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

[John Groves <John@groves.net>]

On 24/02/26 01:20PM, Jonathan Cameron wrote:
> 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;
> 

Good one - I can be derpy this way. Although I'd bet I just copied that
from ramfs...

> 
> > +		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.

Fixed in more than one place.

> 
> > +
> > +	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..

Done

> 
> > +
> > +	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;

Done

> 
> 	return 0;

Done

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

Direct copy from ramfs

> 
> > +};
> > +
> 
> ...
> 
> > +
> > +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(...

Hey, I like this one. Thanks!

John