Comment 20 for bug 1887742

On focal/linux-gcp 5.4.0-1093, instance type n2d-standard-2, saw:

   18425 tst_test.c:1526: TINFO: Timeout per run is 0h 00m 30s
      18426 zram03.c:181: TINFO: zram module already loaded, kernel supports zram-control interface
      18427 zram03.c:40: TINFO: create a zram device with 536870912 bytes in size
      18428 zram03.c:50: TINFO: map this zram device into memory
      18429 zram03.c:54: TINFO: write all the memory
      18430 zram03.c:105: TINFO: /sys/block/zram1
      18431 zram03.c:108: TINFO: /sys/block/zram1/initstate is 1
      18432 zram03.c:105: TINFO: /sys/block/zram1
      18433 zram03.c:108: TINFO: /sys/block/zram1/disksize is 536870912
      18434 zram03.c:131: TINFO: orig_data_size from /sys/block/zram1/mm_stat is 536870912
      18435 zram03.c:132: TINFO: compr_data_size from /sys/block/zram1/mm_stat is 46
      18436 zram03.c:133: TINFO: mem_used_total from /sys/block/zram1/mm_stat is 4096
      18437 zram03.c:134: TINFO: zero/same_pages from /sys/block/zram1/mm_stat is 131071
      18438 zram03.c:118: TINFO: num_reads from /sys/block/zram1/stat is 131072
      18439 zram03.c:119: TINFO: num_writes from /sys/block/zram1/stat is 131072
      18440 zram03.c:68: TINFO: verify contents from device
      18441 zram03.c:85: TPASS: data read from zram device is consistent with those are written
      18442 zram03.c:96: TINFO: Reset zram
      18443 zram03.c:98: TBROK: Failed to close FILE '/sys/block/zram1/reset': EBUSY (16)
      18444 zram03.c:230: TWARN: Failed to close FILE '/sys/class/zram-control/hot_remove': EBUSY (16)

This may be caused by fclose calling write, and the reset_store and zram_remove may return -EBUSY in case there are still openers of the block device. This could be caused by udev looking at the block device, for example.