A recent patch to protect the rdev list with rcu locking leaves us
with a problem because we can sleep on memalloc while holding the
rcu lock.
The rcu lock is only needed while walking the linked list as
uninteresting devices (failed or spares) can be removed at any time.
So only take the rcu lock while actually walking the linked list.
Take a refcount on the rdev during the time when we drop the lock
and do the memalloc to start IO.
When we return to the locked code, all the interesting devices
on the list will not have moved, so we can simply use
list_for_each_continue_rcu to pick up where we left off.
Signed-off-by: NeilBrown <neilb@suse.de>
All modifications and most access to the mddev->disks list are made
under the reconfig_mutex lock. However there are three places where
the list is walked without any locking. If a reconfig happens at this
time, havoc (and oops) can ensue.
So use RCU to protect these accesses:
- wrap them in rcu_read_{,un}lock()
- use list_for_each_entry_rcu
- add to the list with list_add_rcu
- delete from the list with list_del_rcu
- delay the 'free' with call_rcu rather than schedule_work
Note that export_rdev did a list_del_init on this list. In almost all
cases the entry was not in the list anymore so it was a no-op and so
safe. It is no longer safe as after list_del_rcu we may not touch
the list_head.
An audit shows that export_rdev is called:
- after unbind_rdev_from_array, in which case the delete has
already been done,
- after bind_rdev_to_array fails, in which case the delete isn't needed.
- before the device has been put on a list at all (e.g. in
add_new_disk where reading the superblock fails).
- and in autorun devices after a failure when the device is on a
different list.
So remove the list_del_init call from export_rdev, and add it back
immediately before the called to export_rdev for that last case.
Note also that ->same_set is sometimes used for lists other than
mddev->list (e.g. candidates). In these cases rcu is not needed.
Signed-off-by: NeilBrown <neilb@suse.de>
Rename it to sb_start to make sure all users have been converted.
Signed-off-by: Andre Noll <maan@systemlinux.org>
Signed-off-by: Neil Brown <neilb@suse.de>
When an array is degraded, bits in the write-intent bitmap are not
cleared, so that if the missing device is re-added, it can be synced
by only updated those parts of the device that have changed since
it was removed.
The enable this a 'events_cleared' value is stored. It is the event
counter for the array the last time that any bits were cleared.
Sometimes - if a device disappears from an array while it is 'clean' -
the events_cleared value gets updated incorrectly (there are subtle
ordering issues between updateing events in the main metadata and the
bitmap metadata) resulting in the missing device appearing to require
a full resync when it is re-added.
With this patch, we update events_cleared precisely when we are about
to clear a bit in the bitmap. We record events_cleared when we clear
the bit internally, and copy that to the superblock which is written
out before the bit on storage. This makes it more "obviously correct".
We also need to update events_cleared when the event_count is going
backwards (as happens on a dirty->clean transition of a non-degraded
array).
Thanks to Mike Snitzer for identifying this problem and testing early
"fixes".
Cc: "Mike Snitzer" <snitzer@gmail.com>
Signed-off-by: Neil Brown <neilb@suse.de>
Recent patch titled
Reduce CPU wastage on idle md array with a write-intent bitmap.
would sometimes leave the array with dirty bitmap bits that stay dirty. A
subsequent write would sort things out so it isn't a big problem, but should
be fixed nonetheless.
We need to make sure that when the bitmap becomes not "allclean", the
daemon_sleep really does get set to a sensible value.
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>
On an md array with a write-intent bitmap, a thread wakes up every few seconds
and scans the bitmap looking for work to do. If the array is idle, there will
be no work to do, but a lot of scanning is done to discover this.
So cache the fact that the bitmap is completely clean, and avoid scanning the
whole bitmap when the cache is known to be clean.
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>
d_path() is used on a <dentry,vfsmount> pair. Lets use a struct path to
reflect this.
[akpm@linux-foundation.org: fix build in mm/memory.c]
Signed-off-by: Jan Blunck <jblunck@suse.de>
Acked-by: Bryan Wu <bryan.wu@analog.com>
Acked-by: Christoph Hellwig <hch@infradead.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Neil Brown <neilb@suse.de>
Cc: Michael Halcrow <mhalcrow@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
As this is more in line with common practice in the kernel. Also swap the
args around to be more like list_for_each.
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>
Currently an md array with a write-intent bitmap does not updated that bitmap
to reflect successful partial resync. Rather the entire bitmap is updated
when the resync completes.
This is because there is no guarentee that resync requests will complete in
order, and tracking each request individually is unnecessarily burdensome.
However there is value in regularly updating the bitmap, so add code to
periodically pause while all pending sync requests complete, then update the
bitmap. Doing this only every few seconds (the same as the bitmap update
time) does not notciably affect resync performance.
[snitzer@gmail.com: export bitmap_cond_end_sync]
Signed-off-by: Neil Brown <neilb@suse.de>
Cc: "Mike Snitzer" <snitzer@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Added blk_unplug interface, allowing all invocations of unplugs to result
in a generated blktrace UNPLUG.
Signed-off-by: Alan D. Brunelle <Alan.Brunelle@hp.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
bitmap_unplug only ever returns 0, so it may as well be void. Two callers try
to print a message if it returns non-zero, but that message is already printed
by bitmap_file_kick.
write_page returns an error which is not consistently checked. It always
causes BITMAP_WRITE_ERROR to be set on an error, and that can more
conveniently be checked.
When the return of write_page is checked, an error causes bitmap_file_kick to
be called - so move that call into write_page - and protect against recursive
calls into bitmap_file_kick.
bitmap_update_sb returns an error that is never checked.
So make these 'void' and be consistent about checking the bit.
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>
We current completely trust user-space to set up metadata describing an
consistant array. In particlar, that the metadata, data, and bitmap do not
overlap.
But userspace can be buggy, and it is better to report an error than corrupt
data. So put in some appropriate checks.
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>
It is possible that real data or metadata follows the bitmap without full page
alignment.
So limit the last write to be only the required number of bytes, rounded up to
the hard sector size of the device.
Signed-off-by: Neil Brown <neilb@suse.de>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
If 'num_pages' were ever 1 more than a multiple of 8 (32bit platforms)
or of 16 (64 bit platforms). filemap_attr would be allocated one
'unsigned long' shorter than required. We need a round-up in there.
Signed-off-by: Neil Brown <neilb@suse.de>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Convert all calls to invalidate_inode_pages() into open-coded calls to
invalidate_mapping_pages().
Leave the invalidate_inode_pages() wrapper in place for now, marked as
deprecated.
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
md/bitmap tracks how many active write requests are pending on blocks
associated with each bit in the bitmap, so that it knows when it can clear
the bit (when count hits zero).
The counter has 14 bits of space, so if there are ever more than 16383, we
cannot cope.
Currently the code just calles BUG_ON as "all" drivers have request queue
limits much smaller than this.
However is seems that some don't. Apparently some multipath configurations
can allow more than 16383 concurrent write requests.
So, in this unlikely situation, instead of calling BUG_ON we now wait
for the count to drop down a bit. This requires a new wait_queue_head,
some waiting code, and a wakeup call.
Tested by limiting the counter to 20 instead of 16383 (writes go a lot slower
in that case...).
Signed-off-by: Neil Brown <neilb@suse.de>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In most cases we check the size of the bitmap file before reading data from
it. However when reading the superblock, we always read the first PAGE_SIZE
bytes, which might not always be appropriate. So limit that read to the size
of the file if appropriate.
Also, we get the count of available bytes wrong in one place, so that too can
read past the end of the file.
Cc: "yang yin" <yinyang801120@gmail.com>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
And a couple of bug fixes found by sparse.
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
find_first_set doesn't find the least-significant bit on bigendian machines,
so it is really wrong to use it.
ffs is closer, but takes an 'int' and we have a 'unsigned long'. So use
ffz(~X) to convert a chunksize into a chunkshift.
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
