From: Pankaj Raghav <p.raghav@xxxxxxxxxxx>
Add [alloc|free]_block_bdev_range() which accepts number of blocks to
allocate or free from the block bitmap.
alloc_block_bdev_range() tries to allocate a range of bitmap based in
the input nr_of_blocks whenever possible, or else it will retry with a
smaller value. This is done so that we don't unnecessarily return EIO
when the underlying device is fragmented.
alloc_block_bdev_range() is not an atomic operation as this function can
be called only from writeback_store() and init_lock is anyway taken
making sure there cannot be two processes allocating from bdev bitmap.
free_block_bdev_range() is just a simple loop that calls the atomic
free_block_bdev() function. As bdev bitmap free can be called from
two different process simulataneously without a lock, atomicity needs
to be maintained.
This is useful when we want to send larger IOs to the backing dev.
Signed-off-by: Pankaj Raghav <p.raghav@xxxxxxxxxxx>
---
drivers/block/zram/zram_drv.c | 33 +++++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index bd93ed653b99..0b8f814e11dd 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -576,6 +576,39 @@ static void free_block_bdev(struct zram *zram, unsigned long blk_idx)
atomic64_dec(&zram->stats.bd_count);
}
+static unsigned long alloc_block_bdev_range(struct zram *zram,
+ unsigned int *nr_of_blocksp)
+{
+ unsigned long blk_idx;
+ unsigned int nr_of_blocks = *nr_of_blocksp;
+retry:
+ /* skip 0 bit to confuse zram.handle = 0 */
+ blk_idx = 1;
+ blk_idx = bitmap_find_next_zero_area(zram->bitmap, zram->nr_pages,
+ blk_idx, nr_of_blocks, 0);
+
+ if ((blk_idx + nr_of_blocks) > zram->nr_pages) {
+ if (nr_of_blocks == 1)
+ return 0;
+
+ nr_of_blocks = nr_of_blocks / 2;
+ goto retry;
+ }
+
+ bitmap_set(zram->bitmap, blk_idx, nr_of_blocks);
+ atomic64_add(nr_of_blocks, &zram->stats.bd_count);
+ *nr_of_blocksp = nr_of_blocks;
+
+ return blk_idx;
+}
+
+static void free_block_bdev_range(struct zram *zram, unsigned long blk_idx,
+ unsigned int nr_of_blocks)
+{
+ for (unsigned int i = 0; i < nr_of_blocks; i++)
+ free_block_bdev(zram, blk_idx + i);
+}
+
static void read_from_bdev_async(struct zram *zram, struct page *page,
unsigned long entry, struct bio *parent)
{
--
2.40.1
