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Ming-Hung Tsai 30341be4a6 dm array: fix cursor index when skipping across block boundaries 
[ Upstream commit 0bb1968da2 ]

dm_array_cursor_skip() seeks to the target position by loading array
blocks iteratively until the specified number of entries to skip is
reached. When seeking across block boundaries, it uses
dm_array_cursor_next() to step into the next block.
dm_array_cursor_skip() must first move the cursor index to the end
of the current block; otherwise, the cursor position could incorrectly
remain in the same block, causing the actual number of skipped entries
to be much smaller than expected.

This bug affects cache resizing in v2 metadata and could lead to data
loss if the fast device is shrunk during the first-time resume. For
example:

1. create a cache metadata consists of 32768 blocks, with a dirty block
   assigned to the second bitmap block. cache_restore v1.0 is required.

cat <<EOF >> cmeta.xml
<superblock uuid="" block_size="64" nr_cache_blocks="32768" \
policy="smq" hint_width="4">
  <mappings>
    <mapping cache_block="32767" origin_block="0" dirty="true"/>
  </mappings>
</superblock>
EOF
dmsetup create cmeta --table "0 8192 linear /dev/sdc 0"
cache_restore -i cmeta.xml -o /dev/mapper/cmeta --metadata-version=2

2. bring up the cache while attempt to discard all the blocks belonging
   to the second bitmap block (block# 32576 to 32767). The last command
   is expected to fail, but it actually succeeds.

dmsetup create cdata --table "0 2084864 linear /dev/sdc 8192"
dmsetup create corig --table "0 65536 linear /dev/sdc 2105344"
dmsetup create cache --table "0 65536 cache /dev/mapper/cmeta \
/dev/mapper/cdata /dev/mapper/corig 64 2 metadata2 writeback smq \
2 migration_threshold 0"

In addition to the reproducer described above, this fix can be
verified using the "array_cursor/skip" tests in dm-unit:
  dm-unit run /pdata/array_cursor/skip/ --kernel-dir <KERNEL_DIR>

Signed-off-by: Ming-Hung Tsai <mtsai@redhat.com>
Fixes: 9b696229aa ("dm persistent data: add cursor skip functions to the cursor APIs")
Reviewed-by: Joe Thornber <thornber@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2025-01-17 13:40:34 +01:00
arch ARC: build: Try to guess GCC variant of cross compiler 2025-01-09 13:33:47 +01:00
block block: lift bio_is_zone_append to bio.h 2025-01-09 13:33:32 +01:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: ecdsa - Avoid signed integer overflow on signature decoding 2024-12-14 20:03:36 +01:00
Documentation fs/writeback: convert wbc_account_cgroup_owner to take a folio 2025-01-17 13:40:33 +01:00
drivers dm array: fix cursor index when skipping across block boundaries 2025-01-17 13:40:34 +01:00
fs iomap: fix zero padding data issue in concurrent append writes 2025-01-17 13:40:34 +01:00
include iomap: fix zero padding data issue in concurrent append writes 2025-01-17 13:40:34 +01:00
init Compiler Attributes: disable __counted_by for clang < 19.1.3 2024-12-05 14:02:45 +01:00
io_uring io_uring/rw: fix downgraded mshot read 2025-01-09 13:33:51 +01:00
ipc ipc: fix memleak if msg_init_ns failed in create_ipc_ns 2024-12-05 14:03:02 +01:00
kernel fgraph: Add READ_ONCE() when accessing fgraph_array[] 2025-01-09 13:33:52 +01:00
lib maple_tree: reload mas before the second call for mas_empty_area 2025-01-09 13:33:50 +01:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm: hugetlb: independent PMD page table shared count 2025-01-09 13:33:54 +01:00
net mptcp: don't always assume copied data in mptcp_cleanup_rbuf() 2025-01-09 13:33:55 +01:00
rust rust: kbuild: set bindgen's Rust target version 2024-12-19 18:13:22 +01:00
samples samples/bpf: Fix a resource leak 2024-12-14 20:03:46 +01:00
scripts scripts/sorttable: fix orc_sort_cmp() to maintain symmetry and transitivity 2025-01-09 13:33:50 +01:00
security selinux: ignore unknown extended permissions 2025-01-09 13:33:32 +01:00
sound ALSA: seq: oss: Fix races at processing SysEx messages 2025-01-09 13:33:49 +01:00
tools bpf: consider that tail calls invalidate packet pointers 2025-01-09 13:33:47 +01:00
usr initramfs: shorten cmd_initfs in usr/Makefile 2024-07-16 01:07:52 +09:00
virt KVM: x86: switch hugepage recovery thread to vhost_task 2024-12-05 14:02:43 +01:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Kbuild updates for v6.12 2024-09-24 13:02:06 -07:00
.mailmap mailmap: add entry for Thorsten Blum 2024-11-07 14:14:59 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Remove self from DSA entry 2024-11-03 12:52:38 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: update location of media main tree 2024-12-05 14:02:42 +01:00
Makefile Linux 6.12.9 2025-01-09 13:33:55 +01:00
README README: Fix spelling 2024-03-18 03:36:32 -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 reStructuredText 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.