Revert "knfsd: avoid overloading the CPU scheduler with enormous load averages"

[safe/jmp/linux-2.6] / block / blk-barrier.c

diff --git a/block/blk-barrier.c b/block/blk-barrier.c
index 0d98054..8873b9b 100644 (file)
--- a/block/blk-barrier.c
+++ b/block/blk-barrier.c
@@ -348,6 +348,10 @@ static void blkdev_discard_end_io(struct bio *bio, int err)
                clear_bit(BIO_UPTODATE, &bio->bi_flags);
        }
 
+       if (bio->bi_private)
+               complete(bio->bi_private);
+       __free_page(bio_page(bio));
+
        bio_put(bio);
 }
 
@@ -357,49 +361,73 @@ static void blkdev_discard_end_io(struct bio *bio, int err)
  * @sector:    start sector
  * @nr_sects:  number of sectors to discard
  * @gfp_mask:  memory allocation flags (for bio_alloc)
+ * @flags:     DISCARD_FL_* flags to control behaviour
  *
  * Description:
- *    Issue a discard request for the sectors in question. Does not wait.
+ *    Issue a discard request for the sectors in question.
  */
-int blkdev_issue_discard(struct block_device *bdev,
-                        sector_t sector, sector_t nr_sects, gfp_t gfp_mask)
+int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
+               sector_t nr_sects, gfp_t gfp_mask, int flags)
 {
-       struct request_queue *q;
+       DECLARE_COMPLETION_ONSTACK(wait);
+       struct request_queue *q = bdev_get_queue(bdev);
+       int type = flags & DISCARD_FL_BARRIER ?
+               DISCARD_BARRIER : DISCARD_NOBARRIER;
        struct bio *bio;
+       struct page *page;
        int ret = 0;
 
-       if (bdev->bd_disk == NULL)
-               return -ENXIO;
-
-       q = bdev_get_queue(bdev);
        if (!q)
                return -ENXIO;
 
-       if (!q->prepare_discard_fn)
+       if (!blk_queue_discard(q))
                return -EOPNOTSUPP;
 
        while (nr_sects && !ret) {
-               bio = bio_alloc(gfp_mask, 0);
-               if (!bio)
-                       return -ENOMEM;
+               unsigned int sector_size = q->limits.logical_block_size;
+               unsigned int max_discard_sectors =
+                       min(q->limits.max_discard_sectors, UINT_MAX >> 9);
 
+               bio = bio_alloc(gfp_mask, 1);
+               if (!bio)
+                       goto out;
+               bio->bi_sector = sector;
                bio->bi_end_io = blkdev_discard_end_io;
                bio->bi_bdev = bdev;
+               if (flags & DISCARD_FL_WAIT)
+                       bio->bi_private = &wait;
 
-               bio->bi_sector = sector;
+               /*
+                * Add a zeroed one-sector payload as that's what
+                * our current implementations need.  If we'll ever need
+                * more the interface will need revisiting.
+                */
+               page = alloc_page(GFP_KERNEL | __GFP_ZERO);
+               if (!page)
+                       goto out_free_bio;
+               if (bio_add_pc_page(q, bio, page, sector_size, 0) < sector_size)
+                       goto out_free_page;
 
-               if (nr_sects > q->max_hw_sectors) {
-                       bio->bi_size = q->max_hw_sectors << 9;
-                       nr_sects -= q->max_hw_sectors;
-                       sector += q->max_hw_sectors;
+               /*
+                * And override the bio size - the way discard works we
+                * touch many more blocks on disk than the actual payload
+                * length.
+                */
+               if (nr_sects > max_discard_sectors) {
+                       bio->bi_size = max_discard_sectors << 9;
+                       nr_sects -= max_discard_sectors;
+                       sector += max_discard_sectors;
                } else {
                        bio->bi_size = nr_sects << 9;
                        nr_sects = 0;
                }
+
                bio_get(bio);
-               submit_bio(DISCARD_BARRIER, bio);
+               submit_bio(type, bio);
+
+               if (flags & DISCARD_FL_WAIT)
+                       wait_for_completion(&wait);
 
-               /* Check if it failed immediately */
                if (bio_flagged(bio, BIO_EOPNOTSUPP))
                        ret = -EOPNOTSUPP;
                else if (!bio_flagged(bio, BIO_UPTODATE))
@@ -407,5 +435,11 @@ int blkdev_issue_discard(struct block_device *bdev,
                bio_put(bio);
        }
        return ret;
+out_free_page:
+       __free_page(page);
+out_free_bio:
+       bio_put(bio);
+out:
+       return -ENOMEM;
 }
 EXPORT_SYMBOL(blkdev_issue_discard);