Re: [PATCH v2] generic/446: make sure all background processes are dead before umount

[Eryu Guan <eguan@redhat.com>]

Hi Xiao Yang,

On Tue, Jul 25, 2017 at 04:04:21PM +0800, Eryu Guan wrote:
> The $dread_pid refers to the while-true-do loop, wait for $dread_pid
> doesn't mean the xfs_io direct read process is already dead,
> sometimes xfs_io process is still running and blocking
> _scratch_unmount.
> 
> Fix it by making the direct read does a fixed number of loop and
> break out the second mmap-fpunch loop if the first loop exits. At
> this point we're sure that there's no unfinished background process
> blocking the umount.
> 
> Signed-off-by: Eryu Guan <eguan@redhat.com>
> ---
> v2:
> - move 'kill' to while loop condition to simplify the second loop
> - add more comments about when to exit the loop

Would you please help test & review and provide reviewed-by tag if you
think it's OK? Thanks a lot!

Eryu

> 
>  tests/generic/446 | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/tests/generic/446 b/tests/generic/446
> index 62ae449de6b1..6a1b69aa2edc 100755
> --- a/tests/generic/446
> +++ b/tests/generic/446
> @@ -61,20 +61,20 @@ filesz=$((65536 * 2))
>  $XFS_IO_PROG -f -c "truncate $((filesz * 2))" $SCRATCH_MNT/file >> $seqres.full
>  
>  # run a background dio read to a hole in a loop
> -while true; do
> +for i in `seq 0 999`; do
>  	$XFS_IO_PROG -d -c "pread 0 $filesz" $SCRATCH_MNT/file > /dev/null 2>&1
>  done &
>  
>  dread_pid=$!
>  
>  # run mapped write to the same hole as dio read
> -for i in `seq 0 999`; do
> +# loop until background dio read exits
> +while kill -s 0 $dread_pid >/dev/null 2>&1; do
>  	$XFS_IO_PROG -c "mmap 0 $filesz" -c "mwrite 0 $filesz" $SCRATCH_MNT/file \
>  		> /dev/null
>  	$XFS_IO_PROG -c "fpunch 0 $filesz" $SCRATCH_MNT/file > /dev/null
>  done
>  
> -kill -9 $dread_pid > /dev/null 2>&1
>  wait $dread_pid > /dev/null 2>&1
>  
>  echo "Silence is golden"
> -- 
> 2.13.3
>