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    SubjectRe: [PATCH 4/7] sysfs: Implement sysfs_rename_link
    Quoting Eric W. Biederman (ebiederm@xmission.com):
    > From: Eric W. Biederman <ebiederm@xmission.com>
    >
    > Because of rename ordering problems we occassionally give false
    > warnings about invalid sysfs operations. So using sysfs_rename
    > create a sysfs_rename_link function that doesn't need strange
    > workarounds.

    It looks nice and clean esp compared to the code you're replacing.
    OTOH I do wonder whether your sysfs_type(sd) != SYSFS_KOBJ_LINK check
    will catch unexpected ways that device_rename() was being called.
    Shouldn't, I realize, since sysfs_create_link() always sets SYSFS_KOBJ_LINK,
    but the check wasn't there before, so stranger things have happened.

    > Cc: Benjamin Thery <benjamin.thery@bull.net>
    > Cc: Daniel Lezcano <dlezcano@fr.ibm.com>
    > Cc: Tejun Heo <tj@kernel.org>
    > Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>

    Acked-by: Serge Hallyn <serue@us.ibm.com>

    > ---
    > fs/sysfs/symlink.c | 38 ++++++++++++++++++++++++++++++++++++++
    > include/linux/sysfs.h | 9 +++++++++
    > 2 files changed, 47 insertions(+), 0 deletions(-)
    >
    > diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c
    > index c5eff49..1b9a3a1 100644
    > --- a/fs/sysfs/symlink.c
    > +++ b/fs/sysfs/symlink.c
    > @@ -123,6 +123,44 @@ void sysfs_remove_link(struct kobject * kobj, const char * name)
    > sysfs_hash_and_remove(parent_sd, name);
    > }
    >
    > +/**
    > + * sysfs_rename_link - rename symlink in object's directory.
    > + * @kobj: object we're acting for.
    > + * @targ: object we're pointing to.
    > + * @old: previous name of the symlink.
    > + * @new: new name of the symlink.
    > + *
    > + * A helper function for the common rename symlink idiom.
    > + */
    > +int sysfs_rename_link(struct kobject *kobj, struct kobject *targ,
    > + const char *old, const char *new)
    > +{
    > + struct sysfs_dirent *parent_sd, *sd = NULL;
    > + int result;
    > +
    > + if (!kobj)
    > + parent_sd = &sysfs_root;
    > + else
    > + parent_sd = kobj->sd;
    > +
    > + result = -ENOENT;
    > + sd = sysfs_get_dirent(parent_sd, old);
    > + if (!sd)
    > + goto out;
    > +
    > + result = -EINVAL;
    > + if (sysfs_type(sd) != SYSFS_KOBJ_LINK)
    > + goto out;
    > + if (sd->s_symlink.target_sd->s_dir.kobj != targ)
    > + goto out;
    > +
    > + result = sysfs_rename(sd, parent_sd, new);
    > +
    > +out:
    > + sysfs_put(sd);
    > + return result;
    > +}
    > +
    > static int sysfs_get_target_path(struct sysfs_dirent *parent_sd,
    > struct sysfs_dirent *target_sd, char *path)
    > {
    > diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
    > index cfa8308..e322573 100644
    > --- a/include/linux/sysfs.h
    > +++ b/include/linux/sysfs.h
    > @@ -110,6 +110,9 @@ int __must_check sysfs_create_link_nowarn(struct kobject *kobj,
    > const char *name);
    > void sysfs_remove_link(struct kobject *kobj, const char *name);
    >
    > +int sysfs_rename_link(struct kobject *kobj, struct kobject *target,
    > + const char *old_name, const char *new_name);
    > +
    > int __must_check sysfs_create_group(struct kobject *kobj,
    > const struct attribute_group *grp);
    > int sysfs_update_group(struct kobject *kobj,
    > @@ -203,6 +206,12 @@ static inline void sysfs_remove_link(struct kobject *kobj, const char *name)
    > {
    > }
    >
    > +static inline int sysfs_rename_link(struct kobject *k, struct kobject *t,
    > + const char *old_name, const char *new_name)
    > +{
    > + return 0;
    > +}
    > +
    > static inline int sysfs_create_group(struct kobject *kobj,
    > const struct attribute_group *grp)
    > {
    > --
    > 1.6.5.2.143.g8cc62


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