[PATCH] dm-io: device-mapper i/o library for kcopyd

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/md/Makefile

@@ -3,7 +3,7 @@
 #
 
 dm-mod-objs	:= dm.o dm-table.o dm-target.o dm-linear.o dm-stripe.o \
-		   dm-ioctl.o
+		   dm-ioctl.o dm-io.o
 raid6-objs	:= raid6main.o raid6algos.o raid6recov.o raid6tables.o \
 		   raid6int1.o raid6int2.o raid6int4.o \
 		   raid6int8.o raid6int16.o raid6int32.o \

drivers/md/dm-io.c

+/*
+ * Copyright (C) 2003 Sistina Software
+ *
+ * This file is released under the GPL.
+ */
+
+#include "dm-io.h"
+
+#include <linux/bio.h>
+#include <linux/mempool.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+
+#define BIO_POOL_SIZE 256
+
+
+/*-----------------------------------------------------------------
+ * Bio set, move this to bio.c
+ *---------------------------------------------------------------*/
+#define BV_NAME_SIZE 16
+struct biovec_pool {
+	int nr_vecs;
+	char name[BV_NAME_SIZE];
+	kmem_cache_t *slab;
+	mempool_t *pool;
+	atomic_t allocated;	/* FIXME: debug */
+};
+
+#define BIOVEC_NR_POOLS 6
+struct bio_set {
+	char name[BV_NAME_SIZE];
+	kmem_cache_t *bio_slab;
+	mempool_t *bio_pool;
+	struct biovec_pool pools[BIOVEC_NR_POOLS];
+};
+
+static void bio_set_exit(struct bio_set *bs)
+{
+	unsigned i;
+	struct biovec_pool *bp;
+
+	if (bs->bio_pool)
+		mempool_destroy(bs->bio_pool);
+
+	if (bs->bio_slab)
+		kmem_cache_destroy(bs->bio_slab);
+
+	for (i = 0; i < BIOVEC_NR_POOLS; i++) {
+		bp = bs->pools + i;
+		if (bp->pool)
+			mempool_destroy(bp->pool);
+
+		if (bp->slab)
+			kmem_cache_destroy(bp->slab);
+	}
+}
+
+static void mk_name(char *str, size_t len, const char *prefix, unsigned count)
+{
+	snprintf(str, len, "%s-%u", prefix, count);
+}
+
+static int bio_set_init(struct bio_set *bs, const char *slab_prefix,
+			 unsigned pool_entries, unsigned scale)
+{
+	/* FIXME: this must match bvec_index(), why not go the
+	 * whole hog and have a pool per power of 2 ? */
+	static unsigned _vec_lengths[BIOVEC_NR_POOLS] = {
+		1, 4, 16, 64, 128, BIO_MAX_PAGES
+	};
+
+
+	unsigned i, size;
+	struct biovec_pool *bp;
+
+	/* zero the bs so we can tear down properly on error */
+	memset(bs, 0, sizeof(*bs));
+
+	/*
+	 * Set up the bio pool.
+	 */
+	snprintf(bs->name, sizeof(bs->name), "%s-bio", slab_prefix);
+
+	bs->bio_slab = kmem_cache_create(bs->name, sizeof(struct bio), 0,
+					 SLAB_HWCACHE_ALIGN, NULL, NULL);
+	if (!bs->bio_slab) {
+		DMWARN("can't init bio slab");
+		goto bad;
+	}
+
+	bs->bio_pool = mempool_create(pool_entries, mempool_alloc_slab,
+				      mempool_free_slab, bs->bio_slab);
+	if (!bs->bio_pool) {
+		DMWARN("can't init bio pool");
+		goto bad;
+	}
+
+	/*
+	 * Set up the biovec pools.
+	 */
+	for (i = 0; i < BIOVEC_NR_POOLS; i++) {
+		bp = bs->pools + i;
+		bp->nr_vecs = _vec_lengths[i];
+		atomic_set(&bp->allocated, 1); /* FIXME: debug */
+
+
+		size = bp->nr_vecs * sizeof(struct bio_vec);
+
+		mk_name(bp->name, sizeof(bp->name), slab_prefix, i);
+		bp->slab = kmem_cache_create(bp->name, size, 0,
+					     SLAB_HWCACHE_ALIGN, NULL, NULL);
+		if (!bp->slab) {
+			DMWARN("can't init biovec slab cache");
+			goto bad;
+		}
+
+		if (i >= scale)
+			pool_entries >>= 1;
+
+		bp->pool = mempool_create(pool_entries, mempool_alloc_slab,
+					  mempool_free_slab, bp->slab);
+		if (!bp->pool) {
+			DMWARN("can't init biovec mempool");
+			goto bad;
+		}
+	}
+
+	return 0;
+
+ bad:
+	bio_set_exit(bs);
+	return -ENOMEM;
+}
+
+/* FIXME: blech */
+static inline unsigned bvec_index(unsigned nr)
+{
+	switch (nr) {
+	case 1:		return 0;
+	case 2 ... 4: 	return 1;
+	case 5 ... 16:	return 2;
+	case 17 ... 64:	return 3;
+	case 65 ... 128:return 4;
+	case 129 ... BIO_MAX_PAGES: return 5;
+	}
+
+	BUG();
+	return 0;
+}
+
+static inline void bs_bio_init(struct bio *bio)
+{
+	bio->bi_next = NULL;
+	bio->bi_flags = 1 << BIO_UPTODATE;
+	bio->bi_rw = 0;
+	bio->bi_vcnt = 0;
+	bio->bi_idx = 0;
+	bio->bi_phys_segments = 0;
+	bio->bi_hw_segments = 0;
+	bio->bi_size = 0;
+	bio->bi_max_vecs = 0;
+	bio->bi_end_io = NULL;
+	atomic_set(&bio->bi_cnt, 1);
+	bio->bi_private = NULL;
+}
+
+static unsigned _bio_count = 0;
+struct bio *bio_set_alloc(struct bio_set *bs, int gfp_mask, int nr_iovecs)
+{
+	struct biovec_pool *bp;
+	struct bio_vec *bv = NULL;
+	unsigned long idx;
+	struct bio *bio;
+
+	bio = mempool_alloc(bs->bio_pool, gfp_mask);
+	if (unlikely(!bio))
+		return NULL;
+
+	bio_init(bio);
+
+	if (likely(nr_iovecs)) {
+		idx = bvec_index(nr_iovecs);
+		bp = bs->pools + idx;
+		bv = mempool_alloc(bp->pool, gfp_mask);
+		if (!bv) {
+			mempool_free(bio, bs->bio_pool);
+			return NULL;
+		}
+
+		memset(bv, 0, bp->nr_vecs * sizeof(*bv));
+		bio->bi_flags |= idx << BIO_POOL_OFFSET;
+		bio->bi_max_vecs = bp->nr_vecs;
+		atomic_inc(&bp->allocated);
+	}
+
+	bio->bi_io_vec = bv;
+	return bio;
+}
+
+static void bio_set_free(struct bio_set *bs, struct bio *bio)
+{
+	struct biovec_pool *bp = bs->pools + BIO_POOL_IDX(bio);
+
+	if (atomic_dec_and_test(&bp->allocated))
+		BUG();
+
+	mempool_free(bio->bi_io_vec, bp->pool);
+	mempool_free(bio, bs->bio_pool);
+}
+
+/*-----------------------------------------------------------------
+ * dm-io proper
+ *---------------------------------------------------------------*/
+static struct bio_set _bios;
+
+/* FIXME: can we shrink this ? */
+struct io {
+	unsigned long error;
+	atomic_t count;
+	struct task_struct *sleeper;
+	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 buffer heads ! (FIXME:
+ * must reduce this).
+ */
+static unsigned _num_ios;
+static mempool_t *_io_pool;
+
+static void *alloc_io(int gfp_mask, void *pool_data)
+{
+	return kmalloc(sizeof(struct io), gfp_mask);
+}
+
+static void free_io(void *element, void *pool_data)
+{
+	kfree(element);
+}
+
+static unsigned int pages_to_ios(unsigned int pages)
+{
+	return 4 * pages;	/* too many ? */
+}
+
+static int resize_pool(unsigned int new_ios)
+{
+	int r = 0;
+
+	if (_io_pool) {
+		if (new_ios == 0) {
+			/* free off the pool */
+			mempool_destroy(_io_pool);
+			_io_pool = NULL;
+			bio_set_exit(&_bios);
+
+		} else {
+			/* resize the pool */
+			r = mempool_resize(_io_pool, new_ios, GFP_KERNEL);
+		}
+
+	} else {
+		/* create new pool */
+		_io_pool = mempool_create(new_ios, alloc_io, free_io, NULL);
+		if (!_io_pool)
+			r = -ENOMEM;
+
+		r = bio_set_init(&_bios, "dm-io", 512, 1);
+		if (r) {
+			mempool_destroy(_io_pool);
+			_io_pool = NULL;
+		}
+	}
+
+	if (!r)
+		_num_ios = new_ios;
+
+	return r;
+}
+
+int dm_io_get(unsigned int num_pages)
+{
+	return resize_pool(_num_ios + pages_to_ios(num_pages));
+}
+
+void dm_io_put(unsigned int num_pages)
+{
+	resize_pool(_num_ios - pages_to_ios(num_pages));
+}
+
+/*-----------------------------------------------------------------
+ * 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).
+ *---------------------------------------------------------------*/
+static inline void bio_set_region(struct bio *bio, unsigned region)
+{
+	bio->bi_io_vec[bio->bi_max_vecs - 1].bv_len = region;
+}
+
+static inline unsigned bio_get_region(struct bio *bio)
+{
+	return bio->bi_io_vec[bio->bi_max_vecs - 1].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);
+
+	if (atomic_dec_and_test(&io->count)) {
+		if (io->sleeper)
+			wake_up_process(io->sleeper);
+
+		else {
+			int r = io->error;
+			io_notify_fn fn = io->callback;
+			void *context = io->context;
+
+			mempool_free(io, _io_pool);
+			fn(r, context);
+		}
+	}
+}
+
+/* FIXME Move this to bio.h? */
+static void zero_fill_bio(struct bio *bio)
+{
+	unsigned long flags;
+	struct bio_vec *bv;
+	int i;
+
+	bio_for_each_segment(bv, bio, i) {
+		char *data = bvec_kmap_irq(bv, &flags);
+		memset(data, 0, bv->bv_len);
+		flush_dcache_page(bv->bv_page);
+		bvec_kunmap_irq(data, &flags);
+	}
+}
+
+static int endio(struct bio *bio, unsigned int done, int error)
+{
+	struct io *io = (struct io *) bio->bi_private;
+
+	/* keep going until we've finished */
+	if (bio->bi_size)
+		return 1;
+
+	if (error && bio_data_dir(bio) == READ)
+		zero_fill_bio(bio);
+
+	dec_count(io, bio_get_region(bio), error);
+	bio_put(bio);
+
+	return 0;
+}
+
+static void bio_dtr(struct bio *bio)
+{
+	_bio_count--;
+	bio_set_free(&_bios, bio);
+}
+
+/*-----------------------------------------------------------------
+ * 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;
+}
+
+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;
+}
+
+/*-----------------------------------------------------------------
+ * IO routines that accept a list of pages.
+ *---------------------------------------------------------------*/
+static void do_region(int rw, unsigned int region, struct 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().
+		 */
+		num_bvecs = (remaining / (PAGE_SIZE >> 9)) + 2;
+		_bio_count++;
+		bio = bio_set_alloc(&_bios, GFP_NOIO, num_bvecs);
+		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 = bio_dtr;
+		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 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 refence that we were holding to avoid
+	 * the io being completed too early.
+	 */
+	dec_count(io, 0, 0);
+}
+
+static int sync_io(unsigned int num_regions, struct io_region *where,
+	    int rw, struct dpages *dp, unsigned long *error_bits)
+{
+	struct io io;
+
+	BUG_ON(num_regions > 1 && rw != WRITE);
+
+	io.error = 0;
+	atomic_set(&io.count, 1); /* see dispatch_io() */
+	io.sleeper = current;
+
+	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;
+
+	*error_bits = io.error;
+	return io.error ? -EIO : 0;
+}
+
+static int async_io(unsigned int num_regions, struct io_region *where, int rw,
+	     struct dpages *dp, io_notify_fn fn, void *context)
+{
+	struct io *io = mempool_alloc(_io_pool, GFP_NOIO);
+
+	io->error = 0;
+	atomic_set(&io->count, 1); /* see dispatch_io() */
+	io->sleeper = NULL;
+	io->callback = fn;
+	io->context = context;
+
+	dispatch_io(rw, num_regions, where, dp, io, 0);
+	return 0;
+}
+
+int dm_io_sync(unsigned int num_regions, struct io_region *where, int rw,
+	       struct page_list *pl, unsigned int offset,
+	       unsigned long *error_bits)
+{
+	struct dpages dp;
+	list_dp_init(&dp, pl, offset);
+	return sync_io(num_regions, where, rw, &dp, error_bits);
+}
+
+int dm_io_sync_bvec(unsigned int num_regions, struct io_region *where, int rw,
+		    struct bio_vec *bvec, unsigned long *error_bits)
+{
+	struct dpages dp;
+	bvec_dp_init(&dp, bvec);
+	return sync_io(num_regions, where, rw, &dp, error_bits);
+}
+
+int dm_io_sync_vm(unsigned int num_regions, struct io_region *where, int rw,
+		  void *data, unsigned long *error_bits)
+{
+	struct dpages dp;
+	vm_dp_init(&dp, data);
+	return sync_io(num_regions, where, rw, &dp, error_bits);
+}
+
+int dm_io_async(unsigned int num_regions, struct io_region *where, int rw,
+		struct page_list *pl, unsigned int offset,
+		io_notify_fn fn, void *context)
+{
+	struct dpages dp;
+	list_dp_init(&dp, pl, offset);
+	return async_io(num_regions, where, rw, &dp, fn, context);
+}
+
+int dm_io_async_bvec(unsigned int num_regions, struct io_region *where, int rw,
+		     struct bio_vec *bvec, io_notify_fn fn, void *context)
+{
+	struct dpages dp;
+	bvec_dp_init(&dp, bvec);
+	return async_io(num_regions, where, rw, &dp, fn, context);
+}
+
+int dm_io_async_vm(unsigned int num_regions, struct io_region *where, int rw,
+		   void *data, io_notify_fn fn, void *context)
+{
+	struct dpages dp;
+	vm_dp_init(&dp, data);
+	return async_io(num_regions, where, rw, &dp, fn, context);
+}
+
+EXPORT_SYMBOL(dm_io_get);
+EXPORT_SYMBOL(dm_io_put);
+EXPORT_SYMBOL(dm_io_sync);
+EXPORT_SYMBOL(dm_io_async);
+EXPORT_SYMBOL(dm_io_sync_bvec);
+EXPORT_SYMBOL(dm_io_async_bvec);
+EXPORT_SYMBOL(dm_io_sync_vm);
+EXPORT_SYMBOL(dm_io_async_vm);

drivers/md/dm-io.h

+/*
+ * Copyright (C) 2003 Sistina Software
+ *
+ * This file is released under the GPL.
+ */
+
+#ifndef _DM_IO_H
+#define _DM_IO_H
+
+#include "dm.h"
+
+/* FIXME make this configurable */
+#define DM_MAX_IO_REGIONS 8
+
+struct io_region {
+	struct block_device *bdev;
+	sector_t sector;
+	sector_t count;
+};
+
+struct page_list {
+	struct page_list *next;
+	struct page *page;
+};
+
+
+/*
+ * 'error' is a bitset, with each bit indicating whether an error
+ * occurred doing io to the corresponding region.
+ */
+typedef void (*io_notify_fn)(unsigned long error, void *context);
+
+
+/*
+ * Before anyone uses the IO interface they should call
+ * dm_io_get(), specifying roughly how many pages they are
+ * expecting to perform io on concurrently.
+ *
+ * This function may block.
+ */
+int dm_io_get(unsigned int num_pages);
+void dm_io_put(unsigned int num_pages);
+
+/*
+ * Synchronous IO.
+ *
+ * Please ensure that the rw flag in the next two functions is
+ * either READ or WRITE, ie. we don't take READA.  Any
+ * regions with a zero count field will be ignored.
+ */
+int dm_io_sync(unsigned int num_regions, struct io_region *where, int rw,
+	       struct page_list *pl, unsigned int offset,
+	       unsigned long *error_bits);
+
+int dm_io_sync_bvec(unsigned int num_regions, struct io_region *where, int rw,
+		    struct bio_vec *bvec, unsigned long *error_bits);
+
+int dm_io_sync_vm(unsigned int num_regions, struct io_region *where, int rw,
+		  void *data, unsigned long *error_bits);
+
+/*
+ * Aynchronous IO.
+ *
+ * The 'where' array may be safely allocated on the stack since
+ * the function takes a copy.
+ */
+int dm_io_async(unsigned int num_regions, struct io_region *where, int rw,
+		struct page_list *pl, unsigned int offset,
+		io_notify_fn fn, void *context);
+
+int dm_io_async_bvec(unsigned int num_regions, struct io_region *where, int rw,
+		     struct bio_vec *bvec, io_notify_fn fn, void *context);
+
+int dm_io_async_vm(unsigned int num_regions, struct io_region *where, int rw,
+		   void *data, io_notify_fn fn, void *context);
+
+#endif

mm/mempool.c

@@ -89,11 +89,6 @@ mempool_t * mempool_create(int min_nr, mempool_alloc_t *alloc_fn,
 }
 EXPORT_SYMBOL(mempool_create);
 
-/*
- * mempool_resize is disabled for now, because it has no callers.  Feel free
- * to turn it back on if needed.
- */
-#if 0
 /**
  * mempool_resize - resize an existing memory pool
  * @pool:       pointer to the memory pool which was allocated via
@@ -163,7 +158,6 @@ int mempool_resize(mempool_t *pool, int new_min_nr, int gfp_mask)
 	return 0;
 }
 EXPORT_SYMBOL(mempool_resize);
-#endif
 
 /**
  * mempool_destroy - deallocate a memory pool