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authorLinus Torvalds <torvalds@linux-foundation.org>2019-03-09 17:40:27 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2019-03-09 17:40:27 -0800
commit6cdc577a18a616c331f57e268c97466171cfc45f (patch)
tree95fba928918a06b32ed59efb2de7e8ba1513e78b /Documentation
parent92fff53b7191cae566be9ca6752069426c7f8241 (diff)
parent225557446856448039a9e495da37b72c20071ef2 (diff)
Merge tag 'for-5.1/dm-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm
Pull device mapper updates from Mike Snitzer: - Update bio-based DM core to always call blk_queue_split() and update DM targets to properly advertise discard limits that blk_queue_split() looks at when dtermining to split discard. Whereby allowing DM core's own 'split_discard_bios' to be removed. - Improve DM cache target to provide support for discard passdown to the origin device. - Introduce support to directly boot to a DM mapped device from init by using dm-mod.create= module param. This eliminates the need for an elaborate initramfs that is otherwise needed to create DM devices. This feature's implementation has been worked on for quite some time (got up to v12) and is of particular interest to Android and other more embedded platforms (e.g. ARM). - Rate limit errors from the DM integrity target that were identified as the cause for recent NMI hangs due to console limitations. - Add sanity checks for user input to thin-pool and external snapshot creation. - Remove some unused leftover kmem caches from when old .request_fn request-based support was removed. - Various small cleanups and fixes to targets (e.g. typos, needless unlikely() annotations, use struct_size(), remove needless .direct_access method from dm-snapshot) * tag 'for-5.1/dm-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm: dm integrity: limit the rate of error messages dm snapshot: don't define direct_access if we don't support it dm cache: add support for discard passdown to the origin device dm writecache: fix typo in name for writeback_wq dm: add support to directly boot to a mapped device dm thin: add sanity checks to thin-pool and external snapshot creation dm block manager: remove redundant unlikely annotation dm verity fec: remove redundant unlikely annotation dm integrity: remove redundant unlikely annotation dm: always call blk_queue_split() in dm_process_bio() dm: fix to_sector() for 32bit dm switch: use struct_size() in kzalloc() dm: remove unused _rq_tio_cache and _rq_cache dm: eliminate 'split_discard_bios' flag from DM target interface dm: update dm_process_bio() to split bio if in ->make_request_fn()
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/device-mapper/cache.txt3
-rw-r--r--Documentation/device-mapper/dm-init.txt114
2 files changed, 117 insertions, 0 deletions
diff --git a/Documentation/device-mapper/cache.txt b/Documentation/device-mapper/cache.txt
index ff0841711fd5..8ae1cf8e94da 100644
--- a/Documentation/device-mapper/cache.txt
+++ b/Documentation/device-mapper/cache.txt
@@ -206,6 +206,9 @@ Optional feature arguments are:
in a separate btree, which improves speed of shutting
down the cache.
+ no_discard_passdown : disable passing down discards from the cache
+ to the origin's data device.
+
A policy called 'default' is always registered. This is an alias for
the policy we currently think is giving best all round performance.
diff --git a/Documentation/device-mapper/dm-init.txt b/Documentation/device-mapper/dm-init.txt
new file mode 100644
index 000000000000..8464ee7c01b8
--- /dev/null
+++ b/Documentation/device-mapper/dm-init.txt
@@ -0,0 +1,114 @@
+Early creation of mapped devices
+====================================
+
+It is possible to configure a device-mapper device to act as the root device for
+your system in two ways.
+
+The first is to build an initial ramdisk which boots to a minimal userspace
+which configures the device, then pivot_root(8) in to it.
+
+The second is to create one or more device-mappers using the module parameter
+"dm-mod.create=" through the kernel boot command line argument.
+
+The format is specified as a string of data separated by commas and optionally
+semi-colons, where:
+ - a comma is used to separate fields like name, uuid, flags and table
+ (specifies one device)
+ - a semi-colon is used to separate devices.
+
+So the format will look like this:
+
+ dm-mod.create=<name>,<uuid>,<minor>,<flags>,<table>[,<table>+][;<name>,<uuid>,<minor>,<flags>,<table>[,<table>+]+]
+
+Where,
+ <name> ::= The device name.
+ <uuid> ::= xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx | ""
+ <minor> ::= The device minor number | ""
+ <flags> ::= "ro" | "rw"
+ <table> ::= <start_sector> <num_sectors> <target_type> <target_args>
+ <target_type> ::= "verity" | "linear" | ... (see list below)
+
+The dm line should be equivalent to the one used by the dmsetup tool with the
+--concise argument.
+
+Target types
+============
+
+Not all target types are available as there are serious risks in allowing
+activation of certain DM targets without first using userspace tools to check
+the validity of associated metadata.
+
+ "cache": constrained, userspace should verify cache device
+ "crypt": allowed
+ "delay": allowed
+ "era": constrained, userspace should verify metadata device
+ "flakey": constrained, meant for test
+ "linear": allowed
+ "log-writes": constrained, userspace should verify metadata device
+ "mirror": constrained, userspace should verify main/mirror device
+ "raid": constrained, userspace should verify metadata device
+ "snapshot": constrained, userspace should verify src/dst device
+ "snapshot-origin": allowed
+ "snapshot-merge": constrained, userspace should verify src/dst device
+ "striped": allowed
+ "switch": constrained, userspace should verify dev path
+ "thin": constrained, requires dm target message from userspace
+ "thin-pool": constrained, requires dm target message from userspace
+ "verity": allowed
+ "writecache": constrained, userspace should verify cache device
+ "zero": constrained, not meant for rootfs
+
+If the target is not listed above, it is constrained by default (not tested).
+
+Examples
+========
+An example of booting to a linear array made up of user-mode linux block
+devices:
+
+ dm-mod.create="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" root=/dev/dm-0
+
+This will boot to a rw dm-linear target of 8192 sectors split across two block
+devices identified by their major:minor numbers. After boot, udev will rename
+this target to /dev/mapper/lroot (depending on the rules). No uuid was assigned.
+
+An example of multiple device-mappers, with the dm-mod.create="..." contents is shown here
+split on multiple lines for readability:
+
+ vroot,,,ro,
+ 0 1740800 verity 254:0 254:0 1740800 sha1
+ 76e9be054b15884a9fa85973e9cb274c93afadb6
+ 5b3549d54d6c7a3837b9b81ed72e49463a64c03680c47835bef94d768e5646fe;
+ vram,,,rw,
+ 0 32768 linear 1:0 0,
+ 32768 32768 linear 1:1 0
+
+Other examples (per target):
+
+"crypt":
+ dm-crypt,,8,ro,
+ 0 1048576 crypt aes-xts-plain64
+ babebabebabebabebabebabebabebabebabebabebabebabebabebabebabebabe 0
+ /dev/sda 0 1 allow_discards
+
+"delay":
+ dm-delay,,4,ro,0 409600 delay /dev/sda1 0 500
+
+"linear":
+ dm-linear,,,rw,
+ 0 32768 linear /dev/sda1 0,
+ 32768 1024000 linear /dev/sda2 0,
+ 1056768 204800 linear /dev/sda3 0,
+ 1261568 512000 linear /dev/sda4 0
+
+"snapshot-origin":
+ dm-snap-orig,,4,ro,0 409600 snapshot-origin 8:2
+
+"striped":
+ dm-striped,,4,ro,0 1638400 striped 4 4096
+ /dev/sda1 0 /dev/sda2 0 /dev/sda3 0 /dev/sda4 0
+
+"verity":
+ dm-verity,,4,ro,
+ 0 1638400 verity 1 8:1 8:2 4096 4096 204800 1 sha256
+ fb1a5a0f00deb908d8b53cb270858975e76cf64105d412ce764225d53b8f3cfd
+ 51934789604d1b92399c52e7cb149d1b3a1b74bbbcb103b2a0aaacbed5c08584