dmz_fetch_mblock() called from dmz_get_mblock() has a race since the
allocation of the new metadata block descriptor and its insertion in
the cache rbtree with the READING state is not atomic. Two different
contexts requesting the same block may end up each adding two different
descriptors of the same block to the cache.
Another problem for this function is that the BIO for processing the
block read is allocated after the metadata block descriptor is inserted
in the cache rbtree. If the BIO allocation fails, the metadata block
descriptor is freed without first being removed from the rbtree.
Fix the first problem by checking again if the requested block is not in
the cache right before inserting the newly allocated descriptor,
atomically under the mblk_lock spinlock. The second problem is fixed by
simply allocating the BIO before inserting the new block in the cache.
Finally, since dmz_fetch_mblock() also increments a block reference
counter, rename the function to dmz_get_mblock_slow(). To be symmetric
and clear, also rename dmz_lookup_mblock() to dmz_get_mblock_fast() and
increment the block reference counter directly in that function rather
than in dmz_get_mblock().
Fixes: 3b1a94c88b ("dm zoned: drive-managed zoned block device target")
Cc: stable@vger.kernel.org
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Since the ref field of struct dmz_mblock is always used with the
spinlock of struct dmz_metadata locked, there is no need to use an
atomic_t type. Change the type of the ref field to an unsigne
integer.
Fixes: 3b1a94c88b ("dm zoned: drive-managed zoned block device target")
Cc: stable@vger.kernel.org
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This way we don't need a block_device structure to submit I/O. The
block_device has different life time rules from the gendisk and
request_queue and is usually only available when the block device node
is open. Other callers need to explicitly create one (e.g. the lightnvm
passthrough code, or the new nvme multipathing code).
For the actual I/O path all that we need is the gendisk, which exists
once per block device. But given that the block layer also does
partition remapping we additionally need a partition index, which is
used for said remapping in generic_make_request.
Note that all the block drivers generally want request_queue or
sometimes the gendisk, so this removes a layer of indirection all
over the stack.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Use GFP_NOIO for memory allocations in the I/O path. Other memory
allocations in the initialization path can use GFP_KERNEL.
Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
A zone ID is a 32 bits unsigned int which can overflow when doing the
bit shifts in dmz_start_sect(). With a 256 MB zone size drive, the
overflow happens for a zone ID >= 8192.
Fix this by casting the zone ID to a sector_t before doing the bit
shift. While at it, similarly fix dmz_start_block().
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
The dm-zoned device mapper target provides transparent write access
to zoned block devices (ZBC and ZAC compliant block devices).
dm-zoned hides to the device user (a file system or an application
doing raw block device accesses) any constraint imposed on write
requests by the device, equivalent to a drive-managed zoned block
device model.
Write requests are processed using a combination of on-disk buffering
using the device conventional zones and direct in-place processing for
requests aligned to a zone sequential write pointer position.
A background reclaim process implemented using dm_kcopyd_copy ensures
that conventional zones are always available for executing unaligned
write requests. The reclaim process overhead is minimized by managing
buffer zones in a least-recently-written order and first targeting the
oldest buffer zones. Doing so, blocks under regular write access (such
as metadata blocks of a file system) remain stored in conventional
zones, resulting in no apparent overhead.
dm-zoned implementation focus on simplicity and on minimizing overhead
(CPU, memory and storage overhead). For a 14TB host-managed disk with
256 MB zones, dm-zoned memory usage per disk instance is at most about
3 MB and as little as 5 zones will be used internally for storing metadata
and performing buffer zone reclaim operations. This is achieved using
zone level indirection rather than a full block indirection system for
managing block movement between zones.
dm-zoned primary target is host-managed zoned block devices but it can
also be used with host-aware device models to mitigate potential
device-side performance degradation due to excessive random writing.
Zoned block devices can be formatted and checked for use with the dm-zoned
target using the dmzadm utility available at:
https://github.com/hgst/dm-zoned-tools
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
[Mike Snitzer partly refactored Damien's original work to cleanup the code]
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
