On Tue, Oct 20, 2015 at 02:32:32PM +0200, Andrzej Pietrasiewicz wrote:
> From: Krzysztof Opasiak <k.opasiak@xxxxxxxxxxx>
>
> This change is necessary for the SCSI target usb gadget composed with
> configfs. In this case configfs will be used for two different purposes:
> to compose a usb gadget and to configure the target part. If an instance
> of tcm function is created in $CONFIGFS_ROOT/usb_gadget/<gadget>/functions
> a tpg can be created in $CONFIGFS_ROOT/target/usb_gadget/<wwn>/, but after
> a tpg is created the tcm function must not be removed until its
> corresponding tpg is gone. While the configfs_depend/undepend_item() are
> meant exactly for creating this kind of dependencies, they are not suitable
> if the other kernel subsystem happens to be another subsystem in configfs,
> so this patch adds unlocked versions meant for configfs callbacks.
>
> Signed-off-by: Krzysztof Opasiak <k.opasiak@xxxxxxxxxxx>
> [updated the commit log]
> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@xxxxxxxxxxx>
> ---
> fs/configfs/dir.c | 29 +++++++++++++++++++++++++++++
> include/linux/configfs.h | 9 +++++++++
> 2 files changed, 38 insertions(+)
>
> diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
> index c81ce7f..1e1ae76 100644
> --- a/fs/configfs/dir.c
> +++ b/fs/configfs/dir.c
> @@ -1152,6 +1152,35 @@ void configfs_undepend_item(struct configfs_subsystem *subsys,
> }
> EXPORT_SYMBOL(configfs_undepend_item);
>
> +int configfs_depend_item_unlocked(struct config_item *target)
> +{
> + struct configfs_dirent *sd;
> + int ret = -ENOENT;
> +
> + spin_lock(&configfs_dirent_lock);
> + BUG_ON(!target->ci_dentry);
> +
> + sd = target->ci_dentry->d_fsdata;
> + if ((sd->s_type & CONFIGFS_DIR) &&
> + ((sd->s_type & CONFIGFS_USET_DROPPING) ||
> + (sd->s_type & CONFIGFS_USET_CREATING)))
> + goto out_unlock_dirent_lock;
> +
> + sd->s_dependent_count += 1;
> + ret = 0;
> +
> +out_unlock_dirent_lock:
> + spin_unlock(&configfs_dirent_lock);
> + return ret;
> +}
> +EXPORT_SYMBOL(configfs_depend_item_unlocked);
This version lacks configfs_depend_prep(); how do you guard against
parents being in the middle of removal? It's not just this entry being
DROPPING, it's also parents.
I also worry about the lack of pinning the fs. I think that might be
OK, because your source already has a hold on the fs, but I'm not 100%
sure.
Joel
--
"What does it say about a society's priorities when the time you
spend in meetings on Monday is greater than the total number of
hours you spent sleeping over the weekend?"
- Nat Friedman
http://www.jlbec.org/
jlbec@xxxxxxxxxxxx
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