> Ira Weiny wrote:
> > Dinghao Liu wrote:
>
> [snip]
>
> -static int btt_freelist_init(struct arena_info *arena)
> +static int btt_freelist_init(struct device *dev, struct arena_info *arena)
>
> Both struct arena_info and struct btt contain references to struct nd_btt
> which is the device you are passing down this call stack.
>
> Just use the device in the arena/btt rather than passing a device
> structure. That makes the code easier to read and ensures that the device
> associated with this arena or btt is used.
Thanks for this suggestion! I will fix this in the v3 patch.
> [snip]
> > >
> > > -static int btt_maplocks_init(struct arena_info *arena)
> > > +static int btt_maplocks_init(struct device *dev, struct arena_info
> > > *arena)
> > > {
> > > u32 i;
> > >
> > > - arena->map_locks = kcalloc(arena->nfree, sizeof(struct aligned_lock),
> > > + arena->map_locks = devm_kcalloc(dev, arena->nfree, sizeof(struct
> > > aligned_lock),
> > > GFP_KERNEL);
> > > if (!arena->map_locks)
> > > return -ENOMEM;
> > > @@ -805,9 +805,6 @@ static void free_arenas(struct btt *btt)
> > >
> > > list_for_each_entry_safe(arena, next, &btt->arena_list, list) {
> > > list_del(&arena->list);
> > > - kfree(arena->rtt);
> > > - kfree(arena->map_locks);
> > > - kfree(arena->freelist);
> >
> > This does not quite work.
> >
> > free_arenas() is used in the error paths of create_arenas() and
> > discover_arenas(). In those cases devm_kfree() is probably a better way
> > to clean up this.
Here I'm a little confused about when devm_kfree() should be used.
Code in btt_init() implies that resources allocated by devm_* could be
auto freed in both error and success paths of probe/attach (e.g., btt
allocated by devm_kzalloc is never freed by devm_kfree).
Using devm_kfree() in free_arenas() is ok for me, but I want to know
whether not using devm_kfree() constitutes a bug.
> >
> > However...
> >
> > > debugfs_remove_recursive(arena->debugfs_dir);
> > > kfree(arena);
> >
> > Why can't arena be allocated with devm_*?
> >
> > We need to change this up a bit more to handle the error path vs regular
> > device shutdown free (automatic devm frees).
>
At first, I think the use of arena is correct. Therefore, allocating arena
with devm_* should be a code style optimization. However, I rechecked
discover_arenas and found arena might also be leaked (e.g., if alloc_arena()
fails in the second loop, the previously allocated resources in the loop is
leaked). The correct code could be found in create_arenas(), where free_arenas
is called on failure of alloc_arena().
To fix this issue, I think it's better to change the 'goto out_super' tag
to 'goto out'. We could also use devm_* for arena to simplify the error path
in discover_arenas().
> We might want to look at using no_free_ptr() in this code. See this
> patch[1] for an example of how to inhibit the cleanup and pass the pointer
> on when the function succeeds.
>
> [1]
> https://lore.kernel.org/all/170261791914.1714654.6447680285357545638.st...@dwillia2-xfh.jf.intel.com/
>
> Ira
Thanks for this example. But it seems that no_free_ptr() is used to handle
the scope based resource management. Changes in this patch does not introduce
this feature. Do I understand this correctly?
Regards,
Dinghao
