Re: [RFC PATCH 11/20] famfs: Add fs_context_operations

Jonathan Cameron
2024-02-26T13:20:24Z

On Fri, 23 Feb 2024 11:41:55 -0600
John Groves <John@Groves.net> wrote:

> 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>
Trivial comments inline.

> ---
> 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) {
reverse logic would be simpler and reduce indent.

if (!inode)
return NULL;

> + 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;
Always initialized so no need to do it here.

> +
> + 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;
return rc; //unless you need to do more in out in later patch..

> +
> + 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;
return -ENOMEM;

return 0;

> +
> +out:
> + return rc;
> +}
> +
> +enum famfs_param {
> + Opt_mode,
> + Opt_dax,
Why capital O?

> +};
> +

...

> +
> +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);

New toys might be good to use from start to avoid need for explicit
unlocks in error paths.

scoped_guard(mutex, &famfs_context_mutex) {
list_for_each_entry(fsi_entry, &famfs_context_list, fsi_list) {
if (strcmp(fsi_entry->rootdev, cs_source) == 0) {
//could invert with a continue to reduce indent
// or factor this out as a little helper.
// famfs_check_not_mounted()
pr_err();
return -EALREADY;
}
}
list_add(&fsi->fs_list, &famfs_context_list);
}

return get_tree_nodev(...

> + 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);
> +
> +}

>
> MODULE_LICENSE("GPL");