lightnvm: pblk: do not overwrite ppa list with meta list

Ehen using pblk with 0 sized metadata both ppa list and meta list
points to the same memory since pblk_dma_meta_size() returns 0 in
that case.

This patch fix that issue by ensuring that pblk_dma_meta_size()
always returns space equal to sizeof(struct pblk_sec_meta) and thus
ppa list and meta list points to different memory address.

Even that in that case drive does not really care about meta_list
pointer, this is the easiest way to fix that issue without introducing
changes in many places in the code just for 0 sized metadata case.

The same approach needs to be also done for pblk_get_sec_meta()
since we also cannot point to the same memory address in meta buffer
when we are using it for pblk recovery process
Reported-by: Hans Holmberg <hans.holmberg@cnexlabs.com>
Tested-by: Hans Holmberg <hans.holmberg@cnexlabs.com>
Signed-off-by: Igor Konopko <igor.j.konopko@intel.com>
Signed-off-by: Matias Bjørling <mb@lightnvm.io>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/lightnvm/pblk.h

@@ -1388,12 +1388,15 @@ static inline unsigned int pblk_get_min_chks(struct pblk *pblk)
 static inline struct pblk_sec_meta *pblk_get_meta(struct pblk *pblk,
 							 void *meta, int index)
 {
-	return meta + pblk->oob_meta_size * index;
+	return meta +
+	       max_t(int, sizeof(struct pblk_sec_meta), pblk->oob_meta_size)
+	       * index;
 }
 
 static inline int pblk_dma_meta_size(struct pblk *pblk)
 {
-	return pblk->oob_meta_size * NVM_MAX_VLBA;
+	return max_t(int, sizeof(struct pblk_sec_meta), pblk->oob_meta_size)
+	       * NVM_MAX_VLBA;
 }
 
 static inline int pblk_is_oob_meta_supported(struct pblk *pblk)