[LTP] [v2] readahead02: fix read_ahead_kb file not found

[Jan Stancek <jstancek@redhat.com>]

----- Original Message -----
> From: "naresh kamboju" <naresh.kamboju@linaro.org>
> To: chrubis@suse.cz, ltp@lists.linux.it
> Cc: akpm@linux-foundation.org, "fengguang wu" <fengguang.wu@intel.com>, "graeme gregory" <graeme.gregory@linaro.org>,
> "milosz wasilewski" <milosz.wasilewski@linaro.org>
> Sent: Friday, 2 September, 2016 12:42:33 PM
> Subject: [LTP] [v2] readahead02: fix read_ahead_kb file not found
> 
> From: Naresh Kamboju <naresh.kamboju@linaro.org>
> 
> Test case is looking for read_ahead_kb file on a partition device (8:2) and
> not on block device (8:0/8:16/8:32/8:48). The appropriate block device that
> holds the partition can be found at queue/read_ahead_kb entry.
> 
> Before patch readahead02 test broken,
> readahead02    1  TBROK  :  safe_file_ops.c:144: Failed to open FILE
> '/sys/dev/block/8:2/queue/read_ahead_kb' for reading at
> readahead02.c:197: errno=ENOENT(2): No such file or directory
> 
> After applying patch,
> readahead02    0  TINFO  :  creating test file of size: 67108864
> readahead02    0  TINFO  :  max readahead size is: 131072
> readahead02    0  TINFO  :  read_testfile(0)
> readahead02    0  TINFO  :  max readahead size is: 131072
> readahead02    0  TINFO  :  read_testfile(1)
> readahead02    0  TINFO  :  max readahead size is: 131072
> readahead02    1  TPASS  :  expected ret success - returned value = 0
> readahead02    2  TPASS  :  offset is still at 0 as expected
> readahead02    0  TINFO  :  read_testfile(0) took: 1437202 usec
> readahead02    0  TINFO  :  read_testfile(1) took: 1361915 usec
> readahead02    0  TINFO  :  read_testfile(0) read: 67108864 bytes
> readahead02    0  TINFO  :  read_testfile(1) read: 0 bytes
> readahead02    3  TPASS  :  readahead saved some I/O
> readahead02    0  TINFO  :  cache can hold at least: 157404 kB
> readahead02    0  TINFO  :  read_testfile(0) used cache: 65332 kB
> readahead02    0  TINFO  :  read_testfile(1) used cache: 65636 kB
> readahead02    4  TPASS  :  using cache as expected

This doesn't seem to be true for all entries under /sys/dev/block.
If I ran your patch on lvm, testcase fails:

# ./readahead02 
readahead02    0  TINFO  :  creating test file of size: 67108864
readahead02    1  TBROK  :  safe_file_ops.c:144: Failed to open FILE '/sys/dev/block/253:1/../queue/read_ahead_kb' for reading at readahead02.c:202: errno=ENOENT(2): No such file or directory
readahead02    2  TBROK  :  safe_file_ops.c:144: Remaining cases broken

# ll /sys/dev/block/253:1
lrwxrwxrwx. 1 root root 0 Sep  5 09:21 /sys/dev/block/253:1 -> ../../devices/virtual/block/dm-1

# ll /sys/dev/block/253:1/
total 0
-r--r--r--. 1 root root 4096 Sep  5 09:25 alignment_offset
-rw-r--r--. 1 root root 4096 Sep  5 09:25 badblocks
lrwxrwxrwx. 1 root root    0 Sep  5 09:21 bdi -> ../../bdi/253:1
-r--r--r--. 1 root root 4096 Sep  5 09:25 capability
-r--r--r--. 1 root root 4096 Sep  5 09:25 dev
-r--r--r--. 1 root root 4096 Sep  5 09:25 discard_alignment
drwxr-xr-x. 2 root root    0 Sep  5 09:25 dm
-r--r--r--. 1 root root 4096 Sep  5 09:25 ext_range
drwxr-xr-x. 2 root root    0 Sep  5 09:25 holders
-r--r--r--. 1 root root 4096 Sep  5 09:25 inflight
drwxr-xr-x. 2 root root    0 Sep  5 09:25 integrity
drwxr-xr-x. 2 root root    0 Sep  5 09:25 power
drwxr-xr-x. 2 root root    0 Sep  5 09:25 queue
-r--r--r--. 1 root root 4096 Sep  5 09:25 range
-r--r--r--. 1 root root 4096 Sep  5 09:25 removable
-r--r--r--. 1 root root 4096 Sep  5 09:25 ro
-r--r--r--. 1 root root 4096 Sep  5 09:25 size
drwxr-xr-x. 2 root root    0 Sep  5 09:25 slaves
-r--r--r--. 1 root root 4096 Sep  5 09:25 stat
lrwxrwxrwx. 1 root root    0 Sep  5 09:21 subsystem -> ../../../../class/block
drwxr-xr-x. 2 root root    0 Sep  5 09:25 trace
-rw-r--r--. 1 root root 4096 Sep  5 09:25 uevent

# lsblk 
NAME                        MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
vda                         252:0    0   35G  0 disk 
├─vda1                      252:1    0  500M  0 part /boot
└─vda2                      252:2    0 34.5G  0 part 
  ├─rhel_dhcp--27--118-swap 253:0    0    2G  0 lvm  [SWAP]
  └─rhel_dhcp--27--118-root 253:1    0 32.5G  0 lvm  /

# uname -r
4.7.0-rc7+

Regards,
Jan