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?
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index c20b05a84f21..a25d34a8af19 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -425,8 +425,11 @@ 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;
-
- if (!handle)
+ /*
+ * No memory is allocated for same element filled pages.
+ * Simply clear same page flag.
+ */
+ if (!handle || zram_test_flag(meta, index, ZRAM_SAME))
continue;
zs_free(meta->mem_pool, handle);
--
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