1 files changed, 326 insertions, 0 deletions

diff --git a/drivers/block/drbd/drbd_req.h b/drivers/block/drbd/drbd_req.h
new file mode 100644
index 000000000000..f22c1bc8ec7e
--- /dev/null
+++ b/drivers/block/drbd/drbd_req.h
@@ -0,0 +1,326 @@
+/*
+   drbd_req.h
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2006-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 2006-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+   Copyright (C) 2006-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+
+   DRBD is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   DRBD is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#ifndef _DRBD_REQ_H
+#define _DRBD_REQ_H
+
+#include <linux/module.h>
+
+#include <linux/slab.h>
+#include <linux/drbd.h>
+#include "drbd_int.h"
+#include "drbd_wrappers.h"
+
+/* The request callbacks will be called in irq context by the IDE drivers,
+   and in Softirqs/Tasklets/BH context by the SCSI drivers,
+   and by the receiver and worker in kernel-thread context.
+   Try to get the locking right :) */
+
+/*
+ * Objects of type struct drbd_request do only exist on a R_PRIMARY node, and are
+ * associated with IO requests originating from the block layer above us.
+ *
+ * There are quite a few things that may happen to a drbd request
+ * during its lifetime.
+ *
+ *  It will be created.
+ *  It will be marked with the intention to be
+ *    submitted to local disk and/or
+ *    send via the network.
+ *
+ *  It has to be placed on the transfer log and other housekeeping lists,
+ *  In case we have a network connection.
+ *
+ *  It may be identified as a concurrent (write) request
+ *    and be handled accordingly.
+ *
+ *  It may me handed over to the local disk subsystem.
+ *  It may be completed by the local disk subsystem,
+ *    either sucessfully or with io-error.
+ *  In case it is a READ request, and it failed locally,
+ *    it may be retried remotely.
+ *
+ *  It may be queued for sending.
+ *  It may be handed over to the network stack,
+ *    which may fail.
+ *  It may be acknowledged by the "peer" according to the wire_protocol in use.
+ *    this may be a negative ack.
+ *  It may receive a faked ack when the network connection is lost and the
+ *  transfer log is cleaned up.
+ *  Sending may be canceled due to network connection loss.
+ *  When it finally has outlived its time,
+ *    corresponding dirty bits in the resync-bitmap may be cleared or set,
+ *    it will be destroyed,
+ *    and completion will be signalled to the originator,
+ *      with or without "success".
+ */
+
+enum drbd_req_event {
+        created,
+        to_be_send,
+        to_be_submitted,
+
+        /* XXX yes, now I am inconsistent...
+         * these two are not "events" but "actions"
+         * oh, well... */
+        queue_for_net_write,
+        queue_for_net_read,
+
+        send_canceled,
+        send_failed,
+        handed_over_to_network,
+        connection_lost_while_pending,
+        recv_acked_by_peer,
+        write_acked_by_peer,
+        write_acked_by_peer_and_sis, /* and set_in_sync */
+        conflict_discarded_by_peer,
+        neg_acked,
+        barrier_acked, /* in protocol A and B */
+        data_received, /* (remote read) */
+
+        read_completed_with_error,
+        read_ahead_completed_with_error,
+        write_completed_with_error,
+        completed_ok,
+        nothing, /* for tracing only */
+};
+
+/* encoding of request states for now.  we don't actually need that many bits.
+ * we don't need to do atomic bit operations either, since most of the time we
+ * need to look at the connection state and/or manipulate some lists at the
+ * same time, so we should hold the request lock anyways.
+ */
+enum drbd_req_state_bits {
+        /* 210
+         * 000: no local possible
+         * 001: to be submitted
+         *    UNUSED, we could map: 011: submitted, completion still pending
+         * 110: completed ok
+         * 010: completed with error
+         */
+        __RQ_LOCAL_PENDING,
+        __RQ_LOCAL_COMPLETED,
+        __RQ_LOCAL_OK,
+
+        /* 76543
+         * 00000: no network possible
+         * 00001: to be send
+         * 00011: to be send, on worker queue
+         * 00101: sent, expecting recv_ack (B) or write_ack (C)
+         * 11101: sent,
+         *        recv_ack (B) or implicit "ack" (A),
+         *        still waiting for the barrier ack.
+         *        master_bio may already be completed and invalidated.
+         * 11100: write_acked (C),
+         *        data_received (for remote read, any protocol)
+         *        or finally the barrier ack has arrived (B,A)...
+         *        request can be freed
+         * 01100: neg-acked (write, protocol C)
+         *        or neg-d-acked (read, any protocol)
+         *        or killed from the transfer log
+         *        during cleanup after connection loss
+         *        request can be freed
+         * 01000: canceled or send failed...
+         *        request can be freed
+         */
+
+        /* if "SENT" is not set, yet, this can still fail or be canceled.
+         * if "SENT" is set already, we still wait for an Ack packet.
+         * when cleared, the master_bio may be completed.
+         * in (B,A) the request object may still linger on the transaction log
+         * until the corresponding barrier ack comes in */
+        __RQ_NET_PENDING,
+
+        /* If it is QUEUED, and it is a WRITE, it is also registered in the
+         * transfer log. Currently we need this flag to avoid conflicts between
+         * worker canceling the request and tl_clear_barrier killing it from
+         * transfer log.  We should restructure the code so this conflict does
+         * no longer occur. */
+        __RQ_NET_QUEUED,
+
+        /* well, actually only "handed over to the network stack".
+         *
+         * TODO can potentially be dropped because of the similar meaning
+         * of RQ_NET_SENT and ~RQ_NET_QUEUED.
+         * however it is not exactly the same. before we drop it
+         * we must ensure that we can tell a request with network part
+         * from a request without, regardless of what happens to it. */
+        __RQ_NET_SENT,
+
+        /* when set, the request may be freed (if RQ_NET_QUEUED is clear).
+         * basically this means the corresponding P_BARRIER_ACK was received */
+        __RQ_NET_DONE,
+
+        /* whether or not we know (C) or pretend (B,A) that the write
+         * was successfully written on the peer.
+         */
+        __RQ_NET_OK,
+
+        /* peer called drbd_set_in_sync() for this write */
+        __RQ_NET_SIS,
+
+        /* keep this last, its for the RQ_NET_MASK */
+        __RQ_NET_MAX,
+};
+
+#define RQ_LOCAL_PENDING   (1UL << __RQ_LOCAL_PENDING)
+#define RQ_LOCAL_COMPLETED (1UL << __RQ_LOCAL_COMPLETED)
+#define RQ_LOCAL_OK        (1UL << __RQ_LOCAL_OK)
+
+#define RQ_LOCAL_MASK      ((RQ_LOCAL_OK << 1)-1) /* 0x07 */
+
+#define RQ_NET_PENDING     (1UL << __RQ_NET_PENDING)
+#define RQ_NET_QUEUED      (1UL << __RQ_NET_QUEUED)
+#define RQ_NET_SENT        (1UL << __RQ_NET_SENT)
+#define RQ_NET_DONE        (1UL << __RQ_NET_DONE)
+#define RQ_NET_OK          (1UL << __RQ_NET_OK)
+#define RQ_NET_SIS         (1UL << __RQ_NET_SIS)
+
+/* 0x1f8 */
+#define RQ_NET_MASK        (((1UL << __RQ_NET_MAX)-1) & ~RQ_LOCAL_MASK)
+
+/* epoch entries */
+static inline
+struct hlist_head *ee_hash_slot(struct drbd_conf *mdev, sector_t sector)
+{
+        BUG_ON(mdev->ee_hash_s == 0);
+        return mdev->ee_hash +
+                ((unsigned int)(sector>>HT_SHIFT) % mdev->ee_hash_s);
+}
+
+/* transfer log (drbd_request objects) */
+static inline
+struct hlist_head *tl_hash_slot(struct drbd_conf *mdev, sector_t sector)
+{
+        BUG_ON(mdev->tl_hash_s == 0);
+        return mdev->tl_hash +
+                ((unsigned int)(sector>>HT_SHIFT) % mdev->tl_hash_s);
+}
+
+/* application reads (drbd_request objects) */
+static struct hlist_head *ar_hash_slot(struct drbd_conf *mdev, sector_t sector)
+{
+        return mdev->app_reads_hash
+                + ((unsigned int)(sector) % APP_R_HSIZE);
+}
+
+/* when we receive the answer for a read request,
+ * verify that we actually know about it */
+static inline struct drbd_request *_ar_id_to_req(struct drbd_conf *mdev,
+        u64 id, sector_t sector)
+{
+        struct hlist_head *slot = ar_hash_slot(mdev, sector);
+        struct hlist_node *n;
+        struct drbd_request *req;
+
+        hlist_for_each_entry(req, n, slot, colision) {
+                if ((unsigned long)req == (unsigned long)id) {
+                        D_ASSERT(req->sector == sector);
+                        return req;
+                }
+        }
+        return NULL;
+}
+
+static inline struct drbd_request *drbd_req_new(struct drbd_conf *mdev,
+        struct bio *bio_src)
+{
+        struct bio *bio;
+        struct drbd_request *req =
+                mempool_alloc(drbd_request_mempool, GFP_NOIO);
+        if (likely(req)) {
+                bio = bio_clone(bio_src, GFP_NOIO); /* XXX cannot fail?? */
+
+                req->rq_state    = 0;
+                req->mdev        = mdev;
+                req->master_bio  = bio_src;
+                req->private_bio = bio;
+                req->epoch       = 0;
+                req->sector      = bio->bi_sector;
+                req->size        = bio->bi_size;
+                req->start_time  = jiffies;
+                INIT_HLIST_NODE(&req->colision);
+                INIT_LIST_HEAD(&req->tl_requests);
+                INIT_LIST_HEAD(&req->w.list);
+
+                bio->bi_private  = req;
+                bio->bi_end_io   = drbd_endio_pri;
+                bio->bi_next     = NULL;
+        }
+        return req;
+}
+
+static inline void drbd_req_free(struct drbd_request *req)
+{
+        mempool_free(req, drbd_request_mempool);
+}
+
+static inline int overlaps(sector_t s1, int l1, sector_t s2, int l2)
+{
+        return !((s1 + (l1>>9) <= s2) || (s1 >= s2 + (l2>>9)));
+}
+
+/* Short lived temporary struct on the stack.
+ * We could squirrel the error to be returned into
+ * bio->bi_size, or similar. But that would be too ugly. */
+struct bio_and_error {
+        struct bio *bio;
+        int error;
+};
+
+extern void _req_may_be_done(struct drbd_request *req,
+                struct bio_and_error *m);
+extern void __req_mod(struct drbd_request *req, enum drbd_req_event what,
+                struct bio_and_error *m);
+extern void complete_master_bio(struct drbd_conf *mdev,
+                struct bio_and_error *m);
+
+/* use this if you don't want to deal with calling complete_master_bio()
+ * outside the spinlock, e.g. when walking some list on cleanup. */
+static inline void _req_mod(struct drbd_request *req, enum drbd_req_event what)
+{
+        struct drbd_conf *mdev = req->mdev;
+        struct bio_and_error m;
+
+        /* __req_mod possibly frees req, do not touch req after that! */
+        __req_mod(req, what, &m);
+        if (m.bio)
+                complete_master_bio(mdev, &m);
+}
+
+/* completion of master bio is outside of spinlock.
+ * If you need it irqsave, do it your self! */
+static inline void req_mod(struct drbd_request *req,
+                enum drbd_req_event what)
+{
+        struct drbd_conf *mdev = req->mdev;
+        struct bio_and_error m;
+        spin_lock_irq(&mdev->req_lock);
+        __req_mod(req, what, &m);
+        spin_unlock_irq(&mdev->req_lock);
+
+        if (m.bio)
+                complete_master_bio(mdev, &m);
+}
+#endif