[PATCHv2] block: always allocate integrity buffer

[Keith Busch]

From: Keith Busch <kbusch at kernel.org>

The integrity buffer, whether or not you want it generated or verified, is
mandatory for nvme formats that have metadata. The block integrity attributes
read_verify and write_generate had been stopping the metadata buffer from being
allocated and attached to the bio entirely. We only want to suppress the
protection checks on the device and host, but we still need the buffer.

Otherwise, reads and writes will just get IO errors and this nvme warning:

 ------------[ cut here ]------------
 WARNING: CPU: 1 PID: 371 at drivers/nvme/host/core.c:1036 nvme_setup_rw+0x122/0x210
 ...
 RIP: 0010:nvme_setup_rw+0x122/0x210
 ...
 Call Trace:
  <TASK>
  nvme_setup_cmd+0x1b4/0x280
  nvme_queue_rqs+0xc4/0x1f0 [nvme]
  blk_mq_dispatch_queue_requests+0x24a/0x430
  blk_mq_flush_plug_list+0x50/0x140
  __blk_flush_plug+0xc1/0x100
  __submit_bio+0x1c1/0x360
  ? submit_bio_noacct_nocheck+0x2d6/0x3c0
  submit_bio_noacct_nocheck+0x2d6/0x3c0
  ? submit_bio_noacct+0x47/0x4c0
  submit_bio_wait+0x48/0xa0
  __blkdev_direct_IO_simple+0xee/0x210
  ? current_time+0x1d/0x100
  ? current_time+0x1d/0x100
  ? __bio_clone+0xb0/0xb0
  blkdev_read_iter+0xbb/0x140
  vfs_read+0x239/0x310
  ksys_read+0x58/0xc0
  do_syscall_64+0x6c/0x180
  entry_SYSCALL_64_after_hwframe+0x4b/0x53

Cc: Martin K. Petersen <martin.petersen at oracle.com>
Cc: Jens Axboe <axboe at kernel.dk>
Signed-off-by: Keith Busch <kbusch at kernel.org>
---
v1->v2:

  The bip_flags are initialized based on the the bi->flags and don't
  change for the lifetime of the bio. Check this instead to avoid any
  races with bi->flags changing by a user modifying the read_verify and
  write_generate attributes.

  Check if we can skip the verify step before scheduling the deferred
  completion work.

 block/bio-integrity-auto.c | 37 ++++++++++++++++++++++---------------
 1 file changed, 22 insertions(+), 15 deletions(-)

diff --git a/block/bio-integrity-auto.c b/block/bio-integrity-auto.c
index e524c609be506..2c43e27b332ca 100644
--- a/block/bio-integrity-auto.c
+++ b/block/bio-integrity-auto.c
@@ -54,12 +54,12 @@ static void bio_integrity_verify_fn(struct work_struct *work)
  */
 bool __bio_integrity_endio(struct bio *bio)
 {
-	struct blk_integrity *bi = blk_get_integrity(bio->bi_bdev->bd_disk);
 	struct bio_integrity_payload *bip = bio_integrity(bio);
 	struct bio_integrity_data *bid =
 		container_of(bip, struct bio_integrity_data, bip);
 
-	if (bio_op(bio) == REQ_OP_READ && !bio->bi_status && bi->csum_type) {
+	if (bio_op(bio) == REQ_OP_READ && !bio->bi_status &&
+	    bip->bip_flags & BIP_CHECK_GUARD) {
 		INIT_WORK(&bid->work, bio_integrity_verify_fn);
 		queue_work(kintegrityd_wq, &bid->work);
 		return false;
@@ -69,6 +69,16 @@ bool __bio_integrity_endio(struct bio *bio)
 	return true;
 }
 
+static inline void bio_set_bip_flags(struct blk_integrity *bi, u16 *bip_flags)
+{
+	if (bi->csum_type == BLK_INTEGRITY_CSUM_IP)
+		*bip_flags |= BIP_IP_CHECKSUM;
+	if (bi->csum_type)
+		*bip_flags |= BIP_CHECK_GUARD;
+	if (bi->flags & BLK_INTEGRITY_REF_TAG)
+		*bip_flags |= BIP_CHECK_REFTAG;
+}
+
 /**
  * bio_integrity_prep - Prepare bio for integrity I/O
  * @bio:	bio to prepare
@@ -83,6 +93,7 @@ bool __bio_integrity_endio(struct bio *bio)
 bool bio_integrity_prep(struct bio *bio)
 {
 	struct blk_integrity *bi = blk_get_integrity(bio->bi_bdev->bd_disk);
+	unsigned short bip_flags = BIP_BLOCK_INTEGRITY;
 	struct bio_integrity_data *bid;
 	gfp_t gfp = GFP_NOIO;
 	unsigned int len;
@@ -101,19 +112,22 @@ bool bio_integrity_prep(struct bio *bio)
 	switch (bio_op(bio)) {
 	case REQ_OP_READ:
 		if (bi->flags & BLK_INTEGRITY_NOVERIFY)
-			return true;
+			break;
+		bio_set_bip_flags(bi, &bip_flags);
 		break;
 	case REQ_OP_WRITE:
-		if (bi->flags & BLK_INTEGRITY_NOGENERATE)
-			return true;
-
 		/*
 		 * Zero the memory allocated to not leak uninitialized kernel
 		 * memory to disk for non-integrity metadata where nothing else
 		 * initializes the memory.
 		 */
+		if (bi->flags & BLK_INTEGRITY_NOGENERATE) {
+			gfp |= __GFP_ZERO;
+			break;
+		}
 		if (bi->csum_type == BLK_INTEGRITY_CSUM_NONE)
 			gfp |= __GFP_ZERO;
+		bio_set_bip_flags(bi, &bip_flags);
 		break;
 	default:
 		return true;
@@ -134,22 +148,15 @@ bool bio_integrity_prep(struct bio *bio)
 
 	bid->bio = bio;
 
-	bid->bip.bip_flags |= BIP_BLOCK_INTEGRITY;
+	bid->bip.bip_flags = bip_flags;
 	bip_set_seed(&bid->bip, bio->bi_iter.bi_sector);
 
-	if (bi->csum_type == BLK_INTEGRITY_CSUM_IP)
-		bid->bip.bip_flags |= BIP_IP_CHECKSUM;
-	if (bi->csum_type)
-		bid->bip.bip_flags |= BIP_CHECK_GUARD;
-	if (bi->flags & BLK_INTEGRITY_REF_TAG)
-		bid->bip.bip_flags |= BIP_CHECK_REFTAG;
-
 	if (bio_integrity_add_page(bio, virt_to_page(buf), len,
 			offset_in_page(buf)) < len)
 		goto err_end_io;
 
 	/* Auto-generate integrity metadata if this is a write */
-	if (bio_data_dir(bio) == WRITE)
+	if (bio_data_dir(bio) == WRITE && bid->bip.bip_flags & BIP_CHECK_GUARD)
 		blk_integrity_generate(bio);
 	else
 		bid->saved_bio_iter = bio->bi_iter;
-- 
2.47.1