427 lines
10 KiB
C
427 lines
10 KiB
C
/*
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* Copyright (C) 2003 Sistina Software
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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-io.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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static struct bio_set *_bios;
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/* FIXME: can we shrink this ? */
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struct io {
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unsigned long error;
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atomic_t count;
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struct task_struct *sleeper;
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io_notify_fn callback;
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void *context;
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};
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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 buffer heads ! (FIXME:
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* must reduce this).
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*/
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static unsigned _num_ios;
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static mempool_t *_io_pool;
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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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static int resize_pool(unsigned int new_ios)
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{
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int r = 0;
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if (_io_pool) {
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if (new_ios == 0) {
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/* free off the pool */
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mempool_destroy(_io_pool);
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_io_pool = NULL;
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bioset_free(_bios);
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} else {
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/* resize the pool */
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r = mempool_resize(_io_pool, new_ios, GFP_KERNEL);
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}
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} else {
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/* create new pool */
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_io_pool = mempool_create_kmalloc_pool(new_ios,
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sizeof(struct io));
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if (!_io_pool)
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return -ENOMEM;
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_bios = bioset_create(16, 16, 4);
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if (!_bios) {
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mempool_destroy(_io_pool);
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_io_pool = NULL;
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return -ENOMEM;
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}
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}
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if (!r)
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_num_ios = new_ios;
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return r;
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}
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int dm_io_get(unsigned int num_pages)
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{
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return resize_pool(_num_ios + pages_to_ios(num_pages));
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}
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void dm_io_put(unsigned int num_pages)
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{
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resize_pool(_num_ios - pages_to_ios(num_pages));
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}
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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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* In order to save a memory allocation we store this the last
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* bvec which we know is unused (blech).
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* XXX This is ugly and can OOPS with some configs... find another way.
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*---------------------------------------------------------------*/
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static inline void bio_set_region(struct bio *bio, unsigned region)
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{
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bio->bi_io_vec[bio->bi_max_vecs].bv_len = region;
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}
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static inline unsigned bio_get_region(struct bio *bio)
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{
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return bio->bi_io_vec[bio->bi_max_vecs].bv_len;
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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);
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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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int r = io->error;
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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_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 int endio(struct bio *bio, unsigned int done, int error)
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{
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struct io *io = (struct io *) bio->bi_private;
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/* keep going until we've finished */
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if (bio->bi_size)
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return 1;
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if (error && bio_data_dir(bio) == READ)
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zero_fill_bio(bio);
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dec_count(io, bio_get_region(bio), error);
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bio->bi_max_vecs++;
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bio_put(bio);
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return 0;
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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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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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bio_free(bio, _bios);
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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 int region, struct 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: we add an extra
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* bvec for bio_get/set_region() and decrement bi_max_vecs
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* to hide it from bio_add_page().
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*/
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num_bvecs = (remaining / (PAGE_SIZE >> SECTOR_SHIFT)) + 2;
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bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, _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_private = io;
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bio->bi_destructor = dm_bio_destructor;
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bio->bi_max_vecs--;
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bio_set_region(bio, 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 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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if (sync)
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rw |= (1 << BIO_RW_SYNC);
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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(unsigned int num_regions, struct io_region *where,
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int rw, struct dpages *dp, unsigned long *error_bits)
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{
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struct io io;
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if (num_regions > 1 && rw != WRITE) {
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WARN_ON(1);
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return -EIO;
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}
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io.error = 0;
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atomic_set(&io.count, 1); /* see dispatch_io() */
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io.sleeper = current;
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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) || signal_pending(current))
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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 (atomic_read(&io.count))
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return -EINTR;
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*error_bits = io.error;
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return io.error ? -EIO : 0;
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}
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static int async_io(unsigned int num_regions, struct io_region *where, int rw,
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struct dpages *dp, 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 != 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(_io_pool, GFP_NOIO);
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io->error = 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->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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int dm_io_sync(unsigned int num_regions, struct io_region *where, int rw,
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struct page_list *pl, unsigned int offset,
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unsigned long *error_bits)
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{
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struct dpages dp;
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list_dp_init(&dp, pl, offset);
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return sync_io(num_regions, where, rw, &dp, error_bits);
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}
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int dm_io_sync_bvec(unsigned int num_regions, struct io_region *where, int rw,
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struct bio_vec *bvec, unsigned long *error_bits)
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{
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struct dpages dp;
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bvec_dp_init(&dp, bvec);
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return sync_io(num_regions, where, rw, &dp, error_bits);
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}
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int dm_io_sync_vm(unsigned int num_regions, struct io_region *where, int rw,
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void *data, unsigned long *error_bits)
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{
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struct dpages dp;
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vm_dp_init(&dp, data);
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return sync_io(num_regions, where, rw, &dp, error_bits);
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}
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int dm_io_async(unsigned int num_regions, struct io_region *where, int rw,
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struct page_list *pl, unsigned int offset,
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io_notify_fn fn, void *context)
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{
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struct dpages dp;
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list_dp_init(&dp, pl, offset);
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return async_io(num_regions, where, rw, &dp, fn, context);
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}
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int dm_io_async_bvec(unsigned int num_regions, struct io_region *where, int rw,
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struct bio_vec *bvec, io_notify_fn fn, void *context)
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{
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struct dpages dp;
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bvec_dp_init(&dp, bvec);
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return async_io(num_regions, where, rw, &dp, fn, context);
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}
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int dm_io_async_vm(unsigned int num_regions, struct io_region *where, int rw,
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void *data, io_notify_fn fn, void *context)
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{
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struct dpages dp;
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vm_dp_init(&dp, data);
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return async_io(num_regions, where, rw, &dp, fn, context);
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}
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EXPORT_SYMBOL(dm_io_get);
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EXPORT_SYMBOL(dm_io_put);
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EXPORT_SYMBOL(dm_io_sync);
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EXPORT_SYMBOL(dm_io_async);
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EXPORT_SYMBOL(dm_io_sync_bvec);
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EXPORT_SYMBOL(dm_io_async_bvec);
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EXPORT_SYMBOL(dm_io_sync_vm);
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EXPORT_SYMBOL(dm_io_async_vm);
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