[v5,00/10] Read/Write with meta/integrity

This adds a new io_uring interface to exchange meta along with read/write.

The patchset is on top block for-next [1] and keith's cleanup patch [2].

Interface:
A new meta_type field is introduced in SQE, which describes type of meta
that is passed. Currently only one type "PI" is supported. Meta information
is represented using a newly introduced 'struct io_uring_meta_pi'.
Application sets up a SQE128 ring, and prepares io_uring_meta_pi within
second SQE. Application populates 'struct io_uring_meta_pi' fields as below:

* pi_flags: these are meta-type specific flags. Three flags are exposed for
integrity type, namely IO_INTEGRITY_CHK_GUARD/APPTAG/REFTAG.
* len: length of the meta buffer
* addr: address of the meta buffer
* seed: seed value for ref tag remapping
* app_tag: optional application-specific 16b value; this goes along with
INTEGRITY_CHK_APPTAG flag.
* rsvd: reserved space for storage tag.

Block path (direct IO) , NVMe and SCSI driver are modified to support
this.

Patch 1 is an enhancement patch.
Patch 2 is required to make the bounce buffer copy back work correctly.
Patch 3 to 5 are prep patches.
Patch 6 adds the io_uring support.
Patch 7 gives us unified interface for user and kernel generated
integrity.
Patch 8 adds support in SCSI and patch 9 in NVMe.
Patch 10 adds the support for block direct IO.

Some of the design choices came from this discussion [3].

Example program on how to use the interface is appended below [4]
(It also tests whether reftag remapping happens correctly or not)

Tree:
https://github.com/SamsungDS/linux/tree/feat/pi_us_v5
Testing:
has been done by modifying fio to use this interface.
https://github.com/SamsungDS/fio/tree/priv/feat/pi-test-v6

Changes since v4;
https://lore.kernel.org/linux-block/20241016112912.63542-1-anuj20.g@samsung.com/

- better variable names to describe bounce buffer copy back (hch)
- move defintion of flags in the same patch introducing uio_meta (hch)
- move uio_meta definition to include/linux/uio.h (hch)
- bump seed size in uio_meta to 8 bytes (martin)
- move flags definition to include/uapi/linux/fs.h (hch)
- s/meta/metadata in commit description of io-uring (hch)
- rearrange the meta fields in sqe for cleaner layout
- partial submission case is not applicable as, we are only plumbing for async case
- s/META_TYPE_INTEGRITY/META_TYPE_PI (hch, martin)
- remove unlikely branching (hch)
- Better formatting, misc cleanups, better commit descriptions, reordering commits(hch)

Changes since v3:
https://lore.kernel.org/linux-block/20240823103811.2421-1-anuj20.g@samsung.com/

- add reftag seed support (Martin)
- fix incorrect formatting in uio_meta (hch)
- s/IOCB_HAS_META/IOCB_HAS_METADATA (hch)
- move integrity check flags to block layer header (hch)
- add comments for BIP_CHECK_GUARD/REFTAG/APPTAG flags (hch)
- remove bio_integrity check during completion if IOCB_HAS_METADATA is set (hch)
- use goto label to get rid of duplicate error handling (hch)
- add warn_on if trying to do sync io with iocb_has_metadata flag (hch)
- remove check for disabling reftag remapping (hch)
- remove BIP_INTEGRITY_USER flag (hch)
- add comment for app_tag field introduced in bio_integrity_payload (hch)
- pass request to nvme_set_app_tag function (hch)
- right indentation at a place in scsi patch (hch)
- move IOCB_HAS_METADATA to a separate fs patch (hch)

Changes since v2:
https://lore.kernel.org/linux-block/20240626100700.3629-1-anuj20.g@samsung.com/
- io_uring error handling styling (Gabriel)
- add documented helper to get metadata bytes from data iter (hch)
- during clone specify "what flags to clone" rather than
"what not to clone" (hch)
- Move uio_meta defination to bio-integrity.h (hch)
- Rename apptag field to app_tag (hch)
- Change datatype of flags field in uio_meta to bitwise (hch)
- Don't introduce BIP_USER_CHK_FOO flags (hch, martin)
- Driver should rely on block layer flags instead of seeing if it is
user-passthrough (hch)
- update the scsi code for handling user-meta (hch, martin)

Changes since v1:
https://lore.kernel.org/linux-block/20240425183943.6319-1-joshi.k@samsung.com/
- Do not use new opcode for meta, and also add the provision to introduce new
meta types beyond integrity (Pavel)
- Stuff IOCB_HAS_META check in need_complete_io (Jens)
- Split meta handling in NVMe into a separate handler (Keith)
- Add meta handling for __blkdev_direct_IO too (Keith)
- Don't inherit BIP_COPY_USER flag for cloned bio's (Christoph)
- Better commit descriptions (Christoph)

Changes since RFC:
- modify io_uring plumbing based on recent async handling state changes
- fixes/enhancements to correctly handle the split for meta buffer
- add flags to specify guard/reftag/apptag checks
- add support to send apptag


[1] https://git.kernel.dk/cgit/linux-block/log/?h=for-next

[2] https://lore.kernel.org/linux-block/20241016201309.1090320-1-kbusch@meta.com/

[3] https://lore.kernel.org/linux-block/20240705083205.2111277-1-hch@lst.de/

[4]

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <linux/fs.h>
#include <linux/io_uring.h>
#include <linux/types.h>
#include "liburing.h"

/*
 * write data/meta. read both. compare. send apptag too.
 * prerequisite:
 * protected xfer: format namespace with 4KB + 8b, pi_type = 1
 * For testing reftag remapping on device-mapper, create a
 * device-mapper and run this program. Device mapper creation:
 * # echo 0 80 linear /dev/nvme0n1 0 > /tmp/table
 * # echo 80 160 linear /dev/nvme0n1 200 >> /tmp/table
 * # dmsetup create two /tmp/table
 * # ./a.out /dev/dm-0
 */

#define DATA_LEN 4096
#define META_LEN 8

struct t10_pi_tuple {
        __be16  guard;
        __be16  apptag;
        __be32  reftag;
};

int main(int argc, char *argv[])
{
         struct io_uring ring;
         struct io_uring_sqe *sqe = NULL;
         struct io_uring_cqe *cqe = NULL;
         void *wdb,*rdb;
         char wmb[META_LEN], rmb[META_LEN];
         char *data_str = "data buffer";
         int fd, ret, blksize;
         struct stat fstat;
         unsigned long long offset = DATA_LEN * 10;
         struct t10_pi_tuple *pi;
         struct io_uring_meta_pi *md;

         if (argc != 2) {
                 fprintf(stderr, "Usage: %s <block-device>", argv[0]);
                 return 1;
         };

         if (stat(argv[1], &fstat) == 0) {
                 blksize = (int)fstat.st_blksize;
         } else {
                 perror("stat");
                 return 1;
         }

         if (posix_memalign(&wdb, blksize, DATA_LEN)) {
                 perror("posix_memalign failed");
                 return 1;
         }
         if (posix_memalign(&rdb, blksize, DATA_LEN)) {
                 perror("posix_memalign failed");
                 return 1;
         }

         memset(wdb, 0, DATA_LEN);

         fd = open(argv[1], O_RDWR | O_DIRECT);
         if (fd < 0) {
                 printf("Error in opening device\n");
                 return 0;
         }

         ret = io_uring_queue_init(8, &ring, IORING_SETUP_SQE128);
         if (ret) {
                 fprintf(stderr, "ring setup failed: %d\n", ret);
                 return 1;
         }

         /* write data + meta-buffer to device */
         sqe = io_uring_get_sqe(&ring);
         if (!sqe) {
                 fprintf(stderr, "get sqe failed\n");
                 return 1;
         }

         io_uring_prep_write(sqe, fd, wdb, DATA_LEN, offset);

	 sqe->meta_type = META_TYPE_PI;
         md = (struct io_uring_meta_pi *) sqe->big_sqe;
         md->addr = (__u64)wmb;
         md->len = META_LEN;
         /* flags to ask for guard/reftag/apptag*/
         md->pi_flags = IO_INTEGRITY_CHK_GUARD | IO_INTEGRITY_CHK_REFTAG | IO_INTEGRITY_CHK_APPTAG;
         md->app_tag = 0x1234;
         md->seed = 10;

         pi = (struct t10_pi_tuple *)wmb;
         pi->guard = 0;
         pi->reftag = 0x0A000000;
         pi->apptag = 0x3412;

         ret = io_uring_submit(&ring);
         if (ret <= 0) {
                 fprintf(stderr, "sqe submit failed: %d\n", ret);
                 return 1;
         }

         ret = io_uring_wait_cqe(&ring, &cqe);
         if (!cqe) {
                 fprintf(stderr, "cqe is NULL :%d\n", ret);
                 return 1;
         }
         if (cqe->res < 0) {
                 fprintf(stderr, "write cqe failure: %d", cqe->res);
                 return 1;
         }

         io_uring_cqe_seen(&ring, cqe);

         /* read data + meta-buffer back from device */
         sqe = io_uring_get_sqe(&ring);
         if (!sqe) {
                 fprintf(stderr, "get sqe failed\n");
                 return 1;
         }

         io_uring_prep_read(sqe, fd, rdb, DATA_LEN, offset);

         sqe->meta_type = META_TYPE_PI;
	 md = (struct io_uring_meta_pi *) sqe->big_sqe;
         md->addr = (__u64)rmb;
         md->len = META_LEN;
         md->pi_flags = IO_INTEGRITY_CHK_GUARD | IO_INTEGRITY_CHK_REFTAG | IO_INTEGRITY_CHK_APPTAG;
         md->app_tag = 0x1234;
         md->seed = 10;

         ret = io_uring_submit(&ring);
         if (ret <= 0) {
                 fprintf(stderr, "sqe submit failed: %d\n", ret);
                 return 1;
         }

         ret = io_uring_wait_cqe(&ring, &cqe);
         if (!cqe) {
                 fprintf(stderr, "cqe is NULL :%d\n", ret);
                 return 1;
         }

         if (cqe->res < 0) {
                 fprintf(stderr, "read cqe failure: %d", cqe->res);
                 return 1;
         }

	 pi = (struct t10_pi_tuple *)rmb;
	 if (pi->apptag != 0x3412)
		 printf("Failure: apptag mismatch!\n");
	 if (pi->reftag != 0x0A000000)
		 printf("Failure: reftag mismatch!\n");

         io_uring_cqe_seen(&ring, cqe);

         pi = (struct t10_pi_tuple *)rmb;

         if (strncmp(wmb, rmb, META_LEN))
                 printf("Failure: meta mismatch!, wmb=%s, rmb=%s\n", wmb, rmb);

         if (strncmp(wdb, rdb, DATA_LEN))
                 printf("Failure: data mismatch!\n");

         io_uring_queue_exit(&ring);
         free(rdb);
         free(wdb);
         return 0;
}

Anuj Gupta (7):
  block: define set of integrity flags to be inherited by cloned bip
  block: modify bio_integrity_map_user to accept iov_iter as argument
  fs, iov_iter: define meta io descriptor
  fs: introduce IOCB_HAS_METADATA for metadata
  io_uring/rw: add support to send metadata along with read/write
  block: introduce BIP_CHECK_GUARD/REFTAG/APPTAG bip_flags
  scsi: add support for user-meta interface

Christoph Hellwig (1):
  block: copy back bounce buffer to user-space correctly in case of
    split

Kanchan Joshi (2):
  nvme: add support for passing on the application tag
  block: add support to pass user meta buffer

 block/bio-integrity.c         | 84 ++++++++++++++++++++++++++++-------
 block/blk-integrity.c         | 10 ++++-
 block/fops.c                  | 42 ++++++++++++++----
 drivers/nvme/host/core.c      | 21 +++++----
 drivers/scsi/sd.c             |  4 +-
 include/linux/bio-integrity.h | 19 ++++++--
 include/linux/fs.h            |  1 +
 include/linux/uio.h           | 10 +++++
 include/uapi/linux/fs.h       |  9 ++++
 include/uapi/linux/io_uring.h | 29 ++++++++++++
 io_uring/io_uring.c           |  9 ++++
 io_uring/rw.c                 | 79 +++++++++++++++++++++++++++++++-
 io_uring/rw.h                 | 14 +++++-
 13 files changed, 290 insertions(+), 41 deletions(-)

On Tue, Oct 29, 2024 at 09:53:59PM +0530, Anuj Gupta wrote:
> This patch introduces BIP_CHECK_GUARD/REFTAG/APPTAG bip_flags which
> indicate how the hardware should check the integrity payload.
> BIP_CHECK_GUARD/REFTAG are conversion of existing semantics, while
> BIP_CHECK_APPTAG is a new flag. The driver can now just rely on block
> layer flags, and doesn't need to know the integrity source. Submitter
> of PI decides which tags to check. This would also give us a unified
> interface for user and kernel generated integrity.

Looks good.

Reviewed-by: Keith Busch <kbusch@kernel.org>

On Tue, Oct 29, 2024 at 09:54:02PM +0530, Anuj Gupta wrote:
> From: Kanchan Joshi <joshi.k@samsung.com>
> 
> If an iocb contains metadata, extract that and prepare the bip.
> Based on flags specified by the user, set corresponding guard/app/ref
> tags to be checked in bip.

Looks good.

Reviewed-by: Keith Busch <kbusch@kernel.org>