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![Christoph Hellwig](/assets/img/avatar_default.png)
Currently we have two different ways to signal an I/O error on a BIO: (1) by clearing the BIO_UPTODATE flag (2) by returning a Linux errno value to the bi_end_io callback The first one has the drawback of only communicating a single possible error (-EIO), and the second one has the drawback of not beeing persistent when bios are queued up, and are not passed along from child to parent bio in the ever more popular chaining scenario. Having both mechanisms available has the additional drawback of utterly confusing driver authors and introducing bugs where various I/O submitters only deal with one of them, and the others have to add boilerplate code to deal with both kinds of error returns. So add a new bi_error field to store an errno value directly in struct bio and remove the existing mechanisms to clean all this up. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Hannes Reinecke <hare@suse.de> Reviewed-by: NeilBrown <neilb@suse.com> Signed-off-by: Jens Axboe <axboe@fb.com>
540 lines
13 KiB
C
540 lines
13 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/completion.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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atomic_t count;
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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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void *vma_invalidate_address;
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unsigned long vma_invalidate_size;
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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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* Create a client with mempool and bioset.
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*/
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struct dm_io_client *dm_io_client_create(void)
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{
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struct dm_io_client *client;
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unsigned min_ios = dm_get_reserved_bio_based_ios();
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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(min_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(min_ios, 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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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 complete_io(struct io *io)
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{
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unsigned long error_bits = 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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if (io->vma_invalidate_size)
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invalidate_kernel_vmap_range(io->vma_invalidate_address,
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io->vma_invalidate_size);
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mempool_free(io, io->client->pool);
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fn(error_bits, context);
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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 (atomic_dec_and_test(&io->count))
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complete_io(io);
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}
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static void endio(struct bio *bio)
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{
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struct io *io;
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unsigned region;
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if (bio->bi_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, bio->bi_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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void *vma_invalidate_address;
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unsigned long vma_invalidate_size;
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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 bio_get_page(struct dpages *dp, struct page **p,
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unsigned long *len, unsigned *offset)
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{
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struct bio_vec *bvec = dp->context_ptr;
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*p = bvec->bv_page;
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*len = bvec->bv_len - dp->context_u;
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*offset = bvec->bv_offset + dp->context_u;
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}
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static void bio_next_page(struct dpages *dp)
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{
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struct bio_vec *bvec = dp->context_ptr;
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dp->context_ptr = bvec + 1;
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dp->context_u = 0;
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}
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static void bio_dp_init(struct dpages *dp, struct bio *bio)
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{
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dp->get_page = bio_get_page;
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dp->next_page = bio_next_page;
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dp->context_ptr = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
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dp->context_u = bio->bi_iter.bi_bvec_done;
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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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/*
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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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struct request_queue *q = bdev_get_queue(where->bdev);
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unsigned short logical_block_size = queue_logical_block_size(q);
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sector_t num_sectors;
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unsigned int uninitialized_var(special_cmd_max_sectors);
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/*
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* Reject unsupported discard and write same requests.
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*/
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if (rw & REQ_DISCARD)
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special_cmd_max_sectors = q->limits.max_discard_sectors;
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else if (rw & REQ_WRITE_SAME)
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special_cmd_max_sectors = q->limits.max_write_same_sectors;
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if ((rw & (REQ_DISCARD | REQ_WRITE_SAME)) && special_cmd_max_sectors == 0) {
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dec_count(io, region, -EOPNOTSUPP);
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return;
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}
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/*
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* where->count may be zero if rw holds a flush and we need to
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* send a zero-sized flush.
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*/
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do {
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/*
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* Allocate a suitably sized-bio.
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*/
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if ((rw & REQ_DISCARD) || (rw & REQ_WRITE_SAME))
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num_bvecs = 1;
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else
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num_bvecs = min_t(int, bio_get_nr_vecs(where->bdev),
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dm_sector_div_up(remaining, (PAGE_SIZE >> SECTOR_SHIFT)));
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bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
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bio->bi_iter.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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store_io_and_region_in_bio(bio, io, region);
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if (rw & REQ_DISCARD) {
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num_sectors = min_t(sector_t, special_cmd_max_sectors, remaining);
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bio->bi_iter.bi_size = num_sectors << SECTOR_SHIFT;
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remaining -= num_sectors;
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} else if (rw & REQ_WRITE_SAME) {
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/*
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* WRITE SAME only uses a single page.
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*/
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dp->get_page(dp, &page, &len, &offset);
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bio_add_page(bio, page, logical_block_size, offset);
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num_sectors = min_t(sector_t, special_cmd_max_sectors, remaining);
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bio->bi_iter.bi_size = num_sectors << SECTOR_SHIFT;
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offset = 0;
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remaining -= num_sectors;
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dp->next_page(dp);
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} else while (remaining) {
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/*
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* Try and add as many pages as possible.
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*/
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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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} while (remaining);
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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 |= REQ_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 || (rw & REQ_FLUSH))
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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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struct sync_io {
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unsigned long error_bits;
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struct completion wait;
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};
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static void sync_io_complete(unsigned long error, void *context)
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{
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struct sync_io *sio = context;
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sio->error_bits = error;
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complete(&sio->wait);
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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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struct io *io;
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struct sync_io sio;
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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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init_completion(&sio.wait);
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io = mempool_alloc(client->pool, GFP_NOIO);
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io->error_bits = 0;
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atomic_set(&io->count, 1); /* see dispatch_io() */
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io->client = client;
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io->callback = sync_io_complete;
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io->context = &sio;
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io->vma_invalidate_address = dp->vma_invalidate_address;
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io->vma_invalidate_size = dp->vma_invalidate_size;
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dispatch_io(rw, num_regions, where, dp, io, 1);
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wait_for_completion_io(&sio.wait);
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if (error_bits)
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*error_bits = sio.error_bits;
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return sio.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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atomic_set(&io->count, 1); /* see dispatch_io() */
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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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io->vma_invalidate_address = dp->vma_invalidate_address;
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io->vma_invalidate_size = dp->vma_invalidate_size;
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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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unsigned long size)
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{
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/* Set up dpages based on memory type */
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dp->vma_invalidate_address = NULL;
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dp->vma_invalidate_size = 0;
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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_BIO:
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bio_dp_init(dp, io_req->mem.ptr.bio);
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break;
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case DM_IO_VMA:
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flush_kernel_vmap_range(io_req->mem.ptr.vma, size);
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if ((io_req->bi_rw & RW_MASK) == READ) {
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dp->vma_invalidate_address = io_req->mem.ptr.vma;
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dp->vma_invalidate_size = size;
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}
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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 REQ_SYNC in io_req->bi_rw.
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* If you fail to do one of these, the IO will be submitted to the disk after
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* 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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|
{
|
|
int r;
|
|
struct dpages dp;
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|
|
|
r = dp_init(io_req, &dp, (unsigned long)where->count << SECTOR_SHIFT);
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|
if (r)
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|
return r;
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|
|
|
if (!io_req->notify.fn)
|
|
return sync_io(io_req->client, num_regions, where,
|
|
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,
|
|
&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;
|
|
}
|