On Thu, 28 Feb 2013 15:51:01 +0800 majianpeng [off-list ref] wrote:

quoted

For badsector,it took two steps:rewrite and reread.So for
write-operation,it make no sense to rewrite after write-operation.

Please please please please please try to explain yourself better.

Sorry for that. 

This patch doesn't make any sense.  The write succeeded.  We set the MadeGood
flag so that later code will remove the block from the bad-block list.
There will be no re-read or re-write.

For a striep which contain badsector is doing write-operation.
In analyse_stripe, it check badsector and set R5_ReadError.
 write--->MadeGood->clear badblock log. But it can't clear R5_ReadError flag.
So it will exec those code in func handle_stripe:

       /* If the failed drives are just a ReadError, then we might need
        * to progress the repair/check process
        */
       if (s.failed <= conf->max_degraded && !conf->mddev->ro)
               for (i = 0; i < s.failed; i++) {
                       struct r5dev *dev = &sh->dev[s.failed_num[i]];
                       if (test_bit(R5_ReadError, &dev->flags)
                           && !test_bit(R5_LOCKED, &dev->flags)
                           && test_bit(R5_UPTODATE, &dev->flags)
                               ) {  
                               if (!test_bit(R5_ReWrite, &dev->flags)) {
                                       set_bit(R5_Wantwrite, &dev->flags);
                                       set_bit(R5_ReWrite, &dev->flags);
                                       set_bit(R5_LOCKED, &dev->flags);
                                       s.locked++;
                               } else {
                                       /* let's read it back */
                                       set_bit(R5_Wantread, &dev->flags);
                                      set_bit(R5_LOCKED, &dev->flags);
                                      s.locked++;
                               }    
                       }    
               }    

But the flag ReWrite can't set. So it do write-operatoin again.Then do read-operation.

Thanks!
Jianpeng Ma

NeilBrown

quoted

Signed-off-by: Jianpeng Ma <redacted>
---
 drivers/md/raid5.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 19d77a0..59c0569 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c

@@ -1921,8 +1921,10 @@ static void raid5_end_write_request(struct bio *bi, int error)
 					&rdev->mddev->recovery);
 		} else if (is_badblock(rdev, sh->sector,
 				       STRIPE_SECTORS,
-				       &first_bad, &bad_sectors))
+				       &first_bad, &bad_sectors)) {
 			set_bit(R5_MadeGood, &sh->dev[i].flags);
+			set_bit(R5_ReWrite, &sh->dev[i].flags);
+		}
 	}
 	rdev_dec_pending(rdev, conf->mddev);