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. 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 > >
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