brd: fix discard end sector

brd_do_discard() just aligned start sector to page, this can only work
if the discard size if at least one page. For example:

blkdiscard /dev/ram0 -o 5120 -l 1024

In this case, size = (1024 - (8192 - 5120)), which is a huge value.

Fix the problem by round_down() the end sector.

Fixes: 9ead7efc6f3f ("brd: implement discard support")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20250506061756.2970934-4-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index 2753fb21410b350c473ea2f21e2bf0af0847255e..a3725673cf1644d15548f524865eb9fb3d53acab 100644 (file)
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -167,18 +167,21 @@ static void brd_free_one_page(struct rcu_head *head)
 static void brd_do_discard(struct brd_device *brd, sector_t sector, u32 size)
 {
        sector_t aligned_sector = round_up(sector, PAGE_SECTORS);
+       sector_t aligned_end = round_down(
+                       sector + (size >> SECTOR_SHIFT), PAGE_SECTORS);
        struct page *page;
 
-       size -= (aligned_sector - sector) * SECTOR_SIZE;
+       if (aligned_end <= aligned_sector)
+               return;
+
        xa_lock(&brd->brd_pages);
-       while (size >= PAGE_SIZE && aligned_sector < rd_size * 2) {
+       while (aligned_sector < aligned_end && aligned_sector < rd_size * 2) {
                page = __xa_erase(&brd->brd_pages, aligned_sector >> PAGE_SECTORS_SHIFT);
                if (page) {
                        call_rcu(&page->rcu_head, brd_free_one_page);
                        brd->brd_nr_pages--;
                }
                aligned_sector += PAGE_SECTORS;
-               size -= PAGE_SIZE;
        }
        xa_unlock(&brd->brd_pages);
 }