zfs: Fix minor filesystem corruption with gcc 4.8
It turns out that some of gcc 4.8's aggressive optimizations may cause minor filesystem corruption in ZFS. To fix it, a patch was cherry-picked from the upstream's git tree. See: https://github.com/zfsonlinux/zfs/pull/2051
This commit is contained in:
Ricardo M. Correia
parent
02e2431661
commit
d01242edb8
pkgs/os-specific/linux/zfs
@ -8,7 +8,7 @@ stdenv.mkDerivation {
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sha256 = "18b5f18k8mwb17r5ippsilmp1a2sqjw9fwn0z82159dkhsadg33b";
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};
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patches = [ ./mount_zfs_prefix.patch ./nix-build.patch ./libblkid-1db7b9b.patch ];
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patches = [ ./mount_zfs_prefix.patch ./nix-build.patch ./libblkid-1db7b9b.patch ./gcc-4.8.patch ];
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buildInputs = [ spl perl autoconf automake libtool zlib libuuid coreutils ];
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114
pkgs/os-specific/linux/zfs/gcc-4.8.patch
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114
pkgs/os-specific/linux/zfs/gcc-4.8.patch
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@ -0,0 +1,114 @@
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commit 0f62f3f9abc4bfa0bcafee9bfa3d55e91dcb371d
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Author: Brian Behlendorf <behlendorf1@llnl.gov>
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Date: Tue Jan 14 09:39:13 2014 -0800
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Disable GCCs aggressive loop optimization
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GCC >+ 4.8's aggressive loop optimization breaks some of the iterators
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over the dn_blkptr[] pseudo-array in dnode_phys. Since dn_blkptr[] is
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defined as a single-element array, GCC believes an iterator can only
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access index 0 and will unroll the loop into a single iteration.
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One way to resolve the issue would be to cast the array to a pointer
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and fix all the iterators that might break. The only loop where it
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is known to cause a problem is this loop in dmu_objset_write_ready():
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for (i = 0; i < dnp->dn_nblkptr; i++)
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bp->blk_fill += dnp->dn_blkptr[i].blk_fill;
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In the common case where dn_nblkptr is 3, the loop is only executed a
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single time and "i" is equal to 1 following the loop.
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The specific breakage caused by this problem is that the blk_fill of
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root block pointers wouldn't be set properly when more than one blkptr
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is in use (when no indrect blocks are needed).
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The simple reproducing sequence is:
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zpool create tank /tank.img
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zdb -ddddd tank 0
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Notice that "fill=31", however, there are two L0 indirect blocks with
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"F=31" and "F=5". The fill count should be 36 rather than 31. This
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problem causes an assert to be hit in a simple "zdb tank" when built
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with --enable-debug.
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However, this approach was not taken because we need to be absolutely
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sure we catch all instances of this unwanted optimization. Therefore,
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the build system has been updated to detect if GCC supports the
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aggressive loop optimization. If it does the optimization will be
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explicitly disabled using the -fno-aggressive-loop-optimization option.
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Original-fix-by: Tim Chase <tim@chase2k.com>
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Signed-off-by: Tim Chase <tim@chase2k.com>
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Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
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Closes #2010
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Closes #2051
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diff --git a/config/Rules.am b/config/Rules.am
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index e3fa5b5..24f9426 100644
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--- a/config/Rules.am
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+++ b/config/Rules.am
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@@ -1,8 +1,10 @@
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DEFAULT_INCLUDES = -include ${top_builddir}/zfs_config.h
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AM_LIBTOOLFLAGS = --silent
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-AM_CFLAGS = -Wall -Wstrict-prototypes
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-AM_CFLAGS += -fno-strict-aliasing ${NO_UNUSED_BUT_SET_VARIABLE} ${DEBUG_CFLAGS}
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+AM_CFLAGS = ${DEBUG_CFLAGS} -Wall -Wstrict-prototypes
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+AM_CFLAGS += ${NO_UNUSED_BUT_SET_VARIABLE}
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+AM_CFLAGS += ${NO_AGGRESSIVE_LOOP_OPTIMIZATIONS}
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+AM_CFLAGS += -fno-strict-aliasing
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AM_CPPFLAGS = -D_GNU_SOURCE -D__EXTENSIONS__ -D_REENTRANT
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AM_CPPFLAGS += -D_POSIX_PTHREAD_SEMANTICS -D_FILE_OFFSET_BITS=64
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AM_CPPFLAGS += -D_LARGEFILE64_SOURCE -DTEXT_DOMAIN=\"zfs-linux-user\"
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diff --git a/config/always-no-aggressive-loop-optimizations.m4 b/config/always-no-aggressive-loop-optimizations.m4
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new file mode 100644
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index 0000000..8f2115a
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--- /dev/null
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+++ b/config/always-no-aggressive-loop-optimizations.m4
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@@ -0,0 +1,20 @@
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+dnl #
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+dnl # Check if gcc supports -fno-aggressive-loop-optimizations
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+dnl #
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+AC_DEFUN([ZFS_AC_CONFIG_ALWAYS_NO_AGGRESSIVE_LOOP_OPTIMIZATIONS], [
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+ AC_MSG_CHECKING([for -fno-aggressive-loop-optimizations support])
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+
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+ saved_flags="$CFLAGS"
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+ CFLAGS="$CFLAGS -fno-aggressive-loop-optimizations"
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+
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+ AC_RUN_IFELSE([AC_LANG_PROGRAM([], [])], [
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+ NO_AGGRESSIVE_LOOP_OPTIMIZATIONS=-fno-aggressive-loop-optimizations
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+ AC_MSG_RESULT([yes])
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+ ], [
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+ NO_AGGRESSIVE_LOOP_OPTIMIZATIONS=
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+ AC_MSG_RESULT([no])
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+ ])
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+
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+ CFLAGS="$saved_flags"
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+ AC_SUBST([NO_AGGRESSIVE_LOOP_OPTIMIZATIONS])
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+])
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diff --git a/config/kernel.m4 b/config/kernel.m4
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index cbf0ca3..62a9b42 100644
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--- a/config/kernel.m4
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+++ b/config/kernel.m4
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@@ -104,6 +104,7 @@ AC_DEFUN([ZFS_AC_CONFIG_KERNEL], [
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dnl # -Wall -fno-strict-aliasing -Wstrict-prototypes and other
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dnl # compiler options are added by the kernel build system.
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KERNELCPPFLAGS="$KERNELCPPFLAGS $NO_UNUSED_BUT_SET_VARIABLE"
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+ KERNELCPPFLAGS="$KERNELCPPFLAGS $NO_AGGRESSIVE_LOOP_OPTIMIZATIONS"
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KERNELCPPFLAGS="$KERNELCPPFLAGS -DHAVE_SPL -D_KERNEL"
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KERNELCPPFLAGS="$KERNELCPPFLAGS -DTEXT_DOMAIN=\\\"zfs-linux-kernel\\\""
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diff --git a/config/zfs-build.m4 b/config/zfs-build.m4
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index 005185b..477b916 100644
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--- a/config/zfs-build.m4
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+++ b/config/zfs-build.m4
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@@ -62,6 +62,7 @@ AC_DEFUN([ZFS_AC_DEBUG_DMU_TX], [
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AC_DEFUN([ZFS_AC_CONFIG_ALWAYS], [
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ZFS_AC_CONFIG_ALWAYS_NO_UNUSED_BUT_SET_VARIABLE
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+ ZFS_AC_CONFIG_ALWAYS_NO_AGGRESSIVE_LOOP_OPTIMIZATIONS
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])
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AC_DEFUN([ZFS_AC_CONFIG], [
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