On 10/5/22 12:16, Chaitanya Kulkarni wrote:
> Introduce and use two new macros for calculating the page index from
> given sector and index (offset) of the sector in the page.
> The newly added macros makes code easy to read with meaningful name and
> explanation comments attached to it.
>
> While at it adjust the code in the null_free_sector() to return early
> to get rid of the extra identation.
>
> Signed-off-by: Chaitanya Kulkarni <kch@xxxxxxxxxx>
> ---
> drivers/block/null_blk/main.c | 37 ++++++++++++++++++++---------------
> 1 file changed, 21 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
> index 2d592b4eb815..b82c2ffeb086 100644
> --- a/drivers/block/null_blk/main.c
> +++ b/drivers/block/null_blk/main.c
> @@ -14,6 +14,11 @@
> #undef pr_fmt
> #define pr_fmt(fmt) "null_blk: " fmt
>
> +/* Gives page index for which this sector belongs to. */
That is clear from the macro name. Not convinced this comment is useful.
> +#define PAGE_IDX_FROM_SECT(sect) (sect >> PAGE_SECTORS_SHIFT)
> +/* Gives index (offset) of the sector within page. */
> +#define SECT_IDX_IN_PAGE(sect) ((sect & SECTOR_MASK) << SECTOR_SHIFT)
SECT_OFFSET_IN_PAGE() ? A "page" not being an array of sectors, using
index for a sector is a little strange I think. And you use this macro for
things like:
offset = SECT_IDX_IN_PAGE(sect);
So offset in the name makes more sense.
> +
> #define FREE_BATCH 16
>
> #define TICKS_PER_SEC 50ULL
> @@ -860,20 +865,20 @@ static void null_free_sector(struct nullb *nullb, sector_t sector,
> struct radix_tree_root *root;
>
> root = is_cache ? &nullb->dev->cache : &nullb->dev->data;
> - idx = sector >> PAGE_SECTORS_SHIFT;
> + idx = PAGE_IDX_FROM_SECT(sector);
> sector_bit = (sector & SECTOR_MASK);
>
> t_page = radix_tree_lookup(root, idx);
> - if (t_page) {
> - __clear_bit(sector_bit, t_page->bitmap);
> -
> - if (null_page_empty(t_page)) {
> - ret = radix_tree_delete_item(root, idx, t_page);
> - WARN_ON(ret != t_page);
> - null_free_page(ret);
> - if (is_cache)
> - nullb->dev->curr_cache -= PAGE_SIZE;
> - }
> + if (!t_page)
> + return;
> + __clear_bit(sector_bit, t_page->bitmap);
> +
> + if (null_page_empty(t_page)) {
> + ret = radix_tree_delete_item(root, idx, t_page);
> + WARN_ON(ret != t_page);
> + null_free_page(ret);
> + if (is_cache)
> + nullb->dev->curr_cache -= PAGE_SIZE;
> }
> }
>
> @@ -885,11 +890,11 @@ static void null_zero_sector(struct nullb_device *d, sector_t sect,
> unsigned int offset;
> void *dest;
>
> - t_page = radix_tree_lookup(root, sect >> PAGE_SECTORS_SHIFT);
> + t_page = radix_tree_lookup(root, PAGE_IDX_FROM_SECT(sect));
> if (!t_page)
> return;
>
> - offset = (sect & SECTOR_MASK) << SECTOR_SHIFT;
> + offset = SECT_IDX_IN_PAGE(sect);
> dest = kmap_atomic(t_page->page);
> memset(dest + offset, 0, SECTOR_SIZE * nr_sects);
> kunmap_atomic(dest);
> @@ -949,7 +954,7 @@ static struct nullb_page *__null_lookup_page(struct nullb *nullb,
> struct nullb_page *t_page;
> struct radix_tree_root *root;
>
> - idx = sector >> PAGE_SECTORS_SHIFT;
> + idx = PAGE_IDX_FROM_SECT(sector);
> sector_bit = (sector & SECTOR_MASK);
>
> root = is_cache ? &nullb->dev->cache : &nullb->dev->data;
> @@ -1125,7 +1130,7 @@ static int copy_to_nullb(struct nullb *nullb, struct page *source,
> if (null_cache_active(nullb) && !is_fua)
> null_make_cache_space(nullb, PAGE_SIZE);
>
> - offset = (sector & SECTOR_MASK) << SECTOR_SHIFT;
> + offset = SECT_IDX_IN_PAGE(sector);
> t_page = null_insert_page(nullb, sector,
> !null_cache_active(nullb) || is_fua);
> if (!t_page)
> @@ -1159,7 +1164,7 @@ static int copy_from_nullb(struct nullb *nullb, struct page *dest,
> while (count < n) {
> temp = min_t(size_t, nullb->dev->blocksize, n - count);
>
> - offset = (sector & SECTOR_MASK) << SECTOR_SHIFT;
> + offset = SECT_IDX_IN_PAGE(sector);
> t_page = null_lookup_page(nullb, sector, false,
> !null_cache_active(nullb));
>
--
Damien Le Moal
Western Digital Research
