brd: Support discard

To support ramdisk flush, discard is required. So, revert the commit.
Also, this commit has been modified to match the interface of the
kernel v5.15.

This reverts commit f09a06a193d942a12c1a33c153388b3962222006.

Change-Id: Ic66d8331b63e96ed35ae7ca48cb7c7349559ea58
Signed-off-by: Hoegeun Kwon <hoegeun.kwon@samsung.com>

diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index 530b312..f6585ba 100644 (file)
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -124,6 +124,28 @@ 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.
@@ -186,6 +208,24 @@ 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.
  */
@@ -289,6 +329,14 @@ static blk_qc_t brd_submit_bio(struct bio *bio)
        struct bio_vec bvec;
        struct bvec_iter iter;
 
+       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;
@@ -304,6 +352,7 @@ static blk_qc_t brd_submit_bio(struct bio *bio)
                sector += len >> SECTOR_SHIFT;
        }
 
+out:
        bio_endio(bio);
        return BLK_QC_T_NONE;
 io_error:
@@ -419,6 +468,10 @@ static int brd_alloc(int i)
         */
        blk_queue_physical_block_size(disk->queue, PAGE_SIZE);
 
+       disk->queue->limits.discard_granularity = PAGE_SIZE;
+       blk_queue_max_discard_sectors(disk->queue, UINT_MAX);
+       blk_queue_flag_set(QUEUE_FLAG_DISCARD, disk->queue);
+
        /* Tell the block layer that this is not a rotational device */
        blk_queue_flag_set(QUEUE_FLAG_NONROT, disk->queue);
        blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, disk->queue);