On Sun, Jun 14, 2020 at 6:14 AM Qu Wenruo <quwenruo.btrfs@xxxxxxx> wrote: > > > > On 2020/6/12 下午10:06, fdmanana@xxxxxxxxxx wrote: > > From: Filipe Manana <fdmanana@xxxxxxxx> > > > > This test currently always fails on btrfs: > > > > generic/471 2s ... - output mismatch (see ...results//generic/471.out.bad) > > --- tests/generic/471.out 2020-06-10 19:29:03.850519863 +0100 > > +++ /home/fdmanana/git/hub/xfstests/results//generic/471.out.bad ... > > @@ -2,12 +2,10 @@ > > pwrite: Resource temporarily unavailable > > wrote 8388608/8388608 bytes at offset 0 > > XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) > > -RWF_NOWAIT time is within limits. > > +pwrite: Resource temporarily unavailable > > +(standard_in) 1: syntax error > > +RWF_NOWAIT took seconds > > > > This is because btrfs is a COW filesystem and an attempt to write into a > > previously written file range allocating a new extent (or multiple). > > The only exceptions are when attempting to write to a file range with a > > preallocated/unwritten extent or when writing to a NOCOW file that has > > extents allocated in the target range already. > > > > The test currently expects that writing into a previously written file > > range succeeds, but that is not true on btrfs since we are not dealing > > with a NOCOW file. So to make the test pass on btrfs, set the NOCOW bit > > on the file when the filesystem is btrfs. > > Completely agree with the point for btrfs. > > > > > Signed-off-by: Filipe Manana <fdmanana@xxxxxxxx> > > --- > > tests/generic/471 | 11 +++++++++++ > > 1 file changed, 11 insertions(+) > > > > diff --git a/tests/generic/471 b/tests/generic/471 > > index 7513f023..e9856b52 100755 > > --- a/tests/generic/471 > > +++ b/tests/generic/471 > > @@ -37,6 +37,17 @@ fi > > > > mkdir $testdir > > > > +# Btrfs is a COW filesystem, so a RWF_NOWAIT write will always fail with -EAGAIN > > +# when writing to a file range except if it's a NOCOW file and an extent for the > > +# range already exists or if it's a COW file and preallocated/unwritten extent > > +# exists in the target range. So to make sure that the last write succeeds on > > +# all filesystems, use a NOCOW file on btrfs. > > +if [ $FSTYP == "btrfs" ]; then > > Although I'm not sure if really only specific to btrfs. > XFS has its always_cow sysfs interface to make data write to always do > COW, just like what btrfs do by default. > > Thus I believe this may be needed for all fses, and just ignore the > error if the fs doesn't support COW. I don't understand your point. If that flag is enabled on xfs (iirc it's a debug flag), the test would fail on xfs even if we attempt chattr +C (afaics xfs doesn't support +C). So I don't see the benefit of always doing it. Thanks. > > Thanks, > Qu > > > + _require_chattr C > > + touch $testdir/f1 > > + $CHATTR_PROG +C $testdir/f1 > > +fi > > + > > # Create a file with pwrite nowait (will fail with EAGAIN) > > $XFS_IO_PROG -f -d -c "pwrite -N -V 1 -b 1M 0 1M" $testdir/f1 > > > > >
