On 2020/6/15 下午7:53, Filipe Manana wrote: > 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). Oh, my fault. Didn't know that xfs won't support chattr +C. Then forget the comment. Thanks, Qu > 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 >>> >>> >>
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