zram: add recompress flag to read_block_state()

mainline inclusion
from mainline-v6.2-rc1
commit 60e9b39e
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I7TWVA
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=60e9b39ebec56467c36c3da76eee28083196cdf1

-------------------------------------------

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/20221109115047.2921851-6-senozhatsky@chromium.orgSigned-off-by: NSergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: NMinchan Kim <minchan@kernel.org>
Cc: Alexey Romanov <avromanov@sberdevices.ru>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NJinjiang Tu <tujinjiang@huawei.com>

Documentation/admin-guide/blockdev/zram.rst

@@ -392,9 +392,10 @@ pages of the process with*pagemap.
 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.
@@ -411,6 +412,8 @@ Third column
 		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

@@ -918,13 +918,14 @@ static ssize_t read_block_state(struct file *file, char __user *buf,
 
 		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);