On Wed, 9 Sep 2015 09:55:16 +0800 jiangyiwen <jiangyi...@huawei.com> wrote:
> A simplified test case is (this case from Ryan):
> 1) dd if=/dev/zero of=/mnt/hello bs=512 count=1 oflag=direct;
> 2) truncate /mnt/hello -s 2097152
> file 'hello' is not exist before test. After this command,
> file 'hello' should be all zero. But 512~4096 is some random data.
>
> Setting bh state to new when get a new block, if so,
> direct_io_worker()->dio_zero_block() will fill-in the unused portion
> of the block with zero.
>
> ...
>
> --- a/fs/ocfs2/aops.c
> +++ b/fs/ocfs2/aops.c
> @@ -581,6 +581,7 @@ static int ocfs2_direct_IO_get_blocks(struct inode
> *inode, sector_t iblock,
> ret = -EIO;
> goto bail;
> }
> + set_buffer_new(bh_result);
> }
>
You're working against an old kernel. I did this:
---
a/fs/ocfs2/aops.c~ocfs2-fill-in-the-unused-portion-of-the-block-with-zeros-by-dio_zero_block
+++ a/fs/ocfs2/aops.c
@@ -589,6 +589,7 @@ static int ocfs2_direct_IO_get_blocks(st
ret = -EIO;
goto bail;
}
+ set_buffer_new(bh_result);
up_write(&OCFS2_I(inode)->ip_alloc_sem);
}
Probably we could run set_buffer_new() after the up_write(), which
would decrease lok hold times a little bit.
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