zram: add recompress flag to read_block_state()

Add a new flag to zram block state that shows if the page was recompressed
(using alternative compression algorithm).

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Sergey Senozhatsky <[e-mail]>
Acked-by: Minchan Kim <[e-mail]>
Cc: Alexey Romanov <[e-mail]>
Cc: Nhat Pham <[e-mail]>
Cc: Nitin Gupta <[e-mail]>
Cc: Suleiman Souhlal <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

Documentation/admin-guide/blockdev/zram.rst

···
 If you enable the feature, you could see block state via
 /sys/kernel/debug/zram/zram0/block_state". The output is as follows::
 
-	  300    75.033841 .wh.
-	  301    63.806904 s...
-	  302    63.806919 ..hi
+	  300    75.033841 .wh..
+	  301    63.806904 s....
+	  302    63.806919 ..hi.
+	  303    62.801919 ....r
 
 First column
 	zram's block index.
···
 		huge page
 	i:
 		idle page
+	r:
+		recompressed page (secondary compression algorithm)
 
 First line of above example says 300th block is accessed at 75.033841sec
 and the block's state is huge so it is written back to the backing

drivers/block/zram/zram_drv.c

···
 
 		ts = ktime_to_timespec64(zram->table[index].ac_time);
 		copied = snprintf(kbuf + written, count,
-			"%12zd %12lld.%06lu %c%c%c%c\n",
+			"%12zd %12lld.%06lu %c%c%c%c%c\n",
 			index, (s64)ts.tv_sec,
 			ts.tv_nsec / NSEC_PER_USEC,
 			zram_test_flag(zram, index, ZRAM_SAME) ? 's' : '.',
 			zram_test_flag(zram, index, ZRAM_WB) ? 'w' : '.',
 			zram_test_flag(zram, index, ZRAM_HUGE) ? 'h' : '.',
-			zram_test_flag(zram, index, ZRAM_IDLE) ? 'i' : '.');
+			zram_test_flag(zram, index, ZRAM_IDLE) ? 'i' : '.',
+			zram_get_priority(zram, index) ? 'r' : '.');
 
 		if (count <= copied) {
 			zram_slot_unlock(zram, index);