Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 682 insertions, 0 deletions

diff --git a/block/blk-map.c b/block/blk-map.c
new file mode 100644
index 000000000..9cb9605d1
--- /dev/null
+++ b/block/blk-map.c
@@ -0,0 +1,682 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Functions related to mapping data to requests
+ */
+#include <linux/kernel.h>
+#include <linux/sched/task_stack.h>
+#include <linux/module.h>
+#include <linux/bio.h>
+#include <linux/blkdev.h>
+#include <linux/uio.h>
+
+#include "blk.h"
+
+struct bio_map_data {
+	bool is_our_pages : 1;
+	bool is_null_mapped : 1;
+	struct iov_iter iter;
+	struct iovec iov[];
+};
+
+static struct bio_map_data *bio_alloc_map_data(struct iov_iter *data,
+					       gfp_t gfp_mask)
+{
+	struct bio_map_data *bmd;
+
+	if (data->nr_segs > UIO_MAXIOV)
+		return NULL;
+
+	bmd = kmalloc_flex(*bmd, iov, data->nr_segs, gfp_mask);
+	if (!bmd)
+		return NULL;
+	bmd->iter = *data;
+	if (iter_is_iovec(data)) {
+		memcpy(bmd->iov, iter_iov(data), sizeof(struct iovec) * data->nr_segs);
+		bmd->iter.__iov = bmd->iov;
+	}
+	return bmd;
+}
+
+static inline void blk_mq_map_bio_put(struct bio *bio)
+{
+	bio_put(bio);
+}
+
+static struct bio *blk_rq_map_bio_alloc(struct request *rq,
+		unsigned int nr_vecs, gfp_t gfp_mask)
+{
+	struct block_device *bdev = rq->q->disk ? rq->q->disk->part0 : NULL;
+	struct bio *bio;
+
+	bio = bio_alloc_bioset(bdev, nr_vecs, rq->cmd_flags, gfp_mask,
+				&fs_bio_set);
+	if (!bio)
+		return NULL;
+
+	return bio;
+}
+
+/**
+ * bio_copy_from_iter - copy all pages from iov_iter to bio
+ * @bio: The &struct bio which describes the I/O as destination
+ * @iter: iov_iter as source
+ *
+ * Copy all pages from iov_iter to bio.
+ * Returns 0 on success, or error on failure.
+ */
+static int bio_copy_from_iter(struct bio *bio, struct iov_iter *iter)
+{
+	struct bio_vec *bvec;
+	struct bvec_iter_all iter_all;
+
+	bio_for_each_segment_all(bvec, bio, iter_all) {
+		ssize_t ret;
+
+		ret = copy_page_from_iter(bvec->bv_page,
+					  bvec->bv_offset,
+					  bvec->bv_len,
+					  iter);
+
+		if (!iov_iter_count(iter))
+			break;
+
+		if (ret < bvec->bv_len)
+			return -EFAULT;
+	}
+
+	return 0;
+}
+
+/**
+ * bio_copy_to_iter - copy all pages from bio to iov_iter
+ * @bio: The &struct bio which describes the I/O as source
+ * @iter: iov_iter as destination
+ *
+ * Copy all pages from bio to iov_iter.
+ * Returns 0 on success, or error on failure.
+ */
+static int bio_copy_to_iter(struct bio *bio, struct iov_iter iter)
+{
+	struct bio_vec *bvec;
+	struct bvec_iter_all iter_all;
+
+	bio_for_each_segment_all(bvec, bio, iter_all) {
+		ssize_t ret;
+
+		ret = copy_page_to_iter(bvec->bv_page,
+					bvec->bv_offset,
+					bvec->bv_len,
+					&iter);
+
+		if (!iov_iter_count(&iter))
+			break;
+
+		if (ret < bvec->bv_len)
+			return -EFAULT;
+	}
+
+	return 0;
+}
+
+/**
+ *	bio_uncopy_user	-	finish previously mapped bio
+ *	@bio: bio being terminated
+ *
+ *	Free pages allocated from bio_copy_user_iov() and write back data
+ *	to user space in case of a read.
+ */
+static int bio_uncopy_user(struct bio *bio)
+{
+	struct bio_map_data *bmd = bio->bi_private;
+	int ret = 0;
+
+	if (!bmd->is_null_mapped) {
+		/*
+		 * if we're in a workqueue, the request is orphaned, so
+		 * don't copy into a random user address space, just free
+		 * and return -EINTR so user space doesn't expect any data.
+		 */
+		if (!current->mm)
+			ret = -EINTR;
+		else if (bio_data_dir(bio) == READ)
+			ret = bio_copy_to_iter(bio, bmd->iter);
+		if (bmd->is_our_pages)
+			bio_free_pages(bio);
+	}
+	kfree(bmd);
+	return ret;
+}
+
+static int bio_copy_user_iov(struct request *rq, struct rq_map_data *map_data,
+		struct iov_iter *iter, gfp_t gfp_mask)
+{
+	struct bio_map_data *bmd;
+	struct page *page;
+	struct bio *bio;
+	int i = 0, ret;
+	int nr_pages;
+	unsigned int len = iter->count;
+	unsigned int offset = map_data ? offset_in_page(map_data->offset) : 0;
+
+	bmd = bio_alloc_map_data(iter, gfp_mask);
+	if (!bmd)
+		return -ENOMEM;
+
+	/*
+	 * We need to do a deep copy of the iov_iter including the iovecs.
+	 * The caller provided iov might point to an on-stack or otherwise
+	 * shortlived one.
+	 */
+	bmd->is_our_pages = !map_data;
+	bmd->is_null_mapped = (map_data && map_data->null_mapped);
+
+	nr_pages = bio_max_segs(DIV_ROUND_UP(offset + len, PAGE_SIZE));
+
+	ret = -ENOMEM;
+	bio = blk_rq_map_bio_alloc(rq, nr_pages, gfp_mask);
+	if (!bio)
+		goto out_bmd;
+
+	if (map_data) {
+		nr_pages = 1U << map_data->page_order;
+		i = map_data->offset / PAGE_SIZE;
+	}
+	while (len) {
+		unsigned int bytes = PAGE_SIZE;
+
+		bytes -= offset;
+
+		if (bytes > len)
+			bytes = len;
+
+		if (map_data) {
+			if (i == map_data->nr_entries * nr_pages) {
+				ret = -ENOMEM;
+				goto cleanup;
+			}
+
+			page = map_data->pages[i / nr_pages];
+			page += (i % nr_pages);
+
+			i++;
+		} else {
+			page = alloc_page(GFP_NOIO | gfp_mask);
+			if (!page) {
+				ret = -ENOMEM;
+				goto cleanup;
+			}
+		}
+
+		if (bio_add_page(bio, page, bytes, offset) < bytes) {
+			if (!map_data)
+				__free_page(page);
+			break;
+		}
+
+		len -= bytes;
+		offset = 0;
+	}
+
+	if (map_data)
+		map_data->offset += bio->bi_iter.bi_size;
+
+	/*
+	 * success
+	 */
+	if (iov_iter_rw(iter) == WRITE &&
+	     (!map_data || !map_data->null_mapped)) {
+		ret = bio_copy_from_iter(bio, iter);
+		if (ret)
+			goto cleanup;
+	} else if (map_data && map_data->from_user) {
+		struct iov_iter iter2 = *iter;
+
+		/* This is the copy-in part of SG_DXFER_TO_FROM_DEV. */
+		iter2.data_source = ITER_SOURCE;
+		ret = bio_copy_from_iter(bio, &iter2);
+		if (ret)
+			goto cleanup;
+	} else {
+		if (bmd->is_our_pages)
+			zero_fill_bio(bio);
+		iov_iter_advance(iter, bio->bi_iter.bi_size);
+	}
+
+	bio->bi_private = bmd;
+
+	ret = blk_rq_append_bio(rq, bio);
+	if (ret)
+		goto cleanup;
+	return 0;
+cleanup:
+	if (!map_data)
+		bio_free_pages(bio);
+	blk_mq_map_bio_put(bio);
+out_bmd:
+	kfree(bmd);
+	return ret;
+}
+
+static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
+		gfp_t gfp_mask)
+{
+	unsigned int nr_vecs = iov_iter_npages(iter, BIO_MAX_VECS);
+	struct bio *bio;
+	int ret;
+
+	if (!iov_iter_count(iter))
+		return -EINVAL;
+
+	bio = blk_rq_map_bio_alloc(rq, nr_vecs, gfp_mask);
+	if (!bio)
+		return -ENOMEM;
+	/*
+	 * No alignment requirements on our part to support arbitrary
+	 * passthrough commands.
+	 */
+	ret = bio_iov_iter_get_pages(bio, iter, 0, 0);
+	if (ret)
+		goto out_put;
+	ret = blk_rq_append_bio(rq, bio);
+	if (ret)
+		goto out_release;
+	return 0;
+
+out_release:
+	bio_release_pages(bio, false);
+out_put:
+	blk_mq_map_bio_put(bio);
+	return ret;
+}
+
+static void bio_invalidate_vmalloc_pages(struct bio *bio)
+{
+#ifdef ARCH_IMPLEMENTS_FLUSH_KERNEL_VMAP_RANGE
+	if (bio->bi_private && !op_is_write(bio_op(bio))) {
+		unsigned long i, len = 0;
+
+		for (i = 0; i < bio->bi_vcnt; i++)
+			len += bio->bi_io_vec[i].bv_len;
+		invalidate_kernel_vmap_range(bio->bi_private, len);
+	}
+#endif
+}
+
+static void bio_map_kern_endio(struct bio *bio)
+{
+	bio_invalidate_vmalloc_pages(bio);
+	blk_mq_map_bio_put(bio);
+}
+
+static struct bio *bio_map_kern(struct request *rq, void *data, unsigned int len,
+		gfp_t gfp_mask)
+{
+	unsigned int nr_vecs = bio_add_max_vecs(data, len);
+	struct bio *bio;
+
+	bio = blk_rq_map_bio_alloc(rq, nr_vecs, gfp_mask);
+	if (!bio)
+		return ERR_PTR(-ENOMEM);
+
+	if (is_vmalloc_addr(data)) {
+		bio->bi_private = data;
+		if (!bio_add_vmalloc(bio, data, len)) {
+			blk_mq_map_bio_put(bio);
+			return ERR_PTR(-EINVAL);
+		}
+	} else {
+		bio_add_virt_nofail(bio, data, len);
+	}
+	bio->bi_end_io = bio_map_kern_endio;
+	return bio;
+}
+
+static void bio_copy_kern_endio(struct bio *bio)
+{
+	bio_free_pages(bio);
+	blk_mq_map_bio_put(bio);
+}
+
+static void bio_copy_kern_endio_read(struct bio *bio)
+{
+	char *p = bio->bi_private;
+	struct bio_vec *bvec;
+	struct bvec_iter_all iter_all;
+
+	bio_for_each_segment_all(bvec, bio, iter_all) {
+		memcpy_from_bvec(p, bvec);
+		p += bvec->bv_len;
+	}
+
+	bio_copy_kern_endio(bio);
+}
+
+/**
+ *	bio_copy_kern	-	copy kernel address into bio
+ *	@rq: request to fill
+ *	@data: pointer to buffer to copy
+ *	@len: length in bytes
+ *	@op: bio/request operation
+ *	@gfp_mask: allocation flags for bio and page allocation
+ *
+ *	copy the kernel address into a bio suitable for io to a block
+ *	device. Returns an error pointer in case of error.
+ */
+static struct bio *bio_copy_kern(struct request *rq, void *data, unsigned int len,
+		gfp_t gfp_mask)
+{
+	enum req_op op = req_op(rq);
+	unsigned long kaddr = (unsigned long)data;
+	unsigned long end = (kaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	unsigned long start = kaddr >> PAGE_SHIFT;
+	struct bio *bio;
+	void *p = data;
+	int nr_pages = 0;
+
+	/*
+	 * Overflow, abort
+	 */
+	if (end < start)
+		return ERR_PTR(-EINVAL);
+
+	nr_pages = end - start;
+	bio = blk_rq_map_bio_alloc(rq, nr_pages, gfp_mask);
+	if (!bio)
+		return ERR_PTR(-ENOMEM);
+
+	while (len) {
+		struct page *page;
+		unsigned int bytes = PAGE_SIZE;
+
+		if (bytes > len)
+			bytes = len;
+
+		page = alloc_page(GFP_NOIO | __GFP_ZERO | gfp_mask);
+		if (!page)
+			goto cleanup;
+
+		if (op_is_write(op))
+			memcpy(page_address(page), p, bytes);
+
+		__bio_add_page(bio, page, bytes, 0);
+
+		len -= bytes;
+		p += bytes;
+	}
+
+	if (op_is_write(op)) {
+		bio->bi_end_io = bio_copy_kern_endio;
+	} else {
+		bio->bi_end_io = bio_copy_kern_endio_read;
+		bio->bi_private = data;
+	}
+
+	return bio;
+
+cleanup:
+	bio_free_pages(bio);
+	blk_mq_map_bio_put(bio);
+	return ERR_PTR(-ENOMEM);
+}
+
+/*
+ * Append a bio to a passthrough request.  Only works if the bio can be merged
+ * into the request based on the driver constraints.
+ */
+int blk_rq_append_bio(struct request *rq, struct bio *bio)
+{
+	const struct queue_limits *lim = &rq->q->limits;
+	unsigned int max_bytes = lim->max_hw_sectors << SECTOR_SHIFT;
+	unsigned int nr_segs = 0;
+	int ret;
+
+	/* check that the data layout matches the hardware restrictions */
+	ret = bio_split_io_at(bio, lim, &nr_segs, max_bytes, 0);
+	if (ret) {
+		/* if we would have to split the bio, copy instead */
+		if (ret > 0)
+			ret = -EREMOTEIO;
+		return ret;
+	}
+
+	if (rq->bio) {
+		if (!ll_back_merge_fn(rq, bio, nr_segs))
+			return -EINVAL;
+		rq->phys_gap_bit = bio_seg_gap(rq->q, rq->biotail, bio,
+					       rq->phys_gap_bit);
+		rq->biotail->bi_next = bio;
+		rq->biotail = bio;
+		rq->__data_len += bio->bi_iter.bi_size;
+		bio_crypt_free_ctx(bio);
+		return 0;
+	}
+
+	rq->nr_phys_segments = nr_segs;
+	rq->bio = rq->biotail = bio;
+	rq->__data_len = bio->bi_iter.bi_size;
+	rq->phys_gap_bit = bio->bi_bvec_gap_bit;
+	return 0;
+}
+EXPORT_SYMBOL(blk_rq_append_bio);
+
+/* Prepare bio for passthrough IO given ITER_BVEC iter */
+static int blk_rq_map_user_bvec(struct request *rq, const struct iov_iter *iter)
+{
+	unsigned int max_bytes = rq->q->limits.max_hw_sectors << SECTOR_SHIFT;
+	struct bio *bio;
+	int ret;
+
+	if (!iov_iter_count(iter) || iov_iter_count(iter) > max_bytes)
+		return -EINVAL;
+
+	/* reuse the bvecs from the iterator instead of allocating new ones */
+	bio = blk_rq_map_bio_alloc(rq, 0, GFP_KERNEL);
+	if (!bio)
+		return -ENOMEM;
+	bio_iov_iter_set(bio, iter);
+
+	ret = blk_rq_append_bio(rq, bio);
+	if (ret)
+		blk_mq_map_bio_put(bio);
+	return ret;
+}
+
+/**
+ * blk_rq_map_user_iov - map user data to a request, for passthrough requests
+ * @q:		request queue where request should be inserted
+ * @rq:		request to map data to
+ * @map_data:   pointer to the rq_map_data holding pages (if necessary)
+ * @iter:	iovec iterator
+ * @gfp_mask:	memory allocation flags
+ *
+ * Description:
+ *    Data will be mapped directly for zero copy I/O, if possible. Otherwise
+ *    a kernel bounce buffer is used.
+ *
+ *    A matching blk_rq_unmap_user() must be issued at the end of I/O, while
+ *    still in process context.
+ */
+int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
+			struct rq_map_data *map_data,
+			const struct iov_iter *iter, gfp_t gfp_mask)
+{
+	bool copy = false, map_bvec = false;
+	unsigned long align = blk_lim_dma_alignment_and_pad(&q->limits);
+	struct bio *bio = NULL;
+	struct iov_iter i;
+	int ret = -EINVAL;
+
+	if (map_data)
+		copy = true;
+	else if (iov_iter_alignment(iter) & align)
+		copy = true;
+	else if (iov_iter_is_bvec(iter))
+		map_bvec = true;
+	else if (!user_backed_iter(iter))
+		copy = true;
+	else if (queue_virt_boundary(q))
+		copy = queue_virt_boundary(q) & iov_iter_gap_alignment(iter);
+
+	if (map_bvec) {
+		ret = blk_rq_map_user_bvec(rq, iter);
+		if (!ret)
+			return 0;
+		if (ret != -EREMOTEIO)
+			goto fail;
+		/* fall back to copying the data on limits mismatches */
+		copy = true;
+	}
+
+	i = *iter;
+	do {
+		if (copy)
+			ret = bio_copy_user_iov(rq, map_data, &i, gfp_mask);
+		else
+			ret = bio_map_user_iov(rq, &i, gfp_mask);
+		if (ret) {
+			if (ret == -EREMOTEIO)
+				ret = -EINVAL;
+			goto unmap_rq;
+		}
+		if (!bio)
+			bio = rq->bio;
+	} while (iov_iter_count(&i));
+
+	return 0;
+
+unmap_rq:
+	blk_rq_unmap_user(bio);
+fail:
+	rq->bio = NULL;
+	return ret;
+}
+EXPORT_SYMBOL(blk_rq_map_user_iov);
+
+int blk_rq_map_user(struct request_queue *q, struct request *rq,
+		    struct rq_map_data *map_data, void __user *ubuf,
+		    unsigned long len, gfp_t gfp_mask)
+{
+	struct iov_iter i;
+	int ret = import_ubuf(rq_data_dir(rq), ubuf, len, &i);
+
+	if (unlikely(ret < 0))
+		return ret;
+
+	return blk_rq_map_user_iov(q, rq, map_data, &i, gfp_mask);
+}
+EXPORT_SYMBOL(blk_rq_map_user);
+
+int blk_rq_map_user_io(struct request *req, struct rq_map_data *map_data,
+		void __user *ubuf, unsigned long buf_len, gfp_t gfp_mask,
+		bool vec, int iov_count, bool check_iter_count, int rw)
+{
+	int ret = 0;
+
+	if (vec) {
+		struct iovec fast_iov[UIO_FASTIOV];
+		struct iovec *iov = fast_iov;
+		struct iov_iter iter;
+
+		ret = import_iovec(rw, ubuf, iov_count ? iov_count : buf_len,
+				UIO_FASTIOV, &iov, &iter);
+		if (ret < 0)
+			return ret;
+
+		if (iov_count) {
+			/* SG_IO howto says that the shorter of the two wins */
+			iov_iter_truncate(&iter, buf_len);
+			if (check_iter_count && !iov_iter_count(&iter)) {
+				kfree(iov);
+				return -EINVAL;
+			}
+		}
+
+		ret = blk_rq_map_user_iov(req->q, req, map_data, &iter,
+				gfp_mask);
+		kfree(iov);
+	} else if (buf_len) {
+		ret = blk_rq_map_user(req->q, req, map_data, ubuf, buf_len,
+				gfp_mask);
+	}
+	return ret;
+}
+EXPORT_SYMBOL(blk_rq_map_user_io);
+
+/**
+ * blk_rq_unmap_user - unmap a request with user data
+ * @bio:	       start of bio list
+ *
+ * Description:
+ *    Unmap a rq previously mapped by blk_rq_map_user(). The caller must
+ *    supply the original rq->bio from the blk_rq_map_user() return, since
+ *    the I/O completion may have changed rq->bio.
+ */
+int blk_rq_unmap_user(struct bio *bio)
+{
+	struct bio *next_bio;
+	int ret = 0, ret2;
+
+	while (bio) {
+		if (bio->bi_private) {
+			ret2 = bio_uncopy_user(bio);
+			if (ret2 && !ret)
+				ret = ret2;
+		} else {
+			bio_release_pages(bio, bio_data_dir(bio) == READ);
+		}
+
+		if (bio_integrity(bio))
+			bio_integrity_unmap_user(bio);
+
+		next_bio = bio;
+		bio = bio->bi_next;
+		blk_mq_map_bio_put(next_bio);
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(blk_rq_unmap_user);
+
+/**
+ * blk_rq_map_kern - map kernel data to a request, for passthrough requests
+ * @rq:		request to fill
+ * @kbuf:	the kernel buffer
+ * @len:	length of user data
+ * @gfp_mask:	memory allocation flags
+ *
+ * Description:
+ *    Data will be mapped directly if possible. Otherwise a bounce
+ *    buffer is used. Can be called multiple times to append multiple
+ *    buffers.
+ */
+int blk_rq_map_kern(struct request *rq, void *kbuf, unsigned int len,
+		gfp_t gfp_mask)
+{
+	unsigned long addr = (unsigned long) kbuf;
+	bool do_copy;
+	struct bio *bio;
+	int ret;
+
+	if (len > (queue_max_hw_sectors(rq->q) << SECTOR_SHIFT))
+		return -EINVAL;
+	if (!len || !kbuf)
+		return -EINVAL;
+
+	do_copy = !blk_rq_aligned(rq->q, addr, len) || object_is_on_stack(kbuf);
+	if (do_copy)
+		bio = bio_copy_kern(rq, kbuf, len, gfp_mask);
+	else
+		bio = bio_map_kern(rq, kbuf, len, gfp_mask);
+
+	if (IS_ERR(bio))
+		return PTR_ERR(bio);
+
+	ret = blk_rq_append_bio(rq, bio);
+	if (unlikely(ret)) {
+		if (do_copy)
+			bio_free_pages(bio);
+		blk_mq_map_bio_put(bio);
+	}
+	return ret;
+}
+EXPORT_SYMBOL(blk_rq_map_kern);