From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
iomap complete routine can deadlock with btrfs_fallocate because of the
call to generic_write_sync().
P0 P1
inode_lock() fallocate(FALLOC_FL_ZERO_RANGE)
__iomap_dio_rw() inode_lock()
<block>
<submits IO>
<completes IO>
inode_unlock()
<gets inode_lock()>
inode_dio_wait()
iomap_dio_complete()
generic_write_sync()
btrfs_file_fsync()
inode_lock()
<deadlock>
inode_dio_end() is used to notify the end of DIO data in order
to synchronize with truncate. Call inode_dio_end() before calling
generic_write_sync(), so filesystems can lock i_rwsem during a sync.
---
fs/iomap/direct-io.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index d970c6bbbe11..e01f81e7b76f 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -118,6 +118,7 @@ ssize_t iomap_dio_complete(struct iomap_dio *dio)
dio_warn_stale_pagecache(iocb->ki_filp);
}
+ inode_dio_end(file_inode(iocb->ki_filp));
/*
* If this is a DSYNC write, make sure we push it to stable storage now
* that we've written data.
@@ -125,7 +126,6 @@ ssize_t iomap_dio_complete(struct iomap_dio *dio)
if (ret > 0 && (dio->flags & IOMAP_DIO_NEED_SYNC))
ret = generic_write_sync(iocb, ret);
- inode_dio_end(file_inode(iocb->ki_filp));
kfree(dio);
return ret;
--
2.26.2
