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NVMe: Split non-mergeable bio requests

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It is possible a bio request can not be submitted as a single NVMe IO
command if the bio_vec is not mergeable with the NVMe PRP alignement
constraints. This condition was handled by submitting an IO for the
mergeable portion then submitting a follow on IO for the remaining data
after the previous IO completes. The remainder to be sent was tracked
by manipulating the bio->bi_idx and bio->bi_sector. This patch splits
the request as many times as necessary and submits the bios together.

Since submitting the bio may cause it to be requeued on split,
nvme_resubmit_bios had to be modified to remove the wait queue when
the bio list is empty prior to submitting the bio since a split would
have added the wait queue a second time, corrupting the wait queue head
task list.

There are a few other benefits from doing this: it fixes a potential
issue with the previous handling of a non-mergeable bio as the requeuing
method could would use an unlocked nvme_queue if the callback isn't
invoked on the queue's associated cpu; it will be possible to retry a
failed bio if desired at some later time since it does not manipulate
the original bio; the bio integrity extensions require the bio to be in
its original condition for the checks to work correctly if we implement
the end-to-end data protection in the future.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>
This commit is contained in:
Keith Busch 2013-04-09 11:59:32 -06:00 committed by Matthew Wilcox
parent cbb6218fd4
commit 427e970801
1 changed files with 123 additions and 31 deletions
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154
drivers/block/nvme-core.c
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@ -308,16 +308,6 @@ void nvme_free_iod(struct nvme_dev *dev, struct nvme_iod *iod)
kfree(iod);
}
static void requeue_bio(struct nvme_dev *dev, struct bio *bio)
{
struct nvme_queue *nvmeq = get_nvmeq(dev);
if (bio_list_empty(&nvmeq->sq_cong))
add_wait_queue(&nvmeq->sq_full, &nvmeq->sq_cong_wait);
bio_list_add(&nvmeq->sq_cong, bio);
put_nvmeq(nvmeq);
wake_up_process(nvme_thread);
}
static void bio_completion(struct nvme_dev *dev, void *ctx,
struct nvme_completion *cqe)
{
@ -329,13 +319,10 @@ static void bio_completion(struct nvme_dev *dev, void *ctx,
dma_unmap_sg(&dev->pci_dev->dev, iod->sg, iod->nents,
bio_data_dir(bio) ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
nvme_free_iod(dev, iod);
if (status) {
if (status)
bio_endio(bio, -EIO);
} else if (bio->bi_vcnt > bio->bi_idx) {
requeue_bio(dev, bio);
} else {
else
bio_endio(bio, 0);
}
}
/* length is in bytes. gfp flags indicates whether we may sleep. */
@ -419,25 +406,130 @@ int nvme_setup_prps(struct nvme_dev *dev, struct nvme_common_command *cmd,
return total_len;
}
struct nvme_bio_pair {
struct bio b1, b2, *parent;
struct bio_vec *bv1, *bv2;
int err;
atomic_t cnt;
};
static void nvme_bio_pair_endio(struct bio *bio, int err)
{
struct nvme_bio_pair *bp = bio->bi_private;
if (err)
bp->err = err;
if (atomic_dec_and_test(&bp->cnt)) {
bio_endio(bp->parent, bp->err);
if (bp->bv1)
kfree(bp->bv1);
if (bp->bv2)
kfree(bp->bv2);
kfree(bp);
}
}
static struct nvme_bio_pair *nvme_bio_split(struct bio *bio, int idx,
int len, int offset)
{
struct nvme_bio_pair *bp;
BUG_ON(len > bio->bi_size);
BUG_ON(idx > bio->bi_vcnt);
bp = kmalloc(sizeof(*bp), GFP_ATOMIC);
if (!bp)
return NULL;
bp->err = 0;
bp->b1 = *bio;
bp->b2 = *bio;
bp->b1.bi_size = len;
bp->b2.bi_size -= len;
bp->b1.bi_vcnt = idx;
bp->b2.bi_idx = idx;
bp->b2.bi_sector += len >> 9;
if (offset) {
bp->bv1 = kmalloc(bio->bi_max_vecs * sizeof(struct bio_vec),
GFP_ATOMIC);
if (!bp->bv1)
goto split_fail_1;
bp->bv2 = kmalloc(bio->bi_max_vecs * sizeof(struct bio_vec),
GFP_ATOMIC);
if (!bp->bv2)
goto split_fail_2;
memcpy(bp->bv1, bio->bi_io_vec,
bio->bi_max_vecs * sizeof(struct bio_vec));
memcpy(bp->bv2, bio->bi_io_vec,
bio->bi_max_vecs * sizeof(struct bio_vec));
bp->b1.bi_io_vec = bp->bv1;
bp->b2.bi_io_vec = bp->bv2;
bp->b2.bi_io_vec[idx].bv_offset += offset;
bp->b2.bi_io_vec[idx].bv_len -= offset;
bp->b1.bi_io_vec[idx].bv_len = offset;
bp->b1.bi_vcnt++;
} else
bp->bv1 = bp->bv2 = NULL;
bp->b1.bi_private = bp;
bp->b2.bi_private = bp;
bp->b1.bi_end_io = nvme_bio_pair_endio;
bp->b2.bi_end_io = nvme_bio_pair_endio;
bp->parent = bio;
atomic_set(&bp->cnt, 2);
return bp;
split_fail_2:
kfree(bp->bv1);
split_fail_1:
kfree(bp);
return NULL;
}
static int nvme_split_and_submit(struct bio *bio, struct nvme_queue *nvmeq,
int idx, int len, int offset)
{
struct nvme_bio_pair *bp = nvme_bio_split(bio, idx, len, offset);
if (!bp)
return -ENOMEM;
if (bio_list_empty(&nvmeq->sq_cong))
add_wait_queue(&nvmeq->sq_full, &nvmeq->sq_cong_wait);
bio_list_add(&nvmeq->sq_cong, &bp->b1);
bio_list_add(&nvmeq->sq_cong, &bp->b2);
return 0;
}
/* NVMe scatterlists require no holes in the virtual address */
#define BIOVEC_NOT_VIRT_MERGEABLE(vec1, vec2) ((vec2)->bv_offset || \
(((vec1)->bv_offset + (vec1)->bv_len) % PAGE_SIZE))
static int nvme_map_bio(struct device *dev, struct nvme_iod *iod,
static int nvme_map_bio(struct nvme_queue *nvmeq, struct nvme_iod *iod,
struct bio *bio, enum dma_data_direction dma_dir, int psegs)
{
struct bio_vec *bvec, *bvprv = NULL;
struct scatterlist *sg = NULL;
int i, old_idx, length = 0, nsegs = 0;
int i, length = 0, nsegs = 0;
sg_init_table(iod->sg, psegs);
old_idx = bio->bi_idx;
bio_for_each_segment(bvec, bio, i) {
if (bvprv && BIOVEC_PHYS_MERGEABLE(bvprv, bvec)) {
sg->length += bvec->bv_len;
} else {
if (bvprv && BIOVEC_NOT_VIRT_MERGEABLE(bvprv, bvec))
break;
return nvme_split_and_submit(bio, nvmeq, i,
length, 0);
sg = sg ? sg + 1 : iod->sg;
sg_set_page(sg, bvec->bv_page, bvec->bv_len,
bvec->bv_offset);
@ -446,13 +538,11 @@ static int nvme_map_bio(struct device *dev, struct nvme_iod *iod,
length += bvec->bv_len;
bvprv = bvec;
}
bio->bi_idx = i;
iod->nents = nsegs;
sg_mark_end(sg);
if (dma_map_sg(dev, iod->sg, iod->nents, dma_dir) == 0) {
bio->bi_idx = old_idx;
if (dma_map_sg(nvmeq->q_dmadev, iod->sg, iod->nents, dma_dir) == 0)
return -ENOMEM;
}
return length;
}
@ -581,8 +671,8 @@ static int nvme_submit_bio_queue(struct nvme_queue *nvmeq, struct nvme_ns *ns,
dma_dir = DMA_FROM_DEVICE;
}
result = nvme_map_bio(nvmeq->q_dmadev, iod, bio, dma_dir, psegs);
if (result < 0)
result = nvme_map_bio(nvmeq, iod, bio, dma_dir, psegs);
if (result <= 0)
goto free_cmdid;
length = result;
@ -595,8 +685,6 @@ static int nvme_submit_bio_queue(struct nvme_queue *nvmeq, struct nvme_ns *ns,
cmnd->rw.control = cpu_to_le16(control);
cmnd->rw.dsmgmt = cpu_to_le32(dsmgmt);
bio->bi_sector += length >> 9;
if (++nvmeq->sq_tail == nvmeq->q_depth)
nvmeq->sq_tail = 0;
writel(nvmeq->sq_tail, nvmeq->q_db);
@ -1281,13 +1369,17 @@ static void nvme_resubmit_bios(struct nvme_queue *nvmeq)
while (bio_list_peek(&nvmeq->sq_cong)) {
struct bio *bio = bio_list_pop(&nvmeq->sq_cong);
struct nvme_ns *ns = bio->bi_bdev->bd_disk->private_data;
if (nvme_submit_bio_queue(nvmeq, ns, bio)) {
bio_list_add_head(&nvmeq->sq_cong, bio);
break;
}
if (bio_list_empty(&nvmeq->sq_cong))
remove_wait_queue(&nvmeq->sq_full,
&nvmeq->sq_cong_wait);
if (nvme_submit_bio_queue(nvmeq, ns, bio)) {
if (bio_list_empty(&nvmeq->sq_cong))
add_wait_queue(&nvmeq->sq_full,
&nvmeq->sq_cong_wait);
bio_list_add_head(&nvmeq->sq_cong, bio);
break;
}
}
}