sg: convert the direct IO path to use the block layer

This patch converts the direct IO path (SG_FLAG_DIRECT_IO) to use the
block layer functions (blk_get_request, blk_execute_rq_nowait,
blk_rq_map_user, etc) instead of scsi_execute_async().

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Douglas Gilbert <dougg@torque.net>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 27 insertions, 146 deletions

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 487c7776cc4e..cb6de0752ee1 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -138,6 +138,7 @@ typedef struct sg_request {	/* SG_MAX_QUEUE requests outstanding per file */
         char sg_io_owned;       /* 1 -> packet belongs to SG_IO */
         volatile char done;     /* 0->before bh, 1->before read, 2->read */
         struct request *rq;
+        struct bio *bio;
 } Sg_request;
 
 typedef struct sg_fd {          /* holds the state of a file descriptor */
@@ -1679,21 +1680,29 @@ static int sg_start_req(Sg_request *srp, unsigned char *cmd)
         sg_io_hdr_t *hp = &srp->header;
         int dxfer_len = (int) hp->dxfer_len;
         int dxfer_dir = hp->dxfer_direction;
+        unsigned long uaddr = (unsigned long)hp->dxferp;
         Sg_scatter_hold *req_schp = &srp->data;
         Sg_scatter_hold *rsv_schp = &sfp->reserve;
+        struct request_queue *q = sfp->parentdp->device->request_queue;
+        unsigned long alignment = queue_dma_alignment(q) | q->dma_pad_mask;
 
         SCSI_LOG_TIMEOUT(4, printk("sg_start_req: dxfer_len=%d\n", dxfer_len));
 
         if ((dxfer_len <= 0) || (dxfer_dir == SG_DXFER_NONE))
                 return __sg_start_req(srp, hp, cmd);
 
+#ifdef SG_ALLOW_DIO_CODE
         if (sg_allow_dio && (hp->flags & SG_FLAG_DIRECT_IO) &&
             (dxfer_dir != SG_DXFER_UNKNOWN) && (0 == hp->iovec_count) &&
-            (!sfp->parentdp->device->host->unchecked_isa_dma)) {
-                res = sg_build_direct(srp, sfp, dxfer_len);
-                if (res <= 0)   /* -ve -> error, 0 -> done, 1 -> try indirect */
-                        return res;
+            (!sfp->parentdp->device->host->unchecked_isa_dma) &&
+            !(uaddr & alignment) && !(dxfer_len & alignment)) {
+                res = __sg_start_req(srp, hp, cmd);
+                if (!res)
+                        res = sg_build_direct(srp, sfp, dxfer_len);
+
+                return res;
         }
+#endif
         if ((!sg_res_in_use(sfp)) && (dxfer_len <= rsv_schp->bufflen))
                 sg_link_reserve(sfp, srp, dxfer_len);
         else {
@@ -1718,8 +1727,11 @@ sg_finish_rem_req(Sg_request * srp)
         else
                 sg_remove_scat(req_schp);
 
-        if (srp->rq)
+        if (srp->rq) {
+                if (srp->bio)
+                        blk_rq_unmap_user(srp->bio);
                 blk_put_request(srp->rq);
+        }
 
         sg_remove_request(sfp, srp);
 }
@@ -1746,151 +1758,23 @@ sg_build_sgat(Sg_scatter_hold * schp, const Sg_fd * sfp, int tablesize)
         return tablesize;       /* number of scat_gath elements allocated */
 }
 
-#ifdef SG_ALLOW_DIO_CODE
-/* vvvvvvvv  following code borrowed from st driver's direct IO vvvvvvvvv */
-        /* TODO: hopefully we can use the generic block layer code */
-
-/* Pin down user pages and put them into a scatter gather list. Returns <= 0 if
-   - mapping of all pages not successful
-   (i.e., either completely successful or fails)
-*/
-static int 
-st_map_user_pages(struct scatterlist *sgl, const unsigned int max_pages, 
-                  unsigned long uaddr, size_t count, int rw)
-{
-        unsigned long end = (uaddr + count + PAGE_SIZE - 1) >> PAGE_SHIFT;
-        unsigned long start = uaddr >> PAGE_SHIFT;
-        const int nr_pages = end - start;
-        int res, i, j;
-        struct page **pages;
-
-        /* User attempted Overflow! */
-        if ((uaddr + count) < uaddr)
-                return -EINVAL;
-
-        /* Too big */
-        if (nr_pages > max_pages)
-                return -ENOMEM;
-
-        /* Hmm? */
-        if (count == 0)
-                return 0;
-
-        if ((pages = kmalloc(max_pages * sizeof(*pages), GFP_ATOMIC)) == NULL)
-                return -ENOMEM;
-
-        /* Try to fault in all of the necessary pages */
-        down_read(&current->mm->mmap_sem);
-        /* rw==READ means read from drive, write into memory area */
-        res = get_user_pages(
-                current,
-                current->mm,
-                uaddr,
-                nr_pages,
-                rw == READ,
-                0, /* don't force */
-                pages,
-                NULL);
-        up_read(&current->mm->mmap_sem);
-
-        /* Errors and no page mapped should return here */
-        if (res < nr_pages)
-                goto out_unmap;
-
-        for (i=0; i < nr_pages; i++) {
-                /* FIXME: flush superflous for rw==READ,
-                 * probably wrong function for rw==WRITE
-                 */
-                flush_dcache_page(pages[i]);
-                /* ?? Is locking needed? I don't think so */
-                /* if (!trylock_page(pages[i]))
-                   goto out_unlock; */
-        }
-
-        sg_set_page(sgl, pages[0], 0, uaddr & ~PAGE_MASK);
-        if (nr_pages > 1) {
-                sgl[0].length = PAGE_SIZE - sgl[0].offset;
-                count -= sgl[0].length;
-                for (i=1; i < nr_pages ; i++)
-                        sg_set_page(&sgl[i], pages[i], count < PAGE_SIZE ? count : PAGE_SIZE, 0);
-        }
-        else {
-                sgl[0].length = count;
-        }
-
-        kfree(pages);
-        return nr_pages;
-
- out_unmap:
-        if (res > 0) {
-                for (j=0; j < res; j++)
-                        page_cache_release(pages[j]);
-                res = 0;
-        }
-        kfree(pages);
-        return res;
-}
-
-
-/* And unmap them... */
-static int 
-st_unmap_user_pages(struct scatterlist *sgl, const unsigned int nr_pages,
-                    int dirtied)
-{
-        int i;
-
-        for (i=0; i < nr_pages; i++) {
-                struct page *page = sg_page(&sgl[i]);
-
-                if (dirtied)
-                        SetPageDirty(page);
-                /* unlock_page(page); */
-                /* FIXME: cache flush missing for rw==READ
-                 * FIXME: call the correct reference counting function
-                 */
-                page_cache_release(page);
-        }
-
-        return 0;
-}
-
-/* ^^^^^^^^  above code borrowed from st driver's direct IO ^^^^^^^^^ */
-#endif
-
-
 /* Returns: -ve -> error, 0 -> done, 1 -> try indirect */
 static int
 sg_build_direct(Sg_request * srp, Sg_fd * sfp, int dxfer_len)
 {
-#ifdef SG_ALLOW_DIO_CODE
         sg_io_hdr_t *hp = &srp->header;
         Sg_scatter_hold *schp = &srp->data;
-        int sg_tablesize = sfp->parentdp->sg_tablesize;
-        int mx_sc_elems, res;
-        struct scsi_device *sdev = sfp->parentdp->device;
-
-        if (((unsigned long)hp->dxferp &
-                        queue_dma_alignment(sdev->request_queue)) != 0)
-                return 1;
+        int res;
+        struct request *rq = srp->rq;
+        struct request_queue *q = sfp->parentdp->device->request_queue;
 
-        mx_sc_elems = sg_build_sgat(schp, sfp, sg_tablesize);
-        if (mx_sc_elems <= 0) {
-                return 1;
-        }
-        res = st_map_user_pages(schp->buffer, mx_sc_elems,
-                                (unsigned long)hp->dxferp, dxfer_len, 
-                                (SG_DXFER_TO_DEV == hp->dxfer_direction) ? 1 : 0);
-        if (res <= 0) {
-                sg_remove_scat(schp);
-                return 1;
-        }
-        schp->k_use_sg = res;
+        res = blk_rq_map_user(q, rq, NULL, hp->dxferp, dxfer_len, GFP_ATOMIC);
+        if (res)
+                return res;
+        srp->bio = rq->bio;
         schp->dio_in_use = 1;
         hp->info |= SG_INFO_DIRECT_IO;
         return 0;
-#else
-        return 1;
-#endif
 }
 
 static int
@@ -2069,11 +1953,7 @@ sg_remove_scat(Sg_scatter_hold * schp)
         if (schp->buffer && (schp->sglist_len > 0)) {
                 struct scatterlist *sg = schp->buffer;
 
-                if (schp->dio_in_use) {
-#ifdef SG_ALLOW_DIO_CODE
-                        st_unmap_user_pages(sg, schp->k_use_sg, TRUE);
-#endif
-                } else {
+                if (!schp->dio_in_use) {
                         int k;
 
                         for (k = 0; (k < schp->k_use_sg) && sg_page(sg);
@@ -2083,8 +1963,9 @@ sg_remove_scat(Sg_scatter_hold * schp)
                                     k, sg_page(sg), sg->length));
                                 sg_page_free(sg_page(sg), sg->length);
                         }
+
+                        kfree(schp->buffer);
                 }
-                kfree(schp->buffer);
         }
         memset(schp, 0, sizeof (*schp));
 }