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dm crypt: use io thread for reads only if mempool exhausted

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If there is enough memory, code can directly submit bio
instead queing this operation in separate thread.

Try to alloc bio clone with GFP_NOWAIT and only if it
fails use separate queue (map function cannot block here).

Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Milan Broz 2011-01-13 19:59:53 +00:00 committed by Alasdair G Kergon
parent c029772125
commit 20c82538e4
1 changed files with 23 additions and 14 deletions
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37
drivers/md/dm-crypt.c
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@ -787,26 +787,30 @@ static void clone_init(struct dm_crypt_io *io, struct bio *clone)
clone->bi_destructor = dm_crypt_bio_destructor;
}
static void kcryptd_io_read(struct dm_crypt_io *io)
static void kcryptd_unplug(struct crypt_config *cc)
{
blk_unplug(bdev_get_queue(cc->dev->bdev));
}
static int kcryptd_io_read(struct dm_crypt_io *io, gfp_t gfp)
{
struct crypt_config *cc = io->target->private;
struct bio *base_bio = io->base_bio;
struct bio *clone;
crypt_inc_pending(io);
/*
* The block layer might modify the bvec array, so always
* copy the required bvecs because we need the original
* one in order to decrypt the whole bio data *afterwards*.
*/
clone = bio_alloc_bioset(GFP_NOIO, bio_segments(base_bio), cc->bs);
if (unlikely(!clone)) {
io->error = -ENOMEM;
crypt_dec_pending(io);
return;
clone = bio_alloc_bioset(gfp, bio_segments(base_bio), cc->bs);
if (!clone) {
kcryptd_unplug(cc);
return 1;
}
crypt_inc_pending(io);
clone_init(io, clone);
clone->bi_idx = 0;
clone->bi_vcnt = bio_segments(base_bio);
@ -816,6 +820,7 @@ static void kcryptd_io_read(struct dm_crypt_io *io)
sizeof(struct bio_vec) * clone->bi_vcnt);
generic_make_request(clone);
return 0;
}
static void kcryptd_io_write(struct dm_crypt_io *io)
@ -828,9 +833,12 @@ static void kcryptd_io(struct work_struct *work)
{
struct dm_crypt_io *io = container_of(work, struct dm_crypt_io, work);
if (bio_data_dir(io->base_bio) == READ)
kcryptd_io_read(io);
else
if (bio_data_dir(io->base_bio) == READ) {
crypt_inc_pending(io);
if (kcryptd_io_read(io, GFP_NOIO))
io->error = -ENOMEM;
crypt_dec_pending(io);
} else
kcryptd_io_write(io);
}
@ -1424,9 +1432,10 @@ static int crypt_map(struct dm_target *ti, struct bio *bio,
io = crypt_io_alloc(ti, bio, dm_target_offset(ti, bio->bi_sector));
if (bio_data_dir(io->base_bio) == READ)
kcryptd_queue_io(io);
else
if (bio_data_dir(io->base_bio) == READ) {
if (kcryptd_io_read(io, GFP_NOWAIT))
kcryptd_queue_io(io);
} else
kcryptd_queue_crypt(io);
return DM_MAPIO_SUBMITTED;