Re: [PATCH v1 03/19] fs/anon_inodes: new interface to create new inode

From: Al Viro
Date: Fri Mar 11 2016 - 03:05:25 EST

On Fri, Mar 11, 2016 at 04:30:07PM +0900, Minchan Kim wrote:
> From: Gioh Kim <gurugio@xxxxxxxxxxx>
> The anon_inodes has already complete interfaces to create manage
> many anonymous inodes but don't have interface to get
> new inode. Other sub-modules can create anonymous inode
> without creating and mounting it's own pseudo filesystem.

IMO that's a bad idea. In case of aio "creating and mounting" takes this:
static struct dentry *aio_mount(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data)
static const struct dentry_operations ops = {
.d_dname = simple_dname,
return mount_pseudo(fs_type, "aio:", NULL, &ops, AIO_RING_MAGIC);
static struct file_system_type aio_fs = {
.name = "aio",
.mount = aio_mount,
.kill_sb = kill_anon_super,
aio_mnt = kern_mount(&aio_fs);

All of 12 lines. Your export is not much shorter. To quote old mail on
the same topic:

> Note that anon_inodes.c reason to exist was "it's for situations where
> all context lives on struct file and we don't need separate inode for
> them". Going from that to "it happens to contain a handy function for inode
> allocation"...