Messages in this thread | | | Subject | Re: [PATCH] mm: extend zero pages to same element pages for zram | From | zhouxianrong <> | Date | Tue, 7 Feb 2017 11:24:40 +0800 |
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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.
yes, i am wrong, zram_meta_alloc should not be modified here. because meta->table has already cleared
meta->table = vzalloc(num_pages * sizeof(*meta->table));
> > 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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