1 files changed, 465 insertions, 0 deletions
diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c
new file mode 100644
index 0000000..657e1dd
--- /dev/null
+++ b/drivers/md/dm-io.c
@@ -0,0 +1,465 @@
+/*
+ * Copyright (C) 2003 Sistina Software
+ * Copyright (C) 2006 Red Hat GmbH
+ *
+ * This file is released under the GPL.
+ */
+
+#include <linux/device-mapper.h>
+
+#include <linux/bio.h>
+#include <linux/mempool.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/dm-io.h>
+
+struct dm_io_client {
+	mempool_t *pool;
+	struct bio_set *bios;
+};
+
+/* FIXME: can we shrink this ? */
+struct io {
+	unsigned long error_bits;
+	atomic_t count;
+	struct task_struct *sleeper;
+	struct dm_io_client *client;
+	io_notify_fn callback;
+	void *context;
+};
+
+/*
+ * io contexts are only dynamically allocated for asynchronous
+ * io.  Since async io is likely to be the majority of io we'll
+ * have the same number of io contexts as bios! (FIXME: must reduce this).
+ */
+
+static unsigned int pages_to_ios(unsigned int pages)
+{
+	return 4 * pages;	/* too many ? */
+}
+
+/*
+ * Create a client with mempool and bioset.
+ */
+struct dm_io_client *dm_io_client_create(unsigned num_pages)
+{
+	unsigned ios = pages_to_ios(num_pages);
+	struct dm_io_client *client;
+
+	client = kmalloc(sizeof(*client), GFP_KERNEL);
+	if (!client)
+		return ERR_PTR(-ENOMEM);
+
+	client->pool = mempool_create_kmalloc_pool(ios, sizeof(struct io));
+	if (!client->pool)
+		goto bad;
+
+	client->bios = bioset_create(16, 16);
+	if (!client->bios)
+		goto bad;
+
+	return client;
+
+   bad:
+	if (client->pool)
+		mempool_destroy(client->pool);
+	kfree(client);
+	return ERR_PTR(-ENOMEM);
+}
+EXPORT_SYMBOL(dm_io_client_create);
+
+int dm_io_client_resize(unsigned num_pages, struct dm_io_client *client)
+{
+	return mempool_resize(client->pool, pages_to_ios(num_pages),
+			      GFP_KERNEL);
+}
+EXPORT_SYMBOL(dm_io_client_resize);
+
+void dm_io_client_destroy(struct dm_io_client *client)
+{
+	mempool_destroy(client->pool);
+	bioset_free(client->bios);
+	kfree(client);
+}
+EXPORT_SYMBOL(dm_io_client_destroy);
+
+/*-----------------------------------------------------------------
+ * We need to keep track of which region a bio is doing io for.
+ * In order to save a memory allocation we store this the last
+ * bvec which we know is unused (blech).
+ * XXX This is ugly and can OOPS with some configs... find another way.
+ *---------------------------------------------------------------*/
+static inline void bio_set_region(struct bio *bio, unsigned region)
+{
+	bio->bi_io_vec[bio->bi_max_vecs].bv_len = region;
+}
+
+static inline unsigned bio_get_region(struct bio *bio)
+{
+	return bio->bi_io_vec[bio->bi_max_vecs].bv_len;
+}
+
+/*-----------------------------------------------------------------
+ * We need an io object to keep track of the number of bios that
+ * have been dispatched for a particular io.
+ *---------------------------------------------------------------*/
+static void dec_count(struct io *io, unsigned int region, int error)
+{
+	if (error)
+		set_bit(region, &io->error_bits);
+
+	if (atomic_dec_and_test(&io->count)) {
+		if (io->sleeper)
+			wake_up_process(io->sleeper);
+
+		else {
+			unsigned long r = io->error_bits;
+			io_notify_fn fn = io->callback;
+			void *context = io->context;
+
+			mempool_free(io, io->client->pool);
+			fn(r, context);
+		}
+	}
+}
+
+static void endio(struct bio *bio, int error)
+{
+	struct io *io;
+	unsigned region;
+
+	if (error && bio_data_dir(bio) == READ)
+		zero_fill_bio(bio);
+
+	/*
+	 * The bio destructor in bio_put() may use the io object.
+	 */
+	io = bio->bi_private;
+	region = bio_get_region(bio);
+
+	bio->bi_max_vecs++;
+	bio_put(bio);
+
+	dec_count(io, region, error);
+}
+
+/*-----------------------------------------------------------------
+ * These little objects provide an abstraction for getting a new
+ * destination page for io.
+ *---------------------------------------------------------------*/
+struct dpages {
+	void (*get_page)(struct dpages *dp,
+			 struct page **p, unsigned long *len, unsigned *offset);
+	void (*next_page)(struct dpages *dp);
+
+	unsigned context_u;
+	void *context_ptr;
+};
+
+/*
+ * Functions for getting the pages from a list.
+ */
+static void list_get_page(struct dpages *dp,
+		  struct page **p, unsigned long *len, unsigned *offset)
+{
+	unsigned o = dp->context_u;
+	struct page_list *pl = (struct page_list *) dp->context_ptr;
+
+	*p = pl->page;
+	*len = PAGE_SIZE - o;
+	*offset = o;
+}
+
+static void list_next_page(struct dpages *dp)
+{
+	struct page_list *pl = (struct page_list *) dp->context_ptr;
+	dp->context_ptr = pl->next;
+	dp->context_u = 0;
+}
+
+static void list_dp_init(struct dpages *dp, struct page_list *pl, unsigned offset)
+{
+	dp->get_page = list_get_page;
+	dp->next_page = list_next_page;
+	dp->context_u = offset;
+	dp->context_ptr = pl;
+}
+
+/*
+ * Functions for getting the pages from a bvec.
+ */
+static void bvec_get_page(struct dpages *dp,
+		  struct page **p, unsigned long *len, unsigned *offset)
+{
+	struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
+	*p = bvec->bv_page;
+	*len = bvec->bv_len;
+	*offset = bvec->bv_offset;
+}
+
+static void bvec_next_page(struct dpages *dp)
+{
+	struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
+	dp->context_ptr = bvec + 1;
+}
+
+static void bvec_dp_init(struct dpages *dp, struct bio_vec *bvec)
+{
+	dp->get_page = bvec_get_page;
+	dp->next_page = bvec_next_page;
+	dp->context_ptr = bvec;
+}
+
+/*
+ * Functions for getting the pages from a VMA.
+ */
+static void vm_get_page(struct dpages *dp,
+		 struct page **p, unsigned long *len, unsigned *offset)
+{
+	*p = vmalloc_to_page(dp->context_ptr);
+	*offset = dp->context_u;
+	*len = PAGE_SIZE - dp->context_u;
+}
+
+static void vm_next_page(struct dpages *dp)
+{
+	dp->context_ptr += PAGE_SIZE - dp->context_u;
+	dp->context_u = 0;
+}
+
+static void vm_dp_init(struct dpages *dp, void *data)
+{
+	dp->get_page = vm_get_page;
+	dp->next_page = vm_next_page;
+	dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
+	dp->context_ptr = data;
+}
+
+static void dm_bio_destructor(struct bio *bio)
+{
+	struct io *io = bio->bi_private;
+
+	bio_free(bio, io->client->bios);
+}
+
+/*
+ * Functions for getting the pages from kernel memory.
+ */
+static void km_get_page(struct dpages *dp, struct page **p, unsigned long *len,
+			unsigned *offset)
+{
+	*p = virt_to_page(dp->context_ptr);
+	*offset = dp->context_u;
+	*len = PAGE_SIZE - dp->context_u;
+}
+
+static void km_next_page(struct dpages *dp)
+{
+	dp->context_ptr += PAGE_SIZE - dp->context_u;
+	dp->context_u = 0;
+}
+
+static void km_dp_init(struct dpages *dp, void *data)
+{
+	dp->get_page = km_get_page;
+	dp->next_page = km_next_page;
+	dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
+	dp->context_ptr = data;
+}
+
+/*-----------------------------------------------------------------
+ * IO routines that accept a list of pages.
+ *---------------------------------------------------------------*/
+static void do_region(int rw, unsigned region, struct dm_io_region *where,
+		      struct dpages *dp, struct io *io)
+{
+	struct bio *bio;
+	struct page *page;
+	unsigned long len;
+	unsigned offset;
+	unsigned num_bvecs;
+	sector_t remaining = where->count;
+
+	while (remaining) {
+		/*
+		 * Allocate a suitably sized-bio: we add an extra
+		 * bvec for bio_get/set_region() and decrement bi_max_vecs
+		 * to hide it from bio_add_page().
+		 */
+		num_bvecs = dm_sector_div_up(remaining,
+					     (PAGE_SIZE >> SECTOR_SHIFT));
+		num_bvecs = 1 + min_t(int, bio_get_nr_vecs(where->bdev),
+				      num_bvecs);
+		if (unlikely(num_bvecs > BIO_MAX_PAGES))
+			num_bvecs = BIO_MAX_PAGES;
+		bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
+		bio->bi_sector = where->sector + (where->count - remaining);
+		bio->bi_bdev = where->bdev;
+		bio->bi_end_io = endio;
+		bio->bi_private = io;
+		bio->bi_destructor = dm_bio_destructor;
+		bio->bi_max_vecs--;
+		bio_set_region(bio, region);
+
+		/*
+		 * Try and add as many pages as possible.
+		 */
+		while (remaining) {
+			dp->get_page(dp, &page, &len, &offset);
+			len = min(len, to_bytes(remaining));
+			if (!bio_add_page(bio, page, len, offset))
+				break;
+
+			offset = 0;
+			remaining -= to_sector(len);
+			dp->next_page(dp);
+		}
+
+		atomic_inc(&io->count);
+		submit_bio(rw, bio);
+	}
+}
+
+static void dispatch_io(int rw, unsigned int num_regions,
+			struct dm_io_region *where, struct dpages *dp,
+			struct io *io, int sync)
+{
+	int i;
+	struct dpages old_pages = *dp;
+
+	if (sync)
+		rw |= (1 << BIO_RW_SYNC);
+
+	/*
+	 * For multiple regions we need to be careful to rewind
+	 * the dp object for each call to do_region.
+	 */
+	for (i = 0; i < num_regions; i++) {
+		*dp = old_pages;
+		if (where[i].count)
+			do_region(rw, i, where + i, dp, io);
+	}
+
+	/*
+	 * Drop the extra reference that we were holding to avoid
+	 * the io being completed too early.
+	 */
+	dec_count(io, 0, 0);
+}
+
+static int sync_io(struct dm_io_client *client, unsigned int num_regions,
+		   struct dm_io_region *where, int rw, struct dpages *dp,
+		   unsigned long *error_bits)
+{
+	struct io io;
+
+	if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
+		WARN_ON(1);
+		return -EIO;
+	}
+
+	io.error_bits = 0;
+	atomic_set(&io.count, 1); /* see dispatch_io() */
+	io.sleeper = current;
+	io.client = client;
+
+	dispatch_io(rw, num_regions, where, dp, &io, 1);
+
+	while (1) {
+		set_current_state(TASK_UNINTERRUPTIBLE);
+
+		if (!atomic_read(&io.count) || signal_pending(current))
+			break;
+
+		io_schedule();
+	}
+	set_current_state(TASK_RUNNING);
+
+	if (atomic_read(&io.count))
+		return -EINTR;
+
+	if (error_bits)
+		*error_bits = io.error_bits;
+
+	return io.error_bits ? -EIO : 0;
+}
+
+static int async_io(struct dm_io_client *client, unsigned int num_regions,
+		    struct dm_io_region *where, int rw, struct dpages *dp,
+		    io_notify_fn fn, void *context)
+{
+	struct io *io;
+
+	if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
+		WARN_ON(1);
+		fn(1, context);
+		return -EIO;
+	}
+
+	io = mempool_alloc(client->pool, GFP_NOIO);
+	io->error_bits = 0;
+	atomic_set(&io->count, 1); /* see dispatch_io() */
+	io->sleeper = NULL;
+	io->client = client;
+	io->callback = fn;
+	io->context = context;
+
+	dispatch_io(rw, num_regions, where, dp, io, 0);
+	return 0;
+}
+
+static int dp_init(struct dm_io_request *io_req, struct dpages *dp)
+{
+	/* Set up dpages based on memory type */
+	switch (io_req->mem.type) {
+	case DM_IO_PAGE_LIST:
+		list_dp_init(dp, io_req->mem.ptr.pl, io_req->mem.offset);
+		break;
+
+	case DM_IO_BVEC:
+		bvec_dp_init(dp, io_req->mem.ptr.bvec);
+		break;
+
+	case DM_IO_VMA:
+		vm_dp_init(dp, io_req->mem.ptr.vma);
+		break;
+
+	case DM_IO_KMEM:
+		km_dp_init(dp, io_req->mem.ptr.addr);
+		break;
+
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/*
+ * New collapsed (a)synchronous interface.
+ *
+ * If the IO is asynchronous (i.e. it has notify.fn), you must either unplug
+ * the queue with blk_unplug() some time later or set the BIO_RW_SYNC bit in
+ * io_req->bi_rw. If you fail to do one of these, the IO will be submitted to
+ * the disk after q->unplug_delay, which defaults to 3ms in blk-settings.c.
+ */
+int dm_io(struct dm_io_request *io_req, unsigned num_regions,
+	  struct dm_io_region *where, unsigned long *sync_error_bits)
+{
+	int r;
+	struct dpages dp;
+
+	r = dp_init(io_req, &dp);
+	if (r)
+		return r;
+
+	if (!io_req->notify.fn)
+		return sync_io(io_req->client, num_regions, where,
+			       io_req->bi_rw, &dp, sync_error_bits);
+
+	return async_io(io_req->client, num_regions, where, io_req->bi_rw,
+			&dp, io_req->notify.fn, io_req->notify.context);
+}
+EXPORT_SYMBOL(dm_io);