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![NeilBrown](/assets/img/avatar_default.png)
Also remove remaining accesses to ->queue and ->gendisk when ->queue is NULL (As it is in a DM target). Signed-off-by: NeilBrown <neilb@suse.de>
507 lines
20 KiB
C
507 lines
20 KiB
C
#ifndef _RAID5_H
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#define _RAID5_H
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#include <linux/raid/xor.h>
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#include <linux/dmaengine.h>
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/*
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*
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* Each stripe contains one buffer per disc. Each buffer can be in
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* one of a number of states stored in "flags". Changes between
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* these states happen *almost* exclusively under a per-stripe
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* spinlock. Some very specific changes can happen in bi_end_io, and
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* these are not protected by the spin lock.
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*
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* The flag bits that are used to represent these states are:
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* R5_UPTODATE and R5_LOCKED
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*
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* State Empty == !UPTODATE, !LOCK
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* We have no data, and there is no active request
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* State Want == !UPTODATE, LOCK
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* A read request is being submitted for this block
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* State Dirty == UPTODATE, LOCK
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* Some new data is in this buffer, and it is being written out
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* State Clean == UPTODATE, !LOCK
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* We have valid data which is the same as on disc
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*
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* The possible state transitions are:
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*
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* Empty -> Want - on read or write to get old data for parity calc
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* Empty -> Dirty - on compute_parity to satisfy write/sync request.(RECONSTRUCT_WRITE)
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* Empty -> Clean - on compute_block when computing a block for failed drive
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* Want -> Empty - on failed read
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* Want -> Clean - on successful completion of read request
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* Dirty -> Clean - on successful completion of write request
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* Dirty -> Clean - on failed write
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* Clean -> Dirty - on compute_parity to satisfy write/sync (RECONSTRUCT or RMW)
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*
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* The Want->Empty, Want->Clean, Dirty->Clean, transitions
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* all happen in b_end_io at interrupt time.
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* Each sets the Uptodate bit before releasing the Lock bit.
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* This leaves one multi-stage transition:
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* Want->Dirty->Clean
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* This is safe because thinking that a Clean buffer is actually dirty
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* will at worst delay some action, and the stripe will be scheduled
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* for attention after the transition is complete.
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*
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* There is one possibility that is not covered by these states. That
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* is if one drive has failed and there is a spare being rebuilt. We
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* can't distinguish between a clean block that has been generated
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* from parity calculations, and a clean block that has been
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* successfully written to the spare ( or to parity when resyncing).
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* To distingush these states we have a stripe bit STRIPE_INSYNC that
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* is set whenever a write is scheduled to the spare, or to the parity
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* disc if there is no spare. A sync request clears this bit, and
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* when we find it set with no buffers locked, we know the sync is
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* complete.
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*
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* Buffers for the md device that arrive via make_request are attached
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* to the appropriate stripe in one of two lists linked on b_reqnext.
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* One list (bh_read) for read requests, one (bh_write) for write.
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* There should never be more than one buffer on the two lists
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* together, but we are not guaranteed of that so we allow for more.
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*
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* If a buffer is on the read list when the associated cache buffer is
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* Uptodate, the data is copied into the read buffer and it's b_end_io
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* routine is called. This may happen in the end_request routine only
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* if the buffer has just successfully been read. end_request should
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* remove the buffers from the list and then set the Uptodate bit on
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* the buffer. Other threads may do this only if they first check
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* that the Uptodate bit is set. Once they have checked that they may
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* take buffers off the read queue.
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*
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* When a buffer on the write list is committed for write it is copied
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* into the cache buffer, which is then marked dirty, and moved onto a
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* third list, the written list (bh_written). Once both the parity
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* block and the cached buffer are successfully written, any buffer on
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* a written list can be returned with b_end_io.
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*
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* The write list and read list both act as fifos. The read list is
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* protected by the device_lock. The write and written lists are
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* protected by the stripe lock. The device_lock, which can be
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* claimed while the stipe lock is held, is only for list
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* manipulations and will only be held for a very short time. It can
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* be claimed from interrupts.
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*
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*
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* Stripes in the stripe cache can be on one of two lists (or on
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* neither). The "inactive_list" contains stripes which are not
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* currently being used for any request. They can freely be reused
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* for another stripe. The "handle_list" contains stripes that need
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* to be handled in some way. Both of these are fifo queues. Each
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* stripe is also (potentially) linked to a hash bucket in the hash
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* table so that it can be found by sector number. Stripes that are
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* not hashed must be on the inactive_list, and will normally be at
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* the front. All stripes start life this way.
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*
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* The inactive_list, handle_list and hash bucket lists are all protected by the
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* device_lock.
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* - stripes on the inactive_list never have their stripe_lock held.
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* - stripes have a reference counter. If count==0, they are on a list.
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* - If a stripe might need handling, STRIPE_HANDLE is set.
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* - When refcount reaches zero, then if STRIPE_HANDLE it is put on
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* handle_list else inactive_list
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*
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* This, combined with the fact that STRIPE_HANDLE is only ever
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* cleared while a stripe has a non-zero count means that if the
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* refcount is 0 and STRIPE_HANDLE is set, then it is on the
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* handle_list and if recount is 0 and STRIPE_HANDLE is not set, then
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* the stripe is on inactive_list.
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*
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* The possible transitions are:
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* activate an unhashed/inactive stripe (get_active_stripe())
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* lockdev check-hash unlink-stripe cnt++ clean-stripe hash-stripe unlockdev
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* activate a hashed, possibly active stripe (get_active_stripe())
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* lockdev check-hash if(!cnt++)unlink-stripe unlockdev
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* attach a request to an active stripe (add_stripe_bh())
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* lockdev attach-buffer unlockdev
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* handle a stripe (handle_stripe())
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* lockstripe clrSTRIPE_HANDLE ...
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* (lockdev check-buffers unlockdev) ..
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* change-state ..
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* record io/ops needed unlockstripe schedule io/ops
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* release an active stripe (release_stripe())
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* lockdev if (!--cnt) { if STRIPE_HANDLE, add to handle_list else add to inactive-list } unlockdev
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*
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* The refcount counts each thread that have activated the stripe,
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* plus raid5d if it is handling it, plus one for each active request
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* on a cached buffer, and plus one if the stripe is undergoing stripe
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* operations.
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*
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* Stripe operations are performed outside the stripe lock,
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* the stripe operations are:
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* -copying data between the stripe cache and user application buffers
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* -computing blocks to save a disk access, or to recover a missing block
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* -updating the parity on a write operation (reconstruct write and
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* read-modify-write)
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* -checking parity correctness
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* -running i/o to disk
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* These operations are carried out by raid5_run_ops which uses the async_tx
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* api to (optionally) offload operations to dedicated hardware engines.
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* When requesting an operation handle_stripe sets the pending bit for the
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* operation and increments the count. raid5_run_ops is then run whenever
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* the count is non-zero.
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* There are some critical dependencies between the operations that prevent some
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* from being requested while another is in flight.
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* 1/ Parity check operations destroy the in cache version of the parity block,
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* so we prevent parity dependent operations like writes and compute_blocks
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* from starting while a check is in progress. Some dma engines can perform
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* the check without damaging the parity block, in these cases the parity
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* block is re-marked up to date (assuming the check was successful) and is
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* not re-read from disk.
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* 2/ When a write operation is requested we immediately lock the affected
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* blocks, and mark them as not up to date. This causes new read requests
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* to be held off, as well as parity checks and compute block operations.
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* 3/ Once a compute block operation has been requested handle_stripe treats
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* that block as if it is up to date. raid5_run_ops guaruntees that any
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* operation that is dependent on the compute block result is initiated after
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* the compute block completes.
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*/
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/*
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* Operations state - intermediate states that are visible outside of sh->lock
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* In general _idle indicates nothing is running, _run indicates a data
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* processing operation is active, and _result means the data processing result
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* is stable and can be acted upon. For simple operations like biofill and
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* compute that only have an _idle and _run state they are indicated with
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* sh->state flags (STRIPE_BIOFILL_RUN and STRIPE_COMPUTE_RUN)
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*/
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/**
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* enum check_states - handles syncing / repairing a stripe
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* @check_state_idle - check operations are quiesced
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* @check_state_run - check operation is running
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* @check_state_result - set outside lock when check result is valid
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* @check_state_compute_run - check failed and we are repairing
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* @check_state_compute_result - set outside lock when compute result is valid
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*/
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enum check_states {
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check_state_idle = 0,
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check_state_run, /* xor parity check */
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check_state_run_q, /* q-parity check */
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check_state_run_pq, /* pq dual parity check */
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check_state_check_result,
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check_state_compute_run, /* parity repair */
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check_state_compute_result,
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};
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/**
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* enum reconstruct_states - handles writing or expanding a stripe
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*/
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enum reconstruct_states {
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reconstruct_state_idle = 0,
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reconstruct_state_prexor_drain_run, /* prexor-write */
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reconstruct_state_drain_run, /* write */
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reconstruct_state_run, /* expand */
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reconstruct_state_prexor_drain_result,
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reconstruct_state_drain_result,
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reconstruct_state_result,
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};
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struct stripe_head {
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struct hlist_node hash;
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struct list_head lru; /* inactive_list or handle_list */
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struct raid5_private_data *raid_conf;
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short generation; /* increments with every
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* reshape */
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sector_t sector; /* sector of this row */
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short pd_idx; /* parity disk index */
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short qd_idx; /* 'Q' disk index for raid6 */
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short ddf_layout;/* use DDF ordering to calculate Q */
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unsigned long state; /* state flags */
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atomic_t count; /* nr of active thread/requests */
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spinlock_t lock;
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int bm_seq; /* sequence number for bitmap flushes */
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int disks; /* disks in stripe */
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enum check_states check_state;
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enum reconstruct_states reconstruct_state;
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/**
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* struct stripe_operations
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* @target - STRIPE_OP_COMPUTE_BLK target
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* @target2 - 2nd compute target in the raid6 case
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* @zero_sum_result - P and Q verification flags
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* @request - async service request flags for raid_run_ops
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*/
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struct stripe_operations {
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int target, target2;
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enum sum_check_flags zero_sum_result;
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#ifdef CONFIG_MULTICORE_RAID456
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unsigned long request;
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wait_queue_head_t wait_for_ops;
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#endif
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} ops;
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struct r5dev {
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struct bio req;
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struct bio_vec vec;
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struct page *page;
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struct bio *toread, *read, *towrite, *written;
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sector_t sector; /* sector of this page */
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unsigned long flags;
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} dev[1]; /* allocated with extra space depending of RAID geometry */
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};
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/* stripe_head_state - collects and tracks the dynamic state of a stripe_head
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* for handle_stripe. It is only valid under spin_lock(sh->lock);
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*/
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struct stripe_head_state {
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int syncing, expanding, expanded;
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int locked, uptodate, to_read, to_write, failed, written;
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int to_fill, compute, req_compute, non_overwrite;
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int failed_num;
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unsigned long ops_request;
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};
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/* r6_state - extra state data only relevant to r6 */
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struct r6_state {
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int p_failed, q_failed, failed_num[2];
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};
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/* Flags */
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#define R5_UPTODATE 0 /* page contains current data */
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#define R5_LOCKED 1 /* IO has been submitted on "req" */
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#define R5_OVERWRITE 2 /* towrite covers whole page */
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/* and some that are internal to handle_stripe */
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#define R5_Insync 3 /* rdev && rdev->in_sync at start */
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#define R5_Wantread 4 /* want to schedule a read */
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#define R5_Wantwrite 5
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#define R5_Overlap 7 /* There is a pending overlapping request on this block */
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#define R5_ReadError 8 /* seen a read error here recently */
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#define R5_ReWrite 9 /* have tried to over-write the readerror */
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#define R5_Expanded 10 /* This block now has post-expand data */
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#define R5_Wantcompute 11 /* compute_block in progress treat as
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* uptodate
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*/
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#define R5_Wantfill 12 /* dev->toread contains a bio that needs
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* filling
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*/
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#define R5_Wantdrain 13 /* dev->towrite needs to be drained */
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/*
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* Write method
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*/
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#define RECONSTRUCT_WRITE 1
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#define READ_MODIFY_WRITE 2
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/* not a write method, but a compute_parity mode */
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#define CHECK_PARITY 3
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/* Additional compute_parity mode -- updates the parity w/o LOCKING */
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#define UPDATE_PARITY 4
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/*
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* Stripe state
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*/
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#define STRIPE_HANDLE 2
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#define STRIPE_SYNCING 3
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#define STRIPE_INSYNC 4
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#define STRIPE_PREREAD_ACTIVE 5
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#define STRIPE_DELAYED 6
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#define STRIPE_DEGRADED 7
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#define STRIPE_BIT_DELAY 8
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#define STRIPE_EXPANDING 9
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#define STRIPE_EXPAND_SOURCE 10
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#define STRIPE_EXPAND_READY 11
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#define STRIPE_IO_STARTED 12 /* do not count towards 'bypass_count' */
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#define STRIPE_FULL_WRITE 13 /* all blocks are set to be overwritten */
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#define STRIPE_BIOFILL_RUN 14
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#define STRIPE_COMPUTE_RUN 15
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#define STRIPE_OPS_REQ_PENDING 16
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/*
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* Operation request flags
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*/
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#define STRIPE_OP_BIOFILL 0
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#define STRIPE_OP_COMPUTE_BLK 1
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#define STRIPE_OP_PREXOR 2
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#define STRIPE_OP_BIODRAIN 3
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#define STRIPE_OP_RECONSTRUCT 4
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#define STRIPE_OP_CHECK 5
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/*
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* Plugging:
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*
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* To improve write throughput, we need to delay the handling of some
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* stripes until there has been a chance that several write requests
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* for the one stripe have all been collected.
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* In particular, any write request that would require pre-reading
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* is put on a "delayed" queue until there are no stripes currently
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* in a pre-read phase. Further, if the "delayed" queue is empty when
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* a stripe is put on it then we "plug" the queue and do not process it
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* until an unplug call is made. (the unplug_io_fn() is called).
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*
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* When preread is initiated on a stripe, we set PREREAD_ACTIVE and add
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* it to the count of prereading stripes.
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* When write is initiated, or the stripe refcnt == 0 (just in case) we
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* clear the PREREAD_ACTIVE flag and decrement the count
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* Whenever the 'handle' queue is empty and the device is not plugged, we
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* move any strips from delayed to handle and clear the DELAYED flag and set
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* PREREAD_ACTIVE.
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* In stripe_handle, if we find pre-reading is necessary, we do it if
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* PREREAD_ACTIVE is set, else we set DELAYED which will send it to the delayed queue.
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* HANDLE gets cleared if stripe_handle leave nothing locked.
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*/
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struct disk_info {
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mdk_rdev_t *rdev;
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};
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struct raid5_private_data {
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struct hlist_head *stripe_hashtbl;
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mddev_t *mddev;
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struct disk_info *spare;
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int chunk_sectors;
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int level, algorithm;
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int max_degraded;
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int raid_disks;
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int max_nr_stripes;
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/* reshape_progress is the leading edge of a 'reshape'
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* It has value MaxSector when no reshape is happening
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* If delta_disks < 0, it is the last sector we started work on,
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* else is it the next sector to work on.
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*/
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sector_t reshape_progress;
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/* reshape_safe is the trailing edge of a reshape. We know that
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* before (or after) this address, all reshape has completed.
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*/
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sector_t reshape_safe;
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int previous_raid_disks;
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int prev_chunk_sectors;
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int prev_algo;
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short generation; /* increments with every reshape */
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unsigned long reshape_checkpoint; /* Time we last updated
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* metadata */
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struct list_head handle_list; /* stripes needing handling */
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struct list_head hold_list; /* preread ready stripes */
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struct list_head delayed_list; /* stripes that have plugged requests */
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struct list_head bitmap_list; /* stripes delaying awaiting bitmap update */
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struct bio *retry_read_aligned; /* currently retrying aligned bios */
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struct bio *retry_read_aligned_list; /* aligned bios retry list */
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atomic_t preread_active_stripes; /* stripes with scheduled io */
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atomic_t active_aligned_reads;
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atomic_t pending_full_writes; /* full write backlog */
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int bypass_count; /* bypassed prereads */
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int bypass_threshold; /* preread nice */
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struct list_head *last_hold; /* detect hold_list promotions */
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atomic_t reshape_stripes; /* stripes with pending writes for reshape */
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/* unfortunately we need two cache names as we temporarily have
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* two caches.
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*/
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int active_name;
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char cache_name[2][32];
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struct kmem_cache *slab_cache; /* for allocating stripes */
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int seq_flush, seq_write;
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int quiesce;
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int fullsync; /* set to 1 if a full sync is needed,
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* (fresh device added).
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* Cleared when a sync completes.
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*/
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struct plug_handle plug;
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/* per cpu variables */
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struct raid5_percpu {
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struct page *spare_page; /* Used when checking P/Q in raid6 */
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void *scribble; /* space for constructing buffer
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* lists and performing address
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* conversions
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*/
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} __percpu *percpu;
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size_t scribble_len; /* size of scribble region must be
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* associated with conf to handle
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* cpu hotplug while reshaping
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*/
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#ifdef CONFIG_HOTPLUG_CPU
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struct notifier_block cpu_notify;
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#endif
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/*
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* Free stripes pool
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*/
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atomic_t active_stripes;
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struct list_head inactive_list;
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wait_queue_head_t wait_for_stripe;
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wait_queue_head_t wait_for_overlap;
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int inactive_blocked; /* release of inactive stripes blocked,
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* waiting for 25% to be free
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*/
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int pool_size; /* number of disks in stripeheads in pool */
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spinlock_t device_lock;
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struct disk_info *disks;
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/* When taking over an array from a different personality, we store
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* the new thread here until we fully activate the array.
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*/
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struct mdk_thread_s *thread;
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};
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typedef struct raid5_private_data raid5_conf_t;
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/*
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* Our supported algorithms
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*/
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#define ALGORITHM_LEFT_ASYMMETRIC 0 /* Rotating Parity N with Data Restart */
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#define ALGORITHM_RIGHT_ASYMMETRIC 1 /* Rotating Parity 0 with Data Restart */
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#define ALGORITHM_LEFT_SYMMETRIC 2 /* Rotating Parity N with Data Continuation */
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#define ALGORITHM_RIGHT_SYMMETRIC 3 /* Rotating Parity 0 with Data Continuation */
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/* Define non-rotating (raid4) algorithms. These allow
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* conversion of raid4 to raid5.
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*/
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#define ALGORITHM_PARITY_0 4 /* P or P,Q are initial devices */
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#define ALGORITHM_PARITY_N 5 /* P or P,Q are final devices. */
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/* DDF RAID6 layouts differ from md/raid6 layouts in two ways.
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* Firstly, the exact positioning of the parity block is slightly
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* different between the 'LEFT_*' modes of md and the "_N_*" modes
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* of DDF.
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* Secondly, or order of datablocks over which the Q syndrome is computed
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* is different.
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* Consequently we have different layouts for DDF/raid6 than md/raid6.
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* These layouts are from the DDFv1.2 spec.
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* Interestingly DDFv1.2-Errata-A does not specify N_CONTINUE but
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* leaves RLQ=3 as 'Vendor Specific'
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*/
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#define ALGORITHM_ROTATING_ZERO_RESTART 8 /* DDF PRL=6 RLQ=1 */
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#define ALGORITHM_ROTATING_N_RESTART 9 /* DDF PRL=6 RLQ=2 */
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#define ALGORITHM_ROTATING_N_CONTINUE 10 /*DDF PRL=6 RLQ=3 */
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/* For every RAID5 algorithm we define a RAID6 algorithm
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* with exactly the same layout for data and parity, and
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* with the Q block always on the last device (N-1).
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* This allows trivial conversion from RAID5 to RAID6
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*/
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#define ALGORITHM_LEFT_ASYMMETRIC_6 16
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#define ALGORITHM_RIGHT_ASYMMETRIC_6 17
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#define ALGORITHM_LEFT_SYMMETRIC_6 18
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#define ALGORITHM_RIGHT_SYMMETRIC_6 19
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#define ALGORITHM_PARITY_0_6 20
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#define ALGORITHM_PARITY_N_6 ALGORITHM_PARITY_N
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static inline int algorithm_valid_raid5(int layout)
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{
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return (layout >= 0) &&
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(layout <= 5);
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}
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static inline int algorithm_valid_raid6(int layout)
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{
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return (layout >= 0 && layout <= 5)
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||
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(layout >= 8 && layout <= 10)
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||
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(layout >= 16 && layout <= 20);
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}
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static inline int algorithm_is_DDF(int layout)
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|
{
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return layout >= 8 && layout <= 10;
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}
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extern int md_raid5_congested(mddev_t *mddev, int bits);
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extern void md_raid5_unplug_device(raid5_conf_t *conf);
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extern int raid5_set_cache_size(mddev_t *mddev, int size);
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#endif
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