On 23.10.2017 23:57, Liu Bo wrote:
> Currently drop_caches is used to invalidate file's page cache so that
> buffered read can hit disk, but the problem is that it may also
> invalidate metadata's page cache, so the test case may not get read
> errors (and repair) if reading metadata has consumed the injected
> faults.
>
> This changes it to do 'fadvise -d' to firstly access all metadata it
> needs to locate the file and then only drops the test file's page
> cache. Also this changes it to read the file only if pid%2 == 1.
>
> Reported-by: Nikolay Borisov <nborisov@xxxxxxxx>
> Signed-off-by: Liu Bo <bo.li.liu@xxxxxxxxxx>
> ---
> tests/btrfs/143 | 20 ++++++++++----------
> 1 file changed, 10 insertions(+), 10 deletions(-)
>
> diff --git a/tests/btrfs/143 b/tests/btrfs/143
> index da7bfd8..dabd03d 100755
> --- a/tests/btrfs/143
> +++ b/tests/btrfs/143
> @@ -127,16 +127,16 @@ echo "step 3......repair the bad copy" >>$seqres.full
> # since raid1 consists of two copies, and the bad copy was put on stripe #1
> # while the good copy lies on stripe #0, the bad copy only gets access when the
> # reader's pid % 2 == 1 is true
> -while true; do
> - # start_fail only fails the following buffered read so the repair is
> - # supposed to work.
> - echo 3 > /proc/sys/vm/drop_caches
> - start_fail
> - $XFS_IO_PROG -c "pread 0 4K" "$SCRATCH_MNT/foobar" > /dev/null &
> - pid=$!
> - wait
> - stop_fail
> - [ $((pid % 2)) == 1 ] && break
> +while [[ -z ${result} ]]; do
> + # invalidate the page cache.
> + $XFS_IO_PROG -c "fadvise -d 0 128K" $SCRATCH_MNT/foobar
I'm a bit worried about the expectations of the DONT_NEED:
https://linux.die.net/man/2/posix_fadvise:
The advice is not binding; it merely constitutes an expectation on
behalf of the application.
This might very well be a moot point but still
> +
> + start_fail
> + result=$(bash -c "
> + if [[ \$((\$\$ % 2)) -eq 1 ]]; then
> + exec $XFS_IO_PROG -c \"pread 0 4K\" \"$SCRATCH_MNT/foobar\"
> + fi");
> + stop_fail
> done
>
> _scratch_unmount
>
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