This allows the state of an md/array to be directly controlled via sysfs and
adds the ability to stop and array without tearing it down.
Array states/settings:
clear
No devices, no size, no level
Equivalent to STOP_ARRAY ioctl
inactive
May have some settings, but array is not active
all IO results in error
When written, doesn't tear down array, but just stops it
suspended (not supported yet)
All IO requests will block. The array can be reconfigured.
Writing this, if accepted, will block until array is quiescent
readonly
no resync can happen. no superblocks get written.
write requests fail
read-auto
like readonly, but behaves like 'clean' on a write request.
clean - no pending writes, but otherwise active.
When written to inactive array, starts without resync
If a write request arrives then
if metadata is known, mark 'dirty' and switch to 'active'.
if not known, block and switch to write-pending
If written to an active array that has pending writes, then fails.
active
fully active: IO and resync can be happening.
When written to inactive array, starts with resync
write-pending (not supported yet)
clean, but writes are blocked waiting for 'active' to be written.
active-idle
like active, but no writes have been seen for a while (100msec).
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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