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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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include/sys/uio_impl.h
+1 -1
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@@ -42,7 +42,7 @@
#include <sys/uio.h>
extern int uiomove(void *, size_t, enum uio_rw, uio_t *);
extern void uio_prefaultpages(ssize_t, uio_t *);
extern int uio_prefaultpages(ssize_t, uio_t *);
extern int uiocopy(void *, size_t, enum uio_rw, uio_t *, size_t *);
extern void uioskip(uio_t *, size_t);