Commit 23541d2d authored by Milan Broz's avatar Milan Broz Committed by Linus Torvalds
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[PATCH] dm crypt: move io to workqueue 



This patch is designed to help dm-crypt comply with the
new constraints imposed by the following patch in -mm:
  md-dm-reduce-stack-usage-with-stacked-block-devices.patch

Under low memory the existing implementation relies upon waiting for I/O
submitted recursively to generic_make_request() completing before the original
generic_make_request() call can return.

This patch moves the I/O submission to a workqueue so the original
generic_make_request() can return immediately.

Signed-off-by: default avatarMilan Broz <mbroz@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 93e605c2

drivers/md/dm-crypt.c

+27 −36
Original line number Diff line number Diff line
@@ -35,6 +35,7 @@ struct crypt_io { 
	struct work_struct work;

	atomic_t pending;

	int error;

	int post_process;

};



/*
@@ -445,8 +446,7 @@ static void dec_pending(struct crypt_io *io, int error) 
 * kcryptd:

 *

 * Needed because it would be very unwise to do decryption in an

 * interrupt context, so bios returning from read requests get

 * queued here.

 * interrupt context.

 */

static struct workqueue_struct *_kcryptd_workqueue;

static void kcryptd_do_work(void *data);
@@ -470,12 +470,10 @@ static int crypt_endio(struct bio *clone, unsigned int done, int error) 
	if (!read_io)

		crypt_free_buffer_pages(cc, clone, done);



	/* keep going - not finished yet */

	if (unlikely(clone->bi_size))

		return 1;



	/*

	 * successful reads are decrypted by the worker thread

	 */

	if (!read_io)

		goto out;
@@ -485,6 +483,7 @@ static int crypt_endio(struct bio *clone, unsigned int done, int error) 
	}



	bio_put(clone);

	io->post_process = 1;

	kcryptd_queue_io(io);

	return 0;
@@ -504,7 +503,7 @@ static void clone_init(struct crypt_io *io, struct bio *clone) 
	clone->bi_rw      = io->base_bio->bi_rw;

}



static int process_read(struct crypt_io *io)

static void process_read(struct crypt_io *io)

{

	struct crypt_config *cc = io->target->private;

	struct bio *base_bio = io->base_bio;
@@ -521,7 +520,7 @@ static int process_read(struct crypt_io *io) 
	clone = bio_alloc(GFP_NOIO, bio_segments(base_bio));

	if (unlikely(!clone)) {

		dec_pending(io, -ENOMEM);

		return 0;

		return;

	}



	clone_init(io, clone);
@@ -533,11 +532,9 @@ static int process_read(struct crypt_io *io) 
	       sizeof(struct bio_vec) * clone->bi_vcnt);



	generic_make_request(clone);



	return 0;

}



static int process_write(struct crypt_io *io)

static void process_write(struct crypt_io *io)

{

	struct crypt_config *cc = io->target->private;

	struct bio *base_bio = io->base_bio;
@@ -558,15 +555,18 @@ static int process_write(struct crypt_io *io) 
	while (remaining) {

		clone = crypt_alloc_buffer(cc, base_bio->bi_size,

					   io->first_clone, &bvec_idx);

		if (unlikely(!clone))

			goto cleanup;

		if (unlikely(!clone)) {

			dec_pending(io, -ENOMEM);

			return;

		}



		ctx.bio_out = clone;



		if (unlikely(crypt_convert(cc, &ctx) < 0)) {

			crypt_free_buffer_pages(cc, clone, clone->bi_size);

			bio_put(clone);

			goto cleanup;

			dec_pending(io, -EIO);

			return;

		}



		clone_init(io, clone);
@@ -582,31 +582,20 @@ static int process_write(struct crypt_io *io) 
			io->first_clone = clone;

		}



		atomic_inc(&io->pending);



		remaining -= clone->bi_size;

		sector += bio_sectors(clone);



		/* prevent bio_put of first_clone */

		if (remaining)

			atomic_inc(&io->pending);



		generic_make_request(clone);



		/* out of memory -> run queues */

		if (remaining)

			blk_congestion_wait(bio_data_dir(clone), HZ/100);

	}



	/* drop reference, clones could have returned before we reach this */

	dec_pending(io, 0);

	return 0;



cleanup:

	if (io->first_clone) {

		dec_pending(io, -ENOMEM);

		return 0;

	}



	 /* if no bio has been dispatched yet, we can directly return the error */

	mempool_free(io, cc->io_pool);

	return -ENOMEM;

}



static void process_read_endio(struct crypt_io *io)
@@ -624,7 +613,12 @@ static void kcryptd_do_work(void *data) 
{

	struct crypt_io *io = data;



	if (io->post_process)

		process_read_endio(io);

	else if (bio_data_dir(io->base_bio) == READ)

		process_read(io);

	else

		process_write(io);

}



/*
@@ -889,17 +883,14 @@ static int crypt_map(struct dm_target *ti, struct bio *bio, 
	struct crypt_io *io;



	io = mempool_alloc(cc->io_pool, GFP_NOIO);



	io->target = ti;

	io->base_bio = bio;

	io->first_clone = NULL;

	io->error = 0;

	io->error = io->post_process = 0;

	atomic_set(&io->pending, 0);

	kcryptd_queue_io(io);



	if (bio_data_dir(bio) == WRITE)

		return process_write(io);



	return process_read(io);

	return 0;

}



static int crypt_status(struct dm_target *ti, status_type_t type,
@@ -999,7 +990,7 @@ error: 


static struct target_type crypt_target = {

	.name   = "crypt",

	.version= {1, 2, 0},

	.version= {1, 3, 0},

	.module = THIS_MODULE,

	.ctr    = crypt_ctr,

	.dtr    = crypt_dtr,

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