trying allocating only one page to pass phys. addr

src/block/bio.c

@@ -843,7 +843,7 @@ EXPORT_SYMBOL(bio_add_page);
  * the next non-empty segment of the iov iterator.
  */
 // undefine to skip
-#define SUSPECT_MMAPED (4 * PAGE_SIZE)
+//#define ELPHEL_SUSPECT_MMAPED (4 * PAGE_SIZE)
 static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
 {
 	unsigned short nr_pages = bio->bi_max_vecs - bio->bi_vcnt, idx;
@@ -851,6 +851,7 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
 	struct page **pages = (struct page **)bv;
 	size_t offset;
 	ssize_t size;
+	int single_page = 0;
 	if (bio->bi_disk && (bio->bi_disk->major == 8)) { // sda, sda*
 		pr_debug(" *A* nr_pages=0x%04x,bio->bi_max_vecs=0x%04x, bio->bi_vcnt=0x%04x", nr_pages, bio->bi_max_vecs, bio->bi_vcnt); //  *A* nr_pages=0x009f,bio->bi_max_vecs=0x009f, bio->bi_vcnt==0x0000
 		pr_debug(" *A0* max_hw_sectors=%d,  max_dev_sectors=%d, max_sectors=%d, cluster=%d, max_segment_size=0x%08x",\
@@ -872,24 +873,33 @@ fail.
 		pr_debug(" *B* niter->type=%d, iter->iov_offset=0x%08x, iter->count=0x%08x, iter->nr_segs=0x%08lx",\
 				iter->type, iter->iov_offset,iter->count,iter->nr_segs); // *B* niter->type=1, iter->iov_offset=0x00000000, iter->count=0x0009f000, iter->nr_segs=0x00000001
 	}
+#ifdef ELPHEL_MMAP_PAGED
 // If suspected "Elphel" - try it first?
-#ifdef SUSPECT_MMAPED
-	if (( bio->bi_vcnt == 0) && (iter->iov_offset == 0) && (iter->nr_segs == 1) && (iter->count >= SUSPECT_MMAPED)) {
-		pr_debug(" *B1* Suspecting mmaped memory, iter->count=0x%08x > 0x%08x", iter->count, (int) SUSPECT_MMAPED);
+#ifdef ELPHEL_SUSPECT_MMAPED
+	if (( bio->bi_vcnt == 0) && (iter->iov_offset == 0) && (iter->nr_segs == 1) && (iter->count >= ELPHEL_SUSPECT_MMAPED)) {
+		pr_debug(" *B1* Suspecting mmaped memory, iter->count=0x%08x > 0x%08x", iter->count, (int) ELPHEL_SUSPECT_MMAPED);
 		size= iov_iter_get_pages_elphel(iter, pages, LONG_MAX, nr_pages, &offset);  // try mmap-ed
 		if (size < 0){
 			pr_debug("mmaped failed (err=%d) trying pinning userspace memory", size);
 			size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset);  // regular way with userspace
+#ifdef ELPHEL_MMAP_SINGLE_PAGE
+		} else {
+			single_page = 1;
+#endif
 		}
 	} else {
 		size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset); // regular way with userspace
 	}
+#else
+	size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset);
+#endif
 #else
 	size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset);
 #endif
 	if (unlikely(size <= 0)) {
 		pr_debug("Error=%d, trying continuous mmap-ed pages, bio->bi_vcnt=0x%04x,  bio->bi_max_vecs=0x%04x, offset=0x%08x",
 				size, bio->bi_vcnt,  bio->bi_max_vecs, offset);
+#ifdef ELPHEL_MMAP_PAGED
 		if ((size == -EFAULT) && ( bio->bi_vcnt == 0) && (iter->iov_offset == 0) && (iter->nr_segs == 1)){ // Only for all pages, single segment
 			size= iov_iter_get_pages_elphel(iter, pages, LONG_MAX, nr_pages, &offset);
 		}
@@ -897,32 +907,51 @@ fail.
 			pr_debug("Error after iov_iter_get_pages_elphel: %d, trying continuous mmap-ed pages, bio->bi_vcnt=0x%04x,  bio->bi_max_vecs=0x%04x, offset=0x%08x",
 					size, bio->bi_vcnt,  bio->bi_max_vecs, offset);
 			return size ? size : -EFAULT;
+#ifdef ELPHEL_MMAP_SINGLE_PAGE
+		}  else {
+			single_page = 1;
+#endif
 		}
+#else
+		return size ? size : -EFAULT;
+#endif
 	}
-	idx = nr_pages = (size + offset + PAGE_SIZE - 1) / PAGE_SIZE;
-	if (bio->bi_disk && (bio->bi_disk->major == 8)) { // sda, sda*
-		pr_debug(" *C* nr_pages=0x%04x, size=0x%08x, offset==0x%04x", nr_pages, size, offset); // *C* nr_pages=0x009f, size=0x0009f000, offset==0x0000
-	}
-	/*
-	 * Deep magic below:  We need to walk the pinned pages backwards
-	 * because we are abusing the space allocated for the bio_vecs
-	 * for the page array.  Because the bio_vecs are larger than the
-	 * page pointers by definition this will always work.  But it also
-	 * means we can't use bio_add_page, so any changes to it's semantics
-	 * need to be reflected here as well.
-	 */
-	bio->bi_iter.bi_size += size;
-	bio->bi_vcnt += nr_pages;
+	if (single_page) {
+		nr_pages = 1;
+		bio->bi_iter.bi_size += size;
+		bio->bi_vcnt += nr_pages;
+		bv[0].bv_page = pages[idx];
+		bv[0].bv_len = size;
+		bv[0].bv_offset = offset;
+		if (bio->bi_disk && (bio->bi_disk->major == 8)) { // sda, sda*
+			pr_debug(" *C1* nr_pages=0x%04x, size=0x%08x, offset==0x%04x", nr_pages, size, offset); // *C* nr_pages=0x009f, size=0x0009f000, offset==0x0000
+		}
+	} else {
+		idx = nr_pages = (size + offset + PAGE_SIZE - 1) / PAGE_SIZE;
+		if (bio->bi_disk && (bio->bi_disk->major == 8)) { // sda, sda*
+			pr_debug(" *C0* nr_pages=0x%04x, size=0x%08x, offset==0x%04x", nr_pages, size, offset); // *C* nr_pages=0x009f, size=0x0009f000, offset==0x0000
+		}
+		/*
+		 * Deep magic below:  We need to walk the pinned pages backwards
+		 * because we are abusing the space allocated for the bio_vecs
+		 * for the page array.  Because the bio_vecs are larger than the
+		 * page pointers by definition this will always work.  But it also
+		 * means we can't use bio_add_page, so any changes to it's semantics
+		 * need to be reflected here as well.
+		 */
+		bio->bi_iter.bi_size += size;
+		bio->bi_vcnt += nr_pages;
 
-	while (idx--) {
-		bv[idx].bv_page = pages[idx];
-		bv[idx].bv_len = PAGE_SIZE;
-		bv[idx].bv_offset = 0;
+		while (idx--) {
+			bv[idx].bv_page = pages[idx];
+			bv[idx].bv_len = PAGE_SIZE;
+			bv[idx].bv_offset = 0;
+		}
+		// trim first and last page
+		bv[0].bv_offset += offset;
+		bv[0].bv_len -= offset;
+		bv[nr_pages - 1].bv_len -= nr_pages * PAGE_SIZE - offset - size;
 	}
-    // trim first and last page
-	bv[0].bv_offset += offset;
-	bv[0].bv_len -= offset;
-	bv[nr_pages - 1].bv_len -= nr_pages * PAGE_SIZE - offset - size;
 	if (bio->bi_disk && (bio->bi_disk->major == 8)) { // sda, sda* *D* nr_pages=0x00a0, size=0x000a0000, offset=0x0000, iter->count=0x000a0000, iter->nr_segs=0x00000001
 		pr_debug(" *D* nr_pages=0x%04x, size=0x%08x, offset=0x%04x, iter->count=0x%08x, iter->nr_segs=0x%08lx", nr_pages, size, offset, iter->count, iter->nr_segs);
 	}
@@ -932,7 +961,6 @@ fail.
 				iter->type, iter->iov_offset, iter->count, iter->nr_segs);
 		pr_debug(" *F* nr_pages=0x%04x, size=0x%08x, offset==0x%04x", nr_pages, size, offset); // *F* nr_pages=0x009f, size=0x0009f000, offset==0x0000
 	}
-
 	return 0;
 }
 
@@ -963,6 +991,48 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
 }
 EXPORT_SYMBOL_GPL(bio_iov_iter_get_pages);
 
+int bio_iov_iter_get_pages_elphel(struct bio *bio, struct iov_iter *iter)
+{
+	int indx, n; // page index
+//	size_t offset;
+//	ssize_t size;
+	size_t len;
+	struct bio_vec *bv = bio->bi_io_vec + bio->bi_vcnt; // bio->bi_vcnt should be 0
+	const struct iovec *iov = iter->iov; // only use first in array - supposed to be a single-element
+	unsigned long paddr = 0; // physical address where to write
+	unsigned long addr;
+	unsigned long vaddr = (unsigned long) iov->iov_base;
+	struct vm_area_struct *vm_area;
+	if (iter->nr_segs != 1){
+		pr_debug("nr_segs = %d != 1", iter->nr_segs);
+		return -EINVAL;
+	}
+
+//	pr_debug("sizeof(struct vm_area_struct)=%d", sizeof(struct vm_area_struct));
+	for (vm_area = current->mm->mmap; vm_area;  vm_area = vm_area-> vm_next) {
+		if ((vaddr >= vm_area->vm_start) && (vaddr < vm_area->vm_end)) {
+			pr_debug("physical address = 0x%08lx", (unsigned long) vm_area->vm_private_data);
+			print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, vm_area, sizeof(struct vm_area_struct));
+			paddr = (unsigned long) vm_area->vm_private_data;
+			if (paddr) {
+				paddr += vaddr - vm_area->vm_start; // added offset within buffer
+			}
+			break;
+		}
+	}
+	if (!paddr){
+		pr_debug("mmap-ed physical address is not specified in vm_area->vm_private_data, aborting");
+		return -EINVAL;
+	}
+	pr_debug("virtual address = 0x%08lx, physical address = 0x%08lx", vaddr, paddr);
+
+	bv[0].bv_page = NULL;         // Make sure it will not be tried to release
+	bv[0].bv_len =  iov->iov_len;
+	bv[0].bv_offset = 0;
+
+
+
+}
 
 static void submit_bio_wait_endio(struct bio *bio)
 {

src/block/blk-core.c

@@ -2466,7 +2466,8 @@ blk_qc_t generic_make_request(struct bio *bio)
 			}
 		}
         if (bio->bi_disk && (bio->bi_disk->major == 8)) { // sda, sda*
-        	pr_debug(" *{* bio->bi_flags=0x%04x, bio->bi_phys_segments=0x%08x, enter_succeeded=%d",bio->bi_flags, bio->bi_phys_segments, enter_succeeded);
+        	pr_debug(" *{* state before blk_mq_make_request(): bio->bi_flags=0x%04x, bio->bi_phys_segments=0x%08x, enter_succeeded=%d",bio->bi_flags, bio->bi_phys_segments, enter_succeeded);
+        	print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, bio, sizeof(struct bio));
         }
 		if (enter_succeeded) {
 			struct bio_list lower, same;
@@ -2474,7 +2475,7 @@ blk_qc_t generic_make_request(struct bio *bio)
 			/* Create a fresh bio_list for all subordinate requests */
 			bio_list_on_stack[1] = bio_list_on_stack[0];
 			bio_list_init(&bio_list_on_stack[0]);
-			ret = q->make_request_fn(q, bio);
+			ret = q->make_request_fn(q, bio); // in this case -> blk_mq_make_request()
 			if (bio->bi_disk && (bio->bi_disk->major == 8)) { // sda, sda*
 				pr_debug("q->make_request_fn(q, bio) -> %u", ret);
 			}

src/block/blk-merge.c

@@ -238,6 +238,7 @@ void blk_queue_split(struct request_queue *q, struct bio **bio)
 		split = blk_bio_write_same_split(q, *bio, &q->bio_split, &nsegs);
 		break;
 	default:
+		 // *** INCREASE q->limits.max_segment_size, it is set from  BLK_MAX_SEGMENT_SIZE = 65536 (include/linux/blkdev.h:1429:) Elphel 06/14/2023
 		split = blk_bio_segment_split(q, *bio, &q->bio_split, &nsegs);
 		break;
 	}

src/block/blk-mq.c

@@ -1830,8 +1830,8 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
     if (bio->bi_disk && (bio->bi_disk->major == 8)) { // sda, sda*
     	pr_debug(" *1* bio->bi_flags=0x%04x, bio->bi_phys_segments=0x%08x",bio->bi_flags, bio->bi_phys_segments); // not yet set
     }
+	 // *** INCREASE q->limits.max_segment_size, it is set from  BLK_MAX_SEGMENT_SIZE = 65536 (include/linux/blkdev.h:1429:) Elphel 06/14/2023
 	blk_queue_split(q, &bio);
-
     if (bio->bi_disk && (bio->bi_disk->major == 8)) { // sda, sda* already split - 0xa segments (16 pages each)
     	pr_debug(" *2* bio->bi_flags=0x%04x, bio->bi_phys_segments=0x%08x",bio->bi_flags, bio->bi_phys_segments); // already set
     }
@@ -2592,7 +2592,7 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
 						  struct request_queue *q)
 {
 //    if (bio->bi_disk && (bio->bi_disk->major == 8)) { // sda, sda*
-    	pr_debug(" *-* ");
+    	pr_debug(" *-* "); // never
 //    }
 	/* mark the queue as mq asap */
 	q->mq_ops = set->ops;

src/fs/block_dev.c

@@ -190,7 +190,7 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter,
 {
 	struct file *file = iocb->ki_filp;
 	struct block_device *bdev = I_BDEV(bdev_file_inode(file));
-	struct bio_vec inline_vecs[DIO_INLINE_BIO_VECS], *vecs, *bvec;
+	struct bio_vec inline_vecs[DIO_INLINE_BIO_VECS], *vecs, *bvec; // Elphel: may reduce it again
 	loff_t pos = iocb->ki_pos;
 	bool should_dirty = false;
 	struct bio bio;
@@ -222,7 +222,8 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter,
 	bio.bi_private = current;
 	bio.bi_end_io = blkdev_bio_end_io_simple;
 	bio.bi_ioprio = iocb->ki_ioprio;
-	ret = bio_iov_iter_get_pages(&bio, iter);
+
+	ret = bio_iov_iter_get_pages(&bio, iter); // normally returns 0
 	pr_debug("ret = %d, bio.bi_vcnt=%d", ret, bio.bi_vcnt); // -14
 	if (unlikely(ret))
 		goto out;
@@ -236,6 +237,7 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter,
 		bio.bi_opf = dio_bio_write_op(iocb);
 		task_io_account_write(ret);
 	}
+	pr_debug("bio:");
 	print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, &bio, sizeof(struct bio));
 //	pr_debug("bi_disk=0x%p, bi_sector=%llu, bi_size=%u, bi_private=0x%p, bi_vcnt=%u, bi_max_vecs=%u, bi_io_vec=0x%p, bi_pool=0x%p",
 //			bio.bi_disk, bio.bi_iter.bi_sector, bio.bi_iter.bi_size, bio.bi_private, bio.bi_vcnt, bio.bi_max_vecs, bio.bi_io_vec, bio.bi_pool);
@@ -250,8 +252,14 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter,
 		}
 	}
 	pr_debug("ARCH_PFN_OFFSET =0x%08lx, PHYS_PFN_OFFSET=0x%08lx, mem_map=0x%08x, bi_phys_segments=0x%08x", \
-			ARCH_PFN_OFFSET, PHYS_PFN_OFFSET, (int) mem_map, bio.bi_phys_segments);
+			ARCH_PFN_OFFSET, PHYS_PFN_OFFSET, (int) mem_map, bio.bi_phys_segments); // bi_phys_segments==0
+
+
+
+
 	qc = submit_bio(&bio);
+	pr_debug("After qc = submit_bio(&bio), bio:");
+	print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, &bio, sizeof(struct bio));
 	for (;;) {
 		set_current_state(TASK_UNINTERRUPTIBLE);
 		if (!READ_ONCE(bio.bi_private))

src/lib/iov_iter.c

@@ -1263,7 +1263,11 @@ ssize_t iov_iter_get_pages_elphel(struct iov_iter *i,
 	if (len > maxpages * PAGE_SIZE)
 		len = maxpages * PAGE_SIZE;
 	addr &= ~(PAGE_SIZE - 1);
+#ifdef 	ELPHEL_MMAP_SINGLE_PAGE
+	n = 1; // only pin a single (first) page
+#else
 	n = DIV_ROUND_UP(len, PAGE_SIZE);
+#endif
 	for (indx = 0; indx < n; indx++){
 		if ((cur_page -> compound_head) & 1){
 			pr_debug("**** COMPOUND HEAD! ****");