Revision e2093926a098a8ccf0f1d10f6df8dad452cb28d3 authored by Ross Zwisler on 02 June 2017, 21:46:37 UTC, committed by Linus Torvalds on 02 June 2017, 22:07:37 UTC
We currently have two related PMD vs PTE races in the DAX code. These can both be easily triggered by having two threads reading and writing simultaneously to the same private mapping, with the key being that private mapping reads can be handled with PMDs but private mapping writes are always handled with PTEs so that we can COW. Here is the first race: CPU 0 CPU 1 (private mapping write) __handle_mm_fault() create_huge_pmd() - FALLBACK handle_pte_fault() passes check for pmd_devmap() (private mapping read) __handle_mm_fault() create_huge_pmd() dax_iomap_pmd_fault() inserts PMD dax_iomap_pte_fault() does a PTE fault, but we already have a DAX PMD installed in our page tables at this spot. Here's the second race: CPU 0 CPU 1 (private mapping read) __handle_mm_fault() passes check for pmd_none() create_huge_pmd() dax_iomap_pmd_fault() inserts PMD (private mapping write) __handle_mm_fault() create_huge_pmd() - FALLBACK (private mapping read) __handle_mm_fault() passes check for pmd_none() create_huge_pmd() handle_pte_fault() dax_iomap_pte_fault() inserts PTE dax_iomap_pmd_fault() inserts PMD, but we already have a PTE at this spot. The core of the issue is that while there is isolation between faults to the same range in the DAX fault handlers via our DAX entry locking, there is no isolation between faults in the code in mm/memory.c. This means for instance that this code in __handle_mm_fault() can run: if (pmd_none(*vmf.pmd) && transparent_hugepage_enabled(vma)) { ret = create_huge_pmd(&vmf); But by the time we actually get to run the fault handler called by create_huge_pmd(), the PMD is no longer pmd_none() because a racing PTE fault has installed a normal PMD here as a parent. This is the cause of the 2nd race. The first race is similar - there is the following check in handle_pte_fault(): } else { /* See comment in pte_alloc_one_map() */ if (pmd_devmap(*vmf->pmd) || pmd_trans_unstable(vmf->pmd)) return 0; So if a pmd_devmap() PMD (a DAX PMD) has been installed at vmf->pmd, we will bail and retry the fault. This is correct, but there is nothing preventing the PMD from being installed after this check but before we actually get to the DAX PTE fault handlers. In my testing these races result in the following types of errors: BUG: Bad rss-counter state mm:ffff8800a817d280 idx:1 val:1 BUG: non-zero nr_ptes on freeing mm: 15 Fix this issue by having the DAX fault handlers verify that it is safe to continue their fault after they have taken an entry lock to block other racing faults. [ross.zwisler@linux.intel.com: improve fix for colliding PMD & PTE entries] Link: http://lkml.kernel.org/r/20170526195932.32178-1-ross.zwisler@linux.intel.com Link: http://lkml.kernel.org/r/20170522215749.23516-2-ross.zwisler@linux.intel.com Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> Reported-by: Pawel Lebioda <pawel.lebioda@intel.com> Reviewed-by: Jan Kara <jack@suse.cz> Cc: "Darrick J. Wong" <darrick.wong@oracle.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@lst.de> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Matthew Wilcox <mawilcox@microsoft.com> Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com> Cc: Pawel Lebioda <pawel.lebioda@intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Xiong Zhou <xzhou@redhat.com> Cc: Eryu Guan <eguan@redhat.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent d0f0931
tags.sh
#!/bin/bash
# Generate tags or cscope files
# Usage tags.sh <mode>
#
# mode may be any of: tags, TAGS, cscope
#
# Uses the following environment variables:
# ARCH, SUBARCH, SRCARCH, srctree, src, obj
if [ "$KBUILD_VERBOSE" = "1" ]; then
set -x
fi
# RCS_FIND_IGNORE has escaped ()s -- remove them.
ignore="$(echo "$RCS_FIND_IGNORE" | sed 's|\\||g' )"
# tags and cscope files should also ignore MODVERSION *.mod.c files
ignore="$ignore ( -name *.mod.c ) -prune -o"
# Do not use full path if we do not use O=.. builds
# Use make O=. {tags|cscope}
# to force full paths for a non-O= build
if [ "${KBUILD_SRC}" = "" ]; then
tree=
else
tree=${srctree}/
fi
# ignore userspace tools
ignore="$ignore ( -path ${tree}tools ) -prune -o"
# Find all available archs
find_all_archs()
{
ALLSOURCE_ARCHS=""
for arch in `ls ${tree}arch`; do
ALLSOURCE_ARCHS="${ALLSOURCE_ARCHS} "${arch##\/}
done
}
# Detect if ALLSOURCE_ARCHS is set. If not, we assume SRCARCH
if [ "${ALLSOURCE_ARCHS}" = "" ]; then
ALLSOURCE_ARCHS=${SRCARCH}
elif [ "${ALLSOURCE_ARCHS}" = "all" ]; then
find_all_archs
fi
# find sources in arch/$ARCH
find_arch_sources()
{
for i in $archincludedir; do
prune="$prune -wholename $i -prune -o"
done
find ${tree}arch/$1 $ignore $subarchprune $prune -name "$2" \
-not -type l -print;
}
# find sources in arch/$1/include
find_arch_include_sources()
{
include=$(find ${tree}arch/$1/ $subarchprune \
-name include -type d -print);
if [ -n "$include" ]; then
archincludedir="$archincludedir $include"
find $include $ignore -name "$2" -not -type l -print;
fi
}
# find sources in include/
find_include_sources()
{
find ${tree}include $ignore -name config -prune -o -name "$1" \
-not -type l -print;
}
# find sources in rest of tree
# we could benefit from a list of dirs to search in here
find_other_sources()
{
find ${tree}* $ignore \
\( -name include -o -name arch -o -name '.tmp_*' \) -prune -o \
-name "$1" -not -type l -print;
}
find_sources()
{
find_arch_sources $1 "$2"
}
all_sources()
{
find_arch_include_sources ${SRCARCH} '*.[chS]'
if [ ! -z "$archinclude" ]; then
find_arch_include_sources $archinclude '*.[chS]'
fi
find_include_sources '*.[chS]'
for arch in $ALLSOURCE_ARCHS
do
find_sources $arch '*.[chS]'
done
find_other_sources '*.[chS]'
}
all_compiled_sources()
{
for i in $(all_sources); do
case "$i" in
*.[cS])
j=${i/\.[cS]/\.o}
if [ -e $j ]; then
echo $i
fi
;;
*)
echo $i
;;
esac
done
}
all_target_sources()
{
if [ -n "$COMPILED_SOURCE" ]; then
all_compiled_sources
else
all_sources
fi
}
all_kconfigs()
{
find ${tree}arch/ -maxdepth 1 $ignore \
-name "Kconfig*" -not -type l -print;
for arch in $ALLSOURCE_ARCHS; do
find_sources $arch 'Kconfig*'
done
find_other_sources 'Kconfig*'
}
docscope()
{
(echo \-k; echo \-q; all_target_sources) > cscope.files
cscope -b -f cscope.out
}
dogtags()
{
all_target_sources | gtags -i -f -
}
# Basic regular expressions with an optional /kind-spec/ for ctags and
# the following limitations:
# - No regex modifiers
# - Use \{0,1\} instead of \?, because etags expects an unescaped ?
# - \s is not working with etags, use a space or [ \t]
# - \w works, but does not match underscores in etags
# - etags regular expressions have to match at the start of a line;
# a ^[^#] is prepended by setup_regex unless an anchor is already present
regex_asm=(
'/^\(ENTRY\|_GLOBAL\)(\([[:alnum:]_\\]*\)).*/\2/'
)
regex_c=(
'/^SYSCALL_DEFINE[0-9](\([[:alnum:]_]*\).*/sys_\1/'
'/^COMPAT_SYSCALL_DEFINE[0-9](\([[:alnum:]_]*\).*/compat_sys_\1/'
'/^TRACE_EVENT(\([[:alnum:]_]*\).*/trace_\1/'
'/^TRACE_EVENT(\([[:alnum:]_]*\).*/trace_\1_rcuidle/'
'/^DEFINE_EVENT([^,)]*, *\([[:alnum:]_]*\).*/trace_\1/'
'/^DEFINE_EVENT([^,)]*, *\([[:alnum:]_]*\).*/trace_\1_rcuidle/'
'/^DEFINE_INSN_CACHE_OPS(\([[:alnum:]_]*\).*/get_\1_slot/'
'/^DEFINE_INSN_CACHE_OPS(\([[:alnum:]_]*\).*/free_\1_slot/'
'/^PAGEFLAG(\([[:alnum:]_]*\).*/Page\1/'
'/^PAGEFLAG(\([[:alnum:]_]*\).*/SetPage\1/'
'/^PAGEFLAG(\([[:alnum:]_]*\).*/ClearPage\1/'
'/^TESTSETFLAG(\([[:alnum:]_]*\).*/TestSetPage\1/'
'/^TESTPAGEFLAG(\([[:alnum:]_]*\).*/Page\1/'
'/^SETPAGEFLAG(\([[:alnum:]_]*\).*/SetPage\1/'
'/\<__SETPAGEFLAG(\([[:alnum:]_]*\).*/__SetPage\1/'
'/\<TESTCLEARFLAG(\([[:alnum:]_]*\).*/TestClearPage\1/'
'/\<__TESTCLEARFLAG(\([[:alnum:]_]*\).*/TestClearPage\1/'
'/\<CLEARPAGEFLAG(\([[:alnum:]_]*\).*/ClearPage\1/'
'/\<__CLEARPAGEFLAG(\([[:alnum:]_]*\).*/__ClearPage\1/'
'/^__PAGEFLAG(\([[:alnum:]_]*\).*/__SetPage\1/'
'/^__PAGEFLAG(\([[:alnum:]_]*\).*/__ClearPage\1/'
'/^PAGEFLAG_FALSE(\([[:alnum:]_]*\).*/Page\1/'
'/\<TESTSCFLAG(\([[:alnum:]_]*\).*/TestSetPage\1/'
'/\<TESTSCFLAG(\([[:alnum:]_]*\).*/TestClearPage\1/'
'/\<SETPAGEFLAG_NOOP(\([[:alnum:]_]*\).*/SetPage\1/'
'/\<CLEARPAGEFLAG_NOOP(\([[:alnum:]_]*\).*/ClearPage\1/'
'/\<__CLEARPAGEFLAG_NOOP(\([[:alnum:]_]*\).*/__ClearPage\1/'
'/\<TESTCLEARFLAG_FALSE(\([[:alnum:]_]*\).*/TestClearPage\1/'
'/^PAGE_MAPCOUNT_OPS(\([[:alnum:]_]*\).*/Page\1/'
'/^PAGE_MAPCOUNT_OPS(\([[:alnum:]_]*\).*/__SetPage\1/'
'/^PAGE_MAPCOUNT_OPS(\([[:alnum:]_]*\).*/__ClearPage\1/'
'/^TASK_PFA_TEST([^,]*, *\([[:alnum:]_]*\))/task_\1/'
'/^TASK_PFA_SET([^,]*, *\([[:alnum:]_]*\))/task_set_\1/'
'/^TASK_PFA_CLEAR([^,]*, *\([[:alnum:]_]*\))/task_clear_\1/'
'/^DEF_MMIO_\(IN\|OUT\)_[XD](\([[:alnum:]_]*\),[^)]*)/\2/'
'/^DEBUGGER_BOILERPLATE(\([[:alnum:]_]*\))/\1/'
'/^DEF_PCI_AC_\(\|NO\)RET(\([[:alnum:]_]*\).*/\2/'
'/^PCI_OP_READ(\(\w*\).*[1-4])/pci_bus_read_config_\1/'
'/^PCI_OP_WRITE(\(\w*\).*[1-4])/pci_bus_write_config_\1/'
'/\<DEFINE_\(MUTEX\|SEMAPHORE\|SPINLOCK\)(\([[:alnum:]_]*\)/\2/v/'
'/\<DEFINE_\(RAW_SPINLOCK\|RWLOCK\|SEQLOCK\)(\([[:alnum:]_]*\)/\2/v/'
'/\<DECLARE_\(RWSEM\|COMPLETION\)(\([[:alnum:]_]\+\)/\2/v/'
'/\<DECLARE_BITMAP(\([[:alnum:]_]*\)/\1/v/'
'/\(^\|\s\)\(\|L\|H\)LIST_HEAD(\([[:alnum:]_]*\)/\3/v/'
'/\(^\|\s\)RADIX_TREE(\([[:alnum:]_]*\)/\2/v/'
'/\<DEFINE_PER_CPU([^,]*, *\([[:alnum:]_]*\)/\1/v/'
'/\<DEFINE_PER_CPU_SHARED_ALIGNED([^,]*, *\([[:alnum:]_]*\)/\1/v/'
'/\<DECLARE_WAIT_QUEUE_HEAD(\([[:alnum:]_]*\)/\1/v/'
'/\<DECLARE_\(TASKLET\|WORK\|DELAYED_WORK\)(\([[:alnum:]_]*\)/\2/v/'
'/\(^\s\)OFFSET(\([[:alnum:]_]*\)/\2/v/'
'/\(^\s\)DEFINE(\([[:alnum:]_]*\)/\2/v/'
'/\<DEFINE_HASHTABLE(\([[:alnum:]_]*\)/\1/v/'
)
regex_kconfig=(
'/^[[:blank:]]*\(menu\|\)config[[:blank:]]\+\([[:alnum:]_]\+\)/\2/'
'/^[[:blank:]]*\(menu\|\)config[[:blank:]]\+\([[:alnum:]_]\+\)/CONFIG_\2/'
)
setup_regex()
{
local mode=$1 lang tmp=() r
shift
regex=()
for lang; do
case "$lang" in
asm) tmp=("${regex_asm[@]}") ;;
c) tmp=("${regex_c[@]}") ;;
kconfig) tmp=("${regex_kconfig[@]}") ;;
esac
for r in "${tmp[@]}"; do
if test "$mode" = "exuberant"; then
regex[${#regex[@]}]="--regex-$lang=${r}b"
else
# Remove ctags /kind-spec/
case "$r" in
/*/*/?/)
r=${r%?/}
esac
# Prepend ^[^#] unless already anchored
case "$r" in
/^*) ;;
*)
r="/^[^#]*${r#/}"
esac
regex[${#regex[@]}]="--regex=$r"
fi
done
done
}
exuberant()
{
setup_regex exuberant asm c
all_target_sources | xargs $1 -a \
-I __initdata,__exitdata,__initconst, \
-I __initdata_memblock \
-I __refdata,__attribute,__maybe_unused,__always_unused \
-I __acquires,__releases,__deprecated \
-I __read_mostly,__aligned,____cacheline_aligned \
-I ____cacheline_aligned_in_smp \
-I __cacheline_aligned,__cacheline_aligned_in_smp \
-I ____cacheline_internodealigned_in_smp \
-I __used,__packed,__packed2__,__must_check,__must_hold \
-I EXPORT_SYMBOL,EXPORT_SYMBOL_GPL,ACPI_EXPORT_SYMBOL \
-I DEFINE_TRACE,EXPORT_TRACEPOINT_SYMBOL,EXPORT_TRACEPOINT_SYMBOL_GPL \
-I static,const \
--extra=+fq --c-kinds=+px --fields=+iaS --langmap=c:+.h \
"${regex[@]}"
setup_regex exuberant kconfig
all_kconfigs | xargs $1 -a \
--langdef=kconfig --language-force=kconfig "${regex[@]}"
}
emacs()
{
setup_regex emacs asm c
all_target_sources | xargs $1 -a "${regex[@]}"
setup_regex emacs kconfig
all_kconfigs | xargs $1 -a "${regex[@]}"
}
xtags()
{
if $1 --version 2>&1 | grep -iq exuberant; then
exuberant $1
elif $1 --version 2>&1 | grep -iq emacs; then
emacs $1
else
all_target_sources | xargs $1 -a
fi
}
# Support um (which uses SUBARCH)
if [ "${ARCH}" = "um" ]; then
if [ "$SUBARCH" = "i386" ]; then
archinclude=x86
elif [ "$SUBARCH" = "x86_64" ]; then
archinclude=x86
else
archinclude=${SUBARCH}
fi
elif [ "${SRCARCH}" = "arm" -a "${SUBARCH}" != "" ]; then
subarchdir=$(find ${tree}arch/$SRCARCH/ -name "mach-*" -type d -o \
-name "plat-*" -type d);
mach_suffix=$SUBARCH
plat_suffix=$SUBARCH
# Special cases when $plat_suffix != $mach_suffix
case $mach_suffix in
"omap1" | "omap2")
plat_suffix="omap"
;;
esac
if [ ! -d ${tree}arch/$SRCARCH/mach-$mach_suffix ]; then
echo "Warning: arch/arm/mach-$mach_suffix/ not found." >&2
echo " Fix your \$SUBARCH appropriately" >&2
fi
for i in $subarchdir; do
case "$i" in
*"mach-"${mach_suffix})
;;
*"plat-"${plat_suffix})
;;
*)
subarchprune="$subarchprune \
-wholename $i -prune -o"
;;
esac
done
fi
remove_structs=
case "$1" in
"cscope")
docscope
;;
"gtags")
dogtags
;;
"tags")
rm -f tags
xtags ctags
remove_structs=y
;;
"TAGS")
rm -f TAGS
xtags etags
remove_structs=y
;;
esac
# Remove structure forward declarations.
if [ -n "$remove_structs" ]; then
LANG=C sed -i -e '/^\([a-zA-Z_][a-zA-Z0-9_]*\)\t.*\t\/\^struct \1;.*\$\/;"\tx$/d' $1
fi
![swh spinner](/static/img/swh-spinner.gif)
Computing file changes ...