[PATCH v4 3/9] block: introduce bio_required_sector_alignment()

[Satya Tangirala <satyaprateek2357@gmail.com>]

From: Satya Tangirala <satyat@google.com>

This function returns the required alignment for the number of sectors in
a bio. In particular, the number of sectors passed to bio_split() must be
aligned to this value.

Signed-off-by: Satya Tangirala <satyat@google.com>
---
 block/blk.h | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/block/blk.h b/block/blk.h
index 4b885c0f6708..047d2c2411f2 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -261,6 +261,23 @@ static inline unsigned int bio_allowed_max_sectors(struct request_queue *q)
 	return round_down(UINT_MAX, queue_logical_block_size(q)) >> 9;
 }
 
+/*
+ * Return the number of sectors to which the size of the given bio (and any bios
+ * split from it) must be aligned.
+ *
+ * Normally this is just the disk's logical block size in sectors, but it may be
+ * greater if the bio has an encryption context.
+ */
+static inline unsigned int bio_required_sector_alignment(struct bio *bio)
+{
+	unsigned int alignmask =
+		(bdev_logical_block_size(bio->bi_bdev) >> SECTOR_SHIFT) - 1;
+
+	alignmask |= blk_crypto_bio_sectors_alignment(bio) - 1;
+
+	return alignmask + 1;
+}
+
 /*
  * The max bio size which is aligned to q->limits.discard_granularity. This
  * is a hint to split large discard bio in generic block layer, then if device
-- 
2.25.1