[PATCH] clarify meaning of bio fields in the end_io function

From: Christophe Saout <christophe@saout.de>

The intent of these are to clarify the meaning of the bio fields in the
bi_end_io function (since we are already mostly there).  After these small
modifications bio->bi_idx and the corresponding bio_iovec(bio)->bv_offset
point to the beginning of the completed data, together with the nr_bytes
argument you know exactly what data was finished, e.g.  when you can't
track it otherwise (or it would be unnecessary expensive).  Apart from that
it's a nice-to-have.

The first mini-patch moves the update of bio_iovec(bio)->bv_offset and
->bv_len after the call of bi_end_io where bi_idx gets updated so they get
updated together.  Ok with Jens.

The second part of the patch modifies the multwrite hack in PIO non-
taskfile ide disk code.  It modifies the bi_idx field to walk the bios and
doesn't reset it correctly before ending the request.  The patch uses the
segment counter in the request field to correctly restore the bi_idx field
before ending the request.  Can't possibly break anything since it's
working on the local request copy ("scratchpad") anyway.  Also does this in
legacy/pdc4030.c (similar code).  The code modified here is going to die
anyway any trying to fix it would be too invasive.  Ok with Bartlomiej.

drivers/block/ll_rw_blk.c

@@ -2488,8 +2488,6 @@ static int __end_that_request_first(struct request *req, int uptodate,
 			 * not a complete bvec done
 			 */
 			if (unlikely(nbytes > nr_bytes)) {
-				bio_iovec_idx(bio, idx)->bv_offset += nr_bytes;
-				bio_iovec_idx(bio, idx)->bv_len -= nr_bytes;
 				bio_nbytes += nr_bytes;
 				total_bytes += nr_bytes;
 				break;
@@ -2525,7 +2523,9 @@ static int __end_that_request_first(struct request *req, int uptodate,
 	 */
 	if (bio_nbytes) {
 		bio_endio(bio, bio_nbytes, error);
-		req->bio->bi_idx += next_idx;
+		bio->bi_idx += next_idx;
+		bio_iovec(bio)->bv_offset += nr_bytes;
+		bio_iovec(bio)->bv_len -= nr_bytes;
 	}
 
 	blk_recalc_rq_sectors(req, total_bytes >> 9);

drivers/ide/ide-disk.c

@@ -277,7 +277,7 @@ static void ide_multwrite(ide_drive_t *drive, unsigned int mcount)
 			 * all bvecs in this one.
 			 */
 			if (++bio->bi_idx >= bio->bi_vcnt) {
-				bio->bi_idx = 0;
+				bio->bi_idx = bio->bi_vcnt - rq->nr_cbio_segments;
 				bio = bio->bi_next;
 			}
 
@@ -286,7 +286,8 @@ static void ide_multwrite(ide_drive_t *drive, unsigned int mcount)
 				mcount = 0;
 			} else {
 				rq->bio = bio;
-				rq->current_nr_sectors = bio_iovec(bio)->bv_len >> 9;
+				rq->nr_cbio_segments = bio_segments(bio);
+				rq->current_nr_sectors = bio_cur_sectors(bio);
 				rq->hard_cur_sectors = rq->current_nr_sectors;
 			}
 		}
@@ -308,6 +309,7 @@ static ide_startstop_t multwrite_intr (ide_drive_t *drive)
 	ide_hwgroup_t *hwgroup	= HWGROUP(drive);
 	ide_hwif_t *hwif	= HWIF(drive);
 	struct request *rq	= &hwgroup->wrq;
+	struct bio *bio		= rq->bio;
 	u8 stat;
 
 	stat = hwif->INB(IDE_STATUS_REG);
@@ -328,14 +330,17 @@ static ide_startstop_t multwrite_intr (ide_drive_t *drive)
 			 *	we can end the original request.
 			 */
 			if (!rq->nr_sectors) {	/* all done? */
+				bio->bi_idx = bio->bi_vcnt - rq->nr_cbio_segments;
 				rq = hwgroup->rq;
 				ide_end_request(drive, 1, rq->nr_sectors);
 				return ide_stopped;
 			}
 		}
+		bio->bi_idx = bio->bi_vcnt - rq->nr_cbio_segments;
 		/* the original code did this here (?) */
 		return ide_stopped;
 	}
+	bio->bi_idx = bio->bi_vcnt - rq->nr_cbio_segments;
 	return DRIVER(drive)->error(drive, "multwrite_intr", stat);
 }
 

drivers/ide/legacy/pdc4030.c

@@ -443,7 +443,12 @@ static ide_startstop_t promise_read_intr (ide_drive_t *drive)
 static ide_startstop_t promise_complete_pollfunc(ide_drive_t *drive)
 {
 	ide_hwgroup_t *hwgroup = HWGROUP(drive);
+#ifdef CONFIG_IDE_TASKFILE_IO
 	struct request *rq = hwgroup->rq;
+#else
+	struct request *rq = &hwgroup->wrq;
+	struct bio *bio = rq->bio;
+#endif
 
 	if ((HWIF(drive)->INB(IDE_STATUS_REG)) & BUSY_STAT) {
 		if (time_before(jiffies, hwgroup->poll_timeout)) {
@@ -472,6 +477,8 @@ static ide_startstop_t promise_complete_pollfunc(ide_drive_t *drive)
 	while (rq->bio != rq->cbio)
 		(void) DRIVER(drive)->end_request(drive, 1, bio_sectors(rq->bio));
 #else
+	bio->bi_idx = bio->bi_vcnt - rq->nr_cbio_segments;
+	rq = hwgroup->rq;
 	DRIVER(drive)->end_request(drive, 1, rq->hard_nr_sectors);
 #endif
 	return ide_stopped;
@@ -530,7 +537,7 @@ static void promise_multwrite (ide_drive_t *drive, unsigned int mcount)
 			 * all bvecs in this one.
 			 */
 			if (++bio->bi_idx >= bio->bi_vcnt) {
-				bio->bi_idx = 0;
+				bio->bi_idx = bio->bi_vcnt - rq->nr_cbio_segments;
 				bio = bio->bi_next;
 			}
 
@@ -539,7 +546,8 @@ static void promise_multwrite (ide_drive_t *drive, unsigned int mcount)
 				mcount = 0;
 			} else {
 				rq->bio = bio;
-				rq->current_nr_sectors = bio_iovec(bio)->bv_len >> 9;
+				rq->nr_cbio_segments = bio_segments(bio);
+				rq->current_nr_sectors = bio_cur_sectors(bio);
 				rq->hard_cur_sectors = rq->current_nr_sectors;
 			}
 		}
@@ -561,6 +569,9 @@ static ide_startstop_t promise_write_pollfunc (ide_drive_t *drive)
 	ide_hwgroup_t *hwgroup = HWGROUP(drive);
 #ifdef CONFIG_IDE_TASKFILE_IO
 	struct request *rq = hwgroup->rq;
+#else
+	struct request *rq = &hwgroup->wrq;
+	struct bio *bio = rq->bio;
 #endif
 
 	if (HWIF(drive)->INB(IDE_NSECTOR_REG) != 0) {
@@ -575,6 +586,9 @@ static ide_startstop_t promise_write_pollfunc (ide_drive_t *drive)
 		}
 		hwgroup->poll_timeout = 0;
 		printk(KERN_ERR "%s: write timed-out!\n",drive->name);
+#ifndef CONFIG_IDE_TASKFILE_IO
+		bio->bi_idx = bio->bi_vcnt - rq->nr_cbio_segments;
+#endif
 		return DRIVER(drive)->error(drive, "write timeout",
 				HWIF(drive)->INB(IDE_STATUS_REG));
 	}