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!
diff --git a/include/linux/raid/raid5.h b/include/linux/raid/raid5.h
new file mode 100644
index 0000000..d63ddcb
--- /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