在 2022/1/12 2:55, Darrick J. Wong 写道:
On Tue, Dec 14, 2021 at 04:19:12PM +0800, Shiyang Ruan wrote:
Test for races or FS corruption between reflink and mmap reading the
target file. (MMAP version of generic/164,165)
Hi, now that this test has been running for a couple of weeks, I have
observed periodic false positives from this test:
QA output created by 670
Format and mount
Initialize files
Reflink and mmap reread the files!
00001000: 61 61 61 61 61 61 61 61 62 62 62 62 62 62 62 62 aaaabbbb
Finished reflinking
I suspect that if the _mread_range of file3 races with the page cache
invalidation that FICLONERANGE performs, it is possible that the mread
dump will contain a mix of 0x61 and 0x62. Looking at mread_f, it looks
like it does a byte-at-a-time copy of the mmap...
if (rflag) {
for (tmp = length - 1, c = 0; tmp >= 0; tmp--, c = 1) {
*bp = *(((char *)mapping->addr) + dumpoffset + tmp);
cnt++;
...which is a sufficient window for the page cache mapping to get
invalidated such that the mread will block on the page fault until the
reflink operation finishes.
I think the solution here is to adjust the egrep regexp above to find
any line that does /not/ contain a's or b's, since (in principle) the
reflink could run fast enough that every byte read hits a pgae fault.
What do you think?
Reasonable. I couldn't reproduce it in my test environment, so I didn't
take that situation into consideration.
I'll change the regexp as below:
fbytes() {
- egrep -v '(61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61|62 62 62 62
62 62 62 62 62 62 62 62 62 62 62 62)'
+ egrep -v '((61|62) ){15}(61|62)'
}
--
Thanks,
Ruan.
--D
Signed-off-by: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx>
---
common/reflink | 11 +++++++
tests/generic/913 | 72 +++++++++++++++++++++++++++++++++++++++++++
tests/generic/913.out | 5 +++
3 files changed, 88 insertions(+)
create mode 100755 tests/generic/913
create mode 100644 tests/generic/913.out
diff --git a/common/reflink b/common/reflink
index 68dbdedd..455260c6 100644
--- a/common/reflink
+++ b/common/reflink
@@ -186,6 +186,17 @@ _read_range() {
$XFS_IO_PROG $xfs_io_args -f -c "pread -q -v $offset $len" "$file" | cut -d ' ' -f '3-18'
}
+# Prints a range of a file as a hex dump
+_mread_range() {
+ file="$1"
+ offset="$2"
+ len="$3"
+ xfs_io_args="$4"
+
+ $XFS_IO_PROG $xfs_io_args -f -c "mmap -rw 0 $((offset + len))" \
+ -c "mread -v $offset $len" "$file" | cut -d ' ' -f '3-18'
+}
+
# Compare ranges of two files
_compare_range() {
file1="$1"
diff --git a/tests/generic/913 b/tests/generic/913
new file mode 100755
index 00000000..f709c36c
--- /dev/null
+++ b/tests/generic/913
@@ -0,0 +1,72 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# FS QA Test No. 913
+#
+# Test for races or FS corruption between reflink and mmap reading the
+# target file. (MMAP version of generic/164,165)
+#
+. ./common/preamble
+_begin_fstest auto clone
+
+_register_cleanup "_cleanup" BUS
+
+# Import common functions.
+. ./common/filter
+. ./common/reflink
+
+# real QA test starts here
+_require_scratch_reflink
+_require_cp_reflink
+
+echo "Format and mount"
+_scratch_mkfs > $seqres.full 2>&1
+_scratch_mount >> $seqres.full 2>&1
+
+testdir=$SCRATCH_MNT/test-$seq
+finished_file=/tmp/finished
+rm -rf $finished_file
+mkdir $testdir
+
+loops=512
+nr_loops=$((loops - 1))
+blksz=65536
+
+echo "Initialize files"
+echo >> $seqres.full
+_pwrite_byte 0x61 0 $((loops * blksz)) $testdir/file1 >> $seqres.full
+_pwrite_byte 0x62 0 $((loops * blksz)) $testdir/file2 >> $seqres.full
+_cp_reflink $testdir/file1 $testdir/file3
+_scratch_cycle_mount
+
+fbytes() {
+ egrep -v '(61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61|62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62)'
+}
+
+reader() {
+ while [ ! -e $finished_file ]; do
+ _mread_range $testdir/file3 0 $((loops * blksz)) | fbytes
+ done
+}
+
+echo "Reflink and mmap reread the files!"
+reader &
+for i in `seq 1 2`; do
+ seq $nr_loops -1 0 | while read i; do
+ _reflink_range $testdir/file1 $((i * blksz)) \
+ $testdir/file3 $((i * blksz)) $blksz >> $seqres.full
+ [ $? -ne 0 ] && break
+ done
+ seq $nr_loops -1 0 | while read i; do
+ _reflink_range $testdir/file2 $((i * blksz)) \
+ $testdir/file3 $((i * blksz)) $blksz >> $seqres.full
+ [ $? -ne 0 ] && break
+ done
+done
+echo "Finished reflinking"
+touch $finished_file
+wait
+
+# success, all done
+status=0
+exit
diff --git a/tests/generic/913.out b/tests/generic/913.out
new file mode 100644
index 00000000..a34df6ce
--- /dev/null
+++ b/tests/generic/913.out
@@ -0,0 +1,5 @@
+QA output created by 913
+Format and mount
+Initialize files
+Reflink and mmap reread the files!
+Finished reflinking
--
2.34.1
