[PATCH 04/19] block: add a bio_add_vmalloc helpers

Christoph Hellwig
2025-04-30T21:22:13Z

Add a helper to add a vmalloc region to a bio, abstracting away the
vmalloc addresses from the underlying pages and another one wrapping
it for the simple case where all data fits into a single bio.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
block/bio.c | 55 +++++++++++++++++++++++++++++++++++++++++++++
include/linux/bio.h | 3 +++
2 files changed, 58 insertions(+)

diff --git a/block/bio.c b/block/bio.c
index 8db2db0bba0f..1efe63e375ae 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1074,6 +1074,61 @@ bool bio_add_folio(struct bio *bio, struct folio *folio, size_t len,
}
EXPORT_SYMBOL(bio_add_folio);

+/**
+ * bio_add_vmalloc_chunk - add a vmalloc chunk to a bio
+ * @bio: destination bio
+ * @vaddr: vmalloc address to add
+ * @len: total length in bytes of the data to add
+ *
+ * Add data starting at @vaddr to @bio and return how many bytes were added.
+ * This may be less than the amount originally asked. Returns 0 if no data
+ * could be added to @bio.
+ *
+ * This helper calls flush_kernel_vmap_range() for the range added. For reads
+ * the caller still needs to manually call invalidate_kernel_vmap_range() in
+ * the completion handler.
+ */
+unsigned int bio_add_vmalloc_chunk(struct bio *bio, void *vaddr, unsigned len)
+{
+ unsigned int offset = offset_in_page(vaddr);
+
+ len = min(len, PAGE_SIZE - offset);
+ if (bio_add_page(bio, vmalloc_to_page(vaddr), len, offset) < len)
+ return 0;
+ if (op_is_write(bio_op(bio)))
+ flush_kernel_vmap_range(vaddr, len);
+ return len;
+}
+EXPORT_SYMBOL_GPL(bio_add_vmalloc_chunk);
+
+/**
+ * bio_add_vmalloc - add a vmalloc region to a bio
+ * @bio: destination bio
+ * @vaddr: vmalloc address to add
+ * @len: total length in bytes of the data to add
+ *
+ * Add data starting at @vaddr to @bio. Return %true on success or %false if
+ * @bio does not have enough space for the payload.
+ *
+ * This helper calls flush_kernel_vmap_range() for the range added. For reads
+ * the caller still needs to manually call invalidate_kernel_vmap_range() in
+ * the completion handler.
+ */
+bool bio_add_vmalloc(struct bio *bio, void *vaddr, unsigned int len)
+{
+ do {
+ unsigned int added = bio_add_vmalloc_chunk(bio, vaddr, len);
+
+ if (!added)
+ return false;
+ vaddr += added;
+ len -= added;
+ } while (len);
+
+ return true;
+}
+EXPORT_SYMBOL_GPL(bio_add_vmalloc);
+
void __bio_release_pages(struct bio *bio, bool mark_dirty)
{
struct folio_iter fi;
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 128b1c6ca648..5d880903bcc5 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -433,6 +433,9 @@ static inline unsigned int bio_add_max_vecs(void *kaddr, unsigned int len)
return 1;
}

+unsigned int bio_add_vmalloc_chunk(struct bio *bio, void *vaddr, unsigned len);
+bool bio_add_vmalloc(struct bio *bio, void *vaddr, unsigned int len);
+
int submit_bio_wait(struct bio *bio);
int bdev_rw_virt(struct block_device *bdev, sector_t sector, void *data,
size_t len, enum req_op op);
--
2.47.2