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

John Groves
2024-02-26T22:43:28Z

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