dm vdo vio-pool: allow variable-sized metadata vios

With larger-sized metadata vio pools, vdo will sometimes need to
issue I/O with a smaller size than the allocated size. Since
vio_reset_bio is where the bvec array and I/O size are initialized,
this reset interface must now specify what I/O size to use.

Signed-off-by: Ken Raeburn <[e-mail]>
Signed-off-by: Matthew Sakai <[e-mail]>
Signed-off-by: Mikulas Patocka <[e-mail]>

drivers/md/dm-vdo/io-submitter.c

···
  * @error_handler: the handler for submission or I/O errors (may be NULL)
  * @operation: the type of I/O to perform
  * @data: the buffer to read or write (may be NULL)
+ * @size: the I/O amount in bytes
  *
  * The vio is enqueued on a vdo bio queue so that bio submission (which may block) does not block
  * other vdo threads.
···
  */
 void __submit_metadata_vio(struct vio *vio, physical_block_number_t physical,
 			   bio_end_io_t callback, vdo_action_fn error_handler,
-			   blk_opf_t operation, char *data)
+			   blk_opf_t operation, char *data, int size)
 {
 	int result;
 	struct vdo_completion *completion = &vio->completion;
···
 
 	vdo_reset_completion(completion);
 	completion->error_handler = error_handler;
-	result = vio_reset_bio(vio, data, callback, operation | REQ_META, physical);
+	result = vio_reset_bio_with_size(vio, data, size, callback, operation | REQ_META,
+					 physical);
 	if (result != VDO_SUCCESS) {
 		continue_vio(vio, result);
 		return;

drivers/md/dm-vdo/io-submitter.h

···
 
 #include <linux/bio.h>
 
+#include "constants.h"
 #include "types.h"
 
 struct io_submitter;
···
 
 void __submit_metadata_vio(struct vio *vio, physical_block_number_t physical,
 			   bio_end_io_t callback, vdo_action_fn error_handler,
-			   blk_opf_t operation, char *data);
+			   blk_opf_t operation, char *data, int size);
 
 static inline void vdo_submit_metadata_vio(struct vio *vio, physical_block_number_t physical,
 					   bio_end_io_t callback, vdo_action_fn error_handler,
 					   blk_opf_t operation)
 {
 	__submit_metadata_vio(vio, physical, callback, error_handler,
-			      operation, vio->data);
+			      operation, vio->data, vio->block_count * VDO_BLOCK_SIZE);
+}
+
+static inline void vdo_submit_metadata_vio_with_size(struct vio *vio,
+						     physical_block_number_t physical,
+						     bio_end_io_t callback,
+						     vdo_action_fn error_handler,
+						     blk_opf_t operation,
+						     int size)
+{
+	__submit_metadata_vio(vio, physical, callback, error_handler,
+			      operation, vio->data, size);
 }
 
 static inline void vdo_submit_flush_vio(struct vio *vio, bio_end_io_t callback,
···
 {
 	/* FIXME: Can we just use REQ_OP_FLUSH? */
 	__submit_metadata_vio(vio, 0, callback, error_handler,
-			      REQ_OP_WRITE | REQ_PREFLUSH, NULL);
+			      REQ_OP_WRITE | REQ_PREFLUSH, NULL, 0);
 }
 
 #endif /* VDO_IO_SUBMITTER_H */

drivers/md/dm-vdo/types.h

···
 	/* The size of this vio in blocks */
 	unsigned int block_count;
 
+	/* The amount of data to be read or written, in bytes */
+	unsigned int io_size;
+
 	/* The data being read or written. */
 	char *data;
 

drivers/md/dm-vdo/vio.c

···
 
 /*
  * Prepares the bio to perform IO with the specified buffer. May only be used on a VDO-allocated
- * bio, as it assumes the bio wraps a 4k buffer that is 4k aligned, but there does not have to be a
- * vio associated with the bio.
+ * bio, as it assumes the bio wraps a 4k-multiple buffer that is 4k aligned, but there does not
+ * have to be a vio associated with the bio.
  */
 int vio_reset_bio(struct vio *vio, char *data, bio_end_io_t callback,
 		  blk_opf_t bi_opf, physical_block_number_t pbn)
 {
-	int bvec_count, offset, len, i;
+	return vio_reset_bio_with_size(vio, data, vio->block_count * VDO_BLOCK_SIZE,
+				       callback, bi_opf, pbn);
+}
+
+int vio_reset_bio_with_size(struct vio *vio, char *data, int size, bio_end_io_t callback,
+			    blk_opf_t bi_opf, physical_block_number_t pbn)
+{
+	int bvec_count, offset, i;
 	struct bio *bio = vio->bio;
+	int vio_size = vio->block_count * VDO_BLOCK_SIZE;
+	int remaining;
 
 	bio_reset(bio, bio->bi_bdev, bi_opf);
 	vdo_set_bio_properties(bio, vio, callback, bi_opf, pbn);
···
 	bio->bi_ioprio = 0;
 	bio->bi_io_vec = bio->bi_inline_vecs;
 	bio->bi_max_vecs = vio->block_count + 1;
-	len = VDO_BLOCK_SIZE * vio->block_count;
+	if (VDO_ASSERT(size <= vio_size, "specified size %d is not greater than allocated %d",
+		       size, vio_size) != VDO_SUCCESS)
+		size = vio_size;
+	vio->io_size = size;
 	offset = offset_in_page(data);
-	bvec_count = DIV_ROUND_UP(offset + len, PAGE_SIZE);
+	bvec_count = DIV_ROUND_UP(offset + size, PAGE_SIZE);
+	remaining = size;
 
-	/*
-	 * If we knew that data was always on one page, or contiguous pages, we wouldn't need the
-	 * loop. But if we're using vmalloc, it's not impossible that the data is in different
-	 * pages that can't be merged in bio_add_page...
-	 */
-	for (i = 0; (i < bvec_count) && (len > 0); i++) {
+	for (i = 0; (i < bvec_count) && (remaining > 0); i++) {
 		struct page *page;
 		int bytes_added;
 		int bytes = PAGE_SIZE - offset;
 
-		if (bytes > len)
-			bytes = len;
+		if (bytes > remaining)
+			bytes = remaining;
 
 		page = is_vmalloc_addr(data) ? vmalloc_to_page(data) : virt_to_page(data);
 		bytes_added = bio_add_page(bio, page, bytes, offset);
···
 		}
 
 		data += bytes;
-		len -= bytes;
+		remaining -= bytes;
 		offset = 0;
 	}
 

drivers/md/dm-vdo/vio.h

···
 
 int vio_reset_bio(struct vio *vio, char *data, bio_end_io_t callback,
 		  blk_opf_t bi_opf, physical_block_number_t pbn);
+int vio_reset_bio_with_size(struct vio *vio, char *data, int size, bio_end_io_t callback,
+			    blk_opf_t bi_opf, physical_block_number_t pbn);
 
 void update_vio_error_stats(struct vio *vio, const char *format, ...)
 	__printf(2, 3);