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Mateusz Jończyk 36a5c03f23 md/raid1: set max_sectors during early return from choose_slow_rdev() 
Linux 6.9+ is unable to start a degraded RAID1 array with one drive,
when that drive has a write-mostly flag set. During such an attempt,
the following assertion in bio_split() is hit:

	BUG_ON(sectors <= 0);

Call Trace:
	? bio_split+0x96/0xb0
	? exc_invalid_op+0x53/0x70
	? bio_split+0x96/0xb0
	? asm_exc_invalid_op+0x1b/0x20
	? bio_split+0x96/0xb0
	? raid1_read_request+0x890/0xd20
	? __call_rcu_common.constprop.0+0x97/0x260
	raid1_make_request+0x81/0xce0
	? __get_random_u32_below+0x17/0x70
	? new_slab+0x2b3/0x580
	md_handle_request+0x77/0x210
	md_submit_bio+0x62/0xa0
	__submit_bio+0x17b/0x230
	submit_bio_noacct_nocheck+0x18e/0x3c0
	submit_bio_noacct+0x244/0x670

After investigation, it turned out that choose_slow_rdev() does not set
the value of max_sectors in some cases and because of it,
raid1_read_request calls bio_split with sectors == 0.

Fix it by filling in this variable.

This bug was introduced in
commit dfa8ecd167 ("md/raid1: factor out choose_slow_rdev() from read_balance()")
but apparently hidden until
commit 0091c5a269 ("md/raid1: factor out helpers to choose the best rdev from read_balance()")
shortly thereafter.

Cc: stable@vger.kernel.org # 6.9.x+
Signed-off-by: Mateusz Jończyk <mat.jonczyk@o2.pl>
Fixes: dfa8ecd167 ("md/raid1: factor out choose_slow_rdev() from read_balance()")
Cc: Song Liu <song@kernel.org>
Cc: Yu Kuai <yukuai3@huawei.com>
Cc: Paul Luse <paul.e.luse@linux.intel.com>
Cc: Xiao Ni <xni@redhat.com>
Cc: Mariusz Tkaczyk <mariusz.tkaczyk@linux.intel.com>
Link: https://lore.kernel.org/linux-raid/20240706143038.7253-1-mat.jonczyk@o2.pl/

--

Tested on both Linux 6.10 and 6.9.8.

Inside a VM, mdadm testsuite for RAID1 on 6.10 did not find any problems:
	./test --dev=loop --no-error --raidtype=raid1
(on 6.9.8 there was one failure, caused by external bitmap support not
compiled in).

Notes:
- I was reliably getting deadlocks when adding / removing devices
  on such an array - while the array was loaded with fsstress with 20
  concurrent processes. When the array was idle or loaded with fsstress
  with 8 processes, no such deadlocks happened in my tests.
  This occurred also on unpatched Linux 6.8.0 though, but not on
  6.1.97-rc1, so this is likely an independent regression (to be
  investigated).
- I was also getting deadlocks when adding / removing the bitmap on the
  array in similar conditions - this happened on Linux 6.1.97-rc1
  also though. fsstress with 8 concurrent processes did cause it only
  once during many tests.
- in my testing, there was once a problem with hot adding an
  internal bitmap to the array:
	mdadm: Cannot add bitmap while array is resyncing or reshaping etc.
	mdadm: failed to set internal bitmap.
  even though no such reshaping was happening according to /proc/mdstat.
  This seems unrelated, though.

Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20240711202316.10775-1-mat.jonczyk@o2.pl
2024-07-12 01:30:38 +00:00
arch block: add a bvec_phys helper 2024-07-08 01:51:05 -06:00
block block: take offset into account in blk_bvec_map_sg again 2024-07-09 01:02:44 -06:00
certs kbuild: use $(src) instead of $(srctree)/$(src) for source directory 2024-05-10 04:34:52 +09:00
crypto This push fixes a bug in the new ecc P521 code as well as a buggy 2024-05-20 08:47:54 -07:00
Documentation block: Add core atomic write support 2024-06-20 15:19:17 -06:00
drivers md/raid1: set max_sectors during early return from choose_slow_rdev() 2024-07-12 01:30:38 +00:00
fs block: Add atomic write support for statx 2024-06-20 15:19:17 -06:00
include block: Validate logical block size in blk_validate_limits() 2024-07-09 00:00:17 -06:00
init Driver core changes for 6.10-rc1 2024-05-22 12:13:40 -07:00
io_uring fs: Initial atomic write support 2024-06-20 15:19:17 -06:00
ipc Mainly singleton patches, documented in their respective changelogs. 2024-05-19 14:02:03 -07:00
kernel Fix race between perf_event_free_task() and perf_event_release_kernel() 2024-06-08 09:26:59 -07:00
lib Including fixes from BPF and big collection of fixes for WiFi core 2024-06-06 09:55:27 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm: fix xyz_noprof functions calling profiled functions 2024-06-05 19:19:26 -07:00
net nfsd-6.10 fixes: 2024-06-07 15:07:57 -07:00
rust rust: block: fix generated bindings after refactoring of features 2024-06-28 14:27:45 -06:00
samples tracing/treewide: Remove second parameter of __assign_str() 2024-05-22 20:14:47 -04:00
scripts Kbuild fixes for v6.10 (second) 2024-06-08 10:12:33 -07:00
security tomoyo: update project links 2024-06-03 22:43:11 +09:00
sound ALSA: seq: ump: Fix swapped song position pointer data 2024-05-31 09:51:44 +02:00
tools perf tools fixes for v6.10: 2nd batch 2024-06-09 09:04:51 -07:00
usr kbuild: use $(src) instead of $(srctree)/$(src) for source directory 2024-05-10 04:34:52 +09:00
virt The usual shower of singleton fixes and minor series all over MM, 2024-05-19 09:21:03 -07:00
.clang-format clang-format: Update with v6.7-rc4's for_each macro list 2023-12-08 23:54:38 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig Add .editorconfig file for basic formatting 2023-12-28 16:22:47 +09:00
.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: create a list of all built DTB files 2024-02-19 18:20:39 +09:00
.mailmap mailmap: add entry for Weiwen Hu 2024-06-24 12:53:42 -07:00
.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: Drop Gustavo Pimentel as PCI DWC Maintainer 2024-03-27 13:41:02 -05:00
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: add entry for Rust block device driver API 2024-06-14 07:45:04 -06:00
Makefile Linux 6.10-rc3 2024-06-09 14:19:43 -07:00
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.