https://github.com/torvalds/linux
Revision 914ee295af418e936ec20a08c1663eaabe4cd07a authored by Xin Zhong on 09 December 2010, 09:30:14 UTC, committed by Chris Mason on 10 December 2010, 21:29:10 UTC
This problem is found in meego testing: http://bugs.meego.com/show_bug.cgi?id=6672 A file in btrfs is mmaped and the mmaped buffer is passed to pwrite to write to the same page of the same file. In btrfs_file_aio_write(), the pages is locked by prepare_pages(). So when btrfs_copy_from_user() is called, page fault happens and the same page needs to be locked again in filemap_fault(). The fix is to move iov_iter_fault_in_readable() before prepage_pages() to make page fault happen before pages are locked. And also disable page fault in critical region in btrfs_copy_from_user(). Reviewed-by: Yan, Zheng<zheng.z.yan@intel.com> Signed-off-by: Zhong, Xin <xin.zhong@intel.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
1 parent f106e82
Tip revision: 914ee295af418e936ec20a08c1663eaabe4cd07a authored by Xin Zhong on 09 December 2010, 09:30:14 UTC
Btrfs: pwrite blocked when writing from the mmaped buffer of the same page
Btrfs: pwrite blocked when writing from the mmaped buffer of the same page
Tip revision: 914ee29
coccicheck
#!/bin/sh
SPATCH="`which ${SPATCH:=spatch}`"
if [ "$C" = "1" -o "$C" = "2" ]; then
ONLINE=1
# This requires Coccinelle >= 0.2.3
# FLAGS="-ignore_unknown_options -very_quiet"
# OPTIONS=$*
# Workaround for Coccinelle < 0.2.3
FLAGS="-I $srctree/include -very_quiet"
shift $(( $# - 1 ))
OPTIONS=$1
else
ONLINE=0
FLAGS="-very_quiet"
fi
if [ ! -x "$SPATCH" ]; then
echo 'spatch is part of the Coccinelle project and is available at http://coccinelle.lip6.fr/'
exit 1
fi
if [ "$MODE" = "" ] ; then
if [ "$ONLINE" = "0" ] ; then
echo 'You have not explicitly specify the mode to use. Fallback to "report".'
echo 'You can specify the mode with "make coccicheck MODE=<mode>"'
echo 'Available modes are: report, patch, context, org'
fi
MODE="report"
fi
if [ "$ONLINE" = "0" ] ; then
echo ''
echo 'Please check for false positives in the output before submitting a patch.'
echo 'When using "patch" mode, carefully review the patch before submitting it.'
echo ''
fi
coccinelle () {
COCCI="$1"
OPT=`grep "Option" $COCCI | cut -d':' -f2`
# The option '-parse_cocci' can be used to syntaxically check the SmPL files.
#
# $SPATCH -D $MODE $FLAGS -parse_cocci $COCCI $OPT > /dev/null
if [ "$ONLINE" = "0" ] ; then
FILE=`echo $COCCI | sed "s|$srctree/||"`
echo "Processing `basename $COCCI` with option(s) \"$OPT\""
echo 'Message example to submit a patch:'
sed -e '/\/\/\//!d' -e 's|^///||' $COCCI
echo ' The semantic patch that makes this change is available'
echo " in $FILE."
echo ''
echo ' More information about semantic patching is available at'
echo ' http://coccinelle.lip6.fr/'
echo ''
$SPATCH -D $MODE $FLAGS -sp_file $COCCI $OPT -dir $srctree || exit 1
else
$SPATCH -D $MODE $FLAGS -sp_file $COCCI $OPT $OPTIONS || exit 1
fi
}
if [ "$COCCI" = "" ] ; then
for f in `find $srctree/scripts/coccinelle/ -name '*.cocci' -type f | sort`; do
coccinelle $f
done
else
coccinelle $COCCI
fi
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