Re: [PATCH 00/11] sysfs tagged directories V5

Serge E. Hallyn
2008-06-10T22:50:35Z

Quoting Benjamin Thery (benjamin.thery@bull.net):
> Greg,
>
> Here is an updated version of the sysfs tagged directories that improves
> a bit the situation over the previous one.
>
> I've modified the patch 09 ("Enable tagging for net_class directories in
> sysfs") to be a bit less intrusive in sysfs core. I removed the #ifdef'd
> parts you didn't like in fs/sysfs/mount.c, and replaced it by a generic
> routine sysfs_ns_exit() that is called, if needed, by the namespace when
> it exits. This routine goes through every sysfs super blocks and calls
> the callback passed by the namespace to clean its tag.
>
> The patch is now splitted in two:
> * 09/11: the generic routine,
> * 10/11: the remaining network parts.
>
> The generic part can be merge with patch 05 ("sysfs: Implement sysfs
> tagged directory support.") but I left it separate for now to ease
> reviews.

Thanks. Not nearly as radical as I'd feared.

Greg, does this address your concern? It stops the need to put any
non-braindead code (i.e. the _exit notifier stuff) in fs/sysfs/mount.c for
any new namespaces needing sysfs tagging, leaving only simple
comparison/assignments.

> Serge's patch for user namespace is modified to use this new service too.
> No more #ifdef CONFIG_NET or #ifdef CONFIG_USER_NS in fs/sysfs/mount.c
> now.
>
>
> But, currently, a new namespace that wants to add its tag to sysfs dirs
> still need to modify fs/sysfs/mount.c in a few routines to manage the
> new tag member added in struct sysfs_tag_info: sysfs_fill_super(),
> sysfs_test_super(), sysfs_kill_sb() (see the last two patches).
> These changes are only the initialization and a bunch of comparisons.
>
> If we really want to go further, to get rid of these, I've thought
> about:
>
> * Extending sysfs_tagged_dir_operations with super blocks operations:
> - fill_sb_tag, test_sb_tag, kill_sb_tag
>
> * Add routines in sysfs to allow registration/unregistration of these
> operations structs in a list:
> - sysfs_register_tagged_dir_ops()...
>
> * Each subsystem concerned implements and registers its operations at
> boot.
>
> * In sysfs_fill_super(), sysfs_test_super() and sysfs_kill_sb(), add
> loops to go through all registered operations structs and calls the
> corresponding operations if it's present.
>
> But... I thought it was a bit overkill for the few namespaces that will
> actually need sysfs tagged directories.

Agreed. We expect device namespaces... anything else?

thanks,
-serge