[PATCH] block: support larger block pc requests

This patch modifies blk_rq_map/unmap_user() and the cdrom and scsi_ioctl.c
users so that it supports requests larger than bio by chaining them together.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

2 files changed, 152 insertions, 67 deletions

diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index 9eaee6640535..0f82e12f7b67 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -2322,6 +2322,84 @@ void blk_insert_request(request_queue_t *q, struct request *rq,
 
 EXPORT_SYMBOL(blk_insert_request);
 
+static int __blk_rq_unmap_user(struct bio *bio)
+{
+        int ret = 0;
+
+        if (bio) {
+                if (bio_flagged(bio, BIO_USER_MAPPED))
+                        bio_unmap_user(bio);
+                else
+                        ret = bio_uncopy_user(bio);
+        }
+
+        return ret;
+}
+
+static int __blk_rq_map_user(request_queue_t *q, struct request *rq,
+                             void __user *ubuf, unsigned int len)
+{
+        unsigned long uaddr;
+        struct bio *bio, *orig_bio;
+        int reading, ret;
+
+        reading = rq_data_dir(rq) == READ;
+
+        /*
+         * if alignment requirement is satisfied, map in user pages for
+         * direct dma. else, set up kernel bounce buffers
+         */
+        uaddr = (unsigned long) ubuf;
+        if (!(uaddr & queue_dma_alignment(q)) && !(len & queue_dma_alignment(q)))
+                bio = bio_map_user(q, NULL, uaddr, len, reading);
+        else
+                bio = bio_copy_user(q, uaddr, len, reading);
+
+        if (IS_ERR(bio)) {
+                return PTR_ERR(bio);
+        }
+
+        orig_bio = bio;
+        blk_queue_bounce(q, &bio);
+        /*
+         * We link the bounce buffer in and could have to traverse it
+         * later so we have to get a ref to prevent it from being freed
+         */
+        bio_get(bio);
+
+        /*
+         * for most (all? don't know of any) queues we could
+         * skip grabbing the queue lock here. only drivers with
+         * funky private ->back_merge_fn() function could be
+         * problematic.
+         */
+        spin_lock_irq(q->queue_lock);
+        if (!rq->bio)
+                blk_rq_bio_prep(q, rq, bio);
+        else if (!q->back_merge_fn(q, rq, bio)) {
+                ret = -EINVAL;
+                spin_unlock_irq(q->queue_lock);
+                goto unmap_bio;
+        } else {
+                rq->biotail->bi_next = bio;
+                rq->biotail = bio;
+
+                rq->nr_sectors += bio_sectors(bio);
+                rq->hard_nr_sectors = rq->nr_sectors;
+                rq->data_len += bio->bi_size;
+        }
+        spin_unlock_irq(q->queue_lock);
+
+        return bio->bi_size;
+
+unmap_bio:
+        /* if it was boucned we must call the end io function */
+        bio_endio(bio, bio->bi_size, 0);
+        __blk_rq_unmap_user(orig_bio);
+        bio_put(bio);
+        return ret;
+}
+
 /**
  * blk_rq_map_user - map user data to a request, for REQ_BLOCK_PC usage
  * @q:          request queue where request should be inserted
@@ -2343,42 +2421,44 @@ EXPORT_SYMBOL(blk_insert_request);
  *    unmapping.
  */
 int blk_rq_map_user(request_queue_t *q, struct request *rq, void __user *ubuf,
-                    unsigned int len)
+                    unsigned long len)
 {
-        unsigned long uaddr;
-        struct bio *bio;
-        int reading;
+        unsigned long bytes_read = 0;
+        int ret;
 
         if (len > (q->max_hw_sectors << 9))
                 return -EINVAL;
         if (!len || !ubuf)
                 return -EINVAL;
 
-        reading = rq_data_dir(rq) == READ;
+        while (bytes_read != len) {
+                unsigned long map_len, end, start;
 
-        /*
-         * if alignment requirement is satisfied, map in user pages for
-         * direct dma. else, set up kernel bounce buffers
-         */
-        uaddr = (unsigned long) ubuf;
-        if (!(uaddr & queue_dma_alignment(q)) && !(len & queue_dma_alignment(q)))
-                bio = bio_map_user(q, NULL, uaddr, len, reading);
-        else
-                bio = bio_copy_user(q, uaddr, len, reading);
+                map_len = min_t(unsigned long, len - bytes_read, BIO_MAX_SIZE);
+                end = ((unsigned long)ubuf + map_len + PAGE_SIZE - 1)
+                                                                >> PAGE_SHIFT;
+                start = (unsigned long)ubuf >> PAGE_SHIFT;
 
-        if (!IS_ERR(bio)) {
-                rq->bio = rq->biotail = bio;
-                blk_rq_bio_prep(q, rq, bio);
+                /*
+                 * A bad offset could cause us to require BIO_MAX_PAGES + 1
+                 * pages. If this happens we just lower the requested
+                 * mapping len by a page so that we can fit
+                 */
+                if (end - start > BIO_MAX_PAGES)
+                        map_len -= PAGE_SIZE;
 
-                rq->buffer = rq->data = NULL;
-                rq->data_len = len;
-                return 0;
+                ret = __blk_rq_map_user(q, rq, ubuf, map_len);
+                if (ret < 0)
+                        goto unmap_rq;
+                bytes_read += ret;
+                ubuf += ret;
         }
 
-        /*
-         * bio is the err-ptr
-         */
-        return PTR_ERR(bio);
+        rq->buffer = rq->data = NULL;
+        return 0;
+unmap_rq:
+        blk_rq_unmap_user(rq);
+        return ret;
 }
 
 EXPORT_SYMBOL(blk_rq_map_user);
@@ -2404,7 +2484,7 @@ EXPORT_SYMBOL(blk_rq_map_user);
  *    unmapping.
  */
 int blk_rq_map_user_iov(request_queue_t *q, struct request *rq,
-                        struct sg_iovec *iov, int iov_count)
+                        struct sg_iovec *iov, int iov_count, unsigned int len)
 {
         struct bio *bio;
 
@@ -2418,10 +2498,15 @@ int blk_rq_map_user_iov(request_queue_t *q, struct request *rq,
         if (IS_ERR(bio))
                 return PTR_ERR(bio);
 
-        rq->bio = rq->biotail = bio;
+        if (bio->bi_size != len) {
+                bio_endio(bio, bio->bi_size, 0);
+                bio_unmap_user(bio);
+                return -EINVAL;
+        }
+
+        bio_get(bio);
         blk_rq_bio_prep(q, rq, bio);
         rq->buffer = rq->data = NULL;
-        rq->data_len = bio->bi_size;
         return 0;
 }
 
@@ -2429,23 +2514,26 @@ EXPORT_SYMBOL(blk_rq_map_user_iov);
 
 /**
  * blk_rq_unmap_user - unmap a request with user data
- * @bio:        bio to be unmapped
- * @ulen:       length of user buffer
+ * @rq:         rq to be unmapped
  *
  * Description:
- *    Unmap a bio previously mapped by blk_rq_map_user().
+ *    Unmap a rq previously mapped by blk_rq_map_user().
+ *    rq->bio must be set to the original head of the request.
  */
-int blk_rq_unmap_user(struct bio *bio, unsigned int ulen)
+int blk_rq_unmap_user(struct request *rq)
 {
-        int ret = 0;
+        struct bio *bio, *mapped_bio;
 
-        if (bio) {
-                if (bio_flagged(bio, BIO_USER_MAPPED))
-                        bio_unmap_user(bio);
+        while ((bio = rq->bio)) {
+                if (bio_flagged(bio, BIO_BOUNCED))
+                        mapped_bio = bio->bi_private;
                 else
-                        ret = bio_uncopy_user(bio);
-        }
+                        mapped_bio = bio;
 
+                __blk_rq_unmap_user(mapped_bio);
+                rq->bio = bio->bi_next;
+                bio_put(bio);
+        }
         return 0;
 }
 
@@ -2476,11 +2564,8 @@ int blk_rq_map_kern(request_queue_t *q, struct request *rq, void *kbuf,
         if (rq_data_dir(rq) == WRITE)
                 bio->bi_rw |= (1 << BIO_RW);
 
-        rq->bio = rq->biotail = bio;
         blk_rq_bio_prep(q, rq, bio);
-
         rq->buffer = rq->data = NULL;
-        rq->data_len = len;
         return 0;
 }
 
@@ -3495,6 +3580,7 @@ void blk_rq_bio_prep(request_queue_t *q, struct request *rq, struct bio *bio)
         rq->hard_cur_sectors = rq->current_nr_sectors;
         rq->hard_nr_sectors = rq->nr_sectors = bio_sectors(bio);
         rq->buffer = bio_data(bio);
+        rq->data_len = bio->bi_size;
 
         rq->bio = rq->biotail = bio;
 }
diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
index e55a75621437..5493c2fbbab1 100644
--- a/block/scsi_ioctl.c
+++ b/block/scsi_ioctl.c
@@ -226,7 +226,6 @@ static int sg_io(struct file *file, request_queue_t *q,
         unsigned long start_time;
         int writing = 0, ret = 0;
         struct request *rq;
-        struct bio *bio;
         char sense[SCSI_SENSE_BUFFERSIZE];
         unsigned char cmd[BLK_MAX_CDB];
 
@@ -258,30 +257,6 @@ static int sg_io(struct file *file, request_queue_t *q,
         if (!rq)
                 return -ENOMEM;
 
-        if (hdr->iovec_count) {
-                const int size = sizeof(struct sg_iovec) * hdr->iovec_count;
-                struct sg_iovec *iov;
-
-                iov = kmalloc(size, GFP_KERNEL);
-                if (!iov) {
-                        ret = -ENOMEM;
-                        goto out;
-                }
-
-                if (copy_from_user(iov, hdr->dxferp, size)) {
-                        kfree(iov);
-                        ret = -EFAULT;
-                        goto out;
-                }
-
-                ret = blk_rq_map_user_iov(q, rq, iov, hdr->iovec_count);
-                kfree(iov);
-        } else if (hdr->dxfer_len)
-                ret = blk_rq_map_user(q, rq, hdr->dxferp, hdr->dxfer_len);
-
-        if (ret)
-                goto out;
-
         /*
          * fill in request structure
          */
@@ -294,7 +269,6 @@ static int sg_io(struct file *file, request_queue_t *q,
         rq->sense_len = 0;
 
         rq->cmd_type = REQ_TYPE_BLOCK_PC;
-        bio = rq->bio;
 
         /*
          * bounce this after holding a reference to the original bio, it's
@@ -309,6 +283,31 @@ static int sg_io(struct file *file, request_queue_t *q,
         if (!rq->timeout)
                 rq->timeout = BLK_DEFAULT_TIMEOUT;
 
+        if (hdr->iovec_count) {
+                const int size = sizeof(struct sg_iovec) * hdr->iovec_count;
+                struct sg_iovec *iov;
+
+                iov = kmalloc(size, GFP_KERNEL);
+                if (!iov) {
+                        ret = -ENOMEM;
+                        goto out;
+                }
+
+                if (copy_from_user(iov, hdr->dxferp, size)) {
+                        kfree(iov);
+                        ret = -EFAULT;
+                        goto out;
+                }
+
+                ret = blk_rq_map_user_iov(q, rq, iov, hdr->iovec_count,
+                                          hdr->dxfer_len);
+                kfree(iov);
+        } else if (hdr->dxfer_len)
+                ret = blk_rq_map_user(q, rq, hdr->dxferp, hdr->dxfer_len);
+
+        if (ret)
+                goto out;
+
         rq->retries = 0;
 
         start_time = jiffies;
@@ -339,7 +338,7 @@ static int sg_io(struct file *file, request_queue_t *q,
                         hdr->sb_len_wr = len;
         }
 
-        if (blk_rq_unmap_user(bio, hdr->dxfer_len))
+        if (blk_rq_unmap_user(rq))
                 ret = -EFAULT;
 
         /* may not have succeeded, but output values written to control