linux/drivers/md/dm-io.c
Mikulas Patocka d659e6cc98 dm io: respect BIO_MAX_PAGES limit
dm-io calls bio_get_nr_vecs to get the maximum number of pages to use
for a given device.  It allocates one additional bio_vec to use
internally but failed to respect BIO_MAX_PAGES, so fix this.

This was the likely cause of:
  https://bugzilla.redhat.com/show_bug.cgi?id=173153

Cc: stable@kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-03-16 17:44:30 +00:00

466 lines
11 KiB
C

/*
* Copyright (C) 2003 Sistina Software
* Copyright (C) 2006 Red Hat GmbH
*
* This file is released under the GPL.
*/
#include <linux/device-mapper.h>
#include <linux/bio.h>
#include <linux/mempool.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/dm-io.h>
struct dm_io_client {
mempool_t *pool;
struct bio_set *bios;
};
/* FIXME: can we shrink this ? */
struct io {
unsigned long error_bits;
atomic_t count;
struct task_struct *sleeper;
struct dm_io_client *client;
io_notify_fn callback;
void *context;
};
/*
* io contexts are only dynamically allocated for asynchronous
* io. Since async io is likely to be the majority of io we'll
* have the same number of io contexts as bios! (FIXME: must reduce this).
*/
static unsigned int pages_to_ios(unsigned int pages)
{
return 4 * pages; /* too many ? */
}
/*
* Create a client with mempool and bioset.
*/
struct dm_io_client *dm_io_client_create(unsigned num_pages)
{
unsigned ios = pages_to_ios(num_pages);
struct dm_io_client *client;
client = kmalloc(sizeof(*client), GFP_KERNEL);
if (!client)
return ERR_PTR(-ENOMEM);
client->pool = mempool_create_kmalloc_pool(ios, sizeof(struct io));
if (!client->pool)
goto bad;
client->bios = bioset_create(16, 0);
if (!client->bios)
goto bad;
return client;
bad:
if (client->pool)
mempool_destroy(client->pool);
kfree(client);
return ERR_PTR(-ENOMEM);
}
EXPORT_SYMBOL(dm_io_client_create);
int dm_io_client_resize(unsigned num_pages, struct dm_io_client *client)
{
return mempool_resize(client->pool, pages_to_ios(num_pages),
GFP_KERNEL);
}
EXPORT_SYMBOL(dm_io_client_resize);
void dm_io_client_destroy(struct dm_io_client *client)
{
mempool_destroy(client->pool);
bioset_free(client->bios);
kfree(client);
}
EXPORT_SYMBOL(dm_io_client_destroy);
/*-----------------------------------------------------------------
* We need to keep track of which region a bio is doing io for.
* In order to save a memory allocation we store this the last
* bvec which we know is unused (blech).
* XXX This is ugly and can OOPS with some configs... find another way.
*---------------------------------------------------------------*/
static inline void bio_set_region(struct bio *bio, unsigned region)
{
bio->bi_io_vec[bio->bi_max_vecs].bv_len = region;
}
static inline unsigned bio_get_region(struct bio *bio)
{
return bio->bi_io_vec[bio->bi_max_vecs].bv_len;
}
/*-----------------------------------------------------------------
* We need an io object to keep track of the number of bios that
* have been dispatched for a particular io.
*---------------------------------------------------------------*/
static void dec_count(struct io *io, unsigned int region, int error)
{
if (error)
set_bit(region, &io->error_bits);
if (atomic_dec_and_test(&io->count)) {
if (io->sleeper)
wake_up_process(io->sleeper);
else {
unsigned long r = io->error_bits;
io_notify_fn fn = io->callback;
void *context = io->context;
mempool_free(io, io->client->pool);
fn(r, context);
}
}
}
static void endio(struct bio *bio, int error)
{
struct io *io;
unsigned region;
if (error && bio_data_dir(bio) == READ)
zero_fill_bio(bio);
/*
* The bio destructor in bio_put() may use the io object.
*/
io = bio->bi_private;
region = bio_get_region(bio);
bio->bi_max_vecs++;
bio_put(bio);
dec_count(io, region, error);
}
/*-----------------------------------------------------------------
* These little objects provide an abstraction for getting a new
* destination page for io.
*---------------------------------------------------------------*/
struct dpages {
void (*get_page)(struct dpages *dp,
struct page **p, unsigned long *len, unsigned *offset);
void (*next_page)(struct dpages *dp);
unsigned context_u;
void *context_ptr;
};
/*
* Functions for getting the pages from a list.
*/
static void list_get_page(struct dpages *dp,
struct page **p, unsigned long *len, unsigned *offset)
{
unsigned o = dp->context_u;
struct page_list *pl = (struct page_list *) dp->context_ptr;
*p = pl->page;
*len = PAGE_SIZE - o;
*offset = o;
}
static void list_next_page(struct dpages *dp)
{
struct page_list *pl = (struct page_list *) dp->context_ptr;
dp->context_ptr = pl->next;
dp->context_u = 0;
}
static void list_dp_init(struct dpages *dp, struct page_list *pl, unsigned offset)
{
dp->get_page = list_get_page;
dp->next_page = list_next_page;
dp->context_u = offset;
dp->context_ptr = pl;
}
/*
* Functions for getting the pages from a bvec.
*/
static void bvec_get_page(struct dpages *dp,
struct page **p, unsigned long *len, unsigned *offset)
{
struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
*p = bvec->bv_page;
*len = bvec->bv_len;
*offset = bvec->bv_offset;
}
static void bvec_next_page(struct dpages *dp)
{
struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
dp->context_ptr = bvec + 1;
}
static void bvec_dp_init(struct dpages *dp, struct bio_vec *bvec)
{
dp->get_page = bvec_get_page;
dp->next_page = bvec_next_page;
dp->context_ptr = bvec;
}
/*
* Functions for getting the pages from a VMA.
*/
static void vm_get_page(struct dpages *dp,
struct page **p, unsigned long *len, unsigned *offset)
{
*p = vmalloc_to_page(dp->context_ptr);
*offset = dp->context_u;
*len = PAGE_SIZE - dp->context_u;
}
static void vm_next_page(struct dpages *dp)
{
dp->context_ptr += PAGE_SIZE - dp->context_u;
dp->context_u = 0;
}
static void vm_dp_init(struct dpages *dp, void *data)
{
dp->get_page = vm_get_page;
dp->next_page = vm_next_page;
dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
dp->context_ptr = data;
}
static void dm_bio_destructor(struct bio *bio)
{
struct io *io = bio->bi_private;
bio_free(bio, io->client->bios);
}
/*
* Functions for getting the pages from kernel memory.
*/
static void km_get_page(struct dpages *dp, struct page **p, unsigned long *len,
unsigned *offset)
{
*p = virt_to_page(dp->context_ptr);
*offset = dp->context_u;
*len = PAGE_SIZE - dp->context_u;
}
static void km_next_page(struct dpages *dp)
{
dp->context_ptr += PAGE_SIZE - dp->context_u;
dp->context_u = 0;
}
static void km_dp_init(struct dpages *dp, void *data)
{
dp->get_page = km_get_page;
dp->next_page = km_next_page;
dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
dp->context_ptr = data;
}
/*-----------------------------------------------------------------
* IO routines that accept a list of pages.
*---------------------------------------------------------------*/
static void do_region(int rw, unsigned region, struct dm_io_region *where,
struct dpages *dp, struct io *io)
{
struct bio *bio;
struct page *page;
unsigned long len;
unsigned offset;
unsigned num_bvecs;
sector_t remaining = where->count;
while (remaining) {
/*
* Allocate a suitably sized-bio: we add an extra
* bvec for bio_get/set_region() and decrement bi_max_vecs
* to hide it from bio_add_page().
*/
num_bvecs = dm_sector_div_up(remaining,
(PAGE_SIZE >> SECTOR_SHIFT));
num_bvecs = 1 + min_t(int, bio_get_nr_vecs(where->bdev),
num_bvecs);
if (unlikely(num_bvecs > BIO_MAX_PAGES))
num_bvecs = BIO_MAX_PAGES;
bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
bio->bi_sector = where->sector + (where->count - remaining);
bio->bi_bdev = where->bdev;
bio->bi_end_io = endio;
bio->bi_private = io;
bio->bi_destructor = dm_bio_destructor;
bio->bi_max_vecs--;
bio_set_region(bio, region);
/*
* Try and add as many pages as possible.
*/
while (remaining) {
dp->get_page(dp, &page, &len, &offset);
len = min(len, to_bytes(remaining));
if (!bio_add_page(bio, page, len, offset))
break;
offset = 0;
remaining -= to_sector(len);
dp->next_page(dp);
}
atomic_inc(&io->count);
submit_bio(rw, bio);
}
}
static void dispatch_io(int rw, unsigned int num_regions,
struct dm_io_region *where, struct dpages *dp,
struct io *io, int sync)
{
int i;
struct dpages old_pages = *dp;
if (sync)
rw |= (1 << BIO_RW_SYNCIO) | (1 << BIO_RW_UNPLUG);
/*
* For multiple regions we need to be careful to rewind
* the dp object for each call to do_region.
*/
for (i = 0; i < num_regions; i++) {
*dp = old_pages;
if (where[i].count)
do_region(rw, i, where + i, dp, io);
}
/*
* Drop the extra reference that we were holding to avoid
* the io being completed too early.
*/
dec_count(io, 0, 0);
}
static int sync_io(struct dm_io_client *client, unsigned int num_regions,
struct dm_io_region *where, int rw, struct dpages *dp,
unsigned long *error_bits)
{
struct io io;
if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
WARN_ON(1);
return -EIO;
}
io.error_bits = 0;
atomic_set(&io.count, 1); /* see dispatch_io() */
io.sleeper = current;
io.client = client;
dispatch_io(rw, num_regions, where, dp, &io, 1);
while (1) {
set_current_state(TASK_UNINTERRUPTIBLE);
if (!atomic_read(&io.count) || signal_pending(current))
break;
io_schedule();
}
set_current_state(TASK_RUNNING);
if (atomic_read(&io.count))
return -EINTR;
if (error_bits)
*error_bits = io.error_bits;
return io.error_bits ? -EIO : 0;
}
static int async_io(struct dm_io_client *client, unsigned int num_regions,
struct dm_io_region *where, int rw, struct dpages *dp,
io_notify_fn fn, void *context)
{
struct io *io;
if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
WARN_ON(1);
fn(1, context);
return -EIO;
}
io = mempool_alloc(client->pool, GFP_NOIO);
io->error_bits = 0;
atomic_set(&io->count, 1); /* see dispatch_io() */
io->sleeper = NULL;
io->client = client;
io->callback = fn;
io->context = context;
dispatch_io(rw, num_regions, where, dp, io, 0);
return 0;
}
static int dp_init(struct dm_io_request *io_req, struct dpages *dp)
{
/* Set up dpages based on memory type */
switch (io_req->mem.type) {
case DM_IO_PAGE_LIST:
list_dp_init(dp, io_req->mem.ptr.pl, io_req->mem.offset);
break;
case DM_IO_BVEC:
bvec_dp_init(dp, io_req->mem.ptr.bvec);
break;
case DM_IO_VMA:
vm_dp_init(dp, io_req->mem.ptr.vma);
break;
case DM_IO_KMEM:
km_dp_init(dp, io_req->mem.ptr.addr);
break;
default:
return -EINVAL;
}
return 0;
}
/*
* New collapsed (a)synchronous interface.
*
* If the IO is asynchronous (i.e. it has notify.fn), you must either unplug
* the queue with blk_unplug() some time later or set the BIO_RW_SYNC bit in
* io_req->bi_rw. If you fail to do one of these, the IO will be submitted to
* the disk after q->unplug_delay, which defaults to 3ms in blk-settings.c.
*/
int dm_io(struct dm_io_request *io_req, unsigned num_regions,
struct dm_io_region *where, unsigned long *sync_error_bits)
{
int r;
struct dpages dp;
r = dp_init(io_req, &dp);
if (r)
return r;
if (!io_req->notify.fn)
return sync_io(io_req->client, num_regions, where,
io_req->bi_rw, &dp, sync_error_bits);
return async_io(io_req->client, num_regions, where, io_req->bi_rw,
&dp, io_req->notify.fn, io_req->notify.context);
}
EXPORT_SYMBOL(dm_io);