badblocks: return error if any badblock set fails

_badblocks_set() returns success if at least one badblock is set
successfully, even if others fail. This can lead to data inconsistencies
in raid, where a failed badblock set should trigger the disk to be kicked
out to prevent future reads from failed write areas.

_badblocks_set() should return error if any badblock set fails. Instead
of relying on 'rv', directly returning 'sectors' for clearer logic. If all
badblocks are successfully set, 'sectors' will be 0, otherwise it
indicates the number of badblocks that have not been set yet, thus
signaling failure.

By the way, it can also fix an issue: when a newly set unack badblock is
included in an existing ack badblock, the setting will return an error.
···
  echo "0 100" /sys/block/md0/md/dev-loop1/bad_blocks
  echo "0 100" /sys/block/md0/md/dev-loop1/unacknowledged_bad_blocks
  -bash: echo: write error: No space left on device
```
After fix, it will return success.

Fixes: aa511ff ("badblocks: switch to the improved badblock handling code")
Signed-off-by: Li Nan <[email protected]>
Reviewed-by: Yu Kuai <[email protected]>
Acked-by: Coly Li <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

Author: Li Nan

block/badblocks.c

@@ -843,7 +843,6 @@ static int _badblocks_set(struct badblocks *bb, sector_t s, int sectors,
 	struct badblocks_context bad;
 	int prev = -1, hint = -1;
 	unsigned long flags;
-	int rv = 0;
 	u64 *p;
 
 	if (bb->shift < 0)
@@ -873,10 +872,8 @@ static int _badblocks_set(struct badblocks *bb, sector_t s, int sectors,
 	bad.len = sectors;
 	len = 0;
 
-	if (badblocks_full(bb)) {
-		rv = 1;
+	if (badblocks_full(bb))
 		goto out;
-	}
 
 	if (badblocks_empty(bb)) {
 		len = insert_at(bb, 0, &bad);
@@ -916,10 +913,8 @@ static int _badblocks_set(struct badblocks *bb, sector_t s, int sectors,
 			int extra = 0;
 
 			if (!can_front_overwrite(bb, prev, &bad, &extra)) {
-				if (extra > 0) {
-					rv = 1;
+				if (extra > 0)
 					goto out;
-				}
 
 				len = min_t(sector_t,
 					    BB_END(p[prev]) - s, sectors);
@@ -986,10 +981,7 @@ static int _badblocks_set(struct badblocks *bb, sector_t s, int sectors,
 
 	write_sequnlock_irqrestore(&bb->lock, flags);
 
-	if (!added)
-		rv = 1;
-
-	return rv;
+	return sectors;
 }
 
 /*
@@ -1353,7 +1345,8 @@ EXPORT_SYMBOL_GPL(badblocks_check);
  *
  * Return:
  *  0: success
- *  1: failed to set badblocks (out of space)
+ *  other: failed to set badblocks (out of space). Parital setting will be
+ *  treated as failure.
  */
 int badblocks_set(struct badblocks *bb, sector_t s, int sectors,
 			int acknowledged)