[PATCH v7 1/8] block: ensure bios are not split in middle of crypto data unit

Satya Tangirala
2020-11-17T14:07:20Z

Introduce blk_crypto_bio_sectors_alignment() that returns the required
alignment for the number of sectors in a bio. Any bio split must ensure
that the number of sectors in the resulting bios is aligned to that
returned value. This patch also updates __blk_queue_split(),
__blk_queue_bounce() and blk_crypto_split_bio_if_needed() to respect
blk_crypto_bio_sectors_alignment() when splitting bios.

Signed-off-by: Satya Tangirala <satyat@google.com>
---
block/bio.c | 1 +
block/blk-crypto-fallback.c | 10 ++--
block/blk-crypto-internal.h | 18 +++++++
block/blk-merge.c | 96 ++++++++++++++++++++++++++++++++-----
block/blk-mq.c | 3 ++
block/bounce.c | 4 ++
6 files changed, 117 insertions(+), 15 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index fa01bef35bb1..259cef126df3 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1472,6 +1472,7 @@ struct bio *bio_split(struct bio *bio, int sectors,

BUG_ON(sectors <= 0);
BUG_ON(sectors >= bio_sectors(bio));
+ WARN_ON(!IS_ALIGNED(sectors, blk_crypto_bio_sectors_alignment(bio)));

/* Zone append commands cannot be split */
if (WARN_ON_ONCE(bio_op(bio) == REQ_OP_ZONE_APPEND))
diff --git a/block/blk-crypto-fallback.c b/block/blk-crypto-fallback.c
index c162b754efbd..db2d2c67b308 100644
--- a/block/blk-crypto-fallback.c
+++ b/block/blk-crypto-fallback.c
@@ -209,20 +209,22 @@ static bool blk_crypto_alloc_cipher_req(struct blk_ksm_keyslot *slot,
static bool blk_crypto_split_bio_if_needed(struct bio **bio_ptr)
{
struct bio *bio = *bio_ptr;
+ struct bio_crypt_ctx *bc = bio->bi_crypt_context;
unsigned int i = 0;
- unsigned int num_sectors = 0;
+ unsigned int len = 0;
struct bio_vec bv;
struct bvec_iter iter;

bio_for_each_segment(bv, bio, iter) {
- num_sectors += bv.bv_len >> SECTOR_SHIFT;
+ len += bv.bv_len;
if (++i == BIO_MAX_PAGES)
break;
}
- if (num_sectors < bio_sectors(bio)) {
+ if (len < bio->bi_iter.bi_size) {
struct bio *split_bio;

- split_bio = bio_split(bio, num_sectors, GFP_NOIO, NULL);
+ len = round_down(len, bc->bc_key->crypto_cfg.data_unit_size);
+ split_bio = bio_split(bio, len >> SECTOR_SHIFT, GFP_NOIO, NULL);
if (!split_bio) {
bio->bi_status = BLK_STS_RESOURCE;
return false;
diff --git a/block/blk-crypto-internal.h b/block/blk-crypto-internal.h
index 0d36aae538d7..304e90ed99f5 100644
--- a/block/blk-crypto-internal.h
+++ b/block/blk-crypto-internal.h
@@ -60,6 +60,19 @@ static inline bool blk_crypto_rq_is_encrypted(struct request *rq)
return rq->crypt_ctx;
}

+/*
+ * Returns the alignment requirement for the number of sectors in this bio based
+ * on its bi_crypt_context. Any bios split from this bio must follow this
+ * alignment requirement as well.
+ */
+static inline unsigned int blk_crypto_bio_sectors_alignment(struct bio *bio)
+{
+ if (!bio_has_crypt_ctx(bio))
+ return 1;
+ return bio->bi_crypt_context->bc_key->crypto_cfg.data_unit_size >>
+ SECTOR_SHIFT;
+}
+
#else /* CONFIG_BLK_INLINE_ENCRYPTION */

static inline bool bio_crypt_rq_ctx_compatible(struct request *rq,
@@ -93,6 +106,11 @@ static inline bool blk_crypto_rq_is_encrypted(struct request *rq)
return false;
}

+static inline unsigned int blk_crypto_bio_sectors_alignment(struct bio *bio)
+{
+ return 1;
+}
+
#endif /* CONFIG_BLK_INLINE_ENCRYPTION */

void __bio_crypt_advance(struct bio *bio, unsigned int bytes);
diff --git a/block/blk-merge.c b/block/blk-merge.c
index bcf5e4580603..f34dda7132f9 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -149,13 +149,15 @@ static inline unsigned get_max_io_size(struct request_queue *q,
unsigned pbs = queue_physical_block_size(q) >> SECTOR_SHIFT;
unsigned lbs = queue_logical_block_size(q) >> SECTOR_SHIFT;
unsigned start_offset = bio->bi_iter.bi_sector & (pbs - 1);
+ unsigned int bio_sectors_alignment =
+ blk_crypto_bio_sectors_alignment(bio);

max_sectors += start_offset;
max_sectors &= ~(pbs - 1);
- if (max_sectors > start_offset)
- return max_sectors - start_offset;
+ if (max_sectors - start_offset >= bio_sectors_alignment)
+ return round_down(max_sectors - start_offset, bio_sectors_alignment);

- return sectors & ~(lbs - 1);
+ return round_down(sectors & ~(lbs - 1), bio_sectors_alignment);
}

static inline unsigned get_max_segment_size(const struct request_queue *q,
@@ -174,6 +176,41 @@ static inline unsigned get_max_segment_size(const struct request_queue *q,
(unsigned long)queue_max_segment_size(q));
}

+/**
+ * update_aligned_sectors_and_segs() - Ensures that *@aligned_sectors is aligned
+ * to @bio_sectors_alignment, and that
+ * *@aligned_segs is the value of nsegs
+ * when sectors reached/first exceeded that
+ * value of *@aligned_sectors.
+ *
+ * @nsegs: [in] The current number of segs
+ * @sectors: [in] The current number of sectors
+ * @aligned_segs: [in,out] The number of segments that make up @aligned_sectors
+ * @aligned_sectors: [in,out] The largest number of sectors <= @sectors that is
+ * aligned to @sectors
+ * @bio_sectors_alignment: [in] The alignment requirement for the number of
+ * sectors
+ *
+ * Updates *@aligned_sectors to the largest number <= @sectors that is also a
+ * multiple of @bio_sectors_alignment. This is done by updating *@aligned_sectors
+ * whenever @sectors is at least @bio_sectors_alignment more than
+ * *@aligned_sectors, since that means we can increment *@aligned_sectors while
+ * still keeping it aligned to @bio_sectors_alignment and also keeping it <=
+ * @sectors. *@aligned_segs is updated to the value of nsegs when @sectors first
+ * reaches/exceeds any value that causes *@aligned_sectors to be updated.
+ */
+static inline void update_aligned_sectors_and_segs(const unsigned int nsegs,
+ const unsigned int sectors,
+ unsigned int *aligned_segs,
+ unsigned int *aligned_sectors,
+ const unsigned int bio_sectors_alignment)
+{
+ if (sectors - *aligned_sectors < bio_sectors_alignment)
+ return;
+ *aligned_sectors = round_down(sectors, bio_sectors_alignment);
+ *aligned_segs = nsegs;
+}
+
/**
* bvec_split_segs - verify whether or not a bvec should be split in the middle
* @q: [in] request queue associated with the bio associated with @bv
@@ -195,9 +232,12 @@ static inline unsigned get_max_segment_size(const struct request_queue *q,
* the block driver.
*/
static bool bvec_split_segs(const struct request_queue *q,
- const struct bio_vec *bv, unsigned *nsegs,
- unsigned *sectors, unsigned max_segs,
- unsigned max_sectors)
+ const struct bio_vec *bv, unsigned int *nsegs,
+ unsigned int *sectors, unsigned int *aligned_segs,
+ unsigned int *aligned_sectors,
+ unsigned int bio_sectors_alignment,
+ unsigned int max_segs,
+ unsigned int max_sectors)
{
unsigned max_len = (min(max_sectors, UINT_MAX >> 9) - *sectors) << 9;
unsigned len = min(bv->bv_len, max_len);
@@ -211,6 +251,11 @@ static bool bvec_split_segs(const struct request_queue *q,

(*nsegs)++;
total_len += seg_size;
+ update_aligned_sectors_and_segs(*nsegs,
+ *sectors + (total_len >> 9),
+ aligned_segs,
+ aligned_sectors,
+ bio_sectors_alignment);
len -= seg_size;

if ((bv->bv_offset + total_len) & queue_virt_boundary(q))
@@ -235,6 +280,8 @@ static bool bvec_split_segs(const struct request_queue *q,
* following is guaranteed for the cloned bio:
* - That it has at most get_max_io_size(@q, @bio) sectors.
* - That it has at most queue_max_segments(@q) segments.
+ * - That the number of sectors in the returned bio is aligned to
+ * blk_crypto_bio_sectors_alignment(@bio)
*
* Except for discard requests the cloned bio will point at the bi_io_vec of
* the original bio. It is the responsibility of the caller to ensure that the
@@ -252,6 +299,9 @@ static struct bio *blk_bio_segment_split(struct request_queue *q,
unsigned nsegs = 0, sectors = 0;
const unsigned max_sectors = get_max_io_size(q, bio);
const unsigned max_segs = queue_max_segments(q);
+ const unsigned int bio_sectors_alignment =
+ blk_crypto_bio_sectors_alignment(bio);
+ unsigned int aligned_segs = 0, aligned_sectors = 0;

bio_for_each_bvec(bv, bio, iter) {
/*
@@ -266,8 +316,14 @@ static struct bio *blk_bio_segment_split(struct request_queue *q,
bv.bv_offset + bv.bv_len <= PAGE_SIZE) {
nsegs++;
sectors += bv.bv_len >> 9;
- } else if (bvec_split_segs(q, &bv, &nsegs, &sectors, max_segs,
- max_sectors)) {
+ update_aligned_sectors_and_segs(nsegs, sectors,
+ &aligned_segs,
+ &aligned_sectors,
+ bio_sectors_alignment);
+ } else if (bvec_split_segs(q, &bv, &nsegs, &sectors,
+ &aligned_segs, &aligned_sectors,
+ bio_sectors_alignment, max_segs,
+ max_sectors)) {
goto split;
}

@@ -275,11 +331,24 @@ static struct bio *blk_bio_segment_split(struct request_queue *q,
bvprvp = &bvprv;
}

+ /*
+ * The input bio's number of sectors is assumed to be aligned to
+ * bio_sectors_alignment. If that's the case, then this function should
+ * ensure that aligned_segs == nsegs and aligned_sectors == sectors if
+ * the bio is not going to be split.
+ */
+ WARN_ON(aligned_segs != nsegs || aligned_sectors != sectors);
*segs = nsegs;
return NULL;
split:
- *segs = nsegs;
- return bio_split(bio, sectors, GFP_NOIO, bs);
+ *segs = aligned_segs;
+ if (WARN_ON(aligned_sectors == 0))
+ goto err;
+ return bio_split(bio, aligned_sectors, GFP_NOIO, bs);
+err:
+ bio->bi_status = BLK_STS_IOERR;
+ bio_endio(bio);
+ return bio;
}

/**
@@ -366,6 +435,9 @@ unsigned int blk_recalc_rq_segments(struct request *rq)
{
unsigned int nr_phys_segs = 0;
unsigned int nr_sectors = 0;
+ unsigned int nr_aligned_phys_segs = 0;
+ unsigned int nr_aligned_sectors = 0;
+ unsigned int bio_sectors_alignment;
struct req_iterator iter;
struct bio_vec bv;

@@ -381,9 +453,11 @@ unsigned int blk_recalc_rq_segments(struct request *rq)
return 1;
}

+ bio_sectors_alignment = blk_crypto_bio_sectors_alignment(rq->bio);
rq_for_each_bvec(bv, rq, iter)
bvec_split_segs(rq->q, &bv, &nr_phys_segs, &nr_sectors,
- UINT_MAX, UINT_MAX);
+ &nr_aligned_phys_segs, &nr_aligned_sectors,
+ bio_sectors_alignment, UINT_MAX, UINT_MAX);
return nr_phys_segs;
}

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 55bcee5dc032..de5c97ab8e5a 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2161,6 +2161,9 @@ blk_qc_t blk_mq_submit_bio(struct bio *bio)
blk_queue_bounce(q, &bio);
__blk_queue_split(&bio, &nr_segs);

+ if (bio->bi_status != BLK_STS_OK)
+ goto queue_exit;
+
if (!bio_integrity_prep(bio))
goto queue_exit;

diff --git a/block/bounce.c b/block/bounce.c
index 162a6eee8999..b15224799008 100644
--- a/block/bounce.c
+++ b/block/bounce.c
@@ -295,6 +295,7 @@ static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
bool bounce = false;
int sectors = 0;
bool passthrough = bio_is_passthrough(*bio_orig);
+ unsigned int bio_sectors_alignment;

bio_for_each_segment(from, *bio_orig, iter) {
if (i++ < BIO_MAX_PAGES)
@@ -305,6 +306,9 @@ static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
if (!bounce)
return;

+ bio_sectors_alignment = blk_crypto_bio_sectors_alignment(bio);
+ sectors = round_down(sectors, bio_sectors_alignment);
+
if (!passthrough && sectors < bio_sectors(*bio_orig)) {
bio = bio_split(*bio_orig, sectors, GFP_NOIO, &bounce_bio_split);
bio_chain(bio, *bio_orig);
--
2.29.2.299.gdc1121823c-goog