forked from Minki/linux
f1e5398746
Remove the hack where we allocate an extra bi_io_vec to store additional private data. This hack prevents us from supporting barriers in dm-raid1 without first making another little block layer change. Instead of doing that, this patch eliminates the bi_io_vec abuse by storing the region number directly in the low bits of bi_private. We need to store two things for each bio, the pointer to the main io structure and, if parallel writes were requested, an index indicating which of these writes this bio belongs to. There can be at most BITS_PER_LONG regions - 32 or 64. The index (region number) was stored in the last (hidden) bio vector and the pointer to struct io was stored in bi_private. This patch now aligns "struct io" on BITS_PER_LONG bytes and stores the region number in the low BITS_PER_LONG bits of bi_private. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
515 lines
12 KiB
C
515 lines
12 KiB
C
/*
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* Copyright (C) 2003 Sistina Software
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* Copyright (C) 2006 Red Hat GmbH
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*
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* This file is released under the GPL.
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*/
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#include "dm.h"
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#include <linux/device-mapper.h>
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#include <linux/bio.h>
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#include <linux/mempool.h>
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#include <linux/module.h>
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <linux/dm-io.h>
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#define DM_MSG_PREFIX "io"
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#define DM_IO_MAX_REGIONS BITS_PER_LONG
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struct dm_io_client {
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mempool_t *pool;
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struct bio_set *bios;
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};
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/*
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* Aligning 'struct io' reduces the number of bits required to store
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* its address. Refer to store_io_and_region_in_bio() below.
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*/
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struct io {
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unsigned long error_bits;
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unsigned long eopnotsupp_bits;
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atomic_t count;
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struct task_struct *sleeper;
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struct dm_io_client *client;
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io_notify_fn callback;
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void *context;
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} __attribute__((aligned(DM_IO_MAX_REGIONS)));
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static struct kmem_cache *_dm_io_cache;
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/*
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* io contexts are only dynamically allocated for asynchronous
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* io. Since async io is likely to be the majority of io we'll
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* have the same number of io contexts as bios! (FIXME: must reduce this).
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*/
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static unsigned int pages_to_ios(unsigned int pages)
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{
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return 4 * pages; /* too many ? */
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}
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/*
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* Create a client with mempool and bioset.
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*/
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struct dm_io_client *dm_io_client_create(unsigned num_pages)
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{
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unsigned ios = pages_to_ios(num_pages);
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struct dm_io_client *client;
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client = kmalloc(sizeof(*client), GFP_KERNEL);
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if (!client)
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return ERR_PTR(-ENOMEM);
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client->pool = mempool_create_slab_pool(ios, _dm_io_cache);
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if (!client->pool)
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goto bad;
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client->bios = bioset_create(16, 0);
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if (!client->bios)
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goto bad;
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return client;
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bad:
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if (client->pool)
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mempool_destroy(client->pool);
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kfree(client);
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return ERR_PTR(-ENOMEM);
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}
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EXPORT_SYMBOL(dm_io_client_create);
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int dm_io_client_resize(unsigned num_pages, struct dm_io_client *client)
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{
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return mempool_resize(client->pool, pages_to_ios(num_pages),
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GFP_KERNEL);
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}
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EXPORT_SYMBOL(dm_io_client_resize);
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void dm_io_client_destroy(struct dm_io_client *client)
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{
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mempool_destroy(client->pool);
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bioset_free(client->bios);
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kfree(client);
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}
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EXPORT_SYMBOL(dm_io_client_destroy);
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/*-----------------------------------------------------------------
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* We need to keep track of which region a bio is doing io for.
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* To avoid a memory allocation to store just 5 or 6 bits, we
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* ensure the 'struct io' pointer is aligned so enough low bits are
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* always zero and then combine it with the region number directly in
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* bi_private.
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*---------------------------------------------------------------*/
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static void store_io_and_region_in_bio(struct bio *bio, struct io *io,
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unsigned region)
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{
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if (unlikely(!IS_ALIGNED((unsigned long)io, DM_IO_MAX_REGIONS))) {
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DMCRIT("Unaligned struct io pointer %p", io);
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BUG();
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}
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bio->bi_private = (void *)((unsigned long)io | region);
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}
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static void retrieve_io_and_region_from_bio(struct bio *bio, struct io **io,
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unsigned *region)
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{
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unsigned long val = (unsigned long)bio->bi_private;
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*io = (void *)(val & -(unsigned long)DM_IO_MAX_REGIONS);
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*region = val & (DM_IO_MAX_REGIONS - 1);
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}
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/*-----------------------------------------------------------------
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* We need an io object to keep track of the number of bios that
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* have been dispatched for a particular io.
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*---------------------------------------------------------------*/
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static void dec_count(struct io *io, unsigned int region, int error)
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{
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if (error) {
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set_bit(region, &io->error_bits);
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if (error == -EOPNOTSUPP)
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set_bit(region, &io->eopnotsupp_bits);
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}
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if (atomic_dec_and_test(&io->count)) {
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if (io->sleeper)
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wake_up_process(io->sleeper);
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else {
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unsigned long r = io->error_bits;
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io_notify_fn fn = io->callback;
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void *context = io->context;
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mempool_free(io, io->client->pool);
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fn(r, context);
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}
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}
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}
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static void endio(struct bio *bio, int error)
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{
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struct io *io;
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unsigned region;
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if (error && bio_data_dir(bio) == READ)
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zero_fill_bio(bio);
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/*
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* The bio destructor in bio_put() may use the io object.
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*/
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retrieve_io_and_region_from_bio(bio, &io, ®ion);
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bio_put(bio);
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dec_count(io, region, error);
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}
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/*-----------------------------------------------------------------
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* These little objects provide an abstraction for getting a new
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* destination page for io.
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*---------------------------------------------------------------*/
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struct dpages {
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void (*get_page)(struct dpages *dp,
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struct page **p, unsigned long *len, unsigned *offset);
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void (*next_page)(struct dpages *dp);
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unsigned context_u;
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void *context_ptr;
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};
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/*
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* Functions for getting the pages from a list.
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*/
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static void list_get_page(struct dpages *dp,
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struct page **p, unsigned long *len, unsigned *offset)
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{
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unsigned o = dp->context_u;
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struct page_list *pl = (struct page_list *) dp->context_ptr;
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*p = pl->page;
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*len = PAGE_SIZE - o;
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*offset = o;
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}
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static void list_next_page(struct dpages *dp)
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{
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struct page_list *pl = (struct page_list *) dp->context_ptr;
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dp->context_ptr = pl->next;
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dp->context_u = 0;
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}
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static void list_dp_init(struct dpages *dp, struct page_list *pl, unsigned offset)
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{
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dp->get_page = list_get_page;
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dp->next_page = list_next_page;
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dp->context_u = offset;
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dp->context_ptr = pl;
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}
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/*
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* Functions for getting the pages from a bvec.
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*/
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static void bvec_get_page(struct dpages *dp,
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struct page **p, unsigned long *len, unsigned *offset)
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{
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struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
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*p = bvec->bv_page;
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*len = bvec->bv_len;
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*offset = bvec->bv_offset;
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}
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static void bvec_next_page(struct dpages *dp)
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{
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struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
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dp->context_ptr = bvec + 1;
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}
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static void bvec_dp_init(struct dpages *dp, struct bio_vec *bvec)
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{
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dp->get_page = bvec_get_page;
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dp->next_page = bvec_next_page;
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dp->context_ptr = bvec;
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}
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/*
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* Functions for getting the pages from a VMA.
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*/
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static void vm_get_page(struct dpages *dp,
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struct page **p, unsigned long *len, unsigned *offset)
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{
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*p = vmalloc_to_page(dp->context_ptr);
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*offset = dp->context_u;
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*len = PAGE_SIZE - dp->context_u;
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}
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static void vm_next_page(struct dpages *dp)
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{
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dp->context_ptr += PAGE_SIZE - dp->context_u;
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dp->context_u = 0;
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}
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static void vm_dp_init(struct dpages *dp, void *data)
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{
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dp->get_page = vm_get_page;
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dp->next_page = vm_next_page;
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dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
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dp->context_ptr = data;
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}
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static void dm_bio_destructor(struct bio *bio)
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{
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unsigned region;
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struct io *io;
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retrieve_io_and_region_from_bio(bio, &io, ®ion);
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bio_free(bio, io->client->bios);
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}
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/*
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* Functions for getting the pages from kernel memory.
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*/
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static void km_get_page(struct dpages *dp, struct page **p, unsigned long *len,
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unsigned *offset)
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{
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*p = virt_to_page(dp->context_ptr);
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*offset = dp->context_u;
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*len = PAGE_SIZE - dp->context_u;
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}
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static void km_next_page(struct dpages *dp)
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{
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dp->context_ptr += PAGE_SIZE - dp->context_u;
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dp->context_u = 0;
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}
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static void km_dp_init(struct dpages *dp, void *data)
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{
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dp->get_page = km_get_page;
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dp->next_page = km_next_page;
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dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
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dp->context_ptr = data;
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}
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/*-----------------------------------------------------------------
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* IO routines that accept a list of pages.
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*---------------------------------------------------------------*/
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static void do_region(int rw, unsigned region, struct dm_io_region *where,
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struct dpages *dp, struct io *io)
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{
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struct bio *bio;
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struct page *page;
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unsigned long len;
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unsigned offset;
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unsigned num_bvecs;
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sector_t remaining = where->count;
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while (remaining) {
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/*
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* Allocate a suitably sized-bio.
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*/
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num_bvecs = dm_sector_div_up(remaining,
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(PAGE_SIZE >> SECTOR_SHIFT));
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num_bvecs = min_t(int, bio_get_nr_vecs(where->bdev), num_bvecs);
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bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
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bio->bi_sector = where->sector + (where->count - remaining);
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bio->bi_bdev = where->bdev;
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bio->bi_end_io = endio;
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bio->bi_destructor = dm_bio_destructor;
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store_io_and_region_in_bio(bio, io, region);
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/*
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* Try and add as many pages as possible.
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*/
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while (remaining) {
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dp->get_page(dp, &page, &len, &offset);
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len = min(len, to_bytes(remaining));
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if (!bio_add_page(bio, page, len, offset))
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break;
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offset = 0;
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remaining -= to_sector(len);
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dp->next_page(dp);
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}
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atomic_inc(&io->count);
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submit_bio(rw, bio);
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}
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}
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static void dispatch_io(int rw, unsigned int num_regions,
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struct dm_io_region *where, struct dpages *dp,
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struct io *io, int sync)
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{
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int i;
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struct dpages old_pages = *dp;
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BUG_ON(num_regions > DM_IO_MAX_REGIONS);
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if (sync)
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rw |= (1 << BIO_RW_SYNCIO) | (1 << BIO_RW_UNPLUG);
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/*
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* For multiple regions we need to be careful to rewind
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* the dp object for each call to do_region.
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*/
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for (i = 0; i < num_regions; i++) {
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*dp = old_pages;
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if (where[i].count)
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do_region(rw, i, where + i, dp, io);
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}
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/*
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* Drop the extra reference that we were holding to avoid
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* the io being completed too early.
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*/
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dec_count(io, 0, 0);
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}
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static int sync_io(struct dm_io_client *client, unsigned int num_regions,
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struct dm_io_region *where, int rw, struct dpages *dp,
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unsigned long *error_bits)
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{
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/*
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* gcc <= 4.3 can't do the alignment for stack variables, so we must
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* align it on our own.
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* volatile prevents the optimizer from removing or reusing
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* "io_" field from the stack frame (allowed in ANSI C).
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*/
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volatile char io_[sizeof(struct io) + __alignof__(struct io) - 1];
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struct io *io = (struct io *)PTR_ALIGN(&io_, __alignof__(struct io));
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if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
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WARN_ON(1);
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return -EIO;
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}
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retry:
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io->error_bits = 0;
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io->eopnotsupp_bits = 0;
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atomic_set(&io->count, 1); /* see dispatch_io() */
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io->sleeper = current;
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io->client = client;
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dispatch_io(rw, num_regions, where, dp, io, 1);
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while (1) {
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set_current_state(TASK_UNINTERRUPTIBLE);
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if (!atomic_read(&io->count))
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break;
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io_schedule();
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}
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set_current_state(TASK_RUNNING);
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if (io->eopnotsupp_bits && (rw & (1 << BIO_RW_BARRIER))) {
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rw &= ~(1 << BIO_RW_BARRIER);
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goto retry;
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}
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if (error_bits)
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*error_bits = io->error_bits;
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return io->error_bits ? -EIO : 0;
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}
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static int async_io(struct dm_io_client *client, unsigned int num_regions,
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struct dm_io_region *where, int rw, struct dpages *dp,
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io_notify_fn fn, void *context)
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{
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struct io *io;
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if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
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WARN_ON(1);
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fn(1, context);
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return -EIO;
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}
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io = mempool_alloc(client->pool, GFP_NOIO);
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io->error_bits = 0;
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io->eopnotsupp_bits = 0;
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atomic_set(&io->count, 1); /* see dispatch_io() */
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io->sleeper = NULL;
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io->client = client;
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io->callback = fn;
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io->context = context;
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dispatch_io(rw, num_regions, where, dp, io, 0);
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return 0;
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}
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static int dp_init(struct dm_io_request *io_req, struct dpages *dp)
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{
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/* Set up dpages based on memory type */
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switch (io_req->mem.type) {
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case DM_IO_PAGE_LIST:
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list_dp_init(dp, io_req->mem.ptr.pl, io_req->mem.offset);
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break;
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case DM_IO_BVEC:
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bvec_dp_init(dp, io_req->mem.ptr.bvec);
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break;
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case DM_IO_VMA:
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vm_dp_init(dp, io_req->mem.ptr.vma);
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break;
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case DM_IO_KMEM:
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km_dp_init(dp, io_req->mem.ptr.addr);
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break;
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default:
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return -EINVAL;
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}
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return 0;
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}
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/*
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* New collapsed (a)synchronous interface.
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*
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* If the IO is asynchronous (i.e. it has notify.fn), you must either unplug
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* the queue with blk_unplug() some time later or set the BIO_RW_SYNC bit in
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* io_req->bi_rw. If you fail to do one of these, the IO will be submitted to
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* the disk after q->unplug_delay, which defaults to 3ms in blk-settings.c.
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*/
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int dm_io(struct dm_io_request *io_req, unsigned num_regions,
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struct dm_io_region *where, unsigned long *sync_error_bits)
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{
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int r;
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struct dpages dp;
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r = dp_init(io_req, &dp);
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if (r)
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return r;
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if (!io_req->notify.fn)
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return sync_io(io_req->client, num_regions, where,
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io_req->bi_rw, &dp, sync_error_bits);
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return async_io(io_req->client, num_regions, where, io_req->bi_rw,
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&dp, io_req->notify.fn, io_req->notify.context);
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}
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EXPORT_SYMBOL(dm_io);
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int __init dm_io_init(void)
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{
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_dm_io_cache = KMEM_CACHE(io, 0);
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if (!_dm_io_cache)
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return -ENOMEM;
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return 0;
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}
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void dm_io_exit(void)
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{
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kmem_cache_destroy(_dm_io_cache);
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_dm_io_cache = NULL;
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}
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