blob: 0f86f5e367245da614c99fc0b510777ed5789fec [file] [log] [blame]
#ifndef _RAID5_H
#define _RAID5_H
#include <linux/raid/xor.h>
#include <linux/dmaengine.h>
* Each stripe contains one buffer per disc. Each buffer can be in
* one of a number of states stored in "flags". Changes between
* these states happen *almost* exclusively under a per-stripe
* spinlock. Some very specific changes can happen in bi_end_io, and
* these are not protected by the spin lock.
* The flag bits that are used to represent these states are:
* State Empty == !UPTODATE, !LOCK
* We have no data, and there is no active request
* State Want == !UPTODATE, LOCK
* A read request is being submitted for this block
* State Dirty == UPTODATE, LOCK
* Some new data is in this buffer, and it is being written out
* State Clean == UPTODATE, !LOCK
* We have valid data which is the same as on disc
* The possible state transitions are:
* Empty -> Want - on read or write to get old data for parity calc
* Empty -> Dirty - on compute_parity to satisfy write/sync request.(RECONSTRUCT_WRITE)
* Empty -> Clean - on compute_block when computing a block for failed drive
* Want -> Empty - on failed read
* Want -> Clean - on successful completion of read request
* Dirty -> Clean - on successful completion of write request
* Dirty -> Clean - on failed write
* Clean -> Dirty - on compute_parity to satisfy write/sync (RECONSTRUCT or RMW)
* The Want->Empty, Want->Clean, Dirty->Clean, transitions
* all happen in b_end_io at interrupt time.
* Each sets the Uptodate bit before releasing the Lock bit.
* This leaves one multi-stage transition:
* Want->Dirty->Clean
* This is safe because thinking that a Clean buffer is actually dirty
* will at worst delay some action, and the stripe will be scheduled
* for attention after the transition is complete.
* There is one possibility that is not covered by these states. That
* is if one drive has failed and there is a spare being rebuilt. We
* can't distinguish between a clean block that has been generated
* from parity calculations, and a clean block that has been
* successfully written to the spare ( or to parity when resyncing).
* To distingush these states we have a stripe bit STRIPE_INSYNC that
* is set whenever a write is scheduled to the spare, or to the parity
* disc if there is no spare. A sync request clears this bit, and
* when we find it set with no buffers locked, we know the sync is
* complete.
* Buffers for the md device that arrive via make_request are attached
* to the appropriate stripe in one of two lists linked on b_reqnext.
* One list (bh_read) for read requests, one (bh_write) for write.
* There should never be more than one buffer on the two lists
* together, but we are not guaranteed of that so we allow for more.
* If a buffer is on the read list when the associated cache buffer is
* Uptodate, the data is copied into the read buffer and it's b_end_io
* routine is called. This may happen in the end_request routine only
* if the buffer has just successfully been read. end_request should
* remove the buffers from the list and then set the Uptodate bit on
* the buffer. Other threads may do this only if they first check
* that the Uptodate bit is set. Once they have checked that they may
* take buffers off the read queue.
* When a buffer on the write list is committed for write it is copied
* into the cache buffer, which is then marked dirty, and moved onto a
* third list, the written list (bh_written). Once both the parity
* block and the cached buffer are successfully written, any buffer on
* a written list can be returned with b_end_io.
* The write list and read list both act as fifos. The read list is
* protected by the device_lock. The write and written lists are
* protected by the stripe lock. The device_lock, which can be
* claimed while the stipe lock is held, is only for list
* manipulations and will only be held for a very short time. It can
* be claimed from interrupts.
* Stripes in the stripe cache can be on one of two lists (or on
* neither). The "inactive_list" contains stripes which are not
* currently being used for any request. They can freely be reused
* for another stripe. The "handle_list" contains stripes that need
* to be handled in some way. Both of these are fifo queues. Each
* stripe is also (potentially) linked to a hash bucket in the hash
* table so that it can be found by sector number. Stripes that are
* not hashed must be on the inactive_list, and will normally be at
* the front. All stripes start life this way.
* The inactive_list, handle_list and hash bucket lists are all protected by the
* device_lock.
* - stripes on the inactive_list never have their stripe_lock held.
* - stripes have a reference counter. If count==0, they are on a list.
* - If a stripe might need handling, STRIPE_HANDLE is set.
* - When refcount reaches zero, then if STRIPE_HANDLE it is put on
* handle_list else inactive_list
* This, combined with the fact that STRIPE_HANDLE is only ever
* cleared while a stripe has a non-zero count means that if the
* refcount is 0 and STRIPE_HANDLE is set, then it is on the
* handle_list and if recount is 0 and STRIPE_HANDLE is not set, then
* the stripe is on inactive_list.
* The possible transitions are:
* activate an unhashed/inactive stripe (get_active_stripe())
* lockdev check-hash unlink-stripe cnt++ clean-stripe hash-stripe unlockdev
* activate a hashed, possibly active stripe (get_active_stripe())
* lockdev check-hash if(!cnt++)unlink-stripe unlockdev
* attach a request to an active stripe (add_stripe_bh())
* lockdev attach-buffer unlockdev
* handle a stripe (handle_stripe())
* lockstripe clrSTRIPE_HANDLE ...
* (lockdev check-buffers unlockdev) ..
* change-state ..
* record io/ops needed unlockstripe schedule io/ops
* release an active stripe (release_stripe())
* lockdev if (!--cnt) { if STRIPE_HANDLE, add to handle_list else add to inactive-list } unlockdev
* The refcount counts each thread that have activated the stripe,
* plus raid5d if it is handling it, plus one for each active request
* on a cached buffer, and plus one if the stripe is undergoing stripe
* operations.
* Stripe operations are performed outside the stripe lock,
* the stripe operations are:
* -copying data between the stripe cache and user application buffers
* -computing blocks to save a disk access, or to recover a missing block
* -updating the parity on a write operation (reconstruct write and
* read-modify-write)
* -checking parity correctness
* -running i/o to disk
* These operations are carried out by raid5_run_ops which uses the async_tx
* api to (optionally) offload operations to dedicated hardware engines.
* When requesting an operation handle_stripe sets the pending bit for the
* operation and increments the count. raid5_run_ops is then run whenever
* the count is non-zero.
* There are some critical dependencies between the operations that prevent some
* from being requested while another is in flight.
* 1/ Parity check operations destroy the in cache version of the parity block,
* so we prevent parity dependent operations like writes and compute_blocks
* from starting while a check is in progress. Some dma engines can perform
* the check without damaging the parity block, in these cases the parity
* block is re-marked up to date (assuming the check was successful) and is
* not re-read from disk.
* 2/ When a write operation is requested we immediately lock the affected
* blocks, and mark them as not up to date. This causes new read requests
* to be held off, as well as parity checks and compute block operations.
* 3/ Once a compute block operation has been requested handle_stripe treats
* that block as if it is up to date. raid5_run_ops guaruntees that any
* operation that is dependent on the compute block result is initiated after
* the compute block completes.
* Operations state - intermediate states that are visible outside of sh->lock
* In general _idle indicates nothing is running, _run indicates a data
* processing operation is active, and _result means the data processing result
* is stable and can be acted upon. For simple operations like biofill and
* compute that only have an _idle and _run state they are indicated with
* enum check_states - handles syncing / repairing a stripe
* @check_state_idle - check operations are quiesced
* @check_state_run - check operation is running
* @check_state_result - set outside lock when check result is valid
* @check_state_compute_run - check failed and we are repairing
* @check_state_compute_result - set outside lock when compute result is valid
enum check_states {
check_state_idle = 0,
check_state_run, /* xor parity check */
check_state_run_q, /* q-parity check */
check_state_run_pq, /* pq dual parity check */
check_state_compute_run, /* parity repair */
* enum reconstruct_states - handles writing or expanding a stripe
enum reconstruct_states {
reconstruct_state_idle = 0,
reconstruct_state_prexor_drain_run, /* prexor-write */
reconstruct_state_drain_run, /* write */
reconstruct_state_run, /* expand */
struct stripe_head {
struct hlist_node hash;
struct list_head lru; /* inactive_list or handle_list */
struct raid5_private_data *raid_conf;
short generation; /* increments with every
* reshape */
sector_t sector; /* sector of this row */
short pd_idx; /* parity disk index */
short qd_idx; /* 'Q' disk index for raid6 */
short ddf_layout;/* use DDF ordering to calculate Q */
unsigned long state; /* state flags */
atomic_t count; /* nr of active thread/requests */
spinlock_t lock;
int bm_seq; /* sequence number for bitmap flushes */
int disks; /* disks in stripe */
enum check_states check_state;
enum reconstruct_states reconstruct_state;
* struct stripe_operations
* @target - STRIPE_OP_COMPUTE_BLK target
* @target2 - 2nd compute target in the raid6 case
* @zero_sum_result - P and Q verification flags
* @request - async service request flags for raid_run_ops
struct stripe_operations {
int target, target2;
enum sum_check_flags zero_sum_result;
unsigned long request;
wait_queue_head_t wait_for_ops;
} ops;
struct r5dev {
struct bio req;
struct bio_vec vec;
struct page *page;
struct bio *toread, *read, *towrite, *written;
sector_t sector; /* sector of this page */
unsigned long flags;
} dev[1]; /* allocated with extra space depending of RAID geometry */
/* stripe_head_state - collects and tracks the dynamic state of a stripe_head
* for handle_stripe. It is only valid under spin_lock(sh->lock);
struct stripe_head_state {
int syncing, expanding, expanded;
int locked, uptodate, to_read, to_write, failed, written;
int to_fill, compute, req_compute, non_overwrite;
int failed_num;
unsigned long ops_request;
/* r6_state - extra state data only relevant to r6 */
struct r6_state {
int p_failed, q_failed, failed_num[2];
/* Flags */
#define R5_UPTODATE 0 /* page contains current data */
#define R5_LOCKED 1 /* IO has been submitted on "req" */
#define R5_OVERWRITE 2 /* towrite covers whole page */
/* and some that are internal to handle_stripe */
#define R5_Insync 3 /* rdev && rdev->in_sync at start */
#define R5_Wantread 4 /* want to schedule a read */
#define R5_Wantwrite 5
#define R5_Overlap 7 /* There is a pending overlapping request on this block */
#define R5_ReadError 8 /* seen a read error here recently */
#define R5_ReWrite 9 /* have tried to over-write the readerror */
#define R5_Expanded 10 /* This block now has post-expand data */
#define R5_Wantcompute 11 /* compute_block in progress treat as
* uptodate
#define R5_Wantfill 12 /* dev->toread contains a bio that needs
* filling
#define R5_Wantdrain 13 /* dev->towrite needs to be drained */
* Write method
/* not a write method, but a compute_parity mode */
#define CHECK_PARITY 3
/* Additional compute_parity mode -- updates the parity w/o LOCKING */
* Stripe state
#define STRIPE_IO_STARTED 12 /* do not count towards 'bypass_count' */
#define STRIPE_FULL_WRITE 13 /* all blocks are set to be overwritten */
* Operation request flags
* Plugging:
* To improve write throughput, we need to delay the handling of some
* stripes until there has been a chance that several write requests
* for the one stripe have all been collected.
* In particular, any write request that would require pre-reading
* is put on a "delayed" queue until there are no stripes currently
* in a pre-read phase. Further, if the "delayed" queue is empty when
* a stripe is put on it then we "plug" the queue and do not process it
* until an unplug call is made. (the unplug_io_fn() is called).
* When preread is initiated on a stripe, we set PREREAD_ACTIVE and add
* it to the count of prereading stripes.
* When write is initiated, or the stripe refcnt == 0 (just in case) we
* clear the PREREAD_ACTIVE flag and decrement the count
* Whenever the 'handle' queue is empty and the device is not plugged, we
* move any strips from delayed to handle and clear the DELAYED flag and set
* In stripe_handle, if we find pre-reading is necessary, we do it if
* PREREAD_ACTIVE is set, else we set DELAYED which will send it to the delayed queue.
* HANDLE gets cleared if stripe_handle leave nothing locked.
struct disk_info {
mdk_rdev_t *rdev;
struct raid5_private_data {
struct hlist_head *stripe_hashtbl;
mddev_t *mddev;
struct disk_info *spare;
int chunk_sectors;
int level, algorithm;
int max_degraded;
int raid_disks;
int max_nr_stripes;
/* reshape_progress is the leading edge of a 'reshape'
* It has value MaxSector when no reshape is happening
* If delta_disks < 0, it is the last sector we started work on,
* else is it the next sector to work on.
sector_t reshape_progress;
/* reshape_safe is the trailing edge of a reshape. We know that
* before (or after) this address, all reshape has completed.
sector_t reshape_safe;
int previous_raid_disks;
int prev_chunk_sectors;
int prev_algo;
short generation; /* increments with every reshape */
unsigned long reshape_checkpoint; /* Time we last updated
* metadata */
struct list_head handle_list; /* stripes needing handling */
struct list_head hold_list; /* preread ready stripes */
struct list_head delayed_list; /* stripes that have plugged requests */
struct list_head bitmap_list; /* stripes delaying awaiting bitmap update */
struct bio *retry_read_aligned; /* currently retrying aligned bios */
struct bio *retry_read_aligned_list; /* aligned bios retry list */
atomic_t preread_active_stripes; /* stripes with scheduled io */
atomic_t active_aligned_reads;
atomic_t pending_full_writes; /* full write backlog */
int bypass_count; /* bypassed prereads */
int bypass_threshold; /* preread nice */
struct list_head *last_hold; /* detect hold_list promotions */
atomic_t reshape_stripes; /* stripes with pending writes for reshape */
/* unfortunately we need two cache names as we temporarily have
* two caches.
int active_name;
char cache_name[2][20];
struct kmem_cache *slab_cache; /* for allocating stripes */
int seq_flush, seq_write;
int quiesce;
int fullsync; /* set to 1 if a full sync is needed,
* (fresh device added).
* Cleared when a sync completes.
/* per cpu variables */
struct raid5_percpu {
struct page *spare_page; /* Used when checking P/Q in raid6 */
void *scribble; /* space for constructing buffer
* lists and performing address
* conversions
} __percpu *percpu;
size_t scribble_len; /* size of scribble region must be
* associated with conf to handle
* cpu hotplug while reshaping
struct notifier_block cpu_notify;
* Free stripes pool
atomic_t active_stripes;
struct list_head inactive_list;
wait_queue_head_t wait_for_stripe;
wait_queue_head_t wait_for_overlap;
int inactive_blocked; /* release of inactive stripes blocked,
* waiting for 25% to be free
int pool_size; /* number of disks in stripeheads in pool */
spinlock_t device_lock;
struct disk_info *disks;
/* When taking over an array from a different personality, we store
* the new thread here until we fully activate the array.
struct mdk_thread_s *thread;
typedef struct raid5_private_data raid5_conf_t;
* Our supported algorithms
#define ALGORITHM_LEFT_ASYMMETRIC 0 /* Rotating Parity N with Data Restart */
#define ALGORITHM_RIGHT_ASYMMETRIC 1 /* Rotating Parity 0 with Data Restart */
#define ALGORITHM_LEFT_SYMMETRIC 2 /* Rotating Parity N with Data Continuation */
#define ALGORITHM_RIGHT_SYMMETRIC 3 /* Rotating Parity 0 with Data Continuation */
/* Define non-rotating (raid4) algorithms. These allow
* conversion of raid4 to raid5.
#define ALGORITHM_PARITY_0 4 /* P or P,Q are initial devices */
#define ALGORITHM_PARITY_N 5 /* P or P,Q are final devices. */
/* DDF RAID6 layouts differ from md/raid6 layouts in two ways.
* Firstly, the exact positioning of the parity block is slightly
* different between the 'LEFT_*' modes of md and the "_N_*" modes
* of DDF.
* Secondly, or order of datablocks over which the Q syndrome is computed
* is different.
* Consequently we have different layouts for DDF/raid6 than md/raid6.
* These layouts are from the DDFv1.2 spec.
* Interestingly DDFv1.2-Errata-A does not specify N_CONTINUE but
* leaves RLQ=3 as 'Vendor Specific'
/* For every RAID5 algorithm we define a RAID6 algorithm
* with exactly the same layout for data and parity, and
* with the Q block always on the last device (N-1).
* This allows trivial conversion from RAID5 to RAID6
#define ALGORITHM_PARITY_0_6 20
static inline int algorithm_valid_raid5(int layout)
return (layout >= 0) &&
(layout <= 5);
static inline int algorithm_valid_raid6(int layout)
return (layout >= 0 && layout <= 5)
(layout >= 8 && layout <= 10)
(layout >= 16 && layout <= 20);
static inline int algorithm_is_DDF(int layout)
return layout >= 8 && layout <= 10;