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deadlock between mm_sem and tx assign in zfs_write() and page fault

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The bug time sequence:
1. thread #1, `zfs_write` assign a txg "n".
2. In a same process, thread #2, mmap page fault (which means the
   `mm_sem` is hold) occurred, `zfs_dirty_inode` open a txg failed,
   and wait previous txg "n" completed.
3. thread #1 call `uiomove` to write, however page fault is occurred
   in `uiomove`, which means it need `mm_sem`, but `mm_sem` is hold by
   thread #2, so it stuck and can't complete,  then txg "n" will
   not complete.

So thread #1 and thread #2 are deadlocked.

Reviewed-by: Chunwei Chen <tuxoko@gmail.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Signed-off-by: Grady Wong <grady.w@xtaotech.com>
Closes #7939
This commit is contained in:
ilbsmart
2018-10-17 02:11:24 +08:00
committed by Matthew Ahrens
parent b2030e5d51
commit 779a6c0bf6
6 changed files with 155 additions and 57 deletions
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tests/zfs-tests/tests/functional/mmap/mmap_write_001_pos.ksh
+5 -3
View File
@@ -53,12 +53,14 @@ if ! is_mp; then
fi
log_must chmod 777 $TESTDIR
mmapwrite $TESTDIR/test-write-file &
mmapwrite $TESTDIR/normal_write_file $TESTDIR/map_write_file &
PID_MMAPWRITE=$!
log_note "mmapwrite $TESTDIR/test-write-file pid: $PID_MMAPWRITE"
log_note "mmapwrite $TESTDIR/normal_write_file $TESTDIR/map_write_file"\
"pid: $PID_MMAPWRITE"
log_must sleep 30
log_must kill -9 $PID_MMAPWRITE
log_must ls -l $TESTDIR/test-write-file
log_must ls -l $TESTDIR/normal_write_file
log_must ls -l $TESTDIR/map_write_file
log_pass "write(2) a mmap(2)'ing file succeeded."