Documentation/ABI: Fix typos

Fix typos in Documentation/ABI. The changes are in descriptions or
comments where they shouldn't affect use of the ABIs.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20230814212822.193684-2-helgaas@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

blk-mq: remove hybrid polling

io_uring provides the only way user space can poll completions, and that
always sets BLK_POLL_NOSLEEP. This effectively makes hybrid polling dead
code, so remove it and everything supporting it.

Hybrid polling was effectively killed off with 9650b453a3d4b1, "block:
ignore RWF_HIPRI hint for sync dio", but still potentially reachable
through io_uring until d729cf9acb93119, "io_uring: don't sleep when
polling for I/O", but hybrid polling probably should not have been
reachable through that async interface from the beginning.

Fixes: 9650b453a3d4 ("block: ignore RWF_HIPRI hint for sync dio")
Fixes: d729cf9acb93 ("io_uring: don't sleep when polling for I/O")
Signed-off-by: Keith Busch <kbusch@kernel.org>
Link: https://lore.kernel.org/r/20230320194926.3353144-1-kbusch@meta.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

docs: sysfs-block: document hidden sysfs entry

/sys/block/<disk>/hidden is undocumented. Document it.

Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20230303084323.228098-1-sagi@grimberg.me
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block: save user max_sectors limit

The user can set the max_sectors limit to any valid value via sysfs
/sys/block/<dev>/queue/max_sectors_kb attribute. If the device limits
are ever rescanned, though, the limit reverts back to the potentially
artificially low BLK_DEF_MAX_SECTORS value.

Preserve the user's setting as the max_sectors limit as long as it's
valid. The user can reset back to defaults by writing 0 to the sysfs
file.

Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20230105205146.3610282-3-kbusch@meta.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block: export dma_alignment attribute

User space may want to know how to align their buffers to avoid
bouncing. Export the queue attribute.

Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220610195830.3574005-4-kbusch@fb.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

blk-crypto: show crypto capabilities in sysfs

Add sysfs files that expose the inline encryption capabilities of
request queues:

/sys/block/$disk/queue/crypto/max_dun_bits
/sys/block/$disk/queue/crypto/modes/$mode
/sys/block/$disk/queue/crypto/num_keyslots

Userspace can use these new files to decide what encryption settings to
use, or whether to use inline encryption at all. This also brings the
crypto capabilities in line with the other queue properties, which are
already discoverable via the queue directory in sysfs.

Design notes:

- Place the new files in a new subdirectory "crypto" to group them
together and to avoid complicating the main "queue" directory. This
also makes it possible to replace "crypto" with a symlink later if
we ever make the blk_crypto_profiles into real kobjects (see below).

- It was necessary to define a new kobject that corresponds to the
crypto subdirectory. For now, this kobject just contains a pointer
to the blk_crypto_profile. Note that multiple queues (and hence
multiple such kobjects) may refer to the same blk_crypto_profile.

An alternative design would more closely match the current kernel
data structures: the blk_crypto_profile could be a kobject itself,
located directly under the host controller device's kobject, while
/sys/block/$disk/queue/crypto would be a symlink to it.

I decided not to do that for now because it would require a lot more
changes, such as no longer embedding blk_crypto_profile in other
structures, and also because I'm not sure we can rule out moving the
crypto capabilities into 'struct queue_limits' in the future. (Even
if multiple queues share the same crypto engine, maybe the supported
data unit sizes could differ due to other queue properties.) It
would also still be possible to switch to that design later without
breaking userspace, by replacing the directory with a symlink.

- Use "max_dun_bits" instead of "max_dun_bytes". Currently, the
kernel internally stores this value in bytes, but that's an
implementation detail. It probably makes more sense to talk about
this value in bits, and choosing bits is more future-proof.

- "modes" is a sub-subdirectory, since there may be multiple supported
crypto modes, sysfs is supposed to have one value per file, and it
makes sense to group all the mode files together.

- Each mode had to be named. The crypto API names like "xts(aes)" are
not appropriate because they don't specify the key size. Therefore,
I assigned new names. The exact names chosen are arbitrary, but
they happen to match the names used in log messages in fs/crypto/.

- The "num_keyslots" file is a bit different from the others in that
it is only useful to know for performance reasons. However, it's
included as it can still be useful. For example, a user might not
want to use inline encryption if there aren't very many keyslots.

Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20220124215938.2769-4-ebiggers@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

docs: sysfs-block: document virt_boundary_mask

/sys/block/<disk>/queue/virt_boundary_mask is completely undocumented.
Document it.

Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20211209003833.6396-7-ebiggers@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

docs: sysfs-block: document stable_writes

/sys/block/<disk>/queue/stable_writes is completely undocumented.
Document it.

Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20211209003833.6396-6-ebiggers@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

docs: sysfs-block: fill in missing documentation from queue-sysfs.rst

sysfs documentation is supposed to go in Documentation/ABI/.
However, /sys/block/<disk>/queue/* are documented in
Documentation/block/queue-sysfs.rst, and sometimes redundantly in
Documentation/ABI/stable/sysfs-block too.

Let's consolidate this documentation into Documentation/ABI/.

Therefore, copy the relevant docs from queue-sysfs.rst into sysfs-block.

This primarily means adding the 25 missing files that were documented in
queue-sysfs.rst only, as well as mentioning the RO/RW status of files.

Documentation/ABI/ requires "Date" and "Contact" fields. For the Date
fields, I used the date of the commit which added support for each file.
For the "Contact" fields, I used linux-block.

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20211209003833.6396-5-ebiggers@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

docs: sysfs-block: add contact for nomerges

The nomerges file was missing a "Contact" entry. Use linux-block.

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20211209003833.6396-4-ebiggers@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

docs: sysfs-block: sort alphabetically

Sort the documentation for the files alphabetically by file path so that
there is a logical order and it's clear where to add new files.

With two small exceptions, this patch doesn't change the documentation
itself and just reorders it:

- In /sys/block/<disk>/<part>/stat, I replaced <part> with <partition>
to be consistent with the other files.
- The description for /sys/block/<disk>/<part>/stat referred to another
file "above", which I reworded.

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20211209003833.6396-3-ebiggers@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

docs: sysfs-block: move to stable directory

The block layer sysfs ABI is widely used by userspace software and is
considered stable.

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20211209003833.6396-2-ebiggers@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>