To: Andrew Morton Cc: linux-kernel@vger.kernel.org, Milan Broz , Christophe Saout Subject: [PATCH 21/25] dm crypt: move io to workqueue From: Milan Broz 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: Milan Broz Signed-off-by: Alasdair G Kergon Cc: Christophe Saout Index: linux-2.6.18-rc7/drivers/md/dm-crypt.c =================================================================== --- linux-2.6.18-rc7.orig/drivers/md/dm-crypt.c 2006-10-13 17:10:14.000000000 +0100 +++ linux-2.6.18-rc7/drivers/md/dm-crypt.c 2006-10-13 17:10:15.000000000 +0100 @@ -34,6 +34,7 @@ struct crypt_io { struct work_struct work; atomic_t pending; int error; + int post_process; }; /* @@ -441,8 +442,7 @@ static void dec_pending(struct crypt_io * 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); @@ -466,12 +466,10 @@ static int crypt_endio(struct bio *clone 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; @@ -481,6 +479,7 @@ static int crypt_endio(struct bio *clone } bio_put(clone); + io->post_process = 1; kcryptd_queue_io(io); return 0; @@ -500,7 +499,7 @@ static void clone_init(struct crypt_io * 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; @@ -517,7 +516,7 @@ static int process_read(struct crypt_io clone = bio_alloc(GFP_NOIO, bio_segments(base_bio)); if (unlikely(!clone)) { dec_pending(io, -ENOMEM); - return 0; + return; } clone_init(io, clone); @@ -529,11 +528,9 @@ static int process_read(struct crypt_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; @@ -554,15 +551,18 @@ static int process_write(struct crypt_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); @@ -578,31 +578,20 @@ static int process_write(struct crypt_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) @@ -620,7 +609,12 @@ static void kcryptd_do_work(void *data) { struct crypt_io *io = data; - process_read_endio(io); + if (io->post_process) + process_read_endio(io); + else if (bio_data_dir(io->base_bio) == READ) + process_read(io); + else + process_write(io); } /* @@ -892,17 +886,14 @@ static int crypt_map(struct dm_target *t 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, @@ -1011,7 +1002,7 @@ 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,