On Tue, Feb 07, 2017 at 11:24:40AM +0800, zhouxianrong wrote:
>
>
> On 2017/2/7 10:54, Minchan Kim wrote:
> >On Tue, Feb 07, 2017 at 10:20:57AM +0800, zhouxianrong wrote:
> >
> >< snip >
> >
> >>>>3. the below should be modified.
> >>>>
> >>>>static inline bool zram_meta_get(struct zram *zram)
> >>>>@@ -495,11 +553,17 @@ static void zram_meta_free(struct zram_meta *meta,
> >>>>u64 disksize)
> >>>>
> >>>> /* Free all pages that are still in this zram device */
> >>>> for (index = 0; index < num_pages; index++) {
> >>>>- unsigned long handle = meta->table[index].handle;
> >>>>+ unsigned long handle;
> >>>>+
> >>>>+ bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
> >>>>+ handle = meta->table[index].handle;
> >>>>
> >>>>- if (!handle)
> >>>>+ if (!handle || zram_test_flag(meta, index, ZRAM_SAME)) {
> >>>>+ bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
> >>>> continue;
> >>>>+ }
> >>>>
> >>>>+ bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
> >>>> zs_free(meta->mem_pool, handle);
> >>>
> >>>Could you explain why we need this modification?
> >>>
> >>>> }
> >>>>
> >>>>@@ -511,7 +575,7 @@ static void zram_meta_free(struct zram_meta *meta,
> >>>>u64 disksize)
> >>>>static struct zram_meta *zram_meta_alloc(char *pool_name, u64 disksize)
> >>>>{
> >>>> size_t num_pages;
> >>>>- struct zram_meta *meta = kmalloc(sizeof(*meta), GFP_KERNEL);
> >>>>+ struct zram_meta *meta = kzalloc(sizeof(*meta), GFP_KERNEL);
> >>>
> >>>Ditto
> >>>
> >>>>
> >>>>
> >>>
> >>>.
> >>>
> >>
> >>because of union of handle and element, i think a non-zero element (other
> >>than handle) is prevented from freeing.
> >>if zram_meta_get was modified, zram_meta_alloc did so.
> >
> >Right. Thanks but I don't see why we need the locking in there and
> >modification of
> >zram_meta_alloc.
> >
> >Isn't it enough with this?
>
> i am afraid someone do reset_store, so did lock.
reset_store is protected by zram->claim and and init_done so I don't
think so.
