On Thu, Aug 31, 2023 at 10:31:07AM +0200, Greg KH wrote: > On Mon, Aug 28, 2023 at 03:05:41PM +1000, Alistair Francis wrote: > > On Wed, Aug 23, 2023 at 5:02 PM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > > On Tue, Aug 22, 2023 at 04:20:06PM -0400, Alistair Francis wrote: > > > > On Sat, Aug 19, 2023 at 6:57 AM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > > > > > > On Thu, Aug 17, 2023 at 07:58:09PM -0400, Alistair Francis wrote: > > > > > > The documentation for sysfs_merge_group() specifically says > > > > > > > > > > > > This function returns an error if the group doesn't exist or any of the > > > > > > files already exist in that group, in which case none of the new files > > > > > > are created. > > > > > > > > > > > > So just not adding the group if it's empty doesn't work, at least not > > > > > > with the code we currently have. The code can be changed to support > > > > > > this, but it is difficult to determine how this will affect existing use > > > > > > cases. > > > > > > > > > > Did you try? I'd really really really prefer we do it this way as it's > > > > > much simpler overall to have the sysfs core "do the right thing > > > > > automatically" than to force each and every bus/subsystem to have to > > > > > manually add this type of attribute. > > > > > > > > > > Also, on a personal level, I want this function to work as it will allow > > > > > us to remove some code in some busses that don't really need to be there > > > > > (dynamic creation of some device attributes), which will then also allow > > > > > me to remove some apis in the driver core that should not be used at all > > > > > anymore (but keep creeping back in as there is still a few users.) > > > > > > > > > > So I'll be selfish here and say "please try to get my proposed change to > > > > > work, it's really the correct thing to do here." > > > > > > > > I did try! > > > > > > > > This is an attempt: > > > > https://github.com/alistair23/linux/commit/56b55756a2d7a66f7b6eb8a5692b1b5e2f81a9a9 > > > > > > > > It is based on your original patch with a bunch of: > > > > > > > > if (!parent) { > > > > parent = kernfs_create_dir_ns(kobj->sd, grp->name, > > > > S_IRWXU | S_IRUGO | S_IXUGO, > > > > uid, gid, kobj, NULL); > > > > ... > > > > } > > > > > > > > > > > > added throughout the code base. > > > > > > > > Very basic testing shows that it does what I need it to do and I don't > > > > see any kernel oops on boot. > > > > > > Nice! > > > > > > Mind if I take it and clean it up a bit and test with it here? Again, I > > > need this functionality for other stuff as well, so getting it merged > > > for your feature is fine with me. > > > > Sure! Go ahead. Sorry I was travelling last week. > > > > > > > > > I prefer the approach I have in this mailing list patch. But if you > > > > like the commit mentioned above I can tidy and clean it up and then > > > > use that instead > > > > > > I would rather do it this way. I can work on this on Friday if you want > > > me to. > > > > Yeah, that's fine with me. If you aren't able to let me know and I can > > finish up the patch and send it with this series > > Great, and for the email record, as github links are not stable, here's > the patch that you have above attached below. I'll test this out and > clean it up a bit more and see how it goes... > > thanks, > > greg k-h > > > From 2929d17b58d02dcf52d0345fa966c616e09a5afa Mon Sep 17 00:00:00 2001 > From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > Date: Wed, 24 Aug 2022 15:45:36 +0200 > Subject: [PATCH] sysfs: do not create empty directories if no attributes are > present > > When creating an attribute group, if it is named a subdirectory is > created and the sysfs files are placed into that subdirectory. If no > files are created, normally the directory would still be present, but it > would be empty. Clean this up by removing the directory if no files > were successfully created in the group at all. > > Co-developed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > Co-developed-by: Alistair Francis <alistair.francis@xxxxxxx> > Signed-off-by: Alistair Francis <alistair.francis@xxxxxxx> > --- > fs/sysfs/file.c | 14 ++++++++++-- > fs/sysfs/group.c | 56 ++++++++++++++++++++++++++++++++++++------------ > 2 files changed, 54 insertions(+), 16 deletions(-) > > diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c > index a12ac0356c69..7aab6c09662c 100644 > --- a/fs/sysfs/file.c > +++ b/fs/sysfs/file.c > @@ -391,8 +391,18 @@ int sysfs_add_file_to_group(struct kobject *kobj, > kernfs_get(parent); > } > > - if (!parent) > - return -ENOENT; > + if (!parent) { > + parent = kernfs_create_dir_ns(kobj->sd, group, > + S_IRWXU | S_IRUGO | S_IXUGO, > + uid, gid, kobj, NULL); > + if (IS_ERR(parent)) { > + if (PTR_ERR(parent) == -EEXIST) > + sysfs_warn_dup(kobj->sd, group); > + return PTR_ERR(parent); > + } > + > + kernfs_get(parent); > + } > > kobject_get_ownership(kobj, &uid, &gid); > error = sysfs_add_file_mode_ns(parent, attr, attr->mode, uid, gid, > diff --git a/fs/sysfs/group.c b/fs/sysfs/group.c > index 138676463336..013fa333cd3c 100644 > --- a/fs/sysfs/group.c > +++ b/fs/sysfs/group.c > @@ -31,12 +31,14 @@ static void remove_files(struct kernfs_node *parent, > kernfs_remove_by_name(parent, (*bin_attr)->attr.name); > } > > +/* returns -ERROR if error, or >= 0 for number of files actually created */ > static int create_files(struct kernfs_node *parent, struct kobject *kobj, > kuid_t uid, kgid_t gid, > const struct attribute_group *grp, int update) > { > struct attribute *const *attr; > struct bin_attribute *const *bin_attr; > + int files_created = 0; > int error = 0, i; > > if (grp->attrs) { > @@ -65,6 +67,8 @@ static int create_files(struct kernfs_node *parent, struct kobject *kobj, > gid, NULL); > if (unlikely(error)) > break; > + > + files_created++; > } > if (error) { > remove_files(parent, grp); > @@ -95,12 +99,15 @@ static int create_files(struct kernfs_node *parent, struct kobject *kobj, > NULL); > if (error) > break; > + files_created++; > } > if (error) > remove_files(parent, grp); > } > exit: > - return error; > + if (error) > + return error; > + return files_created; > } > > > @@ -130,9 +137,14 @@ static int internal_create_group(struct kobject *kobj, int update, > if (update) { > kn = kernfs_find_and_get(kobj->sd, grp->name); > if (!kn) { > - pr_warn("Can't update unknown attr grp name: %s/%s\n", > - kobj->name, grp->name); > - return -EINVAL; > + kn = kernfs_create_dir_ns(kobj->sd, grp->name, > + S_IRWXU | S_IRUGO | S_IXUGO, > + uid, gid, kobj, NULL); > + if (IS_ERR(kn)) { > + if (PTR_ERR(kn) == -EEXIST) > + sysfs_warn_dup(kobj->sd, grp->name); > + return PTR_ERR(kn); > + } > } > } else { > kn = kernfs_create_dir_ns(kobj->sd, grp->name, > @@ -150,11 +162,18 @@ static int internal_create_group(struct kobject *kobj, int update, > > kernfs_get(kn); > error = create_files(kn, kobj, uid, gid, grp, update); > - if (error) { > + if (error <= 0) { > + /* > + * If an error happened _OR_ if no files were created in the > + * attribute group, and we have a name for this group, delete > + * the name so there's not an empty directory. > + */ > if (grp->name) > kernfs_remove(kn); > + } else { > + error = 0; > + kernfs_put(kn); > } > - kernfs_put(kn); > > if (grp->name && update) > kernfs_put(kn); > @@ -318,13 +337,12 @@ void sysfs_remove_groups(struct kobject *kobj, > EXPORT_SYMBOL_GPL(sysfs_remove_groups); > > /** > - * sysfs_merge_group - merge files into a pre-existing attribute group. > + * sysfs_merge_group - merge files into a attribute group. > * @kobj: The kobject containing the group. > * @grp: The files to create and the attribute group they belong to. > * > - * This function returns an error if the group doesn't exist or any of the > - * files already exist in that group, in which case none of the new files > - * are created. > + * This function returns an error if any of the files already exist in > + * that group, in which case none of the new files are created. > */ > int sysfs_merge_group(struct kobject *kobj, > const struct attribute_group *grp) > @@ -336,12 +354,22 @@ int sysfs_merge_group(struct kobject *kobj, > struct attribute *const *attr; > int i; > > - parent = kernfs_find_and_get(kobj->sd, grp->name); > - if (!parent) > - return -ENOENT; > - > kobject_get_ownership(kobj, &uid, &gid); > > + parent = kernfs_find_and_get(kobj->sd, grp->name); > + if (!parent) { > + parent = kernfs_create_dir_ns(kobj->sd, grp->name, > + S_IRWXU | S_IRUGO | S_IXUGO, > + uid, gid, kobj, NULL); > + if (IS_ERR(parent)) { > + if (PTR_ERR(parent) == -EEXIST) > + sysfs_warn_dup(kobj->sd, grp->name); > + return PTR_ERR(parent); > + } > + > + kernfs_get(parent); > + } > + > for ((i = 0, attr = grp->attrs); *attr && !error; (++i, ++attr)) > error = sysfs_add_file_mode_ns(parent, *attr, (*attr)->mode, > uid, gid, NULL); > -- > 2.42.0 > And as the 0-day bot just showed, this patch isn't going to work properly, the uid/gid stuff isn't all hooked up properly, I'll work on fixing that up when I get some cycles... thanks, greg k-h
