Tejun Heo <htejun@xxxxxxxxx> writes: > Hello, Eric. > > Eric W. Biederman wrote: >> Looking carefully at the rename code we have a subtle dependency >> that the structure of sysfs not change while we are performing >> a rename. If the parent directory of the object we are renaming >> changes while the rename is being performed nasty things could >> happen when we go to release our locks. >> >> So introduce a sysfs_rename_mutex to prevent this highly >> unlikely theoretical issue. > > Yeah, it's a theoretical issue. Rename/move implementation has always > depended on the parent structure not changing beneath it, but it's nice > to tighten up loose ends. > >> +DEFINE_MUTEX(sysfs_rename_mutex); > > Probably doesn't really matter but wouldn't a rwsem fit better? Maybe. I didn't feel any loss in when I was writing the code. Very few code paths actually seem to care. >> @@ -774,7 +775,7 @@ static struct dentry *__sysfs_get_dentry(struct > super_block *sb, struct sysfs_di >> * down from there looking up dentry for each step. >> * >> * LOCKING: >> - * Kernel thread context (may sleep) >> + * mutex_lock(sysfs_rename_mutex) Well this is weird in that it should be on sysfs_get_dentry more then __sysfs_get_dentry but otherwise it's ok. > LOCKING describes what locks should be held when entering the function, > so proper description would be something like... > > Kernel thread context, grabs sysfs_rename_mutex For rename_dir and move_dir yes. I was updating the rules for sysfs_get_dentry. Which really wants it's parents to hold that lock. Eric _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers