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Message-ID: <20060914215041.GB3928@agk.surrey.redhat.com>
Date: Thu, 14 Sep 2006 22:50:41 +0100
From: Alasdair G Kergon <agk@...hat.com>
To: Andrew Morton <akpm@...l.org>
Cc: linux-kernel@...r.kernel.org, Milan Broz <mbroz@...hat.com>,
Christophe Saout <christophe@...ut.de>
Subject: [PATCH 21/25] dm crypt: move io to workqueue
From: Milan Broz <mbroz@...hat.com>
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 <mbroz@...hat.com>
Signed-off-by: Alasdair G Kergon <agk@...hat.com>
Cc: Christophe Saout <christophe@...ut.de>
Index: linux-2.6.18-rc7/drivers/md/dm-crypt.c
===================================================================
--- linux-2.6.18-rc7.orig/drivers/md/dm-crypt.c 2006-09-14 21:31:18.000000000 +0100
+++ linux-2.6.18-rc7/drivers/md/dm-crypt.c 2006-09-14 21:31:20.000000000 +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,
-
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