The discard block size can change if the origin changes size or if an
old DM cache is upgraded from using a discard block size that was equal
to cache block size.
To fix this an extent of discarded blocks is established for the purpose
of translating the old discard block size to the new in-core discard
block size and set bits. The old (potentially huge) discard bitset is
left ondisk until it is re-written using the new in-core information on
the next successful DM cache shutdown.
Fixes: 7ae34e7778 ("dm cache: improve discard support")
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Commit 7ae34e777 ("dm cache: improve discard support") needed to also:
- discontinue having DM core split the discard bios on cache block
boundaries
- calculate the cache's discard_nr_blocks relative to the determined
discard_block_size rather than using oblock_to_dblock()
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This could've been quite bad (to return success but not update the new
root to point at the old) but in practice the only known consumer of the
dm array code is the DM cache target. And the DM cache target passes in
the same old root to array_resize() anyway.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
rcu_dereference() should be used in sections protected by rcu_read_lock.
For writers, holding some kind of mutex or lock,
rcu_dereference_protected() is the way to go, adding explicit lockdep
bits.
In __unbind(), we are the last user of this mapped device, so can use
the constant '1' instead of a lockdep_is_held(), not consistent with
other uses of rcu_dereference_protected() which use md->suspend_lock
mutex.
Reported-by: Kirill A. Shutemov <kirill@shutemov.name>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Fixes: 33423974bf ("dm: Use rcu_dereference() for accessing rcu pointer")
Cc: Pranith Kumar <bobby.prani@gmail.com>
[snitzer: allow lines longer than 80 columns, refine subject]
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Simplify the pool_io_hints code that works to establish a max_sectors
value that is a power-of-2 factor of the thin-pool's blocksize. The
biggest associated improvement is that the DM thin-pool is no longer
concerning itself with the data device's max_hw_sectors when adjusting
max_sectors.
This fixes the relative fragility of the original "dm thin: adjust
max_sectors_kb based on thinp blocksize" commit that only became
apparent when testing was performed using a DM thin-pool ontop of a
virtio_blk device. One proposed upstream patch detailed the problems
inherent in virtio_blk: https://lkml.org/lkml/2014/11/20/611
So even though virtio_blk incorrectly set its max_hw_sectors it actually
helped make it clear that we need DM thinp to be tolerant of any future
Linux driver that incorrectly sets max_hw_sectors.
We only need to be concerned with modifying the thin-pool device's
max_sectors limit if it is smaller than the thin-pool's blocksize. In
this case the value of max_sectors does become a limiting factor when
upper layers (e.g. filesystems) construct their bios. But if the
hardware can support IOs larger than the thin-pool's blocksize the user
is encouraged to adjust the thin-pool's data device's max_sectors
accordingly -- doing so will enable the thin-pool to inherit the
established user-defined max_sectors.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Before this change it was expected that userspace would first suspend
all active thin devices, reload/resize the thin-pool target, then resume
all active thin devices. Now the thin-pool suspend/resume will trigger
the suspend/resume of all active thins via appropriate calls to
dm_internal_suspend and dm_internal_resume.
Store the mapped_device for each thin device in struct thin_c to make
these calls possible.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>
Rename dm_internal_{suspend,resume} to dm_internal_{suspend,resume}_fast
-- dm-stats will continue using these methods to avoid all the extra
suspend/resume logic that is not needed in order to quickly flush IO.
Introduce dm_internal_suspend_noflush() variant that actually calls the
mapped_device's target callbacks -- otherwise target-specific hooks are
avoided (e.g. dm-thin's thin_presuspend and thin_postsuspend). Common
code between dm_internal_{suspend_noflush,resume} and
dm_{suspend,resume} was factored out as __dm_{suspend,resume}.
Update dm_internal_{suspend_noflush,resume} to always take and release
the mapped_device's suspend_lock. Also update dm_{suspend,resume} to be
aware of potential for DM_INTERNAL_SUSPEND_FLAG to be set and respond
accordingly by interruptibly waiting for the DM_INTERNAL_SUSPEND_FLAG to
be cleared. Add lockdep annotation to dm_suspend() and dm_resume().
The existing DM_SUSPEND_FLAG remains unchanged.
DM_INTERNAL_SUSPEND_FLAG is set by dm_internal_suspend_noflush() and
cleared by dm_internal_resume().
Both DM_SUSPEND_FLAG and DM_INTERNAL_SUSPEND_FLAG may be set if a device
was already suspended when dm_internal_suspend_noflush() was called --
this can be thought of as a "nested suspend". A "nested suspend" can
occur with legacy userspace dm-thin code that might suspend all active
thin volumes before suspending the pool for resize.
But otherwise, in the normal dm-thin-pool suspend case moving forward:
the thin-pool will have DM_SUSPEND_FLAG set and all active thins from
that thin-pool will have DM_INTERNAL_SUSPEND_FLAG set.
Also add DM_INTERNAL_SUSPEND_FLAG to status report. This new
DM_INTERNAL_SUSPEND_FLAG state is being reported to assist with
debugging (e.g. 'dmsetup info' will report an internally suspended
device accordingly).
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>
Otherwise IO could be issued to the pool while it is suspended.
Care was taken to properly interlock between the thin and thin-pool
targets when accessing the pool's 'suspended' flag. The thin_ctr will
not add a new thin device to the pool's active_thins list if the pool is
susepended.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>
The DM thin-pool target now must undo the changes performed during
pool_presuspend() so introduce presuspend_undo hook in target_type.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>
As long as struct thin_c is in the list, anyone can grab a reference of
it. Consequently, we must wait for the reference count to drop to zero
*after* we remove the structure from the list, not before.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Loading and saving millions of block mappings takes time. We may as
well explain what's going on, and encourage people to use a larger
cache block size.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Safely allow the discard blocksize to be larger than the cache blocksize
by using the bio prison's range locking support. This also improves
discard performance considerly because larger discards are issued to the
dm-cache device. The discard blocksize was always intended to be
greater than the cache blocksize. But until now it wasn't implemented
safely.
Also, by safely restoring the ability to have discard blocksize larger
than cache blocksize we're able to significantly reduce the memory used
for the cache's discard bitset. Before, with a small discard blocksize,
the discard bitset could get quite large because its size is a function
of the discard blocksize and the origin device's size. For example,
previously, using a 32KB cache blocksize with a 40TB origin resulted in
1280MB of incore memory use for the discard bitset! Now, the discard
blocksize is scaled up accordingly to ensure the discard bitset is
capped at 2**14 bits, or 16KB.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This reverts commit d132cc6d9e because we
actually do want to allow the discard blocksize to be larger than the
cache blocksize. Further dm-cache discard changes will make this
possible.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This reverts commit 64ab346a36 because we
actually do want to allow the discard blocksize to be larger than the
cache blocksize. Further dm-cache discard changes will make this
possible.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Ranges will be placed in the same cell if they overlap.
Range locking is a prerequisite for more efficient multi-block discard
support in both the cache and thin-provisioning targets.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Before, if the user wanted sequential IO to be promoted to the cache
they'd have to set sequential_threshold to some nebulous large value.
Now, the user may easily disable sequential IO detection (and sequential
IO's implicit bypass of the cache) by setting sequential_threshold to 0.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Rather than maintaining a separate promote_threshold variable that we
periodically update we now use the hit count of the oldest clean
block. Also add a fudge factor to discourage demoting dirty blocks.
With some tests this has a sizeable difference, because the old code
was too eager to demote blocks. For example, device-mapper-test-suite's
git_extract_cache_quick test goes from taking 190 seconds, to 142
(linear on spindle takes 250).
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
When creating new devices dm_sync_table() calls
synchronize_rcu_expedited(), causing _all_ pending RCU pointers to be
flushed. This causes a latency overhead that is especially noticeable
when creating lots of devices.
And all of this is pointless as there are no old maps to be
disconnected, and hence no stale pointers which would need to be
cleared up.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Annotate the map field with __rcu since this is a rcu pointer which is checked
by sparse.
Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
The map field in 'struct mapped_device' is an rcu pointer. Use rcu_dereference()
while accessing it.
Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Sort the cells in logical block order before processing each cell in
process_thin_deferred_cells(). This significantly improves the ondisk
layout on rotational storage, whereby improving read performance.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This use of direct submission in process_shared_bio() reduces latency
for submitting bios in the shared cell by avoiding adding those bios to
the deferred list and waiting for the next iteration of the worker.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This use of direct submission in process_prepared_mapping() reduces
latency for submitting bios in a cell by avoiding adding those bios to
the deferred list and waiting for the next iteration of the worker.
But this direct submission exposes the potential for a race between
releasing a cell and incrementing deferred set. Fix this by introducing
dm_cell_visit_release() and refactoring inc_remap_and_issue_cell()
accordingly.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This avoids dropping the cell, so increases the probability that other
bios will collect within the cell, rather than being passed individually
to the worker.
Also add required process_cell and process_discard_cell error handling
wrappers and set associated pool-mode function pointers accordingly.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
When processing a discard bio, if the block is already quiesced do the
discard immediately rather than adding the mapping to a list for the
next iteration of the worker thread.
Discarding a fully provisioned 100G thin volume with 64k block size goes
from 860s to 95s with this change.
Clearly there's something wrong with the worker architecture, more
investigation needed.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Introduce thin_merge so that any additional constraints from the data
volume may be taken into account when determing the maximum number of
sectors that can be issued relative to the specified logical offset.
This is particularly important if/when the data volume is layered ontop
of a more sophisticated device (e.g. dm-raid or some other DM target).
Reviewed-by: Heinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
These code changes do not introduce a functional change.
But bio_add_page() will never attempt to build up a bio larger than
queue_max_sectors(). Similarly, bio_get_nr_vecs() is also bound by
queue_max_sectors(). Therefore, there is no point in allowing
dm_merge_bvec() to answer "how many sectors can a bio have at this
offset?" with anything larger than queue_max_sectors(). Using
queue_max_sectors() rather than BIO_MAX_SECTORS serves to more
accurately convey the limits that are being imposed.
Also, use unlikely() to clarify the fact that the defensive code in
dm_merge_bvec() relative to max_size going negative shouldn't ever
happen -- if it does happen there is a bug in the block layer for
requesting larger than dm_merge_bvec()'s initial response for a given
offset. Also, update a comment in dm_merge_bvec() relative to
max_hw_sectors_kb. And fix empty newline whitespace.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Allows for filesystems to submit bios that are a factor of the thinp
blocksize, improving dm-thinp efficiency (particularly when the data
volume is RAID).
Also set io_min to max_sectors_kb if it is a factor of the thinp
blocksize.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Throttle IO based on the time it's taking the worker to do one loop.
There were reports of hung task timeouts occuring and it was observed
that the excessively long avgqu-sz (as reported by iostat) was
contributing to these hung tasks.
Throttling definitely helps dm-thinp perform better under heavy IO load
(without being detremental by being overzealous). It reduces avgqu-sz
drastically, e.g.: from 60K to ~6K, and even as low as 150 once metadata
is cached by bufio, when dirty_ratio=5, dirty_background_ratio=2. And
avgqu-sz stays at or below 30K even with dirty_ratio=20,
dirty_background_ratio=10.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Prefetch metadata at the start of the worker thread and then again every
128th bio processed from the deferred list.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Introduce the dm_tm_issue_prefetches interface. If you're using a
non-blocking clone the tm will build up a list of requested blocks that
weren't in core. dm_tm_issue_prefetches will request those blocks to be
prefetched.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This change is a prerequisite for allowing metadata to be prefetched.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Previously it was using a fixed sized hash table. There are times
when very many concurrent cells are held (such as when processing a very
large discard). When this happens the hash table performance becomes
very poor.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
These changes help keep metadata backed by dm-bufio in-core longer which
fixes reports of metadata churn in the face of heavy random IO workloads.
Before, bufio evicted all buffers older than DM_BUFIO_DEFAULT_AGE_SECS.
Having a device (e.g. dm-thinp or dm-cache) lose all metadata just
because associated buffers had been idle for some time is unfriendly.
Now, the user may now configure the number of bytes that bufio retains
using the 'retain_bytes' module parameter. The default is 256K.
Also, the DM_BUFIO_WORK_TIMER_SECS and DM_BUFIO_DEFAULT_AGE_SECS
defaults were quite low so increase them (to 30 and 300 respectively).
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Converting over to using an rbtree eliminates a fixed 8MB allocation
from vmalloc space for the hash table.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
The walk code was using a 'ro_spine' to hold it's locked btree nodes.
But this data structure is designed for the rolling lock scheme, and
as such automatically unlocks blocks that are two steps up the call
chain. This is not suitable for the simple recursive walk algorithm,
which retraces its steps.
This code is only used by the persistent array code, which in turn is
only used by dm-cache. In order to trigger it you need to have a
mapping tree that is more than 2 levels deep; which equates to 8-16
million cache blocks. For instance a 4T ssd with a very small block
size of 32k only just triggers this bug.
The fix just places the locked blocks on the stack, and stops using
the ro_spine altogether.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
Avoids normal IO racing with discard.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
Commit 48cf06bc5f ("dm raid: add discard support for RAID levels 4, 5
and 6") did not properly handle missing metadata device(s). A failing
read of the superblock causes the metadata and data devices to be
removed from the dev array in struct raid_set, setting references to
both devices to NULL. configure_discard_support() nonetheless tries to
access the data dev unconditionally causing an oops.
Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
The dm-raid superblock (struct dm_raid_superblock) is padded to 512
bytes and that size is being used to read it in from the metadata
device into one preallocated page.
Reading or writing this on a 512-byte sector device works fine but on
a 4096-byte sector device this fails.
Set the dm-raid superblock's size to the logical block size of the
metadata device, because IO at that size is guaranteed too work. Also
add a size check to avoid silent partial metadata loss in case the
superblock should ever grow past the logical block size or PAGE_SIZE.
[includes pointer math fix from Dan Carpenter]
Reported-by: "Liuhua Wang" <lwang@suse.com>
Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
The shrinker uses gfp flags to indicate what kind of operation can the
driver wait for. If __GFP_IO flag is present, the driver can wait for
block I/O operations, if __GFP_FS flag is present, the driver can wait on
operations involving the filesystem.
dm-bufio tested for __GFP_IO. However, dm-bufio can run on a loop block
device that makes calls into the filesystem. If __GFP_IO is present and
__GFP_FS isn't, dm-bufio could still block on filesystem operations if it
runs on a loop block device.
The change from __GFP_IO to __GFP_FS supposedly fixes one observed (though
unreproducible) deadlock involving dm-bufio and loop device.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
Fix a potential struct stripe_c leak that would occur if the
chunk_size exceeded the maximum allowed by dm_set_target_max_io_len
(UINT_MAX). However, in practice there is no possibility of this
occuring given that chunk_size is of type uint32_t. But it is good to
fix this to future-proof in case dm_set_target_max_io_len's
implementation were to change.
Signed-off-by: Pavitra Kumar <pavitrak@nvidia.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
If cn_add_callback() fails in dm_ulog_tfr_init(), it does not
deallocate prealloced memory but calls cn_del_callback().
Found by Linux Driver Verification project (linuxtesting.org).
Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Reviewed-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
When __scan frees the required number of buffer entries that the
shrinker requested (nr_to_scan becomes zero) it must return. Before
this fix the __scan code exited only the inner loop and continued in the
outer loop -- which could result in reduced performance due to extra
buffers being freed (e.g. unnecessarily evicted thinp metadata needing
to be synchronously re-read into bufio's cache).
Also, move dm_bufio_cond_resched to __scan's inner loop, so that
iterating the bufio client's lru lists doesn't result in scheduling
latency.
Reported-by: Joe Thornber <thornber@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # 3.2+
The 'last_accessed' member of the dm_buffer structure was only set when
the the buffer was created. This led to each buffer being discarded
after dm_bufio_max_age time even if it was used recently. In practice
this resulted in all thinp metadata being evicted soon after being read
-- this is particularly problematic for metadata intensive workloads
like multithreaded small random IO.
'last_accessed' is now updated each time the buffer is moved to the head
of the LRU list, so the buffer is now properly discarded if it was not
used in dm_bufio_max_age time.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # v3.2+
In case of RAID levels 4, 5 and 6 we have to verify each RAID members'
ability to zero data on discards to avoid stripe data corruption -- if
discard_zeroes_data is not set for each RAID member discard support must
be disabled. But given the uncertainty of whether or not a RAID member
properly supports zeroing data on discard we require the user to
explicitly allow discard support on RAID levels 4, 5, and 6 by setting
a dm-raid module paramter, e.g.: dm-raid.devices_handle_discard_safely=Y
Otherwise, discards could cause data corruption on RAID4/5/6.
Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
