
+
+ inode = famfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
+ sb->s_root = d_make_root(inode);
+ if (!sb->s_root)
+ rc = -ENOMEM;
+
+out:
+ return rc;
+}
+
+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 DEFINE_MUTEX(famfs_context_mutex);
+static LIST_HEAD(famfs_context_list);
+
+static int famfs_get_tree(struct fs_context *fc)
+{
+ struct famfs_fs_info *fsi_entry;
+ struct famfs_fs_info *fsi = fc->s_fs_info;
+
+ fsi->rootdev = kstrdup(fc->source, GFP_KERNEL);
+ if (!fsi->rootdev)
+ return -ENOMEM;
+
+ /* Fail if famfs is already mounted from the same device */
+ mutex_lock(&famfs_context_mutex);
+ list_for_each_entry(fsi_entry, &famfs_context_list, fsi_list) {
+ if (strcmp(fsi_entry->rootdev, fc->source) == 0) {
+ mutex_unlock(&famfs_context_mutex);
+ pr_err("%s: already mounted from rootdev %s\n", __func__, fc->source);
+ return -EALREADY;
+ }
+ }
+
+ list_add(&fsi->fsi_list, &famfs_context_list);
+ mutex_unlock(&famfs_context_mutex);
+
+ return get_tree_nodev(fc, famfs_fill_super);
+
+}
+
+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;
+}

MODULE_LICENSE("GPL");
--
2.43.0