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Merge tag 'for-4.12/dm-changes' of git://git.kernel.org/pub/scm/linux…
…/kernel/git/device-mapper/linux-dm Pull device mapper updates from Mike Snitzer: - A major update for DM cache that reduces the latency for deciding whether blocks should migrate to/from the cache. The bio-prison-v2 interface supports this improvement by enabling direct dispatch of work to workqueues rather than having to delay the actual work dispatch to the DM cache core. So the dm-cache policies are much more nimble by being able to drive IO as they see fit. One immediate benefit from the improved latency is a cache that should be much more adaptive to changing workloads. - Add a new DM integrity target that emulates a block device that has additional per-sector tags that can be used for storing integrity information. - Add a new authenticated encryption feature to the DM crypt target that builds on the capabilities provided by the DM integrity target. - Add MD interface for switching the raid4/5/6 journal mode and update the DM raid target to use it to enable aid4/5/6 journal write-back support. - Switch the DM verity target over to using the asynchronous hash crypto API (this helps work better with architectures that have access to off-CPU algorithm providers, which should reduce CPU utilization). - Various request-based DM and DM multipath fixes and improvements from Bart and Christoph. - A DM thinp target fix for a bio structure leak that occurs for each discard IFF discard passdown is enabled. - A fix for a possible deadlock in DM bufio and a fix to re-check the new buffer allocation watermark in the face of competing admin changes to the 'max_cache_size_bytes' tunable. - A couple DM core cleanups. * tag 'for-4.12/dm-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm: (50 commits) dm bufio: check new buffer allocation watermark every 30 seconds dm bufio: avoid a possible ABBA deadlock dm mpath: make it easier to detect unintended I/O request flushes dm mpath: cleanup QUEUE_IF_NO_PATH bit manipulation by introducing assign_bit() dm mpath: micro-optimize the hot path relative to MPATHF_QUEUE_IF_NO_PATH dm: introduce enum dm_queue_mode to cleanup related code dm mpath: verify __pg_init_all_paths locking assumptions at runtime dm: verify suspend_locking assumptions at runtime dm block manager: remove an unused argument from dm_block_manager_create() dm rq: check blk_mq_register_dev() return value in dm_mq_init_request_queue() dm mpath: delay requeuing while path initialization is in progress dm mpath: avoid that path removal can trigger an infinite loop dm mpath: split and rename activate_path() to prepare for its expanded use dm ioctl: prevent stack leak in dm ioctl call dm integrity: use previously calculated log2 of sectors_per_block dm integrity: use hex2bin instead of open-coded variant dm crypt: replace custom implementation of hex2bin() dm crypt: remove obsolete references to per-CPU state dm verity: switch to using asynchronous hash crypto API dm crypt: use WQ_HIGHPRI for the IO and crypt workqueues ...
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| The dm-integrity target emulates a block device that has additional | ||
| per-sector tags that can be used for storing integrity information. | ||
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| A general problem with storing integrity tags with every sector is that | ||
| writing the sector and the integrity tag must be atomic - i.e. in case of | ||
| crash, either both sector and integrity tag or none of them is written. | ||
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| To guarantee write atomicity, the dm-integrity target uses journal, it | ||
| writes sector data and integrity tags into a journal, commits the journal | ||
| and then copies the data and integrity tags to their respective location. | ||
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| The dm-integrity target can be used with the dm-crypt target - in this | ||
| situation the dm-crypt target creates the integrity data and passes them | ||
| to the dm-integrity target via bio_integrity_payload attached to the bio. | ||
| In this mode, the dm-crypt and dm-integrity targets provide authenticated | ||
| disk encryption - if the attacker modifies the encrypted device, an I/O | ||
| error is returned instead of random data. | ||
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| The dm-integrity target can also be used as a standalone target, in this | ||
| mode it calculates and verifies the integrity tag internally. In this | ||
| mode, the dm-integrity target can be used to detect silent data | ||
| corruption on the disk or in the I/O path. | ||
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| When loading the target for the first time, the kernel driver will format | ||
| the device. But it will only format the device if the superblock contains | ||
| zeroes. If the superblock is neither valid nor zeroed, the dm-integrity | ||
| target can't be loaded. | ||
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| To use the target for the first time: | ||
| 1. overwrite the superblock with zeroes | ||
| 2. load the dm-integrity target with one-sector size, the kernel driver | ||
| will format the device | ||
| 3. unload the dm-integrity target | ||
| 4. read the "provided_data_sectors" value from the superblock | ||
| 5. load the dm-integrity target with the the target size | ||
| "provided_data_sectors" | ||
| 6. if you want to use dm-integrity with dm-crypt, load the dm-crypt target | ||
| with the size "provided_data_sectors" | ||
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| Target arguments: | ||
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| 1. the underlying block device | ||
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| 2. the number of reserved sector at the beginning of the device - the | ||
| dm-integrity won't read of write these sectors | ||
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| 3. the size of the integrity tag (if "-" is used, the size is taken from | ||
| the internal-hash algorithm) | ||
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| 4. mode: | ||
| D - direct writes (without journal) - in this mode, journaling is | ||
| not used and data sectors and integrity tags are written | ||
| separately. In case of crash, it is possible that the data | ||
| and integrity tag doesn't match. | ||
| J - journaled writes - data and integrity tags are written to the | ||
| journal and atomicity is guaranteed. In case of crash, | ||
| either both data and tag or none of them are written. The | ||
| journaled mode degrades write throughput twice because the | ||
| data have to be written twice. | ||
| R - recovery mode - in this mode, journal is not replayed, | ||
| checksums are not checked and writes to the device are not | ||
| allowed. This mode is useful for data recovery if the | ||
| device cannot be activated in any of the other standard | ||
| modes. | ||
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| 5. the number of additional arguments | ||
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| Additional arguments: | ||
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| journal_sectors:number | ||
| The size of journal, this argument is used only if formatting the | ||
| device. If the device is already formatted, the value from the | ||
| superblock is used. | ||
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| interleave_sectors:number | ||
| The number of interleaved sectors. This values is rounded down to | ||
| a power of two. If the device is already formatted, the value from | ||
| the superblock is used. | ||
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| buffer_sectors:number | ||
| The number of sectors in one buffer. The value is rounded down to | ||
| a power of two. | ||
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| The tag area is accessed using buffers, the buffer size is | ||
| configurable. The large buffer size means that the I/O size will | ||
| be larger, but there could be less I/Os issued. | ||
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| journal_watermark:number | ||
| The journal watermark in percents. When the size of the journal | ||
| exceeds this watermark, the thread that flushes the journal will | ||
| be started. | ||
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| commit_time:number | ||
| Commit time in milliseconds. When this time passes, the journal is | ||
| written. The journal is also written immediatelly if the FLUSH | ||
| request is received. | ||
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| internal_hash:algorithm(:key) (the key is optional) | ||
| Use internal hash or crc. | ||
| When this argument is used, the dm-integrity target won't accept | ||
| integrity tags from the upper target, but it will automatically | ||
| generate and verify the integrity tags. | ||
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| You can use a crc algorithm (such as crc32), then integrity target | ||
| will protect the data against accidental corruption. | ||
| You can also use a hmac algorithm (for example | ||
| "hmac(sha256):0123456789abcdef"), in this mode it will provide | ||
| cryptographic authentication of the data without encryption. | ||
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| When this argument is not used, the integrity tags are accepted | ||
| from an upper layer target, such as dm-crypt. The upper layer | ||
| target should check the validity of the integrity tags. | ||
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| journal_crypt:algorithm(:key) (the key is optional) | ||
| Encrypt the journal using given algorithm to make sure that the | ||
| attacker can't read the journal. You can use a block cipher here | ||
| (such as "cbc(aes)") or a stream cipher (for example "chacha20", | ||
| "salsa20", "ctr(aes)" or "ecb(arc4)"). | ||
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| The journal contains history of last writes to the block device, | ||
| an attacker reading the journal could see the last sector nubmers | ||
| that were written. From the sector numbers, the attacker can infer | ||
| the size of files that were written. To protect against this | ||
| situation, you can encrypt the journal. | ||
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| journal_mac:algorithm(:key) (the key is optional) | ||
| Protect sector numbers in the journal from accidental or malicious | ||
| modification. To protect against accidental modification, use a | ||
| crc algorithm, to protect against malicious modification, use a | ||
| hmac algorithm with a key. | ||
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| This option is not needed when using internal-hash because in this | ||
| mode, the integrity of journal entries is checked when replaying | ||
| the journal. Thus, modified sector number would be detected at | ||
| this stage. | ||
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| block_size:number | ||
| The size of a data block in bytes. The larger the block size the | ||
| less overhead there is for per-block integrity metadata. | ||
| Supported values are 512, 1024, 2048 and 4096 bytes. If not | ||
| specified the default block size is 512 bytes. | ||
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| The journal mode (D/J), buffer_sectors, journal_watermark, commit_time can | ||
| be changed when reloading the target (load an inactive table and swap the | ||
| tables with suspend and resume). The other arguments should not be changed | ||
| when reloading the target because the layout of disk data depend on them | ||
| and the reloaded target would be non-functional. | ||
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| The layout of the formatted block device: | ||
| * reserved sectors (they are not used by this target, they can be used for | ||
| storing LUKS metadata or for other purpose), the size of the reserved | ||
| area is specified in the target arguments | ||
| * superblock (4kiB) | ||
| * magic string - identifies that the device was formatted | ||
| * version | ||
| * log2(interleave sectors) | ||
| * integrity tag size | ||
| * the number of journal sections | ||
| * provided data sectors - the number of sectors that this target | ||
| provides (i.e. the size of the device minus the size of all | ||
| metadata and padding). The user of this target should not send | ||
| bios that access data beyond the "provided data sectors" limit. | ||
| * flags - a flag is set if journal_mac is used | ||
| * journal | ||
| The journal is divided into sections, each section contains: | ||
| * metadata area (4kiB), it contains journal entries | ||
| every journal entry contains: | ||
| * logical sector (specifies where the data and tag should | ||
| be written) | ||
| * last 8 bytes of data | ||
| * integrity tag (the size is specified in the superblock) | ||
| every metadata sector ends with | ||
| * mac (8-bytes), all the macs in 8 metadata sectors form a | ||
| 64-byte value. It is used to store hmac of sector | ||
| numbers in the journal section, to protect against a | ||
| possibility that the attacker tampers with sector | ||
| numbers in the journal. | ||
| * commit id | ||
| * data area (the size is variable; it depends on how many journal | ||
| entries fit into the metadata area) | ||
| every sector in the data area contains: | ||
| * data (504 bytes of data, the last 8 bytes are stored in | ||
| the journal entry) | ||
| * commit id | ||
| To test if the whole journal section was written correctly, every | ||
| 512-byte sector of the journal ends with 8-byte commit id. If the | ||
| commit id matches on all sectors in a journal section, then it is | ||
| assumed that the section was written correctly. If the commit id | ||
| doesn't match, the section was written partially and it should not | ||
| be replayed. | ||
| * one or more runs of interleaved tags and data. Each run contains: | ||
| * tag area - it contains integrity tags. There is one tag for each | ||
| sector in the data area | ||
| * data area - it contains data sectors. The number of data sectors | ||
| in one run must be a power of two. log2 of this value is stored | ||
| in the superblock. |
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