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Kernel for Galaxy S24, rebased on CLO sources (WIP)
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Ming Lei 61cbe7888d dm: add dm_bio_rewind() API to DM core 
Commit 7759eb23fd ("block: remove bio_rewind_iter()") removed
a similar API for the following reasons:
    ```
    It is pointed that bio_rewind_iter() is one very bad API[1]:

    1) bio size may not be restored after rewinding

    2) it causes some bogus change, such as 5151842b9d (block: reset
    bi_iter.bi_done after splitting bio)

    3) rewinding really makes things complicated wrt. bio splitting

    4) unnecessary updating of .bi_done in fast path

    [1] https://marc.info/?t=153549924200005&r=1&w=2

    So this patch takes Kent's suggestion to restore one bio into its original
    state via saving bio iterator(struct bvec_iter) in bio_integrity_prep(),
    given now bio_rewind_iter() is only used by bio integrity code.
    ```
However, saving off a copy of the 32 bytes bio->bi_iter in case rewind
needed isn't efficient because it bloats per-bio-data for what is an
unlikely case. That suggestion also ignores the need to restore
crypto and integrity info.

Add dm_bio_rewind() API for a specific use-case that is much more narrow
than the previous more generic rewind code that was reverted:

1) most bios have a fixed end sector since bio split is done from front
   of the bio, if driver just records how many sectors between current
   bio's start sector and the original bio's end sector, the original
   position can be restored. Keeping the original bio's end sector
   fixed is a _hard_ requirement for this interface!

2) if a bio's end sector won't change (usually bio_trim() isn't
   called, or in the case of DM it preserves original bio), user can
   restore the original position by storing sector offset from the
   current ->bi_iter.bi_sector to bio's end sector; together with
   saving bio size, only 8 bytes is needed to restore to original
   bio.

3) DM's requeue use case: when BLK_STS_DM_REQUEUE happens, DM core
   needs to restore to an "original bio" which represents the current
   dm_io to be requeued (which may be a subset of the original bio).
   By storing the sector offset from the original bio's end sector and
   dm_io's size, dm_bio_rewind() can restore such original bio. See
   commit 7dd76d1fee ("dm: improve bio splitting and associated IO
   accounting") for more details on how DM does this. Leveraging this,
   allows DM core to shift the need for bio cloning from bio-split
   time (during IO submission) to the less likely BLK_STS_DM_REQUEUE
   handling (after IO completes with that error).

4) Unlike the original rewind API, dm_bio_rewind() doesn't add .bi_done
   to bvec_iter and there is no effect on the fast path.

Implement dm_bio_rewind() by factoring out clear helpers that it calls:
dm_bio_integrity_rewind, dm_bio_crypt_rewind and dm_bio_rewind_iter.

DM is able to ensure that dm_bio_rewind() is used safely but, given
the constraint that the bio's end must never change, other
hypothetical future callers may not take the same care. So make
dm_bio_rewind() and all supporting code local to DM to avoid risk of
hypothetical abuse. A "dm_" prefix was added to all functions to avoid
any namespace collisions.

Suggested-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
2022-07-07 11:26:55 -04:00
arch block: remove blk_cleanup_disk 2022-06-28 06:33:15 -06:00
block block: simplify disk_set_independent_access_ranges 2022-06-29 08:36:46 -06:00
certs Certs changes 2022-06-21 12:13:53 -05:00
crypto Certs changes 2022-06-21 12:13:53 -05:00
Documentation block: export dma_alignment attribute 2022-06-27 06:29:11 -06:00
drivers dm: add dm_bio_rewind() API to DM core 2022-07-07 11:26:55 -04:00
fs iomap: add support for dma aligned direct-io 2022-06-27 06:29:11 -06:00
include block: move ->ia_ranges from the request_queue to the gendisk 2022-06-29 08:36:46 -06:00
init gcc-12: disable '-Warray-bounds' universally for now 2022-06-09 10:11:12 -07:00
ipc These changes update the ipc sysctls so that they are fundamentally 2022-06-03 15:54:57 -07:00
kernel block: simplify blktrace sysfs attribute creation 2022-06-28 11:32:42 -06:00
lib iov: introduce iov_iter_aligned 2022-06-27 06:29:11 -06:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm Minor things, mainly - mailmap updates, MAINTAINERS updates, etc. 2022-06-26 14:00:55 -07:00
net Networking fixes for 5.19-rc4, including fixes from bpf and netfilter. 2022-06-23 09:01:01 -05:00
samples fprobe, samples: Add use_trace option and show hit/missed counter 2022-06-17 21:53:29 +02:00
scripts kbuild: Ignore __this_module in gen_autoksyms.sh 2022-06-26 06:15:05 +09:00
security selinux: free contexts previously transferred in selinux_add_opt() 2022-06-15 21:20:45 -04:00
sound sound fixes for 5.19-rc4 2022-06-23 08:44:00 -05:00
tools tools headers UAPI: Synch KVM's svm.h header with the kernel 2022-06-26 12:32:55 -03:00
usr Not a lot of material this cycle. Many singleton patches against various 2022-05-27 11:22:03 -07:00
virt KVM: x86: disable preemption around the call to kvm_arch_vcpu_{un|}blocking 2022-06-09 10:52:20 -04:00
.clang-format clang-format: Fix space after for_each macros 2022-05-20 19:27:16 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore kbuild: split the second line of *.mod into *.usyms 2022-05-08 03:16:59 +09:00
.mailmap mailmap: add entry for Christian Marangi 2022-06-16 19:11:32 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: replace a Microchip AT91 maintainer 2022-02-09 11:30:01 +01:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS ARM: SoC fixes for 5.19 2022-06-26 14:12:56 -07:00
Makefile Linux 5.19-rc4 2022-06-26 14:22:10 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.