1 files changed, 71 insertions, 154 deletions

diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index 292f127cae0a..b1be6c510372 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -54,32 +54,33 @@ static struct page *brd_lookup_page(struct brd_device *brd, sector_t sector)
 /*
  * Insert a new page for a given sector, if one does not already exist.
  */
-static int brd_insert_page(struct brd_device *brd, sector_t sector, gfp_t gfp)
+static struct page *brd_insert_page(struct brd_device *brd, sector_t sector,
+		blk_opf_t opf)
+	__releases(rcu)
+	__acquires(rcu)
 {
-	pgoff_t idx = sector >> PAGE_SECTORS_SHIFT;
-	struct page *page;
-	int ret = 0;
-
-	page = brd_lookup_page(brd, sector);
-	if (page)
-		return 0;
+	gfp_t gfp = (opf & REQ_NOWAIT) ? GFP_NOWAIT : GFP_NOIO;
+	struct page *page, *ret;
 
+	rcu_read_unlock();
 	page = alloc_page(gfp | __GFP_ZERO | __GFP_HIGHMEM);
+	rcu_read_lock();
 	if (!page)
-		return -ENOMEM;
+		return ERR_PTR(-ENOMEM);
 
 	xa_lock(&brd->brd_pages);
-	ret = __xa_insert(&brd->brd_pages, idx, page, gfp);
-	if (!ret)
-		brd->brd_nr_pages++;
-	xa_unlock(&brd->brd_pages);
-
-	if (ret < 0) {
+	ret = __xa_cmpxchg(&brd->brd_pages, sector >> PAGE_SECTORS_SHIFT, NULL,
+			page, gfp);
+	if (ret) {
+		xa_unlock(&brd->brd_pages);
 		__free_page(page);
-		if (ret == -EBUSY)
-			ret = 0;
+		if (xa_is_err(ret))
+			return ERR_PTR(xa_err(ret));
+		return ret;
 	}
-	return ret;
+	brd->brd_nr_pages++;
+	xa_unlock(&brd->brd_pages);
+	return page;
 }
 
 /*
@@ -100,143 +101,77 @@ static void brd_free_pages(struct brd_device *brd)
 }
 
 /*
- * copy_to_brd_setup must be called before copy_to_brd. It may sleep.
+ * Process a single segment.  The segment is capped to not cross page boundaries
+ * in both the bio and the brd backing memory.
  */
-static int copy_to_brd_setup(struct brd_device *brd, sector_t sector, size_t n,
-			     gfp_t gfp)
-{
-	unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
-	size_t copy;
-	int ret;
-
-	copy = min_t(size_t, n, PAGE_SIZE - offset);
-	ret = brd_insert_page(brd, sector, gfp);
-	if (ret)
-		return ret;
-	if (copy < n) {
-		sector += copy >> SECTOR_SHIFT;
-		ret = brd_insert_page(brd, sector, gfp);
-	}
-	return ret;
-}
-
-/*
- * Copy n bytes from src to the brd starting at sector. Does not sleep.
- */
-static void copy_to_brd(struct brd_device *brd, const void *src,
-			sector_t sector, size_t n)
+static bool brd_rw_bvec(struct brd_device *brd, struct bio *bio)
 {
+	struct bio_vec bv = bio_iter_iovec(bio, bio->bi_iter);
+	sector_t sector = bio->bi_iter.bi_sector;
+	u32 offset = (sector & (PAGE_SECTORS - 1)) << SECTOR_SHIFT;
+	blk_opf_t opf = bio->bi_opf;
 	struct page *page;
-	void *dst;
-	unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
-	size_t copy;
+	void *kaddr;
 
-	copy = min_t(size_t, n, PAGE_SIZE - offset);
-	page = brd_lookup_page(brd, sector);
-	BUG_ON(!page);
-
-	dst = kmap_atomic(page);
-	memcpy(dst + offset, src, copy);
-	kunmap_atomic(dst);
-
-	if (copy < n) {
-		src += copy;
-		sector += copy >> SECTOR_SHIFT;
-		copy = n - copy;
-		page = brd_lookup_page(brd, sector);
-		BUG_ON(!page);
-
-		dst = kmap_atomic(page);
-		memcpy(dst, src, copy);
-		kunmap_atomic(dst);
-	}
-}
+	bv.bv_len = min_t(u32, bv.bv_len, PAGE_SIZE - offset);
 
-/*
- * Copy n bytes to dst from the brd starting at sector. Does not sleep.
- */
-static void copy_from_brd(void *dst, struct brd_device *brd,
-			sector_t sector, size_t n)
-{
-	struct page *page;
-	void *src;
-	unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
-	size_t copy;
-
-	copy = min_t(size_t, n, PAGE_SIZE - offset);
+	rcu_read_lock();
 	page = brd_lookup_page(brd, sector);
-	if (page) {
-		src = kmap_atomic(page);
-		memcpy(dst, src + offset, copy);
-		kunmap_atomic(src);
-	} else
-		memset(dst, 0, copy);
-
-	if (copy < n) {
-		dst += copy;
-		sector += copy >> SECTOR_SHIFT;
-		copy = n - copy;
-		page = brd_lookup_page(brd, sector);
-		if (page) {
-			src = kmap_atomic(page);
-			memcpy(dst, src, copy);
-			kunmap_atomic(src);
-		} else
-			memset(dst, 0, copy);
+	if (!page && op_is_write(opf)) {
+		page = brd_insert_page(brd, sector, opf);
+		if (IS_ERR(page))
+			goto out_error;
 	}
-}
-
-/*
- * Process a single bvec of a bio.
- */
-static int brd_do_bvec(struct brd_device *brd, struct page *page,
-			unsigned int len, unsigned int off, blk_opf_t opf,
-			sector_t sector)
-{
-	void *mem;
-	int err = 0;
 
+	kaddr = bvec_kmap_local(&bv);
 	if (op_is_write(opf)) {
-		/*
-		 * Must use NOIO because we don't want to recurse back into the
-		 * block or filesystem layers from page reclaim.
-		 */
-		gfp_t gfp = opf & REQ_NOWAIT ? GFP_NOWAIT : GFP_NOIO;
-
-		err = copy_to_brd_setup(brd, sector, len, gfp);
-		if (err)
-			goto out;
-	}
-
-	mem = kmap_atomic(page);
-	if (!op_is_write(opf)) {
-		copy_from_brd(mem + off, brd, sector, len);
-		flush_dcache_page(page);
+		memcpy_to_page(page, offset, kaddr, bv.bv_len);
 	} else {
-		flush_dcache_page(page);
-		copy_to_brd(brd, mem + off, sector, len);
+		if (page)
+			memcpy_from_page(kaddr, page, offset, bv.bv_len);
+		else
+			memset(kaddr, 0, bv.bv_len);
 	}
-	kunmap_atomic(mem);
+	kunmap_local(kaddr);
+	rcu_read_unlock();
+
+	bio_advance_iter_single(bio, &bio->bi_iter, bv.bv_len);
+	return true;
+
+out_error:
+	rcu_read_unlock();
+	if (PTR_ERR(page) == -ENOMEM && (opf & REQ_NOWAIT))
+		bio_wouldblock_error(bio);
+	else
+		bio_io_error(bio);
+	return false;
+}
 
-out:
-	return err;
+static void brd_free_one_page(struct rcu_head *head)
+{
+	struct page *page = container_of(head, struct page, rcu_head);
+
+	__free_page(page);
 }
 
 static void brd_do_discard(struct brd_device *brd, sector_t sector, u32 size)
 {
-	sector_t aligned_sector = (sector + PAGE_SECTORS) & ~PAGE_SECTORS;
+	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) {
-			__free_page(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);
 }
@@ -244,36 +179,18 @@ static void brd_do_discard(struct brd_device *brd, sector_t sector, u32 size)
 static void brd_submit_bio(struct bio *bio)
 {
 	struct brd_device *brd = bio->bi_bdev->bd_disk->private_data;
-	sector_t sector = bio->bi_iter.bi_sector;
-	struct bio_vec bvec;
-	struct bvec_iter iter;
 
 	if (unlikely(op_is_discard(bio->bi_opf))) {
-		brd_do_discard(brd, sector, bio->bi_iter.bi_size);
+		brd_do_discard(brd, bio->bi_iter.bi_sector,
+				bio->bi_iter.bi_size);
 		bio_endio(bio);
 		return;
 	}
 
-	bio_for_each_segment(bvec, bio, iter) {
-		unsigned int len = bvec.bv_len;
-		int err;
-
-		/* Don't support un-aligned buffer */
-		WARN_ON_ONCE((bvec.bv_offset & (SECTOR_SIZE - 1)) ||
-				(len & (SECTOR_SIZE - 1)));
-
-		err = brd_do_bvec(brd, bvec.bv_page, len, bvec.bv_offset,
-				  bio->bi_opf, sector);
-		if (err) {
-			if (err == -ENOMEM && bio->bi_opf & REQ_NOWAIT) {
-				bio_wouldblock_error(bio);
-				return;
-			}
-			bio_io_error(bio);
+	do {
+		if (!brd_rw_bvec(brd, bio))
 			return;
-		}
-		sector += len >> SECTOR_SHIFT;
-	}
+	} while (bio->bi_iter.bi_size);
 
 	bio_endio(bio);
 }