ide-cd: use scatterlists for PIO transfers (fs requests)

* Export ide_pio_bytes().

* Add ->last_xfer_len field to struct ide_cmd.

* Add ide_cd_error_cmd() helper to ide-cd.

* Convert ide-cd to use scatterlists also for PIO transfers (fs requests
  only for now) and get rid of partial completions (except when the error
  happens -- which is still subject to change later because looking at
  ATAPI spec it seems that the device is free to error the whole transfer
  with setting the Error bit only on the last transfer chunk).

* Update ide_cd_{prepare_rw,restore_request,do_request}() accordingly.

* Inline ide_cd_restore_request() into cdrom_start_rw().

Cc: Borislav Petkov <petkovbb@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

3 files changed, 50 insertions, 105 deletions

diff --git a/drivers/ide/ide-cd.c b/drivers/ide/ide-cd.c
index 30113e69c8bb..5f15859c2c73 100644
--- a/drivers/ide/ide-cd.c
+++ b/drivers/ide/ide-cd.c
@@ -539,64 +539,12 @@ static ide_startstop_t ide_cd_prepare_rw_request(ide_drive_t *drive,
 {
         ide_debug_log(IDE_DBG_RQ, "rq->cmd_flags: 0x%x", rq->cmd_flags);
 
-        if (rq_data_dir(rq) == READ) {
-                unsigned short sectors_per_frame =
-                        queue_hardsect_size(drive->queue) >> SECTOR_BITS;
-                int nskip = rq->sector & (sectors_per_frame - 1);
-
-                /*
-                 * If the requested sector doesn't start on a frame boundary,
-                 * we must adjust the start of the transfer so that it does,
-                 * and remember to skip the first few sectors.
-                 *
-                 * If the rq->current_nr_sectors field is larger than the size
-                 * of the buffer, it will mean that we're to skip a number of
-                 * sectors equal to the amount by which rq->current_nr_sectors
-                 * is larger than the buffer size.
-                 */
-                if (nskip > 0) {
-                        /* sanity check... */
-                        if (rq->current_nr_sectors !=
-                            bio_cur_sectors(rq->bio)) {
-                                printk(KERN_ERR PFX "%s: %s: buffer botch (%u)\n",
-                                                drive->name, __func__,
-                                                rq->current_nr_sectors);
-                                return ide_stopped;
-                        }
-                        rq->current_nr_sectors += nskip;
-                }
-        }
-
         /* set up the command */
         rq->timeout = ATAPI_WAIT_PC;
 
         return ide_started;
 }
 
-/*
- * Fix up a possibly partially-processed request so that we can start it over
- * entirely, or even put it back on the request queue.
- */
-static void ide_cd_restore_request(ide_drive_t *drive, struct request *rq)
-{
-
-        ide_debug_log(IDE_DBG_FUNC, "enter");
-
-        if (rq->buffer != bio_data(rq->bio)) {
-                sector_t n =
-                        (rq->buffer - (char *)bio_data(rq->bio)) / SECTOR_SIZE;
-
-                rq->buffer = bio_data(rq->bio);
-                rq->nr_sectors += n;
-                rq->sector -= n;
-        }
-        rq->current_nr_sectors = bio_cur_sectors(rq->bio);
-        rq->hard_cur_sectors = rq->current_nr_sectors;
-        rq->hard_nr_sectors = rq->nr_sectors;
-        rq->hard_sector = rq->sector;
-        rq->q->prep_rq_fn(rq->q, rq);
-}
-
 static void ide_cd_request_sense_fixup(ide_drive_t *drive, struct request *rq)
 {
         ide_debug_log(IDE_DBG_FUNC, "rq->cmd[0]: 0x%x", rq->cmd[0]);
@@ -690,6 +638,17 @@ int ide_cd_queue_pc(ide_drive_t *drive, const unsigned char *cmd,
         return (flags & REQ_FAILED) ? -EIO : 0;
 }
 
+static void ide_cd_error_cmd(ide_drive_t *drive, struct ide_cmd *cmd)
+{
+        unsigned int nr_bytes = cmd->nbytes - cmd->nleft;
+
+        if (cmd->tf_flags & IDE_TFLAG_WRITE)
+                nr_bytes -= cmd->last_xfer_len;
+
+        if (nr_bytes > 0)
+                ide_complete_rq(drive, 0, nr_bytes);
+}
+
 /*
  * Called from blk_end_request_callback() after the data of the request is
  * completed and before the request itself is completed. By returning value '1',
@@ -703,6 +662,7 @@ static int cdrom_newpc_intr_dummy_cb(struct request *rq)
 static ide_startstop_t cdrom_newpc_intr(ide_drive_t *drive)
 {
         ide_hwif_t *hwif = drive->hwif;
+        struct ide_cmd *cmd = &hwif->cmd;
         struct request *rq = hwif->rq;
         xfer_func_t *xferfunc;
         ide_expiry_t *expiry = NULL;
@@ -769,11 +729,10 @@ static ide_startstop_t cdrom_newpc_intr(ide_drive_t *drive)
                          * Otherwise, complete the command normally.
                          */
                         uptodate = 1;
-                        if (rq->current_nr_sectors > 0) {
+                        if (cmd->nleft > 0) {
                                 printk(KERN_ERR PFX "%s: %s: data underrun "
-                                                "(%d blocks)\n",
-                                                drive->name, __func__,
-                                                rq->current_nr_sectors);
+                                        "(%u bytes)\n", drive->name, __func__,
+                                        cmd->nleft);
                                 if (!write)
                                         rq->cmd_flags |= REQ_FAILED;
                                 uptodate = 0;
@@ -795,24 +754,10 @@ static ide_startstop_t cdrom_newpc_intr(ide_drive_t *drive)
 
         if (blk_fs_request(rq)) {
                 if (write == 0) {
-                        int nskip;
-
                         if (ide_cd_check_transfer_size(drive, len))
                                 goto out_end;
-
-                        /*
-                         * First, figure out if we need to bit-bucket
-                         * any of the leading sectors.
-                         */
-                        nskip = min_t(int, rq->current_nr_sectors
-                                           - bio_cur_sectors(rq->bio),
-                                           thislen >> 9);
-                        if (nskip > 0) {
-                                ide_pad_transfer(drive, write, nskip << 9);
-                                rq->current_nr_sectors -= nskip;
-                                thislen -= (nskip << 9);
-                        }
                 }
+                cmd->last_xfer_len = 0;
         }
 
         if (ireason == 0) {
@@ -835,15 +780,15 @@ static ide_startstop_t cdrom_newpc_intr(ide_drive_t *drive)
                 /* bio backed? */
                 if (rq->bio) {
                         if (blk_fs_request(rq)) {
-                                ptr = rq->buffer;
-                                blen = rq->current_nr_sectors << 9;
+                                blen = min_t(int, thislen, cmd->nleft);
                         } else {
                                 ptr = bio_data(rq->bio);
                                 blen = bio_iovec(rq->bio)->bv_len;
                         }
                 }
 
-                if (!ptr) {
+                if ((blk_fs_request(rq) && cmd->nleft == 0) ||
+                    (blk_fs_request(rq) == 0 && ptr == NULL)) {
                         if (blk_fs_request(rq) && !write)
                                 /*
                                  * If the buffers are full, pipe the rest into
@@ -863,26 +808,16 @@ static ide_startstop_t cdrom_newpc_intr(ide_drive_t *drive)
                 if (blen > thislen)
                         blen = thislen;
 
-                xferfunc(drive, NULL, ptr, blen);
+                if (blk_fs_request(rq)) {
+                        ide_pio_bytes(drive, cmd, write, blen);
+                        cmd->last_xfer_len += blen;
+                } else
+                        xferfunc(drive, NULL, ptr, blen);
 
                 thislen -= blen;
                 len -= blen;
 
-                if (blk_fs_request(rq)) {
-                        rq->buffer += blen;
-                        rq->nr_sectors -= (blen >> 9);
-                        rq->current_nr_sectors -= (blen >> 9);
-                        rq->sector += (blen >> 9);
-
-                        if (rq->current_nr_sectors == 0 && rq->nr_sectors) {
-                                nsectors = rq->hard_cur_sectors;
-
-                                if (nsectors == 0)
-                                        nsectors = 1;
-
-                                ide_complete_rq(drive, 0, nsectors << 9);
-                        }
-                } else {
+                if (blk_fs_request(rq) == 0) {
                         rq->data_len -= blen;
 
                         /*
@@ -933,8 +868,10 @@ out_end:
                         ide_cd_complete_failed_rq(drive, rq);
 
                 if (blk_fs_request(rq)) {
-                        if (rq->current_nr_sectors == 0)
+                        if (cmd->nleft == 0)
                                 uptodate = 1;
+                        if (uptodate == 0)
+                                ide_cd_error_cmd(drive, cmd);
                 } else {
                         if (uptodate <= 0 && rq->errors == 0)
                                 rq->errors = -EIO;
@@ -944,7 +881,7 @@ out_end:
                 if (blk_pc_request(rq))
                         nsectors = (rq->data_len + 511) >> 9;
                 else
-                        nsectors = rq->hard_cur_sectors;
+                        nsectors = rq->hard_nr_sectors;
 
                 if (nsectors == 0)
                         nsectors = 1;
@@ -960,9 +897,10 @@ out_end:
 static ide_startstop_t cdrom_start_rw(ide_drive_t *drive, struct request *rq)
 {
         struct cdrom_info *cd = drive->driver_data;
+        struct request_queue *q = drive->queue;
         int write = rq_data_dir(rq) == WRITE;
         unsigned short sectors_per_frame =
-                queue_hardsect_size(drive->queue) >> SECTOR_BITS;
+                queue_hardsect_size(q) >> SECTOR_BITS;
 
         ide_debug_log(IDE_DBG_RQ, "rq->cmd[0]: 0x%x, write: 0x%x, "
                                   "secs_per_frame: %u",
@@ -977,17 +915,16 @@ static ide_startstop_t cdrom_start_rw(ide_drive_t *drive, struct request *rq)
                  * We may be retrying this request after an error.  Fix up any
                  * weirdness which might be present in the request packet.
                  */
-                ide_cd_restore_request(drive, rq);
+                q->prep_rq_fn(q, rq);
         }
 
-        /* use DMA, if possible / writes *must* be hardware frame aligned */
+        /* fs requests *must* be hardware frame aligned */
         if ((rq->nr_sectors & (sectors_per_frame - 1)) ||
-            (rq->sector & (sectors_per_frame - 1))) {
-                if (write)
-                        return ide_stopped;
-                drive->dma = 0;
-        } else
-                drive->dma = !!(drive->dev_flags & IDE_DFLAG_USING_DMA);
+            (rq->sector & (sectors_per_frame - 1)))
+                return ide_stopped;
+
+        /* use DMA, if possible */
+        drive->dma = !!(drive->dev_flags & IDE_DFLAG_USING_DMA);
 
         if (write)
                 cd->devinfo.media_written = 1;
@@ -1050,8 +987,6 @@ static ide_startstop_t ide_cd_do_request(ide_drive_t *drive, struct request *rq,
         if (blk_fs_request(rq)) {
                 if (cdrom_start_rw(drive, rq) == ide_stopped ||
                     ide_cd_prepare_rw_request(drive, rq) == ide_stopped) {
-                        if (rq->current_nr_sectors == 0)
-                                uptodate = 1;
                         goto out_end;
                 }
         } else if (blk_sense_request(rq) || blk_pc_request(rq) ||
@@ -1078,6 +1013,11 @@ static ide_startstop_t ide_cd_do_request(ide_drive_t *drive, struct request *rq,
 
         cmd.rq = rq;
 
+        if (blk_fs_request(rq)) {
+                ide_init_sg_cmd(&cmd, rq->nr_sectors << 9);
+                ide_map_sg(drive, &cmd);
+        }
+
         return ide_issue_pc(drive, &cmd);
 out_end:
         nsectors = rq->hard_nr_sectors;
diff --git a/drivers/ide/ide-taskfile.c b/drivers/ide/ide-taskfile.c
index 0e333ecf2ad6..a3b7a50562b2 100644
--- a/drivers/ide/ide-taskfile.c
+++ b/drivers/ide/ide-taskfile.c
@@ -188,8 +188,8 @@ static u8 wait_drive_not_busy(ide_drive_t *drive)
         return stat;
 }
 
-static void ide_pio_bytes(ide_drive_t *drive, struct ide_cmd *cmd,
-                          unsigned int write, unsigned int len)
+void ide_pio_bytes(ide_drive_t *drive, struct ide_cmd *cmd,
+                   unsigned int write, unsigned int len)
 {
         ide_hwif_t *hwif = drive->hwif;
         struct scatterlist *sg = hwif->sg_table;
@@ -243,6 +243,7 @@ static void ide_pio_bytes(ide_drive_t *drive, struct ide_cmd *cmd,
                 len -= nr_bytes;
         }
 }
+EXPORT_SYMBOL_GPL(ide_pio_bytes);
 
 static void ide_pio_datablock(ide_drive_t *drive, struct ide_cmd *cmd,
                               unsigned int write)
diff --git a/include/linux/ide.h b/include/linux/ide.h
index d5d832271f44..c2841c0c36c8 100644
--- a/include/linux/ide.h
+++ b/include/linux/ide.h
@@ -352,6 +352,8 @@ struct ide_cmd {
 
         unsigned int            nbytes;
         unsigned int            nleft;
+        unsigned int            last_xfer_len;
+
         struct scatterlist      *cursg;
         unsigned int            cursg_ofs;
 
@@ -1226,6 +1228,8 @@ ide_startstop_t ide_issue_pc(ide_drive_t *, struct ide_cmd *);
 
 ide_startstop_t do_rw_taskfile(ide_drive_t *, struct ide_cmd *);
 
+void ide_pio_bytes(ide_drive_t *, struct ide_cmd *, unsigned int, unsigned int);
+
 void ide_finish_cmd(ide_drive_t *, struct ide_cmd *, u8);
 
 int ide_raw_taskfile(ide_drive_t *, struct ide_cmd *, u8 *, u16);