Purge ISA DMA bouncing garbage from scsi_merge.c

Handle unchecked_isa_dma in scsi layer by setting
the bounce_limit for the queue not the segment boundary
mask :-)  Patch sent to Jens.

4 files changed, 13 insertions, 252 deletions

diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 35d336de5..01fcfd78b 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -197,8 +197,6 @@ void  scsi_initialize_queue(Scsi_Device * SDpnt, struct Scsi_Host * SHpnt)
 
 	if (!SHpnt->use_clustering)
 		clear_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
-	if (SHpnt->unchecked_isa_dma)
-		blk_queue_segment_boundary(q, ISA_DMA_THRESHOLD);
 }
 
 #ifdef MODULE
diff --git a/drivers/scsi/scsi.h b/drivers/scsi/scsi.h
index efa95d8a0..74ce5398b 100644
--- a/drivers/scsi/scsi.h
+++ b/drivers/scsi/scsi.h
@@ -449,7 +449,8 @@ int scsi_free(void *, unsigned int);
 /*
  * Prototypes for functions in scsi_merge.c
  */
-extern void scsi_initialize_merge_fn(Scsi_Device * SDpnt);
+extern void scsi_initialize_merge_fn(Scsi_Device *SDpnt);
+extern int scsi_init_io(Scsi_Cmnd *SCpnt);
 
 /*
  * Prototypes for functions in scsi_queue.c
@@ -554,8 +555,6 @@ struct scsi_device {
 	request_queue_t request_queue;
         atomic_t                device_active; /* commands checked out for device */
 	volatile unsigned short device_busy;	/* commands actually active on low-level */
-	int (*scsi_init_io_fn) (Scsi_Cmnd *);	/* Used to initialize
-						   new request */
 	Scsi_Cmnd *device_queue;	/* queue of SCSI Command structures */
 
 /* public: */
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 00e931304..7ce480796 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -996,7 +996,7 @@ void scsi_request_fn(request_queue_t * q)
 			 * required).  Hosts that need bounce buffers will also
 			 * get those allocated here.  
 			 */
-			if (!SDpnt->scsi_init_io_fn(SCpnt)) {
+			if (!scsi_init_io(SCpnt)) {
 				SCpnt = __scsi_end_request(SCpnt, 0, 
 							   SCpnt->request.nr_sectors, 0, 0);
 				if( SCpnt != NULL )
diff --git a/drivers/scsi/scsi_merge.c b/drivers/scsi/scsi_merge.c
index 285f4c218..e37500f56 100644
--- a/drivers/scsi/scsi_merge.c
+++ b/drivers/scsi/scsi_merge.c
@@ -46,81 +46,28 @@
 #include "constants.h"
 #include <scsi/scsi_ioctl.h>
 
-static void dma_exhausted(Scsi_Cmnd  *SCpnt, int i)
-{
-	int jj;
-	struct scatterlist *sgpnt;
-	void **bbpnt;
-	int consumed = 0;
-
-	sgpnt = (struct scatterlist *) SCpnt->request_buffer;
-	bbpnt = SCpnt->bounce_buffers;
-
-	/*
-	 * Now print out a bunch of stats.  First, start with the request
-	 * size.
-	 */
-	printk("dma_free_sectors:%d\n", scsi_dma_free_sectors);
-	printk("use_sg:%d\ti:%d\n", SCpnt->use_sg, i);
-	printk("request_bufflen:%d\n", SCpnt->request_bufflen);
-	/*
-	 * Now dump the scatter-gather table, up to the point of failure.
-	 */
-	for (jj = 0; jj < SCpnt->use_sg; jj++) {
-		printk("[%d]\tlen:%d\taddr:%p\tbounce:%p\n",
-		       jj,
-		       sgpnt[jj].length,
-		       sgpnt[jj].address,
-		       (bbpnt ? bbpnt[jj] : NULL));
-		if (bbpnt && bbpnt[jj])
-			consumed += sgpnt[jj].length;
-	}
-	printk("Total %d sectors consumed\n", consumed);
-	panic("DMA pool exhausted");
-}
-
 /*
- * Function:    __init_io()
+ * Function:    scsi_init_io()
  *
- * Purpose:     Prototype for io initialize function.
+ * Purpose:     SCSI I/O initialize function.
  *
  * Arguments:   SCpnt   - Command descriptor we wish to initialize
- *              dma_host - 1 if this host has ISA DMA issues (bus doesn't
- *                      expose all of the address lines, so that DMA cannot
- *                      be done from an arbitrary address).
  *
  * Returns:     1 on success.
  *
  * Lock status: 
  *
- * Notes:       Only the SCpnt argument should be a non-constant variable.
- *              This function is designed in such a way that it will be
- *              invoked from a series of small stubs, each of which would
- *              be optimized for specific circumstances.
- *
- *              The advantage of this is that hosts that don't do DMA
- *              get versions of the function that essentially don't have
- *              any of the DMA code.  Same goes for clustering - in the
- *              case of hosts with no need for clustering, there is no point
- *              in a whole bunch of overhead.
- *
- *              Finally, in the event that a host has set can_queue to SG_ALL
- *              implying that there is no limit to the length of a scatter
- *              gather list, the sg count in the request won't be valid
- *              (mainly because we don't need queue management functions
- *              which keep the tally uptodate.
+ * Notes:	The generic block layer takes care of ISA bounce
+ *		buffering issues for us.
  */
-__inline static int __init_io(Scsi_Cmnd *SCpnt, int dma_host)
+int scsi_init_io(Scsi_Cmnd *SCpnt)
 {
 	struct bio	   * bio;
 	char		   * buff;
 	int		     count;
-	int		     i;
 	struct request     * req;
-	int		     sectors;
 	struct scatterlist * sgpnt;
 	int		     this_count;
-	void		   ** bbpnt;
 
 	req = &SCpnt->request;
 
@@ -130,16 +77,6 @@ __inline static int __init_io(Scsi_Cmnd *SCpnt, int dma_host)
 	count = req->nr_phys_segments;
 
 	/*
-	 * If the dma pool is nearly empty, then queue a minimal request
-	 * with a single segment.  Typically this will satisfy a single
-	 * buffer.
-	 */
-	if (dma_host && scsi_dma_free_sectors <= 10) {
-		this_count = req->current_nr_sectors;
-		goto single_segment;
-	}
-
-	/*
 	 * we used to not use scatter-gather for single segment request,
 	 * but now we do (it makes highmem I/O easier to support without
 	 * kmapping pages)
@@ -151,12 +88,6 @@ __inline static int __init_io(Scsi_Cmnd *SCpnt, int dma_host)
 	 */
 	SCpnt->sglist_len = (SCpnt->use_sg * sizeof(struct scatterlist));
 
-	/* If we could potentially require ISA bounce buffers, allocate
-	 * space for this array here.
-	 */
-	if (dma_host)
-		SCpnt->sglist_len += (SCpnt->use_sg * sizeof(void *));
-
 	/* scsi_malloc can only allocate in chunks of 512 bytes so
 	 * round it up.
 	 */
@@ -182,14 +113,6 @@ __inline static int __init_io(Scsi_Cmnd *SCpnt, int dma_host)
 	SCpnt->request_bufflen = 0;
 	req->buffer = NULL;
 
-	if (dma_host)
-		bbpnt = (void **) ((char *)sgpnt +
-			 (SCpnt->use_sg * sizeof(struct scatterlist)));
-	else
-		bbpnt = NULL;
-
-	SCpnt->bounce_buffers = bbpnt;
-
 	/* 
 	 * Next, walk the list, and fill in the addresses and sizes of
 	 * each segment.
@@ -211,174 +134,22 @@ __inline static int __init_io(Scsi_Cmnd *SCpnt, int dma_host)
 
 	SCpnt->use_sg = count;
 
-	if (!dma_host)
-		return 1;
-
-	/*
-	 * Now allocate bounce buffers, if needed.
-	 */
-	SCpnt->request_bufflen = 0;
-	for (i = 0; i < count; i++) {
-		sectors = (sgpnt[i].length >> 9);
-		SCpnt->request_bufflen += sgpnt[i].length;
-		if (virt_to_phys(sgpnt[i].address) + sgpnt[i].length - 1 >
-                    ISA_DMA_THRESHOLD) {
-			if( scsi_dma_free_sectors - sectors <= 10  ) {
-				/*
-				 * If this would nearly drain the DMA
-				 * pool empty, then let's stop here.
-				 * Don't make this request any larger.
-				 * This is kind of a safety valve that
-				 * we use - we could get screwed later
-				 * on if we run out completely.  
-				 */
-				SCpnt->request_bufflen -= sgpnt[i].length;
-				SCpnt->use_sg = i;
-				if (i == 0) {
-					goto big_trouble;
-				}
-				break;
-			}
-
-			/*
-			 * this is not a dma host, so it will never
-			 * be a highmem page
-			 */
-			bbpnt[i] = page_address(sgpnt[i].page) +sgpnt[i].offset;
-			sgpnt[i].address = (char *)scsi_malloc(sgpnt[i].length);
-			/*
-			 * If we cannot allocate memory for this DMA bounce
-			 * buffer, then queue just what we have done so far.
-			 */
-			if (sgpnt[i].address == NULL) {
-				printk("Warning - running low on DMA memory\n");
-				SCpnt->request_bufflen -= sgpnt[i].length;
-				SCpnt->use_sg = i;
-				if (i == 0) {
-					goto big_trouble;
-				}
-				break;
-			}
-			if (rq_data_dir(req) == WRITE)
-				memcpy(sgpnt[i].address, bbpnt[i],
-				       sgpnt[i].length);
-		}
-	}
 	return 1;
 
-      big_trouble:
-	/*
-	 * We come here in the event that we get one humongous
-	 * request, where we need a bounce buffer, and the buffer is
-	 * more than we can allocate in a single call to
-	 * scsi_malloc().  In addition, we only come here when it is
-	 * the 0th element of the scatter-gather table that gets us
-	 * into this trouble.  As a fallback, we fall back to
-	 * non-scatter-gather, and ask for a single segment.  We make
-	 * a half-hearted attempt to pick a reasonably large request
-	 * size mainly so that we don't thrash the thing with
-	 * iddy-biddy requests.
-	 */
+single_segment:
 
 	/*
-	 * The original number of sectors in the 0th element of the
-	 * scatter-gather table.  
-	 */
-	sectors = sgpnt[0].length >> 9;
-
-	/* 
-	 * Free up the original scatter-gather table.  Note that since
-	 * it was the 0th element that got us here, we don't have to
-	 * go in and free up memory from the other slots.  
-	 */
-	SCpnt->request_bufflen = 0;
-	SCpnt->use_sg = 0;
-	scsi_free(SCpnt->request_buffer, SCpnt->sglist_len);
-
-	/*
-	 * Make an attempt to pick up as much as we reasonably can.
-	 * Just keep adding sectors until the pool starts running kind of
-	 * low.  The limit of 30 is somewhat arbitrary - the point is that
-	 * it would kind of suck if we dropped down and limited ourselves to
-	 * single-block requests if we had hundreds of free sectors.
-	 */
-	if( scsi_dma_free_sectors > 30 ) {
-		for (this_count = 0, bio = req->bio; bio; bio = bio->bi_next) {
-			if( scsi_dma_free_sectors - this_count < 30 
-			    || this_count == sectors )
-			{
-				break;
-			}
-			this_count += bio_sectors(bio);
-		}
-
-	} else {
-		/*
-		 * Yow!   Take the absolute minimum here.
-		 */
-		this_count = req->current_nr_sectors;
-	}
-
-	/*
-	 * Now drop through into the single-segment case.
-	 */
-	
-      single_segment:
-	/*
 	 * Come here if for any reason we choose to do this as a single
-	 * segment.  Possibly the entire request, or possibly a small
-	 * chunk of the entire request.
+	 * segment.
 	 */
-
 	bio = req->bio;
 	buff = req->buffer = bio_data(bio);
-
-	if (dma_host || PageHighMem(bio_page(bio))) {
-		/*
-		 * Allocate a DMA bounce buffer.  If the allocation fails, fall
-		 * back and allocate a really small one - enough to satisfy
-		 * the first buffer.
-		 */
-		if (bio_to_phys(bio) + bio->bi_size - 1 > ISA_DMA_THRESHOLD) {
-			buff = (char *) scsi_malloc(this_count << 9);
-			if (!buff) {
-				printk("Warning - running low on DMA memory\n");
-				this_count = req->current_nr_sectors;
-				buff = (char *) scsi_malloc(this_count << 9);
-				if (!buff) {
-					dma_exhausted(SCpnt, 0);
-					return 0;
-				}
-			}
-			if (rq_data_dir(req) == WRITE) {
-				unsigned long flags;
-				char *buf = bio_kmap_irq(bio, &flags);
-				memcpy(buff, buf, this_count << 9);
-				bio_kunmap_irq(buf, &flags);
-			}
-		}
-	}
 	SCpnt->request_bufflen = this_count << 9;
 	SCpnt->request_buffer = buff;
 	SCpnt->use_sg = 0;
 	return 1;
 }
 
-#define INITIO(_FUNCTION, _DMA)		\
-static int _FUNCTION(Scsi_Cmnd * SCpnt)		\
-{						\
-    return __init_io(SCpnt, _DMA);	\
-}
-
-/*
- * ll_rw_blk.c now keeps track of the number of segments in
- * a request.  Thus we don't have to do it any more here.
- * We always force "_VALID" to 1.  Eventually clean this up
- * and get rid of the extra argument.
- */
-INITIO(scsi_init_io_v, 0)
-INITIO(scsi_init_io_vd, 1)
-
 /*
  * Function:    scsi_initialize_merge_fn()
  *
@@ -400,16 +171,7 @@ void scsi_initialize_merge_fn(Scsi_Device * SDpnt)
 
 	/*
 	 * The generic merging functions work just fine for us.
-	 */
-
-	if (SHpnt->unchecked_isa_dma == 0) {
-		SDpnt->scsi_init_io_fn = scsi_init_io_v;
-	} else {
-		SDpnt->scsi_init_io_fn = scsi_init_io_vd;
-	}
-
-	/*
-	 * now enable highmem I/O, if appropriate
+	 * Enable highmem I/O, if appropriate.
 	 */
 	bounce_limit = BLK_BOUNCE_HIGH;
 	if (SHpnt->highmem_io && (SDpnt->type == TYPE_DISK)) {
@@ -421,6 +183,8 @@ void scsi_initialize_merge_fn(Scsi_Device * SDpnt)
 		else
 			bounce_limit = SHpnt->pci_dev->dma_mask;
 	}
+	if (SHpnt->unchecked_isa_dma)
+		bounce_limit = ISA_DMA_THRESHOLD;
 
 	blk_queue_bounce_limit(q, bounce_limit);
 }