GCC >+ 4.8's aggressive loop optimization breaks some of the iterators
over the dn_blkptr[] pseudo-array in dnode_phys. Since dn_blkptr[] is
defined as a single-element array, GCC believes an iterator can only
access index 0 and will unroll the loop into a single iteration.
One way to resolve the issue would be to cast the array to a pointer
and fix all the iterators that might break. The only loop where it
is known to cause a problem is this loop in dmu_objset_write_ready():
for (i = 0; i < dnp->dn_nblkptr; i++)
bp->blk_fill += dnp->dn_blkptr[i].blk_fill;
In the common case where dn_nblkptr is 3, the loop is only executed a
single time and "i" is equal to 1 following the loop.
The specific breakage caused by this problem is that the blk_fill of
root block pointers wouldn't be set properly when more than one blkptr
is in use (when no indrect blocks are needed).
The simple reproducing sequence is:
zpool create tank /tank.img
zdb -ddddd tank 0
Notice that "fill=31", however, there are two L0 indirect blocks with
"F=31" and "F=5". The fill count should be 36 rather than 31. This
problem causes an assert to be hit in a simple "zdb tank" when built
with --enable-debug.
However, this approach was not taken because we need to be absolutely
sure we catch all instances of this unwanted optimization. Therefore,
the build system has been updated to detect if GCC supports the
aggressive loop optimization. If it does the optimization will be
explicitly disabled using the -fno-aggressive-loop-optimization option.
Original-fix-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#2010Closes#2051
-D and -I are preprocessor flags, so should preferably be in the
appropriate variable.
Signed-off-by: Jan Engelhardt <jengelh@inai.de>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Gcc versions 4.3.2 and earlier do not support the compiler flag
-Wno-unused-but-set-variable. This can lead to build failures
on older Linux platforms such as Debian Lenny. Since this is
an optional build argument this changes add a new autoconf check
for the option. If it is supported by the installed version of
gcc then it is used otherwise it is omited.
See commit's 12c1acde76 and
79713039a2 for the reason the
-Wno-unused-but-set-variable options was originally added.
As of gcc-4.6 the option -Wunused-but-set-variable is enabled by
default. While this is a useful warning there are numerous places
in the ZFS code when a variable is set and then only checked in an
ASSERT(). To avoid having to update every instance of this in the
code we now set -Wno-unused-but-set-variable to suppress the warning.
Additionally, when building with --enable-debug and -Werror set these
warning also become fatal. We can reevaluate the suppression of these
error at a later time if it becomes an issue. For now we are basically
just reverting to the previous gcc behavior.
One of the neat tricks an autoconf style project is capable of
is allow configurion/building in a directory other than the
source directory. The major advantage to this is that you can
build the project various different ways while making changes
in a single source tree.
For example, this project is designed to work on various different
Linux distributions each of which work slightly differently. This
means that changes need to verified on each of those supported
distributions perferably before the change is committed to the
public git repo.
Using nfs and custom build directories makes this much easier.
I now have a single source tree in nfs mounted on several different
systems each running a supported distribution. When I make a
change to the source base I suspect may break things I can
concurrently build from the same source on all the systems each
in their own subdirectory.
wget -c http://github.com/downloads/behlendorf/zfs/zfs-x.y.z.tar.gz
tar -xzf zfs-x.y.z.tar.gz
cd zfs-x-y-z
------------------------- run concurrently ----------------------
<ubuntu system> <fedora system> <debian system> <rhel6 system>
mkdir ubuntu mkdir fedora mkdir debian mkdir rhel6
cd ubuntu cd fedora cd debian cd rhel6
../configure ../configure ../configure ../configure
make make make make
make check make check make check make check
This change also moves many of the include headers from individual
incude/sys directories under the modules directory in to a single
top level include directory. This has the advantage of making
the build rules cleaner and logically it makes a bit more sense.
Add autoconf style build infrastructure to the ZFS tree. This
includes autogen.sh, configure.ac, m4 macros, some scripts/*,
and makefiles for all the core ZFS components.
Brian Behlendorf
Jan Engelhardt