md: support 'external' metadata for md arrays
- Add a state flag 'external' to indicate that the metadata is managed
externally (by user-space) so important changes need to be
left of user-space to handle.
Alternates are non-persistant ('none') where there is no stable metadata -
after the array is stopped there is no record of it's status - and
internal which can be version 0.90 or version 1.x
These are selected by writing to the 'metadata' attribute.
- move the updating of superblocks (sync_sbs) to after we have checked if
there are any superblocks or not.
- New array state 'write_pending'. This means that the metadata records
the array as 'clean', but a write has been requested, so the metadata has
to be updated to record a 'dirty' array before the write can continue.
This change is reported to md by writing 'active' to the array_state
attribute.
- tidy up marking of sb_dirty:
- don't set sb_dirty when resync finishes as md_check_recovery
calls md_update_sb when the sync thread finishes anyway.
- Don't set sb_dirty in multipath_run as the array might not be dirty.
- don't mark superblock dirty when switching to 'clean' if there
is no internal superblock (if external, userspace can choose to
update the superblock whenever it chooses to).
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/raid/md_k.h b/include/linux/raid/md_k.h
index dcb7292..b579cc6 100644
--- a/include/linux/raid/md_k.h
+++ b/include/linux/raid/md_k.h
@@ -130,6 +130,9 @@
minor_version,
patch_version;
int persistent;
+ int external; /* metadata is
+ * managed externally */
+ char metadata_type[17]; /* externally set*/
int chunk_size;
time_t ctime, utime;
int level, layout;