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Previously, raid array used the maximum logical block size (LBS)
of all member disks. Adding a larger LBS disk at runtime could
unexpectedly increase RAID's LBS, risking corruption of existing
partitions. This can be reproduced by:
```
# LBS of sd[de] is 512 bytes, sdf is 4096 bytes.
mdadm -CRq /dev/md0 -l1 -n3 /dev/sd[de] missing --assume-clean
# LBS is 512
cat /sys/block/md0/queue/logical_block_size
# create partition md0p1
parted -s /dev/md0 mklabel gpt mkpart primary 1MiB 100%
lsblk | grep md0p1
# LBS becomes 4096 after adding sdf
mdadm --add -q /dev/md0 /dev/sdf
cat /sys/block/md0/queue/logical_block_size
# partition lost
partprobe /dev/md0
lsblk | grep md0p1
```
Simply restricting larger-LBS disks is inflexible. In some scenarios,
only disks with 512 bytes LBS are available currently, but later, disks
with 4KB LBS may be added to the array.
Making LBS configurable is the best way to solve this scenario.
After this patch, the raid will:
- store LBS in disk metadata
- add a read-write sysfs 'mdX/logical_block_size'
Future mdadm should support setting LBS via metadata field during RAID
creation and the new sysfs. Though the kernel allows runtime LBS changes,
users should avoid modifying it after creating partitions or filesystems
to prevent compatibility issues.
Only 1.x metadata supports configurable LBS. 0.90 metadata inits all
fields to default values at auto-detect. Supporting 0.90 would require
more extensive changes and no such use case has been observed.
Note that many RAID paths rely on PAGE_SIZE alignment, including for
metadata I/O. A larger LBS than PAGE_SIZE will result in metadata
read/write failures. So this config should be prevented.
Link: https://lore.kernel.org/linux-raid/20251103125757.1405796-6-linan666@huaweicloud.com
Signed-off-by: Li Nan <linan122@huawei.com>
Reviewed-by: Xiao Ni <xni@redhat.com>
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
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Pull documentation updates from Jonathan Corbet:
"It has been a relatively busy cycle in docsland, with changes all
over:
- Bring the kernel memory-model docs into the Sphinx build in the
"literal include" mode.
- Lots of build-infrastructure work, further cleaning up long-term
kernel-doc technical debt. The sphinx-pre-install tool has been
converted to Python and updated for current systems.
- A new tool to detect when documents have been moved and generate
HTML redirects; this can be used on kernel.org (or any other site
hosting the rendered docs) to avoid breaking links.
- Automated processing of the YAML files describing the netlink
protocol.
- A significant update of the maintainer's PGP guide.
... and a seemingly endless series of typo fixes, build-problem fixes,
etc"
* tag 'docs-6.18' of git://git.lwn.net/linux: (193 commits)
Documentation/features: Update feature lists for 6.17-rc7
docs: remove cdomain.py
Documentation/process: submitting-patches: fix typo in "were do"
docs: dev-tools/lkmm: Fix typo of missing file extension
Documentation: trace: histogram: Convert ftrace docs cross-reference
Documentation: trace: histogram-design: Wrap introductory note in note:: directive
Documentation: trace: historgram-design: Separate sched_waking histogram section heading and the following diagram
Documentation: trace: histogram-design: Trim trailing vertices in diagram explanation text
Documentation: trace: histogram: Fix histogram trigger subsection number order
docs: driver-api: fix spelling of "buses".
Documentation: fbcon: Use admonition directives
Documentation: fbcon: Reindent 8th step of attach/detach/unload
Documentation: fbcon: Add boot options and attach/detach/unload section headings
docs: filesystems: sysfs: add remaining top level sysfs directory descriptions
docs: filesystems: sysfs: clarify symlink destinations in dev and bus/devices descriptions
docs: filesystems: sysfs: remove top level sysfs net directory
docs: maintainer: Fix ambiguous subheading formatting
docs: kdoc: a few more dump_typedef() tweaks
docs: kdoc: remove redundant comment stripping in dump_typedef()
docs: kdoc: remove some dead code in dump_typedef()
...
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Redundant data is used to enhance data fault tolerance, and the storage
method for redundant data vary depending on the RAID levels. And it's
important to maintain the consistency of redundant data.
Bitmap is used to record which data blocks have been synchronized and which
ones need to be resynchronized or recovered. Each bit in the bitmap
represents a segment of data in the array. When a bit is set, it indicates
that the multiple redundant copies of that data segment may not be
consistent. Data synchronization can be performed based on the bitmap after
power failure or readding a disk. If there is no bitmap, a full disk
synchronization is required.
Due to known performance issues with md-bitmap and the unreasonable
implementations:
- self-managed IO submitting like filemap_write_page();
- global spin_lock
I have decided not to continue optimizing based on the current bitmap
implementation, this new bitmap is invented without locking from IO fast
path and can be used with fast disks.
For designs and details, see the comments in drivers/md-llbitmap.c.
Link: https://lore.kernel.org/linux-raid/20250829080426.1441678-12-yukuai1@huaweicloud.com
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Li Nan <linan122@huawei.com>
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Currently bitmap_ops is registered while allocating mddev, this is fine
when there is only one bitmap_ops.
Delay setting bitmap_ops until creating bitmap, so that user can choose
which bitmap to use before running the array.
Link: https://lore.kernel.org/linux-raid/20250721171557.34587-7-yukuai@kernel.org
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Li Nan <linan122@huawei.com>
Reviewed-by: Xiao Ni <xni@redhat.com>
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The api will be used by mdadm to set bitmap_type while creating new array
or assembling array, prepare to add a new bitmap.
Currently available options are:
cat /sys/block/md0/md/bitmap_type
none [bitmap]
Link: https://lore.kernel.org/linux-raid/20250829080426.1441678-6-yukuai1@huaweicloud.com
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Xiao Ni <xni@redhat.com>
Reviewed-by: Li Nan <linan122@huawei.com>
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Changed "write-throuth" to "write-through".
Signed-off-by: Vivek Alurkar <primalkenja@gmail.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20250821051622.8341-2-primalkenja@gmail.com
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Correct spelling problems for Documentation/admin-guide/ as reported
by codespell.
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Mukesh Ojha <quic_mojha@quicinc.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Zefan Li <lizefan.x@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: cgroups@vger.kernel.org
Cc: Alasdair Kergon <agk@redhat.com>
Cc: Mike Snitzer <snitzer@kernel.org>
Cc: dm-devel@redhat.com
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: linux-media@vger.kernel.org
Cc: linux-mm@kvack.org
Link: https://lore.kernel.org/r/20230129231053.20863-2-rdunlap@infradead.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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Fix thirty five typos in dm-integrity.rst, dm-raid.rst, dm-zoned.rst,
verity.rst, writecache.rst, tsx_async_abort.rst, md.rst, bttv.rst,
dvb_references.rst, frontend-cardlist.rst, gspca-cardlist.rst, ipu3.rst,
remote-controller.rst, mm/index.rst, numaperf.rst, userfaultfd.rst,
module-signing.rst, imx-ddr.rst, intel-speed-select.rst,
intel_pstate.rst, ramoops.rst, abi.rst, kernel.rst, vm.rst
Signed-off-by: Andrew Klychkov <andrew.a.klychkov@gmail.com>
Link: https://lore.kernel.org/r/20201204072848.GA49895@spblnx124.lan
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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Report the UUID of the MD array in the following format:
xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
This is useful if you don't want to wait for udev to identify array.
And it is also easy for script to monitor it with the format.
Signed-off-by: Sebastian Parschauer <s.parschauer@gmx.de>
[Guoqing: mention the change in md.rst]
Signed-off-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
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Rationale:
Reduces attack surface on kernel devs opening the links for MITM
as HTTPS traffic is much harder to manipulate.
Deterministic algorithm:
For each file:
For each line:
If doesn't contain `\bxmlns\b`:
For each link, `\bhttp://[^# \t\r\n]*(?:\w|/)`:
If both the HTTP and HTTPS versions
return 200 OK and serve the same content:
Replace HTTP with HTTPS.
Signed-off-by: Alexander A. Klimov <grandmaster@al2klimov.de>
Link: https://lore.kernel.org/r/20200526060544.25127-1-grandmaster@al2klimov.de
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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When the Partial Parity Log is enabled, circular buffer is used to store
PPL data. Each write to RAID device causes overwrite of data in this buffer
so some write_hint can be set to those request to help drives handle
garbage collection. This patch adds new sysfs attribute which can be used
to specify which write_hint should be assigned to PPL.
Acked-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: Mariusz Dabrowski <mariusz.dabrowski@intel.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
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Add 'consistency_policy' attribute for array. It indicates how the array
maintains consistency in case of unexpected shutdown.
Add 'ppl_sector' and 'ppl_size' for rdev, which describe the location
and size of the PPL space on the device. They can't be changed for
active members if the array is started and PPL is enabled, so in the
setter functions only basic checks are performed. More checks are done
in ppl_validate_rdev() when starting the log.
These attributes are writable to allow enabling PPL for external
metadata arrays and (later) to enable/disable PPL for a running array.
Signed-off-by: Artur Paszkiewicz <artur.paszkiewicz@intel.com>
Signed-off-by: Shaohua Li <shli@fb.com>
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I'm starting document of the raid5-cache feature. Please note this is a
kernel doc instead of a mdadm manual, so I don't add the details about
how to use the feature in mdadm side.
Cc: NeilBrown <neilb@suse.com>
Reviewed-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Shaohua Li <shli@fb.com>
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Place README, REPORTING-BUGS, SecurityBugs and kernel-parameters
on an user's manual book.
As we'll be numbering the user's manual, remove the manual
numbering from SecurityBugs.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
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