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2021-03-30dm table: Fix zoned model check and zone sectors checkShin'ichiro Kawasaki2-9/+26
[ Upstream commit 2d669ceb69c276f7637cf760287ca4187add082e ] Commit 24f6b6036c9e ("dm table: fix zoned iterate_devices based device capability checks") triggered dm table load failure when dm-zoned device is set up for zoned block devices and a regular device for cache. The commit inverted logic of two callback functions for iterate_devices: device_is_zoned_model() and device_matches_zone_sectors(). The logic of device_is_zoned_model() was inverted then all destination devices of all targets in dm table are required to have the expected zoned model. This is fine for dm-linear, dm-flakey and dm-crypt on zoned block devices since each target has only one destination device. However, this results in failure for dm-zoned with regular cache device since that target has both regular block device and zoned block devices. As for device_matches_zone_sectors(), the commit inverted the logic to require all zoned block devices in each target have the specified zone_sectors. This check also fails for regular block device which does not have zones. To avoid the check failures, fix the zone model check and the zone sectors check. For zone model check, introduce the new feature flag DM_TARGET_MIXED_ZONED_MODEL, and set it to dm-zoned target. When the target has this flag, allow it to have destination devices with any zoned model. For zone sectors check, skip the check if the destination device is not a zoned block device. Also add comments and improve an error message to clarify expectations to the two checks. Fixes: 24f6b6036c9e ("dm table: fix zoned iterate_devices based device capability checks") Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-03-30dm ioctl: fix out of bounds array access when no devicesMikulas Patocka1-1/+1
commit 4edbe1d7bcffcd6269f3b5eb63f710393ff2ec7a upstream. If there are not any dm devices, we need to zero the "dev" argument in the first structure dm_name_list. However, this can cause out of bounds write, because the "needed" variable is zero and len may be less than eight. Fix this bug by reporting DM_BUFFER_FULL_FLAG if the result buffer is too small to hold the "nl->dev" value. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Cc: stable@vger.kernel.org Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-03-30dm verity: fix DM_VERITY_OPTS_MAX valueJeongHyeon Lee1-1/+1
commit 160f99db943224e55906dd83880da1a704c6e6b9 upstream. Three optional parameters must be accepted at once in a DM verity table, e.g.: (verity_error_handling_mode) (ignore_zero_block) (check_at_most_once) Fix this to be possible by incrementing DM_VERITY_OPTS_MAX. Signed-off-by: JeongHyeon Lee <jhs2.lee@samsung.com> Fixes: 843f38d382b1 ("dm verity: add 'check_at_most_once' option to only validate hashes once") Cc: stable@vger.kernel.org Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-03-09dm verity: fix FEC for RS roots unaligned to block sizeMilan Broz1-11/+12
commit df7b59ba9245c4a3115ebaa905e3e5719a3810da upstream. Optional Forward Error Correction (FEC) code in dm-verity uses Reed-Solomon code and should support roots from 2 to 24. The error correction parity bytes (of roots lengths per RS block) are stored on a separate device in sequence without any padding. Currently, to access FEC device, the dm-verity-fec code uses dm-bufio client with block size set to verity data block (usually 4096 or 512 bytes). Because this block size is not divisible by some (most!) of the roots supported lengths, data repair cannot work for partially stored parity bytes. This fix changes FEC device dm-bufio block size to "roots << SECTOR_SHIFT" where we can be sure that the full parity data is always available. (There cannot be partial FEC blocks because parity must cover whole sectors.) Because the optional FEC starting offset could be unaligned to this new block size, we have to use dm_bufio_set_sector_offset() to configure it. The problem is easily reproduced using veritysetup, e.g. for roots=13: # create verity device with RS FEC dd if=/dev/urandom of=data.img bs=4096 count=8 status=none veritysetup format data.img hash.img --fec-device=fec.img --fec-roots=13 | awk '/^Root hash/{ print $3 }' >roothash # create an erasure that should be always repairable with this roots setting dd if=/dev/zero of=data.img conv=notrunc bs=1 count=8 seek=4088 status=none # try to read it through dm-verity veritysetup open data.img test hash.img --fec-device=fec.img --fec-roots=13 $(cat roothash) dd if=/dev/mapper/test of=/dev/null bs=4096 status=noxfer # wait for possible recursive recovery in kernel udevadm settle veritysetup close test With this fix, errors are properly repaired. device-mapper: verity-fec: 7:1: FEC 0: corrected 8 errors ... Without it, FEC code usually ends on unrecoverable failure in RS decoder: device-mapper: verity-fec: 7:1: FEC 0: failed to correct: -74 ... This problem is present in all kernels since the FEC code's introduction (kernel 4.5). It is thought that this problem is not visible in Android ecosystem because it always uses a default RS roots=2. Depends-on: a14e5ec66a7a ("dm bufio: subtract the number of initial sectors in dm_bufio_get_device_size") Signed-off-by: Milan Broz <gmazyland@gmail.com> Tested-by: Jérôme Carretero <cJ-ko@zougloub.eu> Reviewed-by: Sami Tolvanen <samitolvanen@google.com> Cc: stable@vger.kernel.org # 4.5+ Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-03-09dm bufio: subtract the number of initial sectors in dm_bufio_get_device_sizeMikulas Patocka1-0/+4
commit a14e5ec66a7a66e57b24e2469f9212a78460207e upstream. dm_bufio_get_device_size returns the device size in blocks. Before returning the value, we must subtract the nubmer of starting sectors. The number of starting sectors may not be divisible by block size. Note that currently, no target is using dm_bufio_set_sector_offset and dm_bufio_get_device_size simultaneously, so this change has no effect. However, an upcoming dm-verity-fec fix needs this change. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Reviewed-by: Milan Broz <gmazyland@gmail.com> Cc: stable@vger.kernel.org Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-03-04dm era: only resize metadata in preresumeNikos Tsironis1-11/+10
commit cca2c6aebe86f68103a8615074b3578e854b5016 upstream. Metadata resize shouldn't happen in the ctr. The ctr loads a temporary (inactive) table that will only become active upon resume. That is why resize should always be done in terms of resume. Otherwise a load (ctr) whose inactive table never becomes active will incorrectly resize the metadata. Also, perform the resize directly in preresume, instead of using the worker to do it. The worker might run other metadata operations, e.g., it could start digestion, before resizing the metadata. These operations will end up using the old size. This could lead to errors, like: device-mapper: era: metadata_digest_transcribe_writeset: dm_array_set_value failed device-mapper: era: process_old_eras: digest step failed, stopping digestion The reason of the above error is that the worker started the digestion of the archived writeset using the old, larger size. As a result, metadata_digest_transcribe_writeset tried to write beyond the end of the era array. Fixes: eec40579d84873 ("dm: add era target") Cc: stable@vger.kernel.org # v3.15+ Signed-off-by: Nikos Tsironis <ntsironis@arrikto.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-03-04dm era: Reinitialize bitset cache before digesting a new writesetNikos Tsironis1-6/+6
commit 2524933307fd0036d5c32357c693c021ab09a0b0 upstream. In case of devices with at most 64 blocks, the digestion of consecutive eras uses the writeset of the first era as the writeset of all eras to digest, leading to lost writes. That is, we lose the information about what blocks were written during the affected eras. The digestion code uses a dm_disk_bitset object to access the archived writesets. This structure includes a one word (64-bit) cache to reduce the number of array lookups. This structure is initialized only once, in metadata_digest_start(), when we kick off digestion. But, when we insert a new writeset into the writeset tree, before the digestion of the previous writeset is done, or equivalently when there are multiple writesets in the writeset tree to digest, then all these writesets are digested using the same cache and the cache is not re-initialized when moving from one writeset to the next. For devices with more than 64 blocks, i.e., the size of the cache, the cache is indirectly invalidated when we move to a next set of blocks, so we avoid the bug. But for devices with at most 64 blocks we end up using the same cached data for digesting all archived writesets, i.e., the cache is loaded when digesting the first writeset and it never gets reloaded, until the digestion is done. As a result, the writeset of the first era to digest is used as the writeset of all the following archived eras, leading to lost writes. Fix this by reinitializing the dm_disk_bitset structure, and thus invalidating the cache, every time the digestion code starts digesting a new writeset. Fixes: eec40579d84873 ("dm: add era target") Cc: stable@vger.kernel.org # v3.15+ Signed-off-by: Nikos Tsironis <ntsironis@arrikto.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-03-04dm era: Use correct value size in equality function of writeset treeNikos Tsironis1-1/+1
commit 64f2d15afe7b336aafebdcd14cc835ecf856df4b upstream. Fix the writeset tree equality test function to use the right value size when comparing two btree values. Fixes: eec40579d84873 ("dm: add era target") Cc: stable@vger.kernel.org # v3.15+ Signed-off-by: Nikos Tsironis <ntsironis@arrikto.com> Reviewed-by: Ming-Hung Tsai <mtsai@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-03-04dm era: Fix bitset memory leaksNikos Tsironis1-0/+6
commit 904e6b266619c2da5c58b5dce14ae30629e39645 upstream. Deallocate the memory allocated for the in-core bitsets when destroying the target and in error paths. Fixes: eec40579d84873 ("dm: add era target") Cc: stable@vger.kernel.org # v3.15+ Signed-off-by: Nikos Tsironis <ntsironis@arrikto.com> Reviewed-by: Ming-Hung Tsai <mtsai@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-03-04dm era: Verify the data block size hasn't changedNikos Tsironis1-1/+9
commit c8e846ff93d5eaa5384f6f325a1687ac5921aade upstream. dm-era doesn't support changing the data block size of existing devices, so check explicitly that the requested block size for a new target matches the one stored in the metadata. Fixes: eec40579d84873 ("dm: add era target") Cc: stable@vger.kernel.org # v3.15+ Signed-off-by: Nikos Tsironis <ntsironis@arrikto.com> Reviewed-by: Ming-Hung Tsai <mtsai@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-03-04dm era: Update in-core bitset after committing the metadataNikos Tsironis1-6/+19
commit 2099b145d77c1d53f5711f029c37cc537897cee6 upstream. In case of a system crash, dm-era might fail to mark blocks as written in its metadata, although the corresponding writes to these blocks were passed down to the origin device and completed successfully. Consider the following sequence of events: 1. We write to a block that has not been yet written in the current era 2. era_map() checks the in-core bitmap for the current era and sees that the block is not marked as written. 3. The write is deferred for submission after the metadata have been updated and committed. 4. The worker thread processes the deferred write (process_deferred_bios()) and marks the block as written in the in-core bitmap, **before** committing the metadata. 5. The worker thread starts committing the metadata. 6. We do more writes that map to the same block as the write of step (1) 7. era_map() checks the in-core bitmap and sees that the block is marked as written, **although the metadata have not been committed yet**. 8. These writes are passed down to the origin device immediately and the device reports them as completed. 9. The system crashes, e.g., power failure, before the commit from step (5) finishes. When the system recovers and we query the dm-era target for the list of written blocks it doesn't report the aforementioned block as written, although the writes of step (6) completed successfully. The issue is that era_map() decides whether to defer or not a write based on non committed information. The root cause of the bug is that we update the in-core bitmap, **before** committing the metadata. Fix this by updating the in-core bitmap **after** successfully committing the metadata. Fixes: eec40579d84873 ("dm: add era target") Cc: stable@vger.kernel.org # v3.15+ Signed-off-by: Nikos Tsironis <ntsironis@arrikto.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-03-04dm era: Recover committed writeset after crashNikos Tsironis1-8/+9
commit de89afc1e40fdfa5f8b666e5d07c43d21a1d3be0 upstream. Following a system crash, dm-era fails to recover the committed writeset for the current era, leading to lost writes. That is, we lose the information about what blocks were written during the affected era. dm-era assumes that the writeset of the current era is archived when the device is suspended. So, when resuming the device, it just moves on to the next era, ignoring the committed writeset. This assumption holds when the device is properly shut down. But, when the system crashes, the code that suspends the target never runs, so the writeset for the current era is not archived. There are three issues that cause the committed writeset to get lost: 1. dm-era doesn't load the committed writeset when opening the metadata 2. The code that resizes the metadata wipes the information about the committed writeset (assuming it was loaded at step 1) 3. era_preresume() starts a new era, without taking into account that the current era might not have been archived, due to a system crash. To fix this: 1. Load the committed writeset when opening the metadata 2. Fix the code that resizes the metadata to make sure it doesn't wipe the loaded writeset 3. Fix era_preresume() to check for a loaded writeset and archive it, before starting a new era. Fixes: eec40579d84873 ("dm: add era target") Cc: stable@vger.kernel.org # v3.15+ Signed-off-by: Nikos Tsironis <ntsironis@arrikto.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-03-04dm writecache: fix writing beyond end of underlying device when shrinkingMikulas Patocka1-0/+18
commit 4134455f2aafdfeab50cabb4cccb35e916034b93 upstream. Do not attempt to write any data beyond the end of the underlying data device while shrinking it. The DM writecache device must be suspended when the underlying data device is shrunk. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-03-04dm writecache: return the exact table values that were setMikulas Patocka1-24/+30
commit 054bee16163df023e2589db09fd27d81f7ad9e72 upstream. LVM doesn't like it when the target returns different values from what was set in the constructor. Fix dm-writecache so that the returned table values are exactly the same as requested values. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Cc: stable@vger.kernel.org # v4.18+ Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-03-04dm writecache: fix performance degradation in ssd modeMikulas Patocka1-1/+1
commit cb728484a7710c202f02b96aa0962ce9b07aa5c2 upstream. Fix a thinko in ssd_commit_superblock. region.count is in sectors, not bytes. This bug doesn't corrupt data, but it causes performance degradation. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Fixes: dc8a01ae1dbd ("dm writecache: optimize superblock write") Cc: stable@vger.kernel.org # v5.7+ Reported-by: J. Bruce Fields <bfields@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-03-04dm table: fix zoned iterate_devices based device capability checksJeffle Xu1-32/+16
commit 24f6b6036c9eec21191646930ad42808e6180510 upstream. Fix dm_table_supports_zoned_model() and invert logic of both iterate_devices_callout_fn so that all devices' zoned capabilities are properly checked. Add one more parameter to dm_table_any_dev_attr(), which is actually used as the @data parameter of iterate_devices_callout_fn, so that dm_table_matches_zone_sectors() can be replaced by dm_table_any_dev_attr(). Fixes: dd88d313bef02 ("dm table: add zoned block devices validation") Cc: stable@vger.kernel.org Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-03-04dm table: fix DAX iterate_devices based device capability checksJeffle Xu3-29/+12
commit 5b0fab508992c2e120971da658ce80027acbc405 upstream. Fix dm_table_supports_dax() and invert logic of both iterate_devices_callout_fn so that all devices' DAX capabilities are properly checked. Fixes: 545ed20e6df6 ("dm: add infrastructure for DAX support") Cc: stable@vger.kernel.org Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-03-04dm table: fix iterate_devices based device capability checksJeffle Xu1-46/+51
commit a4c8dd9c2d0987cf542a2a0c42684c9c6d78a04e upstream. According to the definition of dm_iterate_devices_fn: * This function must iterate through each section of device used by the * target until it encounters a non-zero return code, which it then returns. * Returns zero if no callout returned non-zero. For some target type (e.g. dm-stripe), one call of iterate_devices() may iterate multiple underlying devices internally, in which case a non-zero return code returned by iterate_devices_callout_fn will stop the iteration in advance. No iterate_devices_callout_fn should return non-zero unless device iteration should stop. Rename dm_table_requires_stable_pages() to dm_table_any_dev_attr() and elevate it for reuse to stop iterating (and return non-zero) on the first device that causes iterate_devices_callout_fn to return non-zero. Use dm_table_any_dev_attr() to properly iterate through devices. Rename device_is_nonrot() to device_is_rotational() and invert logic accordingly to fix improper disposition. Fixes: c3c4555edd10 ("dm table: clear add_random unless all devices have it set") Fixes: 4693c9668fdc ("dm table: propagate non rotational flag") Cc: stable@vger.kernel.org Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-03-04dm: fix deadlock when swapping to encrypted deviceMikulas Patocka3-0/+65
commit a666e5c05e7c4aaabb2c5d58117b0946803d03d2 upstream. The system would deadlock when swapping to a dm-crypt device. The reason is that for each incoming write bio, dm-crypt allocates memory that holds encrypted data. These excessive allocations exhaust all the memory and the result is either deadlock or OOM trigger. This patch limits the number of in-flight swap bios, so that the memory consumed by dm-crypt is limited. The limit is enforced if the target set the "limit_swap_bios" variable and if the bio has REQ_SWAP set. Non-swap bios are not affected becuase taking the semaphore would cause performance degradation. This is similar to request-based drivers - they will also block when the number of requests is over the limit. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-03-04bcache: Move journal work to new flush wqKai Krakow3-2/+19
commit afe78ab46f638ecdf80a35b122ffc92c20d9ae5d upstream. This is potentially long running and not latency sensitive, let's get it out of the way of other latency sensitive events. As observed in the previous commit, the `system_wq` comes easily congested by bcache, and this fixes a few more stalls I was observing every once in a while. Let's not make this `WQ_MEM_RECLAIM` as it showed to reduce performance of boot and file system operations in my tests. Also, without `WQ_MEM_RECLAIM`, I no longer see desktop stalls. This matches the previous behavior as `system_wq` also does no memory reclaim: > // workqueue.c: > system_wq = alloc_workqueue("events", 0, 0); Cc: Coly Li <colyli@suse.de> Cc: stable@vger.kernel.org # 5.4+ Signed-off-by: Kai Krakow <kai@kaishome.de> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-03-04bcache: Give btree_io_wq correct semantics againKai Krakow1-1/+1
commit d797bd9897e3559eb48d68368550d637d32e468c upstream. Before killing `btree_io_wq`, the queue was allocated using `create_singlethread_workqueue()` which has `WQ_MEM_RECLAIM`. After killing it, it no longer had this property but `system_wq` is not single threaded. Let's combine both worlds and make it multi threaded but able to reclaim memory. Cc: Coly Li <colyli@suse.de> Cc: stable@vger.kernel.org # 5.4+ Signed-off-by: Kai Krakow <kai@kaishome.de> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-03-04Revert "bcache: Kill btree_io_wq"Kai Krakow3-2/+25
commit 9f233ffe02e5cef611100cd8c5bcf4de26ca7bef upstream. This reverts commit 56b30770b27d54d68ad51eccc6d888282b568cee. With the btree using the `system_wq`, I seem to see a lot more desktop latency than I should. After some more investigation, it looks like the original assumption of 56b3077 no longer is true, and bcache has a very high potential of congesting the `system_wq`. In turn, this introduces laggy desktop performance, IO stalls (at least with btrfs), and input events may be delayed. So let's revert this. It's important to note that the semantics of using `system_wq` previously mean that `btree_io_wq` should be created before and destroyed after other bcache wqs to keep the same assumptions. Cc: Coly Li <colyli@suse.de> Cc: stable@vger.kernel.org # 5.4+ Signed-off-by: Kai Krakow <kai@kaishome.de> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-02-10md: Set prev_flush_start and flush_bio in an atomic wayXiao Ni1-0/+2
commit dc5d17a3c39b06aef866afca19245a9cfb533a79 upstream. One customer reports a crash problem which causes by flush request. It triggers a warning before crash. /* new request after previous flush is completed */ if (ktime_after(req_start, mddev->prev_flush_start)) { WARN_ON(mddev->flush_bio); mddev->flush_bio = bio; bio = NULL; } The WARN_ON is triggered. We use spin lock to protect prev_flush_start and flush_bio in md_flush_request. But there is no lock protection in md_submit_flush_data. It can set flush_bio to NULL first because of compiler reordering write instructions. For example, flush bio1 sets flush bio to NULL first in md_submit_flush_data. An interrupt or vmware causing an extended stall happen between updating flush_bio and prev_flush_start. Because flush_bio is NULL, flush bio2 can get the lock and submit to underlayer disks. Then flush bio1 updates prev_flush_start after the interrupt or extended stall. Then flush bio3 enters in md_flush_request. The start time req_start is behind prev_flush_start. The flush_bio is not NULL(flush bio2 hasn't finished). So it can trigger the WARN_ON now. Then it calls INIT_WORK again. INIT_WORK() will re-initialize the list pointers in the work_struct, which then can result in a corrupted work list and the work_struct queued a second time. With the work list corrupted, it can lead in invalid work items being used and cause a crash in process_one_work. We need to make sure only one flush bio can be handled at one same time. So add spin lock in md_submit_flush_data to protect prev_flush_start and flush_bio in an atomic way. Reviewed-by: David Jeffery <djeffery@redhat.com> Signed-off-by: Xiao Ni <xni@redhat.com> Signed-off-by: Song Liu <songliubraving@fb.com> Signed-off-by: Jack Wang <jinpu.wang@cloud.ionos.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-02-03bcache: only check feature sets when sb->version >= ↵Coly Li1-0/+6
BCACHE_SB_VERSION_CDEV_WITH_FEATURES commit 0df28cad06eb41cc36bfea69d9c882fb567fd0d6 upstream. For super block version < BCACHE_SB_VERSION_CDEV_WITH_FEATURES, it doesn't make sense to check the feature sets. This patch checks super block version in bch_has_feature_* routines, if the version doesn't have feature sets yet, returns 0 (false) to the caller. Fixes: 5342fd425502 ("bcache: set bcache device into read-only mode for BCH_FEATURE_INCOMPAT_OBSO_LARGE_BUCKET") Fixes: ffa470327572 ("bcache: add bucket_size_hi into struct cache_sb_disk for large bucket") Cc: stable@vger.kernel.org # 5.9+ Reported-and-tested-by: Bockholdt Arne <a.bockholdt@precitec-optronik.de> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-01-27dm integrity: select CRYPTO_SKCIPHERAnthony Iliopoulos1-0/+1
[ Upstream commit f7b347acb5f6c29d9229bb64893d8b6a2c7949fb ] The integrity target relies on skcipher for encryption/decryption, but certain kernel configurations may not enable CRYPTO_SKCIPHER, leading to compilation errors due to unresolved symbols. Explicitly select CRYPTO_SKCIPHER for DM_INTEGRITY, since it is unconditionally dependent on it. Signed-off-by: Anthony Iliopoulos <ailiop@suse.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-01-27dm integrity: conditionally disable "recalculate" featureMikulas Patocka1-2/+24
commit 5c02406428d5219c367c5f53457698c58bc5f917 upstream. Otherwise a malicious user could (ab)use the "recalculate" feature that makes dm-integrity calculate the checksums in the background while the device is already usable. When the system restarts before all checksums have been calculated, the calculation continues where it was interrupted even if the recalculate feature is not requested the next time the dm device is set up. Disable recalculating if we use internal_hash or journal_hash with a key (e.g. HMAC) and we don't have the "legacy_recalculate" flag. This may break activation of a volume, created by an older kernel, that is not yet fully recalculated -- if this happens, the user should add the "legacy_recalculate" flag to constructor parameters. Cc: stable@vger.kernel.org Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Reported-by: Daniel Glockner <dg@emlix.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-01-27dm integrity: fix a crash if "recalculate" used without "internal_hash"Mikulas Patocka1-0/+6
commit 2d06dfecb132a1cc2e374a44eae83b5c4356b8b4 upstream. Recalculate can only be specified with internal_hash. Cc: stable@vger.kernel.org # v4.19+ Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-01-27dm: avoid filesystem lookup in dm_get_dev_t()Hannes Reinecke1-3/+12
commit 809b1e4945774c9ec5619a8f4e2189b7b3833c0c upstream. This reverts commit 644bda6f3460 ("dm table: fall back to getting device using name_to_dev_t()") dm_get_dev_t() is just used to convert an arbitrary 'path' string into a dev_t. It doesn't presume that the device is present; that check will be done later, as the only caller is dm_get_device(), which does a dm_get_table_device() later on, which will properly open the device. So if the path string already _is_ in major:minor representation we can convert it directly, avoiding a recursion into the filesystem to lookup the block device. This avoids a hang in multipath_message() when the filesystem is inaccessible. Fixes: 644bda6f3460 ("dm table: fall back to getting device using name_to_dev_t()") Cc: stable@vger.kernel.org Signed-off-by: Hannes Reinecke <hare@suse.de> Signed-off-by: Martin Wilck <mwilck@suse.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-01-27dm crypt: fix copy and paste bug in crypt_alloc_req_aeadIgnat Korchagin1-3/+3
commit 004b8ae9e2de55ca7857ba8471209dd3179e088c upstream. In commit d68b29584c25 ("dm crypt: use GFP_ATOMIC when allocating crypto requests from softirq") code was incorrectly copy and pasted from crypt_alloc_req_skcipher()'s crypto request allocation code to crypt_alloc_req_aead(). It is OK from runtime perspective as both simple encryption request pointer and AEAD request pointer are part of a union, but may confuse code reviewers. Fixes: d68b29584c25 ("dm crypt: use GFP_ATOMIC when allocating crypto requests from softirq") Cc: stable@vger.kernel.org # v5.9+ Reported-by: Pavel Machek <pavel@denx.de> Signed-off-by: Ignat Korchagin <ignat@cloudflare.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-01-19dm: eliminate potential source of excessive kernel log noiseMike Snitzer1-1/+1
commit 0378c625afe80eb3f212adae42cc33c9f6f31abf upstream. There wasn't ever a real need to log an error in the kernel log for ioctls issued with insufficient permissions. Simply return an error and if an admin/user is sufficiently motivated they can enable DM's dynamic debugging to see an explanation for why the ioctls were disallowed. Reported-by: Nir Soffer <nsoffer@redhat.com> Fixes: e980f62353c6 ("dm: don't allow ioctls to targets that don't map to whole devices") Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-01-19dm zoned: select CONFIG_CRC32Arnd Bergmann1-0/+1
commit b690bd546b227c32b860dae985a18bed8aa946fe upstream. Without crc32 support, this driver fails to link: arm-linux-gnueabi-ld: drivers/md/dm-zoned-metadata.o: in function `dmz_write_sb': dm-zoned-metadata.c:(.text+0xe98): undefined reference to `crc32_le' arm-linux-gnueabi-ld: drivers/md/dm-zoned-metadata.o: in function `dmz_check_sb': dm-zoned-metadata.c:(.text+0x7978): undefined reference to `crc32_le' Fixes: 3b1a94c88b79 ("dm zoned: drive-managed zoned block device target") Signed-off-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-01-19dm crypt: defer decryption to a tasklet if interrupts disabledIgnat Korchagin1-2/+6
commit c87a95dc28b1431c7e77e2c0c983cf37698089d2 upstream. On some specific hardware on early boot we occasionally get: [ 1193.920255][ T0] BUG: sleeping function called from invalid context at mm/mempool.c:381 [ 1193.936616][ T0] in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 0, name: swapper/69 [ 1193.953233][ T0] no locks held by swapper/69/0. [ 1193.965871][ T0] irq event stamp: 575062 [ 1193.977724][ T0] hardirqs last enabled at (575061): [<ffffffffab73f662>] tick_nohz_idle_exit+0xe2/0x3e0 [ 1194.002762][ T0] hardirqs last disabled at (575062): [<ffffffffab74e8af>] flush_smp_call_function_from_idle+0x4f/0x80 [ 1194.029035][ T0] softirqs last enabled at (575050): [<ffffffffad600fd2>] asm_call_irq_on_stack+0x12/0x20 [ 1194.054227][ T0] softirqs last disabled at (575043): [<ffffffffad600fd2>] asm_call_irq_on_stack+0x12/0x20 [ 1194.079389][ T0] CPU: 69 PID: 0 Comm: swapper/69 Not tainted 5.10.6-cloudflare-kasan-2021.1.4-dev #1 [ 1194.104103][ T0] Hardware name: NULL R162-Z12-CD/MZ12-HD4-CD, BIOS R10 06/04/2020 [ 1194.119591][ T0] Call Trace: [ 1194.130233][ T0] dump_stack+0x9a/0xcc [ 1194.141617][ T0] ___might_sleep.cold+0x180/0x1b0 [ 1194.153825][ T0] mempool_alloc+0x16b/0x300 [ 1194.165313][ T0] ? remove_element+0x160/0x160 [ 1194.176961][ T0] ? blk_mq_end_request+0x4b/0x490 [ 1194.188778][ T0] crypt_convert+0x27f6/0x45f0 [dm_crypt] [ 1194.201024][ T0] ? rcu_read_lock_sched_held+0x3f/0x70 [ 1194.212906][ T0] ? module_assert_mutex_or_preempt+0x3e/0x70 [ 1194.225318][ T0] ? __module_address.part.0+0x1b/0x3a0 [ 1194.237212][ T0] ? is_kernel_percpu_address+0x5b/0x190 [ 1194.249238][ T0] ? crypt_iv_tcw_ctr+0x4a0/0x4a0 [dm_crypt] [ 1194.261593][ T0] ? is_module_address+0x25/0x40 [ 1194.272905][ T0] ? static_obj+0x8a/0xc0 [ 1194.283582][ T0] ? lockdep_init_map_waits+0x26a/0x700 [ 1194.295570][ T0] ? __raw_spin_lock_init+0x39/0x110 [ 1194.307330][ T0] kcryptd_crypt_read_convert+0x31c/0x560 [dm_crypt] [ 1194.320496][ T0] ? kcryptd_queue_crypt+0x1be/0x380 [dm_crypt] [ 1194.333203][ T0] blk_update_request+0x6d7/0x1500 [ 1194.344841][ T0] ? blk_mq_trigger_softirq+0x190/0x190 [ 1194.356831][ T0] blk_mq_end_request+0x4b/0x490 [ 1194.367994][ T0] ? blk_mq_trigger_softirq+0x190/0x190 [ 1194.379693][ T0] flush_smp_call_function_queue+0x24b/0x560 [ 1194.391847][ T0] flush_smp_call_function_from_idle+0x59/0x80 [ 1194.403969][ T0] do_idle+0x287/0x450 [ 1194.413891][ T0] ? arch_cpu_idle_exit+0x40/0x40 [ 1194.424716][ T0] ? lockdep_hardirqs_on_prepare+0x286/0x3f0 [ 1194.436399][ T0] ? _raw_spin_unlock_irqrestore+0x39/0x40 [ 1194.447759][ T0] cpu_startup_entry+0x19/0x20 [ 1194.458038][ T0] secondary_startup_64_no_verify+0xb0/0xbb IO completion can be queued to a different CPU by the block subsystem as a "call single function/data". The CPU may run these routines from the idle task, but it does so with interrupts disabled. It is not a good idea to do decryption with irqs disabled even in an idle task context, so just defer it to a tasklet (as is done with requests from hard irqs). Fixes: 39d42fa96ba1 ("dm crypt: add flags to optionally bypass kcryptd workqueues") Cc: stable@vger.kernel.org # v5.9+ Signed-off-by: Ignat Korchagin <ignat@cloudflare.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-01-19dm crypt: do not call bio_endio() from the dm-crypt taskletIgnat Korchagin1-1/+23
commit 8e14f610159d524cd7aac37982826d3ef75c09e8 upstream. Sometimes, when dm-crypt executes decryption in a tasklet, we may get "BUG: KASAN: use-after-free in tasklet_action_common.constprop..." with a kasan-enabled kernel. When the decryption fully completes in the tasklet, dm-crypt will call bio_endio(), which in turn will call clone_endio() from dm.c core code. That function frees the resources associated with the bio, including per bio private structures. For dm-crypt it will free the current struct dm_crypt_io, which contains our tasklet object, causing use-after-free, when the tasklet is being dequeued by the kernel. To avoid this, do not call bio_endio() from the current tasklet context, but delay its execution to the dm-crypt IO workqueue. Fixes: 39d42fa96ba1 ("dm crypt: add flags to optionally bypass kcryptd workqueues") Cc: <stable@vger.kernel.org> # v5.9+ Signed-off-by: Ignat Korchagin <ignat@cloudflare.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-01-19dm crypt: do not wait for backlogged crypto request completion in softirqIgnat Korchagin1-5/+98
commit 8abec36d1274bbd5ae8f36f3658b9abb3db56c31 upstream. Commit 39d42fa96ba1 ("dm crypt: add flags to optionally bypass kcryptd workqueues") made it possible for some code paths in dm-crypt to be executed in softirq context, when the underlying driver processes IO requests in interrupt/softirq context. When Crypto API backlogs a crypto request, dm-crypt uses wait_for_completion to avoid sending further requests to an already overloaded crypto driver. However, if the code is executing in softirq context, we might get the following stacktrace: [ 210.235213][ C0] BUG: scheduling while atomic: fio/2602/0x00000102 [ 210.236701][ C0] Modules linked in: [ 210.237566][ C0] CPU: 0 PID: 2602 Comm: fio Tainted: G W 5.10.0+ #50 [ 210.239292][ C0] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015 [ 210.241233][ C0] Call Trace: [ 210.241946][ C0] <IRQ> [ 210.242561][ C0] dump_stack+0x7d/0xa3 [ 210.243466][ C0] __schedule_bug.cold+0xb3/0xc2 [ 210.244539][ C0] __schedule+0x156f/0x20d0 [ 210.245518][ C0] ? io_schedule_timeout+0x140/0x140 [ 210.246660][ C0] schedule+0xd0/0x270 [ 210.247541][ C0] schedule_timeout+0x1fb/0x280 [ 210.248586][ C0] ? usleep_range+0x150/0x150 [ 210.249624][ C0] ? unpoison_range+0x3a/0x60 [ 210.250632][ C0] ? ____kasan_kmalloc.constprop.0+0x82/0xa0 [ 210.251949][ C0] ? unpoison_range+0x3a/0x60 [ 210.252958][ C0] ? __prepare_to_swait+0xa7/0x190 [ 210.254067][ C0] do_wait_for_common+0x2ab/0x370 [ 210.255158][ C0] ? usleep_range+0x150/0x150 [ 210.256192][ C0] ? bit_wait_io_timeout+0x160/0x160 [ 210.257358][ C0] ? blk_update_request+0x757/0x1150 [ 210.258582][ C0] ? _raw_spin_lock_irq+0x82/0xd0 [ 210.259674][ C0] ? _raw_read_unlock_irqrestore+0x30/0x30 [ 210.260917][ C0] wait_for_completion+0x4c/0x90 [ 210.261971][ C0] crypt_convert+0x19a6/0x4c00 [ 210.263033][ C0] ? _raw_spin_lock_irqsave+0x87/0xe0 [ 210.264193][ C0] ? kasan_set_track+0x1c/0x30 [ 210.265191][ C0] ? crypt_iv_tcw_ctr+0x4a0/0x4a0 [ 210.266283][ C0] ? kmem_cache_free+0x104/0x470 [ 210.267363][ C0] ? crypt_endio+0x91/0x180 [ 210.268327][ C0] kcryptd_crypt_read_convert+0x30e/0x420 [ 210.269565][ C0] blk_update_request+0x757/0x1150 [ 210.270563][ C0] blk_mq_end_request+0x4b/0x480 [ 210.271680][ C0] blk_done_softirq+0x21d/0x340 [ 210.272775][ C0] ? _raw_spin_lock+0x81/0xd0 [ 210.273847][ C0] ? blk_mq_stop_hw_queue+0x30/0x30 [ 210.275031][ C0] ? _raw_read_lock_irq+0x40/0x40 [ 210.276182][ C0] __do_softirq+0x190/0x611 [ 210.277203][ C0] ? handle_edge_irq+0x221/0xb60 [ 210.278340][ C0] asm_call_irq_on_stack+0x12/0x20 [ 210.279514][ C0] </IRQ> [ 210.280164][ C0] do_softirq_own_stack+0x37/0x40 [ 210.281281][ C0] irq_exit_rcu+0x110/0x1b0 [ 210.282286][ C0] common_interrupt+0x74/0x120 [ 210.283376][ C0] asm_common_interrupt+0x1e/0x40 [ 210.284496][ C0] RIP: 0010:_aesni_enc1+0x65/0xb0 Fix this by making crypt_convert function reentrant from the point of a single bio and make dm-crypt defer further bio processing to a workqueue, if Crypto API backlogs a request in interrupt context. Fixes: 39d42fa96ba1 ("dm crypt: add flags to optionally bypass kcryptd workqueues") Cc: stable@vger.kernel.org # v5.9+ Signed-off-by: Ignat Korchagin <ignat@cloudflare.com> Acked-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-01-19dm crypt: use GFP_ATOMIC when allocating crypto requests from softirqIgnat Korchagin1-10/+25
commit d68b29584c25dbacd01ed44a3e45abb35353f1de upstream. Commit 39d42fa96ba1 ("dm crypt: add flags to optionally bypass kcryptd workqueues") made it possible for some code paths in dm-crypt to be executed in softirq context, when the underlying driver processes IO requests in interrupt/softirq context. In this case sometimes when allocating a new crypto request we may get a stacktrace like below: [ 210.103008][ C0] BUG: sleeping function called from invalid context at mm/mempool.c:381 [ 210.104746][ C0] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 2602, name: fio [ 210.106599][ C0] CPU: 0 PID: 2602 Comm: fio Tainted: G W 5.10.0+ #50 [ 210.108331][ C0] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015 [ 210.110212][ C0] Call Trace: [ 210.110921][ C0] <IRQ> [ 210.111527][ C0] dump_stack+0x7d/0xa3 [ 210.112411][ C0] ___might_sleep.cold+0x122/0x151 [ 210.113527][ C0] mempool_alloc+0x16b/0x2f0 [ 210.114524][ C0] ? __queue_work+0x515/0xde0 [ 210.115553][ C0] ? mempool_resize+0x700/0x700 [ 210.116586][ C0] ? crypt_endio+0x91/0x180 [ 210.117479][ C0] ? blk_update_request+0x757/0x1150 [ 210.118513][ C0] ? blk_mq_end_request+0x4b/0x480 [ 210.119572][ C0] ? blk_done_softirq+0x21d/0x340 [ 210.120628][ C0] ? __do_softirq+0x190/0x611 [ 210.121626][ C0] crypt_convert+0x29f9/0x4c00 [ 210.122668][ C0] ? _raw_spin_lock_irqsave+0x87/0xe0 [ 210.123824][ C0] ? kasan_set_track+0x1c/0x30 [ 210.124858][ C0] ? crypt_iv_tcw_ctr+0x4a0/0x4a0 [ 210.125930][ C0] ? kmem_cache_free+0x104/0x470 [ 210.126973][ C0] ? crypt_endio+0x91/0x180 [ 210.127947][ C0] kcryptd_crypt_read_convert+0x30e/0x420 [ 210.129165][ C0] blk_update_request+0x757/0x1150 [ 210.130231][ C0] blk_mq_end_request+0x4b/0x480 [ 210.131294][ C0] blk_done_softirq+0x21d/0x340 [ 210.132332][ C0] ? _raw_spin_lock+0x81/0xd0 [ 210.133289][ C0] ? blk_mq_stop_hw_queue+0x30/0x30 [ 210.134399][ C0] ? _raw_read_lock_irq+0x40/0x40 [ 210.135458][ C0] __do_softirq+0x190/0x611 [ 210.136409][ C0] ? handle_edge_irq+0x221/0xb60 [ 210.137447][ C0] asm_call_irq_on_stack+0x12/0x20 [ 210.138507][ C0] </IRQ> [ 210.139118][ C0] do_softirq_own_stack+0x37/0x40 [ 210.140191][ C0] irq_exit_rcu+0x110/0x1b0 [ 210.141151][ C0] common_interrupt+0x74/0x120 [ 210.142171][ C0] asm_common_interrupt+0x1e/0x40 Fix this by allocating crypto requests with GFP_ATOMIC mask in interrupt context. Fixes: 39d42fa96ba1 ("dm crypt: add flags to optionally bypass kcryptd workqueues") Cc: stable@vger.kernel.org # v5.9+ Reported-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name> Signed-off-by: Ignat Korchagin <ignat@cloudflare.com> Acked-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-01-19dm integrity: fix the maximum number of argumentsMikulas Patocka1-1/+1
commit 17ffc193cdc6dc7a613d00d8ad47fc1f801b9bf0 upstream. Advance the maximum number of arguments from 9 to 15 to account for all potential feature flags that may be supplied. Linux 4.19 added "meta_device" (356d9d52e1221ba0c9f10b8b38652f78a5298329) and "recalculate" (a3fcf7253139609bf9ff901fbf955fba047e75dd) flags. Commit 468dfca38b1a6fbdccd195d875599cb7c8875cd9 added "sectors_per_bit" and "bitmap_flush_interval". Commit 84597a44a9d86ac949900441cea7da0af0f2f473 added "allow_discards". And the commit d537858ac8aaf4311b51240893add2fc62003b97 added "fix_padding". Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Cc: stable@vger.kernel.org # v4.19+ Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-01-19dm integrity: fix flush with external metadata deviceMikulas Patocka2-11/+55
commit 9b5948267adc9e689da609eb61cf7ed49cae5fa8 upstream. With external metadata device, flush requests are not passed down to the data device. Fix this by submitting the flush request in dm_integrity_flush_buffers. In order to not degrade performance, we overlap the data device flush with the metadata device flush. Reported-by: Lukas Straub <lukasstraub2@web.de> Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-01-19dm snapshot: flush merged data before committing metadataAkilesh Kailash1-0/+24
commit fcc42338375a1e67b8568dbb558f8b784d0f3b01 upstream. If the origin device has a volatile write-back cache and the following events occur: 1: After finishing merge operation of one set of exceptions, merge_callback() is invoked. 2: Update the metadata in COW device tracking the merge completion. This update to COW device is flushed cleanly. 3: System crashes and the origin device's cache where the recent merge was completed has not been flushed. During the next cycle when we read the metadata from the COW device, we will skip reading those metadata whose merge was completed in step (1). This will lead to data loss/corruption. To address this, flush the origin device post merge IO before updating the metadata. Cc: stable@vger.kernel.org Signed-off-by: Akilesh Kailash <akailash@google.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>