release/src-rt-6.x.4708/linux/linux-2.6.36/drivers/block/drbd/drbd_req.h

   1 /*
   2    drbd_req.h
   3
   4    This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
   5
   6    Copyright (C) 2006-2008, LINBIT Information Technologies GmbH.
   7    Copyright (C) 2006-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
   8    Copyright (C) 2006-2008, Philipp Reisner <philipp.reisner@linbit.com>.
   9
  10    DRBD is free software; you can redistribute it and/or modify
  11    it under the terms of the GNU General Public License as published by
  12    the Free Software Foundation; either version 2, or (at your option)
  13    any later version.
  14
  15    DRBD is distributed in the hope that it will be useful,
  16    but WITHOUT ANY WARRANTY; without even the implied warranty of
  17    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18    GNU General Public License for more details.
  19
  20    You should have received a copy of the GNU General Public License
  21    along with drbd; see the file COPYING.  If not, write to
  22    the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  23  */
  24
  25 #ifndef _DRBD_REQ_H
  26 #define _DRBD_REQ_H
  27
  28 #include <linux/module.h>
  29
  30 #include <linux/slab.h>
  31 #include <linux/drbd.h>
  32 #include "drbd_int.h"
  33 #include "drbd_wrappers.h"
  34
  35 /* The request callbacks will be called in irq context by the IDE drivers,
  36    and in Softirqs/Tasklets/BH context by the SCSI drivers,
  37    and by the receiver and worker in kernel-thread context.
  38    Try to get the locking right :) */
  39
  40 /*
  41  * Objects of type struct drbd_request do only exist on a R_PRIMARY node, and are
  42  * associated with IO requests originating from the block layer above us.
  43  *
  44  * There are quite a few things that may happen to a drbd request
  45  * during its lifetime.
  46  *
  47  *  It will be created.
  48  *  It will be marked with the intention to be
  49  *    submitted to local disk and/or
  50  *    send via the network.
  51  *
  52  *  It has to be placed on the transfer log and other housekeeping lists,
  53  *  In case we have a network connection.
  54  *
  55  *  It may be identified as a concurrent (write) request
  56  *    and be handled accordingly.
  57  *
  58  *  It may me handed over to the local disk subsystem.
  59  *  It may be completed by the local disk subsystem,
  60  *    either successfully or with io-error.
  61  *  In case it is a READ request, and it failed locally,
  62  *    it may be retried remotely.
  63  *
  64  *  It may be queued for sending.
  65  *  It may be handed over to the network stack,
  66  *    which may fail.
  67  *  It may be acknowledged by the "peer" according to the wire_protocol in use.
  68  *    this may be a negative ack.
  69  *  It may receive a faked ack when the network connection is lost and the
  70  *  transfer log is cleaned up.
  71  *  Sending may be canceled due to network connection loss.
  72  *  When it finally has outlived its time,
  73  *    corresponding dirty bits in the resync-bitmap may be cleared or set,
  74  *    it will be destroyed,
  75  *    and completion will be signalled to the originator,
  76  *      with or without "success".
  77  */
  78
  79 enum drbd_req_event {
  80         created,
  81         to_be_send,
  82         to_be_submitted,
  83
  84         queue_for_net_write,
  85         queue_for_net_read,
  86
  87         send_canceled,
  88         send_failed,
  89         handed_over_to_network,
  90         connection_lost_while_pending,
  91         read_retry_remote_canceled,
  92         recv_acked_by_peer,
  93         write_acked_by_peer,
  94         write_acked_by_peer_and_sis, /* and set_in_sync */
  95         conflict_discarded_by_peer,
  96         neg_acked,
  97         barrier_acked, /* in protocol A and B */
  98         data_received, /* (remote read) */
  99
 100         read_completed_with_error,
 101         read_ahead_completed_with_error,
 102         write_completed_with_error,
 103         completed_ok,
 104         nothing, /* for tracing only */
 105 };
 106
 107 /* encoding of request states for now.  we don't actually need that many bits.
 108  * we don't need to do atomic bit operations either, since most of the time we
 109  * need to look at the connection state and/or manipulate some lists at the
 110  * same time, so we should hold the request lock anyways.
 111  */
 112 enum drbd_req_state_bits {
 113         /* 210
 114          * 000: no local possible
 115          * 001: to be submitted
 116          *    UNUSED, we could map: 011: submitted, completion still pending
 117          * 110: completed ok
 118          * 010: completed with error
 119          */
 120         __RQ_LOCAL_PENDING,
 121         __RQ_LOCAL_COMPLETED,
 122         __RQ_LOCAL_OK,
 123
 124         /* 76543
 125          * 00000: no network possible
 126          * 00001: to be send
 127          * 00011: to be send, on worker queue
 128          * 00101: sent, expecting recv_ack (B) or write_ack (C)
 129          * 11101: sent,
 130          *        recv_ack (B) or implicit "ack" (A),
 131          *        still waiting for the barrier ack.
 132          *        master_bio may already be completed and invalidated.
 133          * 11100: write_acked (C),
 134          *        data_received (for remote read, any protocol)
 135          *        or finally the barrier ack has arrived (B,A)...
 136          *        request can be freed
 137          * 01100: neg-acked (write, protocol C)
 138          *        or neg-d-acked (read, any protocol)
 139          *        or killed from the transfer log
 140          *        during cleanup after connection loss
 141          *        request can be freed
 142          * 01000: canceled or send failed...
 143          *        request can be freed
 144          */
 145
 146         /* if "SENT" is not set, yet, this can still fail or be canceled.
 147          * if "SENT" is set already, we still wait for an Ack packet.
 148          * when cleared, the master_bio may be completed.
 149          * in (B,A) the request object may still linger on the transaction log
 150          * until the corresponding barrier ack comes in */
 151         __RQ_NET_PENDING,
 152
 153         /* If it is QUEUED, and it is a WRITE, it is also registered in the
 154          * transfer log. Currently we need this flag to avoid conflicts between
 155          * worker canceling the request and tl_clear_barrier killing it from
 156          * transfer log.  We should restructure the code so this conflict does
 157          * no longer occur. */
 158         __RQ_NET_QUEUED,
 159
 160         /* well, actually only "handed over to the network stack".
 161          *
 162          * TODO can potentially be dropped because of the similar meaning
 163          * of RQ_NET_SENT and ~RQ_NET_QUEUED.
 164          * however it is not exactly the same. before we drop it
 165          * we must ensure that we can tell a request with network part
 166          * from a request without, regardless of what happens to it. */
 167         __RQ_NET_SENT,
 168
 169         /* when set, the request may be freed (if RQ_NET_QUEUED is clear).
 170          * basically this means the corresponding P_BARRIER_ACK was received */
 171         __RQ_NET_DONE,
 172
 173         /* whether or not we know (C) or pretend (B,A) that the write
 174          * was successfully written on the peer.
 175          */
 176         __RQ_NET_OK,
 177
 178         /* peer called drbd_set_in_sync() for this write */
 179         __RQ_NET_SIS,
 180
 181         /* keep this last, its for the RQ_NET_MASK */
 182         __RQ_NET_MAX,
 183 };
 184
 185 #define RQ_LOCAL_PENDING   (1UL << __RQ_LOCAL_PENDING)
 186 #define RQ_LOCAL_COMPLETED (1UL << __RQ_LOCAL_COMPLETED)
 187 #define RQ_LOCAL_OK        (1UL << __RQ_LOCAL_OK)
 188
 189 #define RQ_LOCAL_MASK      ((RQ_LOCAL_OK << 1)-1) /* 0x07 */
 190
 191 #define RQ_NET_PENDING     (1UL << __RQ_NET_PENDING)
 192 #define RQ_NET_QUEUED      (1UL << __RQ_NET_QUEUED)
 193 #define RQ_NET_SENT        (1UL << __RQ_NET_SENT)
 194 #define RQ_NET_DONE        (1UL << __RQ_NET_DONE)
 195 #define RQ_NET_OK          (1UL << __RQ_NET_OK)
 196 #define RQ_NET_SIS         (1UL << __RQ_NET_SIS)
 197
 198 /* 0x1f8 */
 199 #define RQ_NET_MASK        (((1UL << __RQ_NET_MAX)-1) & ~RQ_LOCAL_MASK)
 200
 201 /* epoch entries */
 202 static inline
 203 struct hlist_head *ee_hash_slot(struct drbd_conf *mdev, sector_t sector)
 204 {
 205         BUG_ON(mdev->ee_hash_s == 0);
 206         return mdev->ee_hash +
 207                 ((unsigned int)(sector>>HT_SHIFT) % mdev->ee_hash_s);
 208 }
 209
 210 /* transfer log (drbd_request objects) */
 211 static inline
 212 struct hlist_head *tl_hash_slot(struct drbd_conf *mdev, sector_t sector)
 213 {
 214         BUG_ON(mdev->tl_hash_s == 0);
 215         return mdev->tl_hash +
 216                 ((unsigned int)(sector>>HT_SHIFT) % mdev->tl_hash_s);
 217 }
 218
 219 /* application reads (drbd_request objects) */
 220 static struct hlist_head *ar_hash_slot(struct drbd_conf *mdev, sector_t sector)
 221 {
 222         return mdev->app_reads_hash
 223                 + ((unsigned int)(sector) % APP_R_HSIZE);
 224 }
 225
 226 /* when we receive the answer for a read request,
 227  * verify that we actually know about it */
 228 static inline struct drbd_request *_ar_id_to_req(struct drbd_conf *mdev,
 229         u64 id, sector_t sector)
 230 {
 231         struct hlist_head *slot = ar_hash_slot(mdev, sector);
 232         struct hlist_node *n;
 233         struct drbd_request *req;
 234
 235         hlist_for_each_entry(req, n, slot, colision) {
 236                 if ((unsigned long)req == (unsigned long)id) {
 237                         D_ASSERT(req->sector == sector);
 238                         return req;
 239                 }
 240         }
 241         return NULL;
 242 }
 243
 244 static inline struct drbd_request *drbd_req_new(struct drbd_conf *mdev,
 245         struct bio *bio_src)
 246 {
 247         struct bio *bio;
 248         struct drbd_request *req =
 249                 mempool_alloc(drbd_request_mempool, GFP_NOIO);
 250         if (likely(req)) {
 251                 bio = bio_clone(bio_src, GFP_NOIO);
 252
 253                 req->rq_state    = 0;
 254                 req->mdev        = mdev;
 255                 req->master_bio  = bio_src;
 256                 req->private_bio = bio;
 257                 req->epoch       = 0;
 258                 req->sector      = bio->bi_sector;
 259                 req->size        = bio->bi_size;
 260                 req->start_time  = jiffies;
 261                 INIT_HLIST_NODE(&req->colision);
 262                 INIT_LIST_HEAD(&req->tl_requests);
 263                 INIT_LIST_HEAD(&req->w.list);
 264
 265                 bio->bi_private  = req;
 266                 bio->bi_end_io   = drbd_endio_pri;
 267                 bio->bi_next     = NULL;
 268         }
 269         return req;
 270 }
 271
 272 static inline void drbd_req_free(struct drbd_request *req)
 273 {
 274         mempool_free(req, drbd_request_mempool);
 275 }
 276
 277 static inline int overlaps(sector_t s1, int l1, sector_t s2, int l2)
 278 {
 279         return !((s1 + (l1>>9) <= s2) || (s1 >= s2 + (l2>>9)));
 280 }
 281
 282 /* Short lived temporary struct on the stack.
 283  * We could squirrel the error to be returned into
 284  * bio->bi_size, or similar. But that would be too ugly. */
 285 struct bio_and_error {
 286         struct bio *bio;
 287         int error;
 288 };
 289
 290 extern void _req_may_be_done(struct drbd_request *req,
 291                 struct bio_and_error *m);
 292 extern void __req_mod(struct drbd_request *req, enum drbd_req_event what,
 293                 struct bio_and_error *m);
 294 extern void complete_master_bio(struct drbd_conf *mdev,
 295                 struct bio_and_error *m);
 296
 297 /* use this if you don't want to deal with calling complete_master_bio()
 298  * outside the spinlock, e.g. when walking some list on cleanup. */
 299 static inline void _req_mod(struct drbd_request *req, enum drbd_req_event what)
 300 {
 301         struct drbd_conf *mdev = req->mdev;
 302         struct bio_and_error m;
 303
 304         /* __req_mod possibly frees req, do not touch req after that! */
 305         __req_mod(req, what, &m);
 306         if (m.bio)
 307                 complete_master_bio(mdev, &m);
 308 }
 309
 310 /* completion of master bio is outside of spinlock.
 311  * If you need it irqsave, do it your self! */
 312 static inline void req_mod(struct drbd_request *req,
 313                 enum drbd_req_event what)
 314 {
 315         struct drbd_conf *mdev = req->mdev;
 316         struct bio_and_error m;
 317         spin_lock_irq(&mdev->req_lock);
 318         __req_mod(req, what, &m);
 319         spin_unlock_irq(&mdev->req_lock);
 320
 321         if (m.bio)
 322                 complete_master_bio(mdev, &m);
 323 }
 324 #endif