[SCSI] seperate max_sectors from max_hw_sectors

- export __blk_put_request and blk_execute_rq_nowait
needed for async REQ_BLOCK_PC requests
- seperate max_hw_sectors and max_sectors for block/scsi_ioctl.c and
SG_IO bio.c helpers per Jens's last comments. Since block/scsi_ioctl.c SG_IO was
already testing against max_sectors and SCSI-ml was setting max_sectors and
max_hw_sectors to the same value this does not change any scsi SG_IO behavior. It only
prepares ll_rw_blk.c, scsi_ioctl.c and bio.c for when SCSI-ml begins to set
a valid max_hw_sectors for all LLDs. Today if a LLD does not set it
SCSI-ml sets it to a safe default and some LLDs set it to a artificial low
value to overcome memory and feedback issues.

Note: Since we now cap max_sectors to BLK_DEF_MAX_SECTORS, which is 1024,
drivers that used to call blk_queue_max_sectors with a large value of
max_sectors will now see the fs requests capped to BLK_DEF_MAX_SECTORS.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

2 files changed, 27 insertions, 9 deletions

diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index c525b5a2b598..d4beb9a89ee0 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -239,7 +239,7 @@ void blk_queue_make_request(request_queue_t * q, make_request_fn * mfn)
         q->backing_dev_info.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
         q->backing_dev_info.state = 0;
         q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
-        blk_queue_max_sectors(q, MAX_SECTORS);
+        blk_queue_max_sectors(q, SAFE_MAX_SECTORS);
         blk_queue_hardsect_size(q, 512);
         blk_queue_dma_alignment(q, 511);
         blk_queue_congestion_threshold(q);
@@ -555,7 +555,12 @@ void blk_queue_max_sectors(request_queue_t *q, unsigned short max_sectors)
                 printk("%s: set to minimum %d\n", __FUNCTION__, max_sectors);
         }
 
-        q->max_sectors = q->max_hw_sectors = max_sectors;
+        if (BLK_DEF_MAX_SECTORS > max_sectors)
+                q->max_hw_sectors = q->max_sectors = max_sectors;
+        else {
+                q->max_sectors = BLK_DEF_MAX_SECTORS;
+                q->max_hw_sectors = max_sectors;
+        }
 }
 
 EXPORT_SYMBOL(blk_queue_max_sectors);
@@ -657,8 +662,8 @@ EXPORT_SYMBOL(blk_queue_hardsect_size);
 void blk_queue_stack_limits(request_queue_t *t, request_queue_t *b)
 {
         /* zero is "infinity" */
-        t->max_sectors = t->max_hw_sectors =
-                min_not_zero(t->max_sectors,b->max_sectors);
+        t->max_sectors = min_not_zero(t->max_sectors,b->max_sectors);
+        t->max_hw_sectors = min_not_zero(t->max_hw_sectors,b->max_hw_sectors);
 
         t->max_phys_segments = min(t->max_phys_segments,b->max_phys_segments);
         t->max_hw_segments = min(t->max_hw_segments,b->max_hw_segments);
@@ -1293,9 +1298,15 @@ static inline int ll_new_hw_segment(request_queue_t *q,
 static int ll_back_merge_fn(request_queue_t *q, struct request *req, 
                             struct bio *bio)
 {
+        unsigned short max_sectors;
         int len;
 
-        if (req->nr_sectors + bio_sectors(bio) > q->max_sectors) {
+        if (unlikely(blk_pc_request(req)))
+                max_sectors = q->max_hw_sectors;
+        else
+                max_sectors = q->max_sectors;
+
+        if (req->nr_sectors + bio_sectors(bio) > max_sectors) {
                 req->flags |= REQ_NOMERGE;
                 if (req == q->last_merge)
                         q->last_merge = NULL;
@@ -1325,9 +1336,16 @@ static int ll_back_merge_fn(request_queue_t *q, struct request *req,
 static int ll_front_merge_fn(request_queue_t *q, struct request *req, 
                              struct bio *bio)
 {
+        unsigned short max_sectors;
         int len;
 
-        if (req->nr_sectors + bio_sectors(bio) > q->max_sectors) {
+        if (unlikely(blk_pc_request(req)))
+                max_sectors = q->max_hw_sectors;
+        else
+                max_sectors = q->max_sectors;
+
+
+        if (req->nr_sectors + bio_sectors(bio) > max_sectors) {
                 req->flags |= REQ_NOMERGE;
                 if (req == q->last_merge)
                         q->last_merge = NULL;
@@ -2144,7 +2162,7 @@ int blk_rq_map_user(request_queue_t *q, struct request *rq, void __user *ubuf,
         struct bio *bio;
         int reading;
 
-        if (len > (q->max_sectors << 9))
+        if (len > (q->max_hw_sectors << 9))
                 return -EINVAL;
         if (!len || !ubuf)
                 return -EINVAL;
@@ -2259,7 +2277,7 @@ int blk_rq_map_kern(request_queue_t *q, struct request *rq, void *kbuf,
 {
         struct bio *bio;
 
-        if (len > (q->max_sectors << 9))
+        if (len > (q->max_hw_sectors << 9))
                 return -EINVAL;
         if (!len || !kbuf)
                 return -EINVAL;
diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
index 382dea7b224c..4e390dfd3157 100644
--- a/block/scsi_ioctl.c
+++ b/block/scsi_ioctl.c
@@ -233,7 +233,7 @@ static int sg_io(struct file *file, request_queue_t *q,
         if (verify_command(file, cmd))
                 return -EPERM;
 
-        if (hdr->dxfer_len > (q->max_sectors << 9))
+        if (hdr->dxfer_len > (q->max_hw_sectors << 9))
                 return -EIO;
 
         if (hdr->dxfer_len)