[PATCH 3/5] zram: add alloc_block_bdev_range() and free_block_bdev_range()
From: Pankaj Raghav <hidden>
Date: 2023-09-11 20:53:01
Also in:
lkml
Subsystem:
block layer, the rest, zram compressed ram block device drvier · Maintainers:
Jens Axboe, Linus Torvalds, Minchan Kim, Sergey Senozhatsky
From: Pankaj Raghav <redacted> 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 <redacted> --- 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) {
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2.40.1