Linux-2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 243 insertions, 0 deletions

diff --git a/include/linux/raid/raid5.h b/include/linux/raid/raid5.h
new file mode 100644
index 000000000000..d63ddcb4afad
--- /dev/null
+++ b/include/linux/raid/raid5.h
@@ -0,0 +1,243 @@
+#ifndef _RAID5_H
+#define _RAID5_H
+
+#include <linux/raid/md.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 needed unlockstripe schedule io
+ *  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.
+ */
+
+struct stripe_head {
+	struct stripe_head	*hash_next, **hash_pprev; /* hash pointers */
+	struct list_head	lru;			/* inactive_list or handle_list */
+	struct raid5_private_data	*raid_conf;
+	sector_t		sector;			/* sector of this row */
+	int			pd_idx;			/* parity disk index */
+	unsigned long		state;			/* state flags */
+	atomic_t		count;			/* nr of active thread/requests */
+	spinlock_t		lock;
+	struct r5dev {
+		struct bio	req;
+		struct bio_vec	vec;
+		struct page	*page;
+		struct bio	*toread, *towrite, *written;
+		sector_t	sector;			/* sector of this page */
+		unsigned long	flags;
+	} dev[1]; /* allocated with extra space depending of RAID geometry */
+};
+/* 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_Syncio	6	/* this io need to be accounted as resync io */
+#define	R5_Overlap	7	/* There is a pending overlapping request on this block */
+
+/*
+ * Write method
+ */
+#define RECONSTRUCT_WRITE	1
+#define READ_MODIFY_WRITE	2
+/* not a write method, but a compute_parity mode */
+#define	CHECK_PARITY		3
+
+/*
+ * Stripe state
+ */
+#define STRIPE_ERROR		1
+#define STRIPE_HANDLE		2
+#define	STRIPE_SYNCING		3
+#define	STRIPE_INSYNC		4
+#define	STRIPE_PREREAD_ACTIVE	5
+#define	STRIPE_DELAYED		6
+
+/*
+ * 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 delayed 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 stripe_head	**stripe_hashtbl;
+	mddev_t			*mddev;
+	struct disk_info	*spare;
+	int			chunk_size, level, algorithm;
+	int			raid_disks, working_disks, failed_disks;
+	int			max_nr_stripes;
+
+	struct list_head	handle_list; /* stripes needing handling */
+	struct list_head	delayed_list; /* stripes that have plugged requests */
+	atomic_t		preread_active_stripes; /* stripes with scheduled io */
+
+	char			cache_name[20];
+	kmem_cache_t		*slab_cache; /* for allocating stripes */
+	/*
+	 * 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
+							 */        
+	spinlock_t		device_lock;
+	struct disk_info	disks[0];
+};
+
+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
+#define ALGORITHM_RIGHT_ASYMMETRIC	1
+#define ALGORITHM_LEFT_SYMMETRIC	2
+#define ALGORITHM_RIGHT_SYMMETRIC	3
+
+#endif