Re: [PATCH v3 08/10] configfs: call fsnotify_rmdir() hook

[Amir Goldstein <amir73il@gmail.com>]

On Sun, May 26, 2019 at 5:34 PM Amir Goldstein <amir73il@gmail.com> wrote:
>
> This will allow generating fsnotify delete events on unregister
> of group/subsystem after the fsnotify_nameremove() hook is removed
> from d_delete().
>
> The rest of the d_delete() calls from this filesystem are either
> called recursively from within debugfs_unregister_{group,subsystem},
> called from a vfs function that already has delete hooks or are
> called from shutdown/cleanup code.
>
> Cc: Joel Becker <jlbec@evilplan.org>
> Cc: Christoph Hellwig <hch@lst.de>

Hi Christoph and Joel,

Per Christoph's request, I cc'ed you guys on the entire patch series
for context,
so my discussion with Greg [1] about the special status of configfs in
this patch set
should already be somewhere in your mailboxes...

Could I ask you to provide an ACK on this patch and on the chosen
policy. To recap:
Before patch set:
1. User gets create/delete events when files/dirs created/removed via vfs_*()
2. User does *not* get create events when files/dirs created via
debugfs_register_*()
3. User *does* get delete events when files/dirs removed via
debugfs_unregister_*()

After patch set:
1. No change
2. No change
3. User will get delete events only on the root group/subsystem dir
when tree is removed via debugfs_unregister_*()

For symmetry, we could also add create events for  root group/subsystem dir
when tree is created via debugfs_unregister_*(), but that would be a
followup patch.
For users though, it may be that delete events are more important than
create events
(i.e. for user cleanup tasks).

Thanks,
Amir.

[1] https://lore.kernel.org/linux-fsdevel/CAOQ4uxjyg5AVPrcR4bPm4zMY9BKmgV8g7TAuH--cfKNJv8pRYQ@mail.gmail.com/

> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> ---
>  fs/configfs/dir.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
> index 5e7932d668ab..ba17881a8d84 100644
> --- a/fs/configfs/dir.c
> +++ b/fs/configfs/dir.c
> @@ -27,6 +27,7 @@
>  #undef DEBUG
>
>  #include <linux/fs.h>
> +#include <linux/fsnotify.h>
>  #include <linux/mount.h>
>  #include <linux/module.h>
>  #include <linux/slab.h>
> @@ -1804,6 +1805,7 @@ void configfs_unregister_group(struct config_group *group)
>         configfs_detach_group(&group->cg_item);
>         d_inode(dentry)->i_flags |= S_DEAD;
>         dont_mount(dentry);
> +       fsnotify_rmdir(d_inode(parent), dentry);
>         d_delete(dentry);
>         inode_unlock(d_inode(parent));
>
> @@ -1932,6 +1934,7 @@ void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
>         configfs_detach_group(&group->cg_item);
>         d_inode(dentry)->i_flags |= S_DEAD;
>         dont_mount(dentry);
> +       fsnotify_rmdir(d_inode(root), dentry);
>         inode_unlock(d_inode(dentry));
>
>         d_delete(dentry);
> --
> 2.17.1
>