[PATCH] block: fix the return errno for direct IO

[Jason Yan]

If the last bio returned is not dio->bio, the status of the bio will
not assigned to dio->bio if it is error. This will cause the whole IO
status wrong.

    ksoftirqd/21-117   [021] ..s.  4017.966090:   8,0    C   N 4883648 [0]
          <idle>-0     [018] ..s.  4017.970888:   8,0    C  WS 4924800 + 1024 
[0]
          <idle>-0     [018] ..s.  4017.970909:   8,0    D  WS 4935424 + 1024 
[<idle>]
          <idle>-0     [018] ..s.  4017.970924:   8,0    D  WS 4936448 + 321 
[<idle>]
    ksoftirqd/21-117   [021] ..s.  4017.995033:   8,0    C   R 4883648 + 336 
[65475]
    ksoftirqd/21-117   [021] d.s.  4018.001988: myprobe1: 
(blkdev_bio_end_io+0x0/0x168) bi_status=7
    ksoftirqd/21-117   [021] d.s.  4018.001992: myprobe: 
(aio_complete_rw+0x0/0x148) x0=0xffff802f2595ad80 res=0x12a000 res2=0x0

We always have to assign bio->bi_status to dio->bio.bi_status because we
will only check dio->bio.bi_status when we return the whole IO to
the upper layer.

Fixes: 542ff7bf18c6 ("block: new direct I/O implementation")
Cc: Christoph Hellwig <h...@lst.de>
Cc: Jens Axboe <ax...@kernel.dk>
Cc: Ming Lei <ming....@redhat.com>
Signed-off-by: Jason Yan <yanai...@huawei.com>
---
 fs/block_dev.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 78d3257435c0..0fead5520a7e 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -84,7 +84,7 @@ void kill_bdev(struct block_device *bdev)
 
        invalidate_bh_lrus();
        truncate_inode_pages(mapping, 0);
-}      
+}
 EXPORT_SYMBOL(kill_bdev);
 
 /* Invalidate clean unused buffers and pagecache. */
@@ -307,10 +307,10 @@ static void blkdev_bio_end_io(struct bio *bio)
        struct blkdev_dio *dio = bio->bi_private;
        bool should_dirty = dio->should_dirty;
 
-       if (dio->multi_bio && !atomic_dec_and_test(&dio->ref)) {
-               if (bio->bi_status && !dio->bio.bi_status)
-                       dio->bio.bi_status = bio->bi_status;
-       } else {
+       if (bio->bi_status && !dio->bio.bi_status)
+               dio->bio.bi_status = bio->bi_status;
+
+       if (!dio->multi_bio || atomic_dec_and_test(&dio->ref)) {
                if (!dio->is_sync) {
                        struct kiocb *iocb = dio->iocb;
                        ssize_t ret;
@@ -670,13 +670,13 @@ static loff_t block_llseek(struct file *file, loff_t 
offset, int whence)
        inode_unlock(bd_inode);
        return retval;
 }
-       
+
 int blkdev_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
 {
        struct inode *bd_inode = bdev_file_inode(filp);
        struct block_device *bdev = I_BDEV(bd_inode);
        int error;
-       
+
        error = file_write_and_wait_range(filp, start, end);
        if (error)
                return error;
@@ -983,7 +983,7 @@ void bdput(struct block_device *bdev)
 }
 
 EXPORT_SYMBOL(bdput);
- 
+
 static struct block_device *bd_acquire(struct inode *inode)
 {
        struct block_device *bdev;
-- 
2.17.2