/* * Copyright (C) 2003 Sistina Software * Copyright (C) 2006 Red Hat GmbH * * This file is released under the GPL. */ #include "dm.h" #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> #define DM_MSG_PREFIX "io" #define DM_IO_MAX_REGIONS BITS_PER_LONG struct dm_io_client { mempool_t *pool; struct bio_set *bios; }; /* * Aligning 'struct io' reduces the number of bits required to store * its address. Refer to store_io_and_region_in_bio() below. */ struct io { unsigned long error_bits; atomic_t count; struct task_struct *sleeper; struct dm_io_client *client; io_notify_fn callback; void *context; } __attribute__((aligned(DM_IO_MAX_REGIONS))); static struct kmem_cache *_dm_io_cache; /* * 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_slab_pool(ios, _dm_io_cache); if (!client->pool) goto bad; client->bios = bioset_create(16, 0); 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. * To avoid a memory allocation to store just 5 or 6 bits, we * ensure the 'struct io' pointer is aligned so enough low bits are * always zero and then combine it with the region number directly in * bi_private. *---------------------------------------------------------------*/ static void store_io_and_region_in_bio(struct bio *bio, struct io *io, unsigned region) { if (unlikely(!IS_ALIGNED((unsigned long)io, DM_IO_MAX_REGIONS))) { DMCRIT("Unaligned struct io pointer %p", io); BUG(); } bio->bi_private = (void *)((unsigned long)io | region); } static void retrieve_io_and_region_from_bio(struct bio *bio, struct io **io, unsigned *region) { unsigned long val = (unsigned long)bio->bi_private; *io = (void *)(val & -(unsigned long)DM_IO_MAX_REGIONS); *region = val & (DM_IO_MAX_REGIONS - 1); } /*----------------------------------------------------------------- * 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. */ retrieve_io_and_region_from_bio(bio, &io, ®ion); 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) { unsigned region; struct io *io; retrieve_io_and_region_from_bio(bio, &io, ®ion); 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; /* * where->count may be zero if rw holds a flush and we need to * send a zero-sized flush. */ do { /* * Allocate a suitably sized-bio. */ num_bvecs = dm_sector_div_up(remaining, (PAGE_SIZE >> SECTOR_SHIFT)); num_bvecs = min_t(int, bio_get_nr_vecs(where->bdev), num_bvecs); 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_destructor = dm_bio_destructor; store_io_and_region_in_bio(bio, io, 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); } while (remaining); } 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; BUG_ON(num_regions > DM_IO_MAX_REGIONS); if (sync) rw |= REQ_SYNC | REQ_UNPLUG; /* * 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 || (rw & REQ_FLUSH)) 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) { /* * gcc <= 4.3 can't do the alignment for stack variables, so we must * align it on our own. * volatile prevents the optimizer from removing or reusing * "io_" field from the stack frame (allowed in ANSI C). */ volatile char io_[sizeof(struct io) + __alignof__(struct io) - 1]; struct io *io = (struct io *)PTR_ALIGN(&io_, __alignof__(struct 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)) break; io_schedule(); } set_current_state(TASK_RUNNING); 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 REQ_SYNC 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); int __init dm_io_init(void) { _dm_io_cache = KMEM_CACHE(io, 0); if (!_dm_io_cache) return -ENOMEM; return 0; } void dm_io_exit(void) { kmem_cache_destroy(_dm_io_cache); _dm_io_cache = NULL; }