Revision 474095e46cd14421821da3201a9fd6a4c070996b authored by Linus Torvalds on 24 April 2015, 16:28:01 UTC, committed by Linus Torvalds on 24 April 2015, 16:28:01 UTC
Pull md updates from Neil Brown: "More updates that usual this time. A few have performance impacts which hould mostly be positive, but RAID5 (in particular) can be very work-load ensitive... We'll have to wait and see. Highlights: - "experimental" code for managing md/raid1 across a cluster using DLM. Code is not ready for general use and triggers a WARNING if used. However it is looking good and mostly done and having in mainline will help co-ordinate development. - RAID5/6 can now batch multiple (4K wide) stripe_heads so as to handle a full (chunk wide) stripe as a single unit. - RAID6 can now perform read-modify-write cycles which should help performance on larger arrays: 6 or more devices. - RAID5/6 stripe cache now grows and shrinks dynamically. The value set is used as a minimum. - Resync is now allowed to go a little faster than the 'mininum' when there is competing IO. How much faster depends on the speed of the devices, so the effective minimum should scale with device speed to some extent" * tag 'md/4.1' of git://neil.brown.name/md: (58 commits) md/raid5: don't do chunk aligned read on degraded array. md/raid5: allow the stripe_cache to grow and shrink. md/raid5: change ->inactive_blocked to a bit-flag. md/raid5: move max_nr_stripes management into grow_one_stripe and drop_one_stripe md/raid5: pass gfp_t arg to grow_one_stripe() md/raid5: introduce configuration option rmw_level md/raid5: activate raid6 rmw feature md/raid6 algorithms: xor_syndrome() for SSE2 md/raid6 algorithms: xor_syndrome() for generic int md/raid6 algorithms: improve test program md/raid6 algorithms: delta syndrome functions raid5: handle expansion/resync case with stripe batching raid5: handle io error of batch list RAID5: batch adjacent full stripe write raid5: track overwrite disk count raid5: add a new flag to track if a stripe can be batched raid5: use flex_array for scribble data md raid0: access mddev->queue (request queue member) conditionally because it is not set when accessed from dm-raid md: allow resync to go faster when there is competing IO. md: remove 'go_faster' option from ->sync_request() ...
init.txt
Explaining the dreaded "No init found." boot hang message
=========================================================
OK, so you've got this pretty unintuitive message (currently located
in init/main.c) and are wondering what the H*** went wrong.
Some high-level reasons for failure (listed roughly in order of execution)
to load the init binary are:
A) Unable to mount root FS
B) init binary doesn't exist on rootfs
C) broken console device
D) binary exists but dependencies not available
E) binary cannot be loaded
Detailed explanations:
0) Set "debug" kernel parameter (in bootloader config file or CONFIG_CMDLINE)
to get more detailed kernel messages.
A) make sure you have the correct root FS type
(and root= kernel parameter points to the correct partition),
required drivers such as storage hardware (such as SCSI or USB!)
and filesystem (ext3, jffs2 etc.) are builtin (alternatively as modules,
to be pre-loaded by an initrd)
C) Possibly a conflict in console= setup --> initial console unavailable.
E.g. some serial consoles are unreliable due to serial IRQ issues (e.g.
missing interrupt-based configuration).
Try using a different console= device or e.g. netconsole= .
D) e.g. required library dependencies of the init binary such as
/lib/ld-linux.so.2 missing or broken. Use readelf -d <INIT>|grep NEEDED
to find out which libraries are required.
E) make sure the binary's architecture matches your hardware.
E.g. i386 vs. x86_64 mismatch, or trying to load x86 on ARM hardware.
In case you tried loading a non-binary file here (shell script?),
you should make sure that the script specifies an interpreter in its shebang
header line (#!/...) that is fully working (including its library
dependencies). And before tackling scripts, better first test a simple
non-script binary such as /bin/sh and confirm its successful execution.
To find out more, add code to init/main.c to display kernel_execve()s
return values.
Please extend this explanation whenever you find new failure causes
(after all loading the init binary is a CRITICAL and hard transition step
which needs to be made as painless as possible), then submit patch to LKML.
Further TODOs:
- Implement the various run_init_process() invocations via a struct array
which can then store the kernel_execve() result value and on failure
log it all by iterating over _all_ results (very important usability fix).
- try to make the implementation itself more helpful in general,
e.g. by providing additional error messages at affected places.
Andreas Mohr <andi at lisas period de>
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