From: Robin Dong <[email protected]>
We are now trying to modify flashcache(https://github.com/facebook/flashcache)
to make it request based so that
we can let cfq io-controller control the bandwidth between different
io cgroups.
A search in the dm directory tells me that only multipath is a request
based dm target and its functionality
is very simple and map_rq() is used to map the request to different underlying
devices.
We can't work in this way because:
1. the request which processed by map_rq() need to be issued to
different lower devices (disk device and cache device, in flashcache),
therefore the request
can't be totally remapped by simply changing its queue and returning
DM_MAPIO_REMAPPED in map_rq() like multipath_map()
2. to submit bios drectly in map_rq() (by return DM_MAPIO_SUBMITTED) will cause
BUG_ON(!irqs_disabled())
in dm_request_fn() because the
submit_bio()->generic_make_request()->blk_queue_bio() will definitly call
spin_unlock_irq to enable the irqs
As above,the interface map_rq() provided by devcie-mapper framework
is not enough for an autonomous target, like flashcache.
We propose to add a new
mk_rq interface so that we can make the requests
by ourselves.
Signed-off-by: Robin Dong <[email protected]>
---
drivers/md/dm-io.c | 58 ++++++++++++++++++++++++++++--------------------
drivers/md/dm-log.c | 1 +
include/linux/dm-io.h | 3 ++
3 files changed, 38 insertions(+), 24 deletions(-)
diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c
index ea5dd28..f767792 100644
--- a/drivers/md/dm-io.c
+++ b/drivers/md/dm-io.c
@@ -287,8 +287,8 @@ static void km_dp_init(struct dpages *dp, void *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)
+static void do_region(struct dm_io_request *io_req, unsigned region,
+ struct dm_io_region *where, struct dpages *dp, struct io *io)
{
struct bio *bio;
struct page *page;
@@ -298,6 +298,7 @@ static void do_region(int rw, unsigned region, struct
dm_io_region *where,
sector_t remaining = where->count;
struct request_queue *q = bdev_get_queue(where->bdev);
sector_t discard_sectors;
+ int rw = io_req->bi_rw;
/*
* where->count may be zero if rw holds a flush and we need to
@@ -339,15 +340,26 @@ static void do_region(int rw, unsigned region, struct
dm_io_region *where,
}
atomic_inc(&io->count);
- submit_bio(rw, bio);
+ if (!io_req->only_create_bio)
+ submit_bio(rw, bio);
+ else {
+ bio->bi_rw |= rw;
+ if (io_req->start) {
+ io_req->end->bi_next = bio;
+ io_req->end = bio;
+ } else
+ io_req->start = io_req->end = bio;
+ bio->bi_next = NULL;
+ }
} while (remaining);
}
-static void dispatch_io(int rw, unsigned int num_regions,
+static void dispatch_io(struct dm_io_request *io_req, unsigned int num_regions,
struct dm_io_region *where, struct dpages *dp,
struct io *io, int sync)
{
int i;
+ int rw = io_req->bi_rw;
struct dpages old_pages = *dp;
BUG_ON(num_regions > DM_IO_MAX_REGIONS);
@@ -362,7 +374,7 @@ static void dispatch_io(int rw, unsigned int num_regions,
for (i = 0; i < num_regions; i++) {
*dp = old_pages;
if (where[i].count || (rw & REQ_FLUSH))
- do_region(rw, i, where + i, dp, io);
+ do_region(io_req, i, where + i, dp, io);
}
/*
@@ -372,8 +384,8 @@ static void dispatch_io(int rw, unsigned int num_regions,
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,
+static int sync_io(struct dm_io_request *io_req, unsigned int num_regions,
+ struct dm_io_region *where, struct dpages *dp,
unsigned long *error_bits)
{
/*
@@ -385,7 +397,7 @@ static int sync_io(struct dm_io_client *client, unsigned
int num_regions,
volatile char io_[sizeof(struct io) + __alignof__(struct io) - 1];
struct io *io = (struct io *)PTR_ALIGN(&io_, __alignof__(struct io));
- if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
+ if (num_regions > 1 && (io_req->bi_rw & RW_MASK) != WRITE) {
WARN_ON(1);
return -EIO;
}
@@ -393,12 +405,12 @@ static int sync_io(struct dm_io_client *client, unsigned
int num_regions,
io->error_bits = 0;
atomic_set(&io->count, 1); /* see dispatch_io() */
io->sleeper = current;
- io->client = client;
+ io->client = io_req->client;
io->vma_invalidate_address = dp->vma_invalidate_address;
io->vma_invalidate_size = dp->vma_invalidate_size;
- dispatch_io(rw, num_regions, where, dp, io, 1);
+ dispatch_io(io_req, num_regions, where, dp, io, 1);
while (1) {
set_current_state(TASK_UNINTERRUPTIBLE);
@@ -416,30 +428,29 @@ static int sync_io(struct dm_io_client *client, unsigned
int num_regions,
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)
+static int async_io(struct dm_io_request *io_req, unsigned int num_regions,
+ struct dm_io_region *where, struct dpages *dp)
{
struct io *io;
- if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
+ if (num_regions > 1 && (io_req->bi_rw & RW_MASK) != WRITE) {
WARN_ON(1);
- fn(1, context);
+ io_req->notify.fn(1, io_req->notify.context);
return -EIO;
}
- io = mempool_alloc(client->pool, GFP_NOIO);
+ io = mempool_alloc(io_req->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;
+ io->client = io_req->client;
+ io->callback = io_req->notify.fn;
+ io->context = io_req->notify.context;
io->vma_invalidate_address = dp->vma_invalidate_address;
io->vma_invalidate_size = dp->vma_invalidate_size;
- dispatch_io(rw, num_regions, where, dp, io, 0);
+ dispatch_io(io_req, num_regions, where, dp, io, 0);
return 0;
}
@@ -499,11 +510,10 @@ int dm_io(struct dm_io_request *io_req, unsigned
num_regions,
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 sync_io(io_req, num_regions, where,
+ &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);
+ return async_io(io_req, num_regions, where, &dp);
}
EXPORT_SYMBOL(dm_io);
diff --git a/drivers/md/dm-log.c b/drivers/md/dm-log.c
index 627d191..3bf065a 100644
--- a/drivers/md/dm-log.c
+++ b/drivers/md/dm-log.c
@@ -463,6 +463,7 @@ static int create_log_context(struct dm_dirty_log *log,
struct dm_target *ti,
kfree(lc);
return r;
}
+ lc->io_req.only_create_bio = 0;
lc->disk_header = vmalloc(buf_size);
if (!lc->disk_header) {
diff --git a/include/linux/dm-io.h b/include/linux/dm-io.h
index f4b0aa3..8782163 100644
--- a/include/linux/dm-io.h
+++ b/include/linux/dm-io.h
@@ -61,6 +61,9 @@ struct dm_io_request {
struct dm_io_memory mem; /* Memory to use for io */
struct dm_io_notify notify; /* Synchronous if notify.fn is NULL */
struct dm_io_client *client; /* Client memory handler */
+ int only_create_bio;
+ struct bio *start;
+ struct bio *end;
};
/*
--
1.7.1
--
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