brd: remove discard support

It's just a in-driver reimplementation of writing zeroes to the pages,
which fails if the discards aren't page aligned.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index 3adc32a3153b2366d2d4deb652f22a1c61e06756..4ec84d504780d9b606efe3dfdfb6910d1380d0bc 100644 (file)
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -134,28 +134,6 @@ static struct page *brd_insert_page(struct brd_device *brd, sector_t sector)
        return page;
 }
 
-static void brd_free_page(struct brd_device *brd, sector_t sector)
-{
-       struct page *page;
-       pgoff_t idx;
-
-       spin_lock(&brd->brd_lock);
-       idx = sector >> PAGE_SECTORS_SHIFT;
-       page = radix_tree_delete(&brd->brd_pages, idx);
-       spin_unlock(&brd->brd_lock);
-       if (page)
-               __free_page(page);
-}
-
-static void brd_zero_page(struct brd_device *brd, sector_t sector)
-{
-       struct page *page;
-
-       page = brd_lookup_page(brd, sector);
-       if (page)
-               clear_highpage(page);
-}
-
 /*
  * Free all backing store pages and radix tree. This must only be called when
  * there are no other users of the device.
@@ -212,24 +190,6 @@ static int copy_to_brd_setup(struct brd_device *brd, sector_t sector, size_t n)
        return 0;
 }
 
-static void discard_from_brd(struct brd_device *brd,
-                       sector_t sector, size_t n)
-{
-       while (n >= PAGE_SIZE) {
-               /*
-                * Don't want to actually discard pages here because
-                * re-allocating the pages can result in writeback
-                * deadlocks under heavy load.
-                */
-               if (0)
-                       brd_free_page(brd, sector);
-               else
-                       brd_zero_page(brd, sector);
-               sector += PAGE_SIZE >> SECTOR_SHIFT;
-               n -= PAGE_SIZE;
-       }
-}
-
 /*
  * Copy n bytes from src to the brd starting at sector. Does not sleep.
  */
@@ -338,14 +298,6 @@ static blk_qc_t brd_make_request(struct request_queue *q, struct bio *bio)
        if (bio_end_sector(bio) > get_capacity(bdev->bd_disk))
                goto io_error;
 
-       if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) {
-               if (sector & ((PAGE_SIZE >> SECTOR_SHIFT) - 1) ||
-                   bio->bi_iter.bi_size & ~PAGE_MASK)
-                       goto io_error;
-               discard_from_brd(brd, sector, bio->bi_iter.bi_size);
-               goto out;
-       }
-
        bio_for_each_segment(bvec, bio, iter) {
                unsigned int len = bvec.bv_len;
                int err;
@@ -357,7 +309,6 @@ static blk_qc_t brd_make_request(struct request_queue *q, struct bio *bio)
                sector += len >> SECTOR_SHIFT;
        }
 
-out:
        bio_endio(bio);
        return BLK_QC_T_NONE;
 io_error:
@@ -464,11 +415,6 @@ static struct brd_device *brd_alloc(int i)
         *  is harmless)
         */
        blk_queue_physical_block_size(brd->brd_queue, PAGE_SIZE);
-
-       brd->brd_queue->limits.discard_granularity = PAGE_SIZE;
-       blk_queue_max_discard_sectors(brd->brd_queue, UINT_MAX);
-       brd->brd_queue->limits.discard_zeroes_data = 1;
-       queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, brd->brd_queue);
 #ifdef CONFIG_BLK_DEV_RAM_DAX
        queue_flag_set_unlocked(QUEUE_FLAG_DAX, brd->brd_queue);
 #endif