btrfs_direct_IO oops

Commit Message

Al Viro Oct. 10, 2016, 3:55 p.m. UTC

On Mon, Oct 10, 2016 at 09:11:22AM -0400, Dave Jones wrote:

> My compiler choked on that, but I fixed it up. The printk didn't
> trigger though..
> 
> idx = 0, offset = 0
> curbuf = 0, nrbufs = 1, buffers = 16
> [ffffffffb9a21100 ffffea00126019c0 0 4096]
> [          (null) ffffea0013746440 0 0]
> [          (null) ffffea00132956c0 0 0]
> [          (null) ffffea0013295700 0 0]
> [          (null) ffffea0013295740 0 0]
> [          (null) ffffea0013295780 0 0]
> [          (null) ffffea00132957c0 0 0]
> [          (null) ffffea0013595c00 0 0]
> [          (null) ffffea0012b1b6c0 0 0]
> [          (null)           (null) 0 0]
> [          (null)           (null) 0 0]
> [          (null)           (null) 0 0]
> [          (null)           (null) 0 0]
> [          (null)           (null) 0 0]
> [          (null)           (null) 0 0]
> [          (null)           (null) 0 0]
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 13581 at lib/iov_iter.c:327 sanity+0x102/0x150
> CPU: 1 PID: 13581 Comm: trinity-c17 Not tainted 4.8.0-think+ #9 
>  ffffc90000963ae8
>  ffffffffb93e22d1
>  0000000000000000
>  0000000000000000
> 
>  ffffffffb9c1e1cb
>  ffffffffb93fa5b2
>  ffffc90000963b28
>  ffffffffb908b010
> 
>  00000147d43c0e7f
>  ffffffffb9c1e1cb
>  0000000000000147
>  0000000000000010

What are these from?  Confused...

> Call Trace:

[via splice_direct_to_actor()]

Hmmm...  I think I see it.  Could you try the following (on top of debugging
in lib/iov_iter.c) and see if anything triggers?

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Comments

Dave Jones Oct. 10, 2016, 5:17 p.m. UTC | #1

On Mon, Oct 10, 2016 at 04:55:03PM +0100, Al Viro wrote:
 
 > > WARNING: CPU: 1 PID: 13581 at lib/iov_iter.c:327 sanity+0x102/0x150
 > > CPU: 1 PID: 13581 Comm: trinity-c17 Not tainted 4.8.0-think+ #9 
 > >  ffffc90000963ae8
 > >  ffffffffb93e22d1
 > >  0000000000000000
 > >  0000000000000000
 > > 
 > >  ffffffffb9c1e1cb
 > >  ffffffffb93fa5b2
 > >  ffffc90000963b28
 > >  ffffffffb908b010
 > > 
 > >  00000147d43c0e7f
 > >  ffffffffb9c1e1cb
 > >  0000000000000147
 > >  0000000000000010
 > 
 > What are these from?  Confused...

That's the stack I think. I don't know why it started printing all weird..

 > [via splice_direct_to_actor()]
 > 
 > Hmmm...  I think I see it.  Could you try the following (on top of debugging
 > in lib/iov_iter.c) and see if anything triggers?
 
Been running for an hour without incident so far, so this looks promising.
I'll follow-up if anything jumps out, but normally I'd have seen this by now.

	Dave
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Patch

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index bfc2aa7..b63d8c5 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -319,7 +319,7 @@  xfs_file_dio_aio_read(
 	data = *to;
 	ret = __blockdev_direct_IO(iocb, inode, target->bt_bdev, &data,
 			xfs_get_blocks_direct, NULL, NULL, 0);
-	if (ret > 0) {
+	if (ret >= 0) {
 		iocb->ki_pos += ret;
 		iov_iter_advance(to, ret);
 	}
diff --git a/mm/filemap.c b/mm/filemap.c
index 68f1813..88e5ddd 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1935,7 +1935,7 @@  generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 		file_accessed(file);
 
 		retval = mapping->a_ops->direct_IO(iocb, &data);
-		if (retval > 0) {
+		if (retval >= 0) {
 			iocb->ki_pos += retval;
 			iov_iter_advance(iter, retval);
 		}