Merge branch 'for-linus' of git://neil.brown.name/md

* 'for-linus' of git://neil.brown.name/md: (53 commits)
  md/raid5 revise rules for when to update metadata during reshape
  md/raid5: minor code cleanups in make_request.
  md: remove CONFIG_MD_RAID_RESHAPE config option.
  md/raid5: be more careful about write ordering when reshaping.
  md: don't display meaningless values in sysfs files resync_start and sync_speed
  md/raid5: allow layout and chunksize to be changed on active array.
  md/raid5: reshape using largest of old and new chunk size
  md/raid5: prepare for allowing reshape to change layout
  md/raid5: prepare for allowing reshape to change chunksize.
  md/raid5: clearly differentiate 'before' and 'after' stripes during reshape.
  Documentation/md.txt update
  md: allow number of drives in raid5 to be reduced
  md/raid5: change reshape-progress measurement to cope with reshaping backwards.
  md: add explicit method to signal the end of a reshape.
  md/raid5: enhance raid5_size to work correctly with negative delta_disks
  md/raid5: drop qd_idx from r6_state
  md/raid6: move raid6 data processing to raid6_pq.ko
  md: raid5 run(): Fix max_degraded for raid level 4.
  md: 'array_size' sysfs attribute
  md: centralize ->array_sectors modifications
  ...

1 files changed, 474 insertions, 0 deletions

diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
new file mode 100644
index 000000000000..52ba99954dec
--- /dev/null
+++ b/drivers/md/raid5.h
@@ -0,0 +1,474 @@
+#ifndef _RAID5_H
+#define _RAID5_H
+
+#include <linux/raid/xor.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:
+ *   R5_UPTODATE and R5_LOCKED
+ *
+ * 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
+ * sh->state flags (STRIPE_BIOFILL_RUN and STRIPE_COMPUTE_RUN)
+ */
+/**
+ * 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, /* parity check */
+        check_state_check_result,
+        check_state_compute_run, /* parity repair */
+        check_state_compute_result,
+};
+
+/**
+ * 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 */
+        reconstruct_state_prexor_drain_result,
+        reconstruct_state_drain_result,
+        reconstruct_state_result,
+};
+
+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;
+        /* stripe_operations
+         * @target - STRIPE_OP_COMPUTE_BLK target
+         */
+        struct stripe_operations {
+                int                target;
+                u32                zero_sum_result;
+        } 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
+ */
+#define RECONSTRUCT_WRITE       1
+#define READ_MODIFY_WRITE       2
+/* not a write method, but a compute_parity mode */
+#define CHECK_PARITY            3
+/* Additional compute_parity mode -- updates the parity w/o LOCKING */
+#define UPDATE_PARITY           4
+
+/*
+ * Stripe state
+ */
+#define STRIPE_HANDLE           2
+#define STRIPE_SYNCING          3
+#define STRIPE_INSYNC           4
+#define STRIPE_PREREAD_ACTIVE   5
+#define STRIPE_DELAYED          6
+#define STRIPE_DEGRADED         7
+#define STRIPE_BIT_DELAY        8
+#define STRIPE_EXPANDING        9
+#define STRIPE_EXPAND_SOURCE    10
+#define STRIPE_EXPAND_READY     11
+#define STRIPE_IO_STARTED       12 /* do not count towards 'bypass_count' */
+#define STRIPE_FULL_WRITE       13 /* all blocks are set to be overwritten */
+#define STRIPE_BIOFILL_RUN      14
+#define STRIPE_COMPUTE_RUN      15
+/*
+ * Operation request flags
+ */
+#define STRIPE_OP_BIOFILL       0
+#define STRIPE_OP_COMPUTE_BLK   1
+#define STRIPE_OP_PREXOR        2
+#define STRIPE_OP_BIODRAIN      3
+#define STRIPE_OP_POSTXOR       4
+#define STRIPE_OP_CHECK 5
+
+/*
+ * 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
+ * PREREAD_ACTIVE.
+ * 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_size, 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, 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.
+                                            */
+
+        struct page             *spare_page; /* Used when checking P/Q in raid6 */
+
+        /*
+         * 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;
+
+#define mddev_to_conf(mddev) ((raid5_conf_t *) mddev->private)
+
+/*
+ * 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'
+ */
+
+#define ALGORITHM_ROTATING_ZERO_RESTART 8 /* DDF PRL=6 RLQ=1 */
+#define ALGORITHM_ROTATING_N_RESTART    9 /* DDF PRL=6 RLQ=2 */
+#define ALGORITHM_ROTATING_N_CONTINUE   10 /*DDF PRL=6 RLQ=3 */
+
+
+/* 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_LEFT_ASYMMETRIC_6     16
+#define ALGORITHM_RIGHT_ASYMMETRIC_6    17
+#define ALGORITHM_LEFT_SYMMETRIC_6      18
+#define ALGORITHM_RIGHT_SYMMETRIC_6     19
+#define ALGORITHM_PARITY_0_6            20
+#define ALGORITHM_PARITY_N_6            ALGORITHM_PARITY_N
+
+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;
+}
+#endif