Re: [PATCH 2/5] reflink: fix off-by-one errors when iterating file blocks in a loop

Filipe Manana
2016-01-23T22:00:06Z

On Sat, Jan 23, 2016 at 8:52 PM, Darrick J. Wong
<darrick.wong@oracle.com> wrote:
> On Sat, Jan 23, 2016 at 11:32:27AM +0000, Filipe Manana wrote:
>> On Sat, Jan 23, 2016 at 12:36 AM, Darrick J. Wong
>> <darrick.wong@oracle.com> wrote:
>> > When we're iterating file blocks in a loop (via seq), we have to
>> > end at $nr-1, not $nr.
>> >
>> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
>> > ---
>> > tests/generic/183 | 2 +-
>> > tests/generic/185 | 2 +-
>> > tests/generic/186 | 2 +-
>> > tests/generic/187 | 2 +-
>> > tests/generic/194 | 2 +-
>> > tests/generic/195 | 2 +-
>> > tests/xfs/129 | 6 +++---
>> > tests/xfs/140 | 2 +-
>> > 8 files changed, 10 insertions(+), 10 deletions(-)
>> >
>> >
>> > diff --git a/tests/generic/183 b/tests/generic/183
>> > index 5c65e9a..2cf9ce4 100755
>> > --- a/tests/generic/183
>> > +++ b/tests/generic/183
>> > @@ -69,7 +69,7 @@ seq 0 2 $((NR-1)) | while read f; do
>> > _reflink_range "$TESTDIR/file1" $((BLKSZ * f)) "$TESTDIR/file3" $((BLKSZ * f)) $BLKSZ >> "$seqres.full"
>> > _pwrite_byte 0x61 $((BLKSZ * f)) $BLKSZ "$TESTDIR/file3.chk" >> "$seqres.full"
>> > done
>> > -seq 1 2 $NR | while read f; do
>> > +seq 1 2 $((NR-1)) | while read f; do
>>
>> Just curious (and no bike shedding intended), why not make the loop in
>> a much more simple and common way such as:
>>
>> for ((i = 1; i < $NR; i += 2)); do
>> ...
>> done
>
> Not that it matters here, but that's a bashism, isn't it?

Yep, but all tests and scripts (./check, common/rc, etc) start with a
shebang referring to bash.

>
>> or for i in `seq 1 2 $((NR - 1))`; do .... done
>
> <shrug> No particular reason. :)
>
> I suppose if NR is large then "seq | while read" avoids spraying a large number
> of arguments into the command interpreter, though that clearly isn't the case
> here.

Right.
Thanks.

>
> --D
>
>>
>>
>>
>> > _reflink_range "$TESTDIR/file2" $((BLKSZ * f)) "$TESTDIR/file3" $((BLKSZ * f)) $BLKSZ >> "$seqres.full"
>> > _pwrite_byte 0x62 $((BLKSZ * f)) $BLKSZ "$TESTDIR/file3.chk" >> "$seqres.full"
>> > done
>> > diff --git a/tests/generic/185 b/tests/generic/185
>> > index 384c9aa..55c54ac 100755
>> > --- a/tests/generic/185
>> > +++ b/tests/generic/185
>> > @@ -69,7 +69,7 @@ seq 0 2 $((NR-1)) | while read f; do
>> > _reflink_range "$TESTDIR/file1" $((BLKSZ * f)) "$TESTDIR/file3" $((BLKSZ * f)) $BLKSZ >> "$seqres.full"
>> > _pwrite_byte 0x61 $((BLKSZ * f)) $BLKSZ "$TESTDIR/file3.chk" >> "$seqres.full"
>> > done
>> > -seq 1 2 $NR | while read f; do
>> > +seq 1 2 $((NR-1)) | while read f; do
>> > _reflink_range "$TESTDIR/file2" $((BLKSZ * f)) "$TESTDIR/file3" $((BLKSZ * f)) $BLKSZ >> "$seqres.full"
>> > _pwrite_byte 0x62 $((BLKSZ * f)) $BLKSZ "$TESTDIR/file3.chk" >> "$seqres.full"
>> > done
>> > diff --git a/tests/generic/186 b/tests/generic/186
>> > index d84166d..f1c0e6b 100755
>> > --- a/tests/generic/186
>> > +++ b/tests/generic/186
>> > @@ -112,7 +112,7 @@ seq 0 2 $((NR-1)) | while read f; do
>> > _reflink_range "$TESTDIR/file1" $((BLKSZ * f)) "$TESTDIR/file3" $((BLKSZ * f)) $BLKSZ >> "$seqres.full"
>> > _pwrite_byte 0x61 $((BLKSZ * f)) $BLKSZ "$TESTDIR/file3.chk" >> "$seqres.full"
>> > done
>> > -seq 1 2 $NR | while read f; do
>> > +seq 1 2 $((NR-1)) | while read f; do
>> > _reflink_range "$TESTDIR/file2" $((BLKSZ * f)) "$TESTDIR/file3" $((BLKSZ * f)) $BLKSZ >> "$seqres.full"
>> > _pwrite_byte 0x62 $((BLKSZ * f)) $BLKSZ "$TESTDIR/file3.chk" >> "$seqres.full"
>> > done
>> > diff --git a/tests/generic/187 b/tests/generic/187
>> > index c85a0a9..ce35ec0 100755
>> > --- a/tests/generic/187
>> > +++ b/tests/generic/187
>> > @@ -112,7 +112,7 @@ seq 0 2 $((NR-1)) | while read f; do
>> > _reflink_range "$TESTDIR/file1" $((BLKSZ * f)) "$TESTDIR/file3" $((BLKSZ * f)) $BLKSZ >> "$seqres.full"
>> > _pwrite_byte 0x61 $((BLKSZ * f)) $BLKSZ "$TESTDIR/file3.chk" >> "$seqres.full"
>> > done
>> > -seq 1 2 $NR | while read f; do
>> > +seq 1 2 $((NR-1)) | while read f; do
>> > _reflink_range "$TESTDIR/file2" $((BLKSZ * f)) "$TESTDIR/file3" $((BLKSZ * f)) $BLKSZ >> "$seqres.full"
>> > _pwrite_byte 0x62 $((BLKSZ * f)) $BLKSZ "$TESTDIR/file3.chk" >> "$seqres.full"
>> > done
>> > diff --git a/tests/generic/194 b/tests/generic/194
>> > index a441aee..b88297e 100755
>> > --- a/tests/generic/194
>> > +++ b/tests/generic/194
>> > @@ -79,7 +79,7 @@ md5sum "$TESTDIR/file3" | _filter_scratch
>> > md5sum "$TESTDIR/file3.chk" | _filter_scratch
>> >
>> > echo "directio CoW across the transition"
>> > -seq 1 2 $NR | while read f; do
>> > +seq 1 2 $((NR-1)) | while read f; do
>> > _pwrite_byte 0x62 $((BLKSZ * f)) $BLKSZ "$TESTDIR/file3" >> "$seqres.full"
>> > _pwrite_byte 0x62 $((BLKSZ * f)) $BLKSZ "$TESTDIR/file3.chk" >> "$seqres.full"
>> > done
>> > diff --git a/tests/generic/195 b/tests/generic/195
>> > index 83e7b23..464a4d4 100755
>> > --- a/tests/generic/195
>> > +++ b/tests/generic/195
>> > @@ -79,7 +79,7 @@ md5sum "$TESTDIR/file3" | _filter_scratch
>> > md5sum "$TESTDIR/file3.chk" | _filter_scratch
>> >
>> > echo "CoW across the transition"
>> > -seq 1 2 $NR | while read f; do
>> > +seq 1 2 $((NR-1)) | while read f; do
>> > _pwrite_byte 0x62 $((BLKSZ * f)) $BLKSZ "$TESTDIR/file3" >> "$seqres.full"
>> > _pwrite_byte 0x62 $((BLKSZ * f)) $BLKSZ "$TESTDIR/file3.chk" >> "$seqres.full"
>> > done
>> > diff --git a/tests/xfs/129 b/tests/xfs/129
>> > index c8c47a2..3b7c59c 100755
>> > --- a/tests/xfs/129
>> > +++ b/tests/xfs/129
>> > @@ -65,9 +65,9 @@ NR_BLKS=$((4 * BLKSZ / 12))
>> > _pwrite_byte 0x61 0 $((BLKSZ * NR_BLKS)) "$TESTDIR/file1" >> "$seqres.full"
>> >
>> > echo "Reflink every other block"
>> > -seq 1 $((NR_BLKS / 2)) | while read nr; do
>> > - _reflink_range "$TESTDIR/file1" $((nr * 2 * BLKSZ)) \
>> > - "$TESTDIR/file2" $((nr * 2 * BLKSZ)) $BLKSZ >> "$seqres.full"
>> > +seq 1 2 $((NR_BLKS - 1)) | while read nr; do
>> > + _reflink_range "$TESTDIR/file1" $((nr * BLKSZ)) \
>> > + "$TESTDIR/file2" $((nr * BLKSZ)) $BLKSZ >> "$seqres.full"
>> > done
>> >
>> > echo "Create metadump file"
>> > diff --git a/tests/xfs/140 b/tests/xfs/140
>> > index e20cd3f..45be9f4 100644
>> > --- a/tests/xfs/140
>> > +++ b/tests/xfs/140
>> > @@ -70,7 +70,7 @@ cmp -s "$TESTDIR/file1" "$TESTDIR/file2" || echo "file1 and file2 do not match"
>> > cmp -s "$TESTDIR/file2" "$TESTDIR/file2.chk" || echo "file2 and file2.chk do not match"
>> >
>> > echo "CoW every other block"
>> > -seq 1 2 $NR | while read f; do
>> > +seq 1 2 $((NR - 1)) | while read f; do
>> > _pwrite_byte 0x62 $((f * BLKSZ)) $BLKSZ "$TESTDIR/file2" >> "$seqres.full"
>> > _pwrite_byte 0x62 $((f * BLKSZ)) $BLKSZ "$TESTDIR/file2.chk" >> "$seqres.full"
>> > done
>> >
>> > --
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>>
>>
>>
>> --
>> Filipe David Manana,
>>
>> "Reasonable men adapt themselves to the world.
>> Unreasonable men adapt the world to themselves.
>> That's why all progress depends on unreasonable men."

--
Filipe David Manana,

"Reasonable men adapt themselves to the world.
Unreasonable men adapt the world to themselves.
That's why all progress depends on unreasonable men."