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

From: Gioh Kim
Date: Fri Mar 11 2016 - 09:24:51 EST

On 11.03.2016 09:05, Al Viro wrote:
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:
I know what aio_setup() does. It can be a solution.
But I thought creating anon_inode_new() is simpler than several drivers create its own pseudo filesystem.
Creating a filesystem requires memory allocation and locking some lists even though it is pseudo.

Could you inform me if there is a reason we should avoid creating anonymous inode?

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

Best regards,
Gioh Kim