ide-tape: remove pipeline-specific code from idetape_add_chrdev_read_request()

In order to do away with queueing read requests on the pipeline, several things
have to be done:

1. Do not allocate additional pipeline stages in idetape_init_read() until
(tape->nr_stages < max_stages) and do only read operation preparations. As a
collateral result, idetape_add_stage_tail() becomes unused so remove it.

2. Queue the read request's buffer directly thru idetape_queue_rw_tail().

3. Remove now unused idetape_kmalloc_stage() and idetape_switch_buffers().

[bart: simplify the original patch]

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

1 files changed, 5 insertions, 91 deletions

diff --git a/drivers/ide/ide-tape.c b/drivers/ide/ide-tape.c
index e785145abb47..e176b5c1b208 100644
--- a/drivers/ide/ide-tape.c
+++ b/drivers/ide/ide-tape.c
@@ -1586,15 +1586,6 @@ abort:
         return NULL;
 }
 
-static idetape_stage_t *idetape_kmalloc_stage(idetape_tape_t *tape)
-{
-        debug_log(DBG_PROCS, "Enter %s\n", __func__);
-
-        if (tape->nr_stages >= tape->max_stages)
-                return NULL;
-        return __idetape_kmalloc_stage(tape, 0, 0);
-}
-
 static int idetape_copy_stage_from_user(idetape_tape_t *tape,
                 idetape_stage_t *stage, const char __user *buf, int n)
 {
@@ -1672,39 +1663,6 @@ static void idetape_init_merge_stage(idetape_tape_t *tape)
         }
 }
 
-static void idetape_switch_buffers(idetape_tape_t *tape, idetape_stage_t *stage)
-{
-        struct idetape_bh *tmp;
-
-        tmp = stage->bh;
-        stage->bh = tape->merge_stage->bh;
-        tape->merge_stage->bh = tmp;
-        idetape_init_merge_stage(tape);
-}
-
-/* Add a new stage at the end of the pipeline. */
-static void idetape_add_stage_tail(ide_drive_t *drive, idetape_stage_t *stage)
-{
-        idetape_tape_t *tape = drive->driver_data;
-        unsigned long flags;
-
-        debug_log(DBG_PROCS, "Enter %s\n", __func__);
-
-        spin_lock_irqsave(&tape->lock, flags);
-        stage->next = NULL;
-        if (tape->last_stage != NULL)
-                tape->last_stage->next = stage;
-        else
-                tape->first_stage = stage;
-                tape->next_stage  = stage;
-        tape->last_stage = stage;
-        if (tape->next_stage == NULL)
-                tape->next_stage = tape->last_stage;
-        tape->nr_stages++;
-        tape->nr_pending_stages++;
-        spin_unlock_irqrestore(&tape->lock, flags);
-}
-
 /* Install a completion in a pending request and sleep until it is serviced. The
  * caller should ensure that the request will not be serviced before we install
  * the completion (usually by disabling interrupts).
@@ -2228,10 +2186,7 @@ static void idetape_empty_write_pipeline(ide_drive_t *drive)
 static int idetape_init_read(ide_drive_t *drive, int max_stages)
 {
         idetape_tape_t *tape = drive->driver_data;
-        idetape_stage_t *new_stage;
-        struct request rq;
         int bytes_read;
-        u16 blocks = *(u16 *)&tape->caps[12];
 
         /* Initialize read operation */
         if (tape->chrdev_dir != IDETAPE_DIR_READ) {
@@ -2267,21 +2222,7 @@ static int idetape_init_read(ide_drive_t *drive, int max_stages)
                         }
                 }
         }
-        idetape_init_rq(&rq, REQ_IDETAPE_READ);
-        rq.sector = tape->first_frame;
-        rq.nr_sectors = blocks;
-        rq.current_nr_sectors = blocks;
-        if (!test_bit(IDETAPE_FLAG_PIPELINE_ERR, &tape->flags) &&
-            tape->nr_stages < max_stages) {
-                new_stage = idetape_kmalloc_stage(tape);
-                while (new_stage != NULL) {
-                        new_stage->rq = rq;
-                        idetape_add_stage_tail(drive, new_stage);
-                        if (tape->nr_stages >= max_stages)
-                                break;
-                        new_stage = idetape_kmalloc_stage(tape);
-                }
-        }
+
         if (!test_bit(IDETAPE_FLAG_PIPELINE_ACTIVE, &tape->flags)) {
                 if (tape->nr_pending_stages >= 3 * max_stages / 4) {
                         tape->measure_insert_time = 1;
@@ -2301,9 +2242,6 @@ static int idetape_init_read(ide_drive_t *drive, int max_stages)
 static int idetape_add_chrdev_read_request(ide_drive_t *drive, int blocks)
 {
         idetape_tape_t *tape = drive->driver_data;
-        unsigned long flags;
-        struct request *rq_ptr;
-        int bytes_read;
 
         debug_log(DBG_PROCS, "Enter %s, %d blocks\n", __func__, blocks);
 
@@ -2311,37 +2249,13 @@ static int idetape_add_chrdev_read_request(ide_drive_t *drive, int blocks)
         if (test_bit(IDETAPE_FLAG_FILEMARK, &tape->flags))
                 return 0;
 
-        /* Wait for the next block to reach the head of the pipeline. */
         idetape_init_read(drive, tape->max_stages);
-        if (tape->first_stage == NULL) {
-                if (test_bit(IDETAPE_FLAG_PIPELINE_ERR, &tape->flags))
-                        return 0;
-                return idetape_queue_rw_tail(drive, REQ_IDETAPE_READ, blocks,
-                                        tape->merge_stage->bh);
-        }
-        idetape_wait_first_stage(drive);
-        rq_ptr = &tape->first_stage->rq;
-        bytes_read = tape->blk_size * (rq_ptr->nr_sectors -
-                                        rq_ptr->current_nr_sectors);
-        rq_ptr->nr_sectors = 0;
-        rq_ptr->current_nr_sectors = 0;
 
-        if (rq_ptr->errors == IDETAPE_ERROR_EOD)
+        if (test_bit(IDETAPE_FLAG_PIPELINE_ERR, &tape->flags))
                 return 0;
-        else {
-                idetape_switch_buffers(tape, tape->first_stage);
-                if (rq_ptr->errors == IDETAPE_ERROR_FILEMARK)
-                        set_bit(IDETAPE_FLAG_FILEMARK, &tape->flags);
-                spin_lock_irqsave(&tape->lock, flags);
-                idetape_remove_stage_head(drive);
-                spin_unlock_irqrestore(&tape->lock, flags);
-        }
-        if (bytes_read > blocks * tape->blk_size) {
-                printk(KERN_ERR "ide-tape: bug: trying to return more bytes"
-                                " than requested\n");
-                bytes_read = blocks * tape->blk_size;
-        }
-        return (bytes_read);
+
+        return idetape_queue_rw_tail(drive, REQ_IDETAPE_READ, blocks,
+                                     tape->merge_stage->bh);
 }
 
 static void idetape_pad_zeros(ide_drive_t *drive, int bcount)