Rust-for-Linux
diff --git a/‎block/bio.c‎
Lines changed: 205 additions & 127 deletions b/‎block/bio.c‎
Lines changed: 205 additions & 127 deletions
@@ -958,7 +958,7 @@ static inline bool bio_full(struct bio *bio, unsigned len)
 {
 	if (bio->bi_vcnt >= bio->bi_max_vecs)
 		return true;
-	if (bio->bi_iter.bi_size > UINT_MAX - len)
+	if (bio->bi_iter.bi_size > BIO_MAX_SIZE - len)
 		return true;
 	return false;
 }
@@ -1064,7 +1064,7 @@ int bio_add_page(struct bio *bio, struct page *page,
 {
 	if (WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)))
 		return 0;
-	if (bio->bi_iter.bi_size > UINT_MAX - len)
+	if (bio->bi_iter.bi_size > BIO_MAX_SIZE - len)
 		return 0;
 
 	if (bio->bi_vcnt > 0) {
@@ -1091,7 +1091,7 @@ void bio_add_folio_nofail(struct bio *bio, struct folio *folio, size_t len,
 {
 	unsigned long nr = off / PAGE_SIZE;
 
-	WARN_ON_ONCE(len > UINT_MAX);
+	WARN_ON_ONCE(len > BIO_MAX_SIZE);
 	__bio_add_page(bio, folio_page(folio, nr), len, off % PAGE_SIZE);
 }
 EXPORT_SYMBOL_GPL(bio_add_folio_nofail);
@@ -1115,7 +1115,7 @@ bool bio_add_folio(struct bio *bio, struct folio *folio, size_t len,
 {
 	unsigned long nr = off / PAGE_SIZE;
 
-	if (len > UINT_MAX)
+	if (len > BIO_MAX_SIZE)
 		return false;
 	return bio_add_page(bio, folio_page(folio, nr), len, off % PAGE_SIZE) > 0;
 }
@@ -1206,122 +1206,6 @@ void bio_iov_bvec_set(struct bio *bio, const struct iov_iter *iter)
 	bio_set_flag(bio, BIO_CLONED);
 }
 
-static unsigned int get_contig_folio_len(unsigned int *num_pages,
-					 struct page **pages, unsigned int i,
-					 struct folio *folio, size_t left,
-					 size_t offset)
-{
-	size_t bytes = left;
-	size_t contig_sz = min_t(size_t, PAGE_SIZE - offset, bytes);
-	unsigned int j;
-
-	/*
-	 * We might COW a single page in the middle of
-	 * a large folio, so we have to check that all
-	 * pages belong to the same folio.
-	 */
-	bytes -= contig_sz;
-	for (j = i + 1; j < i + *num_pages; j++) {
-		size_t next = min_t(size_t, PAGE_SIZE, bytes);
-
-		if (page_folio(pages[j]) != folio ||
-		    pages[j] != pages[j - 1] + 1) {
-			break;
-		}
-		contig_sz += next;
-		bytes -= next;
-	}
-	*num_pages = j - i;
-
-	return contig_sz;
-}
-
-#define PAGE_PTRS_PER_BVEC     (sizeof(struct bio_vec) / sizeof(struct page *))
-
-/**
- * __bio_iov_iter_get_pages - pin user or kernel pages and add them to a bio
- * @bio: bio to add pages to
- * @iter: iov iterator describing the region to be mapped
- *
- * Extracts pages from *iter and appends them to @bio's bvec array.  The pages
- * will have to be cleaned up in the way indicated by the BIO_PAGE_PINNED flag.
- * For a multi-segment *iter, this function only adds pages from the next
- * non-empty segment of the iov iterator.
- */
-static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
-{
-	iov_iter_extraction_t extraction_flags = 0;
-	unsigned short nr_pages = bio->bi_max_vecs - bio->bi_vcnt;
-	unsigned short entries_left = bio->bi_max_vecs - bio->bi_vcnt;
-	struct bio_vec *bv = bio->bi_io_vec + bio->bi_vcnt;
-	struct page **pages = (struct page **)bv;
-	ssize_t size;
-	unsigned int num_pages, i = 0;
-	size_t offset, folio_offset, left, len;
-	int ret = 0;
-
-	/*
-	 * Move page array up in the allocated memory for the bio vecs as far as
-	 * possible so that we can start filling biovecs from the beginning
-	 * without overwriting the temporary page array.
-	 */
-	BUILD_BUG_ON(PAGE_PTRS_PER_BVEC < 2);
-	pages += entries_left * (PAGE_PTRS_PER_BVEC - 1);
-
-	if (bio->bi_bdev && blk_queue_pci_p2pdma(bio->bi_bdev->bd_disk->queue))
-		extraction_flags |= ITER_ALLOW_P2PDMA;
-
-	size = iov_iter_extract_pages(iter, &pages,
-				      UINT_MAX - bio->bi_iter.bi_size,
-				      nr_pages, extraction_flags, &offset);
-	if (unlikely(size <= 0))
-		return size ? size : -EFAULT;
-
-	nr_pages = DIV_ROUND_UP(offset + size, PAGE_SIZE);
-	for (left = size, i = 0; left > 0; left -= len, i += num_pages) {
-		struct page *page = pages[i];
-		struct folio *folio = page_folio(page);
-		unsigned int old_vcnt = bio->bi_vcnt;
-
-		folio_offset = ((size_t)folio_page_idx(folio, page) <<
-			       PAGE_SHIFT) + offset;
-
-		len = min(folio_size(folio) - folio_offset, left);
-
-		num_pages = DIV_ROUND_UP(offset + len, PAGE_SIZE);
-
-		if (num_pages > 1)
-			len = get_contig_folio_len(&num_pages, pages, i,
-						   folio, left, offset);
-
-		if (!bio_add_folio(bio, folio, len, folio_offset)) {
-			WARN_ON_ONCE(1);
-			ret = -EINVAL;
-			goto out;
-		}
-
-		if (bio_flagged(bio, BIO_PAGE_PINNED)) {
-			/*
-			 * We're adding another fragment of a page that already
-			 * was part of the last segment.  Undo our pin as the
-			 * page was pinned when an earlier fragment of it was
-			 * added to the bio and __bio_release_pages expects a
-			 * single pin per page.
-			 */
-			if (offset && bio->bi_vcnt == old_vcnt)
-				unpin_user_folio(folio, 1);
-		}
-		offset = 0;
-	}
-
-	iov_iter_revert(iter, left);
-out:
-	while (i < nr_pages)
-		bio_release_page(bio, pages[i++]);
-
-	return ret;
-}
-
 /*
  * Aligns the bio size to the len_align_mask, releasing excessive bio vecs that
  * __bio_iov_iter_get_pages may have inserted, and reverts the trimmed length
@@ -1345,7 +1229,9 @@ static int bio_iov_iter_align_down(struct bio *bio, struct iov_iter *iter,
 			break;
 		}
 
-		bio_release_page(bio, bv->bv_page);
+		if (bio_flagged(bio, BIO_PAGE_PINNED))
+			unpin_user_page(bv->bv_page);
+
 		bio->bi_vcnt--;
 		nbytes -= bv->bv_len;
 	} while (nbytes);
@@ -1379,7 +1265,7 @@ static int bio_iov_iter_align_down(struct bio *bio, struct iov_iter *iter,
 int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter,
 			   unsigned len_align_mask)
 {
-	int ret = 0;
+	iov_iter_extraction_t flags = 0;
 
 	if (WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)))
 		return -EIO;
@@ -1392,13 +1278,205 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter,
 
 	if (iov_iter_extract_will_pin(iter))
 		bio_set_flag(bio, BIO_PAGE_PINNED);
+	if (bio->bi_bdev && blk_queue_pci_p2pdma(bio->bi_bdev->bd_disk->queue))
+		flags |= ITER_ALLOW_P2PDMA;
+
 	do {
-		ret = __bio_iov_iter_get_pages(bio, iter);
-	} while (!ret && iov_iter_count(iter) && !bio_full(bio, 0));
+		ssize_t ret;
+
+		ret = iov_iter_extract_bvecs(iter, bio->bi_io_vec,
+				BIO_MAX_SIZE - bio->bi_iter.bi_size,
+				&bio->bi_vcnt, bio->bi_max_vecs, flags);
+		if (ret <= 0) {
+			if (!bio->bi_vcnt)
+				return ret;
+			break;
+		}
+		bio->bi_iter.bi_size += ret;
+	} while (iov_iter_count(iter) && !bio_full(bio, 0));
 
-	if (bio->bi_vcnt)
-		return bio_iov_iter_align_down(bio, iter, len_align_mask);
-	return ret;
+	if (is_pci_p2pdma_page(bio->bi_io_vec->bv_page))
+		bio->bi_opf |= REQ_NOMERGE;
+	return bio_iov_iter_align_down(bio, iter, len_align_mask);
+}
+
+static struct folio *folio_alloc_greedy(gfp_t gfp, size_t *size)
+{
+	struct folio *folio;
+
+	while (*size > PAGE_SIZE) {
+		folio = folio_alloc(gfp | __GFP_NORETRY, get_order(*size));
+		if (folio)
+			return folio;
+		*size = rounddown_pow_of_two(*size - 1);
+	}
+
+	return folio_alloc(gfp, get_order(*size));
+}
+
+static void bio_free_folios(struct bio *bio)
+{
+	struct bio_vec *bv;
+	int i;
+
+	bio_for_each_bvec_all(bv, bio, i) {
+		struct folio *folio = page_folio(bv->bv_page);
+
+		if (!is_zero_folio(folio))
+			folio_put(folio);
+	}
+}
+
+static int bio_iov_iter_bounce_write(struct bio *bio, struct iov_iter *iter)
+{
+	size_t total_len = iov_iter_count(iter);
+
+	if (WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)))
+		return -EINVAL;
+	if (WARN_ON_ONCE(bio->bi_iter.bi_size))
+		return -EINVAL;
+	if (WARN_ON_ONCE(bio->bi_vcnt >= bio->bi_max_vecs))
+		return -EINVAL;
+
+	do {
+		size_t this_len = min(total_len, SZ_1M);
+		struct folio *folio;
+
+		if (this_len > PAGE_SIZE * 2)
+			this_len = rounddown_pow_of_two(this_len);
+
+		if (bio->bi_iter.bi_size > BIO_MAX_SIZE - this_len)
+			break;
+
+		folio = folio_alloc_greedy(GFP_KERNEL, &this_len);
+		if (!folio)
+			break;
+		bio_add_folio_nofail(bio, folio, this_len, 0);
+
+		if (copy_from_iter(folio_address(folio), this_len, iter) !=
+				this_len) {
+			bio_free_folios(bio);
+			return -EFAULT;
+		}
+
+		total_len -= this_len;
+	} while (total_len && bio->bi_vcnt < bio->bi_max_vecs);
+
+	if (!bio->bi_iter.bi_size)
+		return -ENOMEM;
+	return 0;
+}
+
+static int bio_iov_iter_bounce_read(struct bio *bio, struct iov_iter *iter)
+{
+	size_t len = min(iov_iter_count(iter), SZ_1M);
+	struct folio *folio;
+
+	folio = folio_alloc_greedy(GFP_KERNEL, &len);
+	if (!folio)
+		return -ENOMEM;
+
+	do {
+		ssize_t ret;
+
+		ret = iov_iter_extract_bvecs(iter, bio->bi_io_vec + 1, len,
+				&bio->bi_vcnt, bio->bi_max_vecs - 1, 0);
+		if (ret <= 0) {
+			if (!bio->bi_vcnt)
+				return ret;
+			break;
+		}
+		len -= ret;
+		bio->bi_iter.bi_size += ret;
+	} while (len && bio->bi_vcnt < bio->bi_max_vecs - 1);
+
+	/*
+	 * Set the folio directly here.  The above loop has already calculated
+	 * the correct bi_size, and we use bi_vcnt for the user buffers.  That
+	 * is safe as bi_vcnt is only used by the submitter and not the actual
+	 * I/O path.
+	 */
+	bvec_set_folio(&bio->bi_io_vec[0], folio, bio->bi_iter.bi_size, 0);
+	if (iov_iter_extract_will_pin(iter))
+		bio_set_flag(bio, BIO_PAGE_PINNED);
+	return 0;
+}
+
+/**
+ * bio_iov_iter_bounce - bounce buffer data from an iter into a bio
+ * @bio:	bio to send
+ * @iter:	iter to read from / write into
+ *
+ * Helper for direct I/O implementations that need to bounce buffer because
+ * we need to checksum the data or perform other operations that require
+ * consistency.  Allocates folios to back the bounce buffer, and for writes
+ * copies the data into it.  Needs to be paired with bio_iov_iter_unbounce()
+ * called on completion.
+ */
+int bio_iov_iter_bounce(struct bio *bio, struct iov_iter *iter)
+{
+	if (op_is_write(bio_op(bio)))
+		return bio_iov_iter_bounce_write(bio, iter);
+	return bio_iov_iter_bounce_read(bio, iter);
+}
+
+static void bvec_unpin(struct bio_vec *bv, bool mark_dirty)
+{
+	struct folio *folio = page_folio(bv->bv_page);
+	size_t nr_pages = (bv->bv_offset + bv->bv_len - 1) / PAGE_SIZE -
+			bv->bv_offset / PAGE_SIZE + 1;
+
+	if (mark_dirty)
+		folio_mark_dirty_lock(folio);
+	unpin_user_folio(folio, nr_pages);
+}
+
+static void bio_iov_iter_unbounce_read(struct bio *bio, bool is_error,
+		bool mark_dirty)
+{
+	unsigned int len = bio->bi_io_vec[0].bv_len;
+
+	if (likely(!is_error)) {
+		void *buf = bvec_virt(&bio->bi_io_vec[0]);
+		struct iov_iter to;
+
+		iov_iter_bvec(&to, ITER_DEST, bio->bi_io_vec + 1, bio->bi_vcnt,
+				len);
+		/* copying to pinned pages should always work */
+		WARN_ON_ONCE(copy_to_iter(buf, len, &to) != len);
+	} else {
+		/* No need to mark folios dirty if never copied to them */
+		mark_dirty = false;
+	}
+
+	if (bio_flagged(bio, BIO_PAGE_PINNED)) {
+		int i;
+
+		for (i = 0; i < bio->bi_vcnt; i++)
+			bvec_unpin(&bio->bi_io_vec[1 + i], mark_dirty);
+	}
+
+	folio_put(page_folio(bio->bi_io_vec[0].bv_page));
+}
+
+/**
+ * bio_iov_iter_unbounce - finish a bounce buffer operation
+ * @bio:	completed bio
+ * @is_error:	%true if an I/O error occurred and data should not be copied
+ * @mark_dirty:	If %true, folios will be marked dirty.
+ *
+ * Helper for direct I/O implementations that need to bounce buffer because
+ * we need to checksum the data or perform other operations that require
+ * consistency.  Called to complete a bio set up by bio_iov_iter_bounce().
+ * Copies data back for reads, and marks the original folios dirty if
+ * requested and then frees the bounce buffer.
+ */
+void bio_iov_iter_unbounce(struct bio *bio, bool is_error, bool mark_dirty)
+{
+	if (op_is_write(bio_op(bio)))
+		bio_free_folios(bio);
+	else
+		bio_iov_iter_unbounce_read(bio, is_error, mark_dirty);
 }
 
 static void submit_bio_wait_endio(struct bio *bio)