On Wed, Jun 15, 2022 at 04:02:36PM -0400, Mike Snitzer wrote:
> On Wed, Jun 15 2022 at 1:50P -0400,
> Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>
> > On 6/15/22 08:29, Mike Snitzer wrote:
> > > On Wed, Jun 15 2022 at 10:36P -0400,
> > > Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> > >
> > > > On Mon, Jun 13, 2022 at 11:13:21AM +0200, Greg KH wrote:
> > > > > On Fri, Jun 10, 2022 at 11:11:00AM -0400, Mike Snitzer wrote:
> > > > > > On Fri, Jun 10 2022 at 1:15P -0400,
> > > > > > Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> > > > > >
> > > > > > > On Fri, Jun 10, 2022 at 04:22:00AM +0000, Oleksandr Tymoshenko wrote:
> > > > > > > > I believe this commit introduced a regression in dm verity on systems
> > > > > > > > where data device is an NVME one. Loading table fails with the
> > > > > > > > following diagnostics:
> > > > > > > >
> > > > > > > > device-mapper: table: table load rejected: including non-request-stackable devices
> > > > > > > >
> > > > > > > > The same kernel works with the same data drive on the SCSI interface.
> > > > > > > > NVME-backed dm verity works with just this commit reverted.
> > > > > > > >
> > > > > > > > I believe the presence of the immutable partition is used as an indicator
> > > > > > > > of special case NVME configuration and if the data device's name starts
> > > > > > > > with "nvme" the code tries to switch the target type to
> > > > > > > > DM_TYPE_NVME_BIO_BASED (drivers/md/dm-table.c lines 1003-1010).
> > > > > > > >
> > > > > > > > The special NVME optimization case was removed in
> > > > > > > > 5.10 by commit 9c37de297f6590937f95a28bec1b7ac68a38618f, so only 5.4 is
> > > > > > > > affected.
> > > > > > > >
> > > > > > >
> > > > > > > Why wouldn't 4.9, 4.14, and 4.19 also be affected here? Should I also
> > > > > > > just queue up 9c37de297f65 ("dm: remove special-casing of bio-based
> > > > > > > immutable singleton target on NVMe") to those older kernels? If so,
> > > > > > > have you tested this and verified that it worked?
> > > > > >
> > > > > > Sorry for the unforeseen stable@ troubles here!
> > > > > >
> > > > > > In general we'd be fine to apply commit 9c37de297f65 but to do it
> > > > > > properly would require also making sure commits that remove
> > > > > > "DM_TYPE_NVME_BIO_BASED", like 8d47e65948dd ("dm mpath: remove
> > > > > > unnecessary NVMe branching in favor of scsi_dh checks") are applied --
> > > > > > basically any lingering references to DM_TYPE_NVME_BIO_BASED need to
> > > > > > be removed.
> > > > > >
> > > > > > The commit header for 8d47e65948dd documents what
> > > > > > DM_TYPE_NVME_BIO_BASED was used for.. it was dm-mpath specific and
> > > > > > "nvme" mode really never got used by any userspace that I'm aware of.
> > > > > >
> > > > > > Sadly I currently don't have the time to do this backport for all N
> > > > > > stable kernels... :(
> > > > > >
> > > > > > But if that backport gets out of control: A simpler, albeit stable@
> > > > > > unicorn, way to resolve this is to simply revert 9c37de297f65 and make
> > > >
> > > > 9c37de297f65 can not be reverted in 5.4 and older because it isn't there,
> > > > and trying to apply it results in conflicts which at least I can not
> > > > resolve.
> > > >
> > > > > > it so that DM-mpath and DM core just used bio-based if "nvme" is
> > > > > > requested by dm-mpath, so also in drivers/md/dm-mpath.c e.g.:
> > > > > >
> > > > > > @@ -1091,8 +1088,6 @@ static int parse_features(struct dm_arg_set *as, struct multipath *m)
> > > > > >
> > > > > > if (!strcasecmp(queue_mode_name, "bio"))
> > > > > > m->queue_mode = DM_TYPE_BIO_BASED;
> > > > > > else if (!strcasecmp(queue_mode_name, "nvme"))
> > > > > > - m->queue_mode = DM_TYPE_NVME_BIO_BASED;
> > > > > > + m->queue_mode = DM_TYPE_BIO_BASED;
> > > > > > else if (!strcasecmp(queue_mode_name, "rq"))
> > > > > > m->queue_mode = DM_TYPE_REQUEST_BASED;
> > > > > > else if (!strcasecmp(queue_mode_name, "mq"))
> > > > > >
> > > > > > Mike
> > > > > >
> > > > >
> > > > > Ok, please submit a working patch for the kernels that need it so that
> > > > > we can review and apply it to solve this regression.
> > > > >
> > > >
> > > > So, effectively, v5.4.y and older are broken right now for use cases
> > > > with dm on NVME drives.
> > > >
> > > > Given that the regression does affect older branches, and given that we
> > > > have to revert this patch to avoid regressions in ChromeOS, would it be
> > > > possible to revert it from v5.4.y and older until a fix is found ?
> > >
> > > I obviously would prefer to not have this false-start.
> > >
> > The false start has already happened since we had to revert the patch
> > from chromeos-5.4 and older branches.
>
> OK, well this is pretty easy to fix in general. If there are slight
> differences across older trees they are easily resolved. Fact that
> stable@ couldn't cope with backporting 9c37de297f65 is.. what it is.
>
> But this will fix the issue on 5.4.y:
>
> From: Mike Snitzer <snitzer@xxxxxxxxxx>
> Date: Wed, 15 Jun 2022 14:07:09 -0400
> Subject: [5.4.y PATCH] dm: remove special-casing of bio-based immutable singleton target on NVMe
>
> Commit 9c37de297f6590937f95a28bec1b7ac68a38618f upstream.
>
> There is no benefit to DM special-casing NVMe. Remove all code used to
> establish DM_TYPE_NVME_BIO_BASED.
>
> Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
> ---
> drivers/md/dm-table.c | 32 ++----------------
> drivers/md/dm.c | 64 +++--------------------------------
> include/linux/device-mapper.h | 1 -
> 3 files changed, 7 insertions(+), 90 deletions(-)
>
> diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
> index 06b382304d92..81bc36a43b32 100644
> --- a/drivers/md/dm-table.c
> +++ b/drivers/md/dm-table.c
> @@ -872,8 +872,7 @@ EXPORT_SYMBOL(dm_consume_args);
> static bool __table_type_bio_based(enum dm_queue_mode table_type)
> {
> return (table_type == DM_TYPE_BIO_BASED ||
> - table_type == DM_TYPE_DAX_BIO_BASED ||
> - table_type == DM_TYPE_NVME_BIO_BASED);
> + table_type == DM_TYPE_DAX_BIO_BASED);
> }
>
> static bool __table_type_request_based(enum dm_queue_mode table_type)
> @@ -929,8 +928,6 @@ bool dm_table_supports_dax(struct dm_table *t,
> return true;
> }
>
> -static bool dm_table_does_not_support_partial_completion(struct dm_table *t);
> -
> static int device_is_rq_stackable(struct dm_target *ti, struct dm_dev *dev,
> sector_t start, sector_t len, void *data)
> {
> @@ -960,7 +957,6 @@ static int dm_table_determine_type(struct dm_table *t)
> goto verify_bio_based;
> }
> BUG_ON(t->type == DM_TYPE_DAX_BIO_BASED);
> - BUG_ON(t->type == DM_TYPE_NVME_BIO_BASED);
> goto verify_rq_based;
> }
>
> @@ -999,15 +995,6 @@ static int dm_table_determine_type(struct dm_table *t)
> if (dm_table_supports_dax(t, device_not_dax_capable, &page_size) ||
> (list_empty(devices) && live_md_type == DM_TYPE_DAX_BIO_BASED)) {
> t->type = DM_TYPE_DAX_BIO_BASED;
> - } else {
> - /* Check if upgrading to NVMe bio-based is valid or required */
> - tgt = dm_table_get_immutable_target(t);
> - if (tgt && !tgt->max_io_len && dm_table_does_not_support_partial_completion(t)) {
> - t->type = DM_TYPE_NVME_BIO_BASED;
> - goto verify_rq_based; /* must be stacked directly on NVMe (blk-mq) */
> - } else if (list_empty(devices) && live_md_type == DM_TYPE_NVME_BIO_BASED) {
> - t->type = DM_TYPE_NVME_BIO_BASED;
> - }
> }
> return 0;
> }
> @@ -1024,8 +1011,7 @@ static int dm_table_determine_type(struct dm_table *t)
> * (e.g. request completion process for partial completion.)
> */
> if (t->num_targets > 1) {
> - DMERR("%s DM doesn't support multiple targets",
> - t->type == DM_TYPE_NVME_BIO_BASED ? "nvme bio-based" : "request-based");
> + DMERR("request-based DM doesn't support multiple targets");
> return -EINVAL;
> }
>
> @@ -1714,20 +1700,6 @@ static int device_is_not_random(struct dm_target *ti, struct dm_dev *dev,
> return q && !blk_queue_add_random(q);
> }
>
> -static int device_is_partial_completion(struct dm_target *ti, struct dm_dev *dev,
> - sector_t start, sector_t len, void *data)
> -{
> - char b[BDEVNAME_SIZE];
> -
> - /* For now, NVMe devices are the only devices of this class */
> - return (strncmp(bdevname(dev->bdev, b), "nvme", 4) != 0);
> -}
> -
> -static bool dm_table_does_not_support_partial_completion(struct dm_table *t)
> -{
> - return !dm_table_any_dev_attr(t, device_is_partial_completion, NULL);
> -}
> -
> static int device_not_write_same_capable(struct dm_target *ti, struct dm_dev *dev,
> sector_t start, sector_t len, void *data)
> {
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 37b8bb4d80f0..3c45c389ded9 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -1000,7 +1000,7 @@ static void clone_endio(struct bio *bio)
> struct mapped_device *md = tio->io->md;
> dm_endio_fn endio = tio->ti->type->end_io;
>
> - if (unlikely(error == BLK_STS_TARGET) && md->type != DM_TYPE_NVME_BIO_BASED) {
> + if (unlikely(error == BLK_STS_TARGET)) {
> if (bio_op(bio) == REQ_OP_DISCARD &&
> !bio->bi_disk->queue->limits.max_discard_sectors)
> disable_discard(md);
> @@ -1340,10 +1340,7 @@ static blk_qc_t __map_bio(struct dm_target_io *tio)
> /* the bio has been remapped so dispatch it */
> trace_block_bio_remap(clone->bi_disk->queue, clone,
> bio_dev(io->orig_bio), sector);
> - if (md->type == DM_TYPE_NVME_BIO_BASED)
> - ret = direct_make_request(clone);
> - else
> - ret = generic_make_request(clone);
drivers/md/dm.c:1340:24: error: unused variable 'md'
I'll try again with this fixed.
Guenter
> + ret = generic_make_request(clone);
> break;
> case DM_MAPIO_KILL:
> if (unlikely(swap_bios_limit(ti, clone))) {
> @@ -1732,51 +1729,6 @@ static blk_qc_t __split_and_process_bio(struct mapped_device *md,
> return ret;
> }
>
> -/*
> - * Optimized variant of __split_and_process_bio that leverages the
> - * fact that targets that use it do _not_ have a need to split bios.
> - */
> -static blk_qc_t __process_bio(struct mapped_device *md, struct dm_table *map,
> - struct bio *bio, struct dm_target *ti)
> -{
> - struct clone_info ci;
> - blk_qc_t ret = BLK_QC_T_NONE;
> - int error = 0;
> -
> - init_clone_info(&ci, md, map, bio);
> -
> - if (bio->bi_opf & REQ_PREFLUSH) {
> - struct bio flush_bio;
> -
> - /*
> - * Use an on-stack bio for this, it's safe since we don't
> - * need to reference it after submit. It's just used as
> - * the basis for the clone(s).
> - */
> - bio_init(&flush_bio, NULL, 0);
> - flush_bio.bi_opf = REQ_OP_WRITE | REQ_PREFLUSH | REQ_SYNC;
> - ci.bio = &flush_bio;
> - ci.sector_count = 0;
> - error = __send_empty_flush(&ci);
> - bio_uninit(ci.bio);
> - /* dec_pending submits any data associated with flush */
> - } else {
> - struct dm_target_io *tio;
> -
> - ci.bio = bio;
> - ci.sector_count = bio_sectors(bio);
> - if (__process_abnormal_io(&ci, ti, &error))
> - goto out;
> -
> - tio = alloc_tio(&ci, ti, 0, GFP_NOIO);
> - ret = __clone_and_map_simple_bio(&ci, tio, NULL);
> - }
> -out:
> - /* drop the extra reference count */
> - dec_pending(ci.io, errno_to_blk_status(error));
> - return ret;
> -}
> -
> static blk_qc_t dm_process_bio(struct mapped_device *md,
> struct dm_table *map, struct bio *bio)
> {
> @@ -1807,8 +1759,6 @@ static blk_qc_t dm_process_bio(struct mapped_device *md,
> /* regular IO is split by __split_and_process_bio */
> }
>
> - if (dm_get_md_type(md) == DM_TYPE_NVME_BIO_BASED)
> - return __process_bio(md, map, bio, ti);
> return __split_and_process_bio(md, map, bio);
> }
>
> @@ -2200,12 +2150,10 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
> if (request_based)
> dm_stop_queue(q);
>
> - if (request_based || md->type == DM_TYPE_NVME_BIO_BASED) {
> + if (request_based) {
> /*
> - * Leverage the fact that request-based DM targets and
> - * NVMe bio based targets are immutable singletons
> - * - used to optimize both dm_request_fn and dm_mq_queue_rq;
> - * and __process_bio.
> + * Leverage the fact that request-based DM targets are
> + * immutable singletons - used to optimize dm_mq_queue_rq.
> */
> md->immutable_target = dm_table_get_immutable_target(t);
> }
> @@ -2334,7 +2282,6 @@ int dm_setup_md_queue(struct mapped_device *md, struct dm_table *t)
> break;
> case DM_TYPE_BIO_BASED:
> case DM_TYPE_DAX_BIO_BASED:
> - case DM_TYPE_NVME_BIO_BASED:
> dm_init_congested_fn(md);
> break;
> case DM_TYPE_NONE:
> @@ -3070,7 +3017,6 @@ struct dm_md_mempools *dm_alloc_md_mempools(struct mapped_device *md, enum dm_qu
> switch (type) {
> case DM_TYPE_BIO_BASED:
> case DM_TYPE_DAX_BIO_BASED:
> - case DM_TYPE_NVME_BIO_BASED:
> pool_size = max(dm_get_reserved_bio_based_ios(), min_pool_size);
> front_pad = roundup(per_io_data_size, __alignof__(struct dm_target_io)) + offsetof(struct dm_target_io, clone);
> io_front_pad = roundup(front_pad, __alignof__(struct dm_io)) + offsetof(struct dm_io, tio);
> diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
> index a53d7d2c2d95..60631f3abddb 100644
> --- a/include/linux/device-mapper.h
> +++ b/include/linux/device-mapper.h
> @@ -28,7 +28,6 @@ enum dm_queue_mode {
> DM_TYPE_BIO_BASED = 1,
> DM_TYPE_REQUEST_BASED = 2,
> DM_TYPE_DAX_BIO_BASED = 3,
> - DM_TYPE_NVME_BIO_BASED = 4,
> };
>
> typedef enum { STATUSTYPE_INFO, STATUSTYPE_TABLE } status_type_t;
> --
> 2.30.0
>
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