zram: remove unused stats fields

We don't show num_reads and num_writes since we removed corresponding
sysfs nodes in 2017.  Block layer stats are exposed via
/sys/block/zramX/stat file.

However, we still increment those atomic vars and store them in zram
stats.  Remove leftovers.

Link: https://lkml.kernel.org/r/20221117141326.1105181-1-senozhatsky@chromium.orgSigned-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

drivers/block/zram/zram_drv.c

@@ -1981,11 +1981,9 @@ static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
 	int ret;
 
 	if (!op_is_write(op)) {
-		atomic64_inc(&zram->stats.num_reads);
 		ret = zram_bvec_read(zram, bvec, index, offset, bio);
 		flush_dcache_page(bvec->bv_page);
 	} else {
-		atomic64_inc(&zram->stats.num_writes);
 		ret = zram_bvec_write(zram, bvec, index, offset, bio);
 	}
 

drivers/block/zram/zram_drv.h

@@ -76,8 +76,6 @@ struct zram_table_entry {
 
 struct zram_stats {
 	atomic64_t compr_data_size;	/* compressed size of pages stored */
-	atomic64_t num_reads;	/* failed + successful */
-	atomic64_t num_writes;	/* --do-- */
 	atomic64_t failed_reads;	/* can happen when memory is too low */
 	atomic64_t failed_writes;	/* can happen when memory is too low */
 	atomic64_t invalid_io;	/* non-page-aligned I/O requests */