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         /* XXX yes, now I am inconsistent...
  85          * these two are not "events" but "actions"
  86          * oh, well... */
  87         queue_for_net_write,
  88         queue_for_net_read,
  89
  90         send_canceled,
  91         send_failed,
  92         handed_over_to_network,
  93         connection_lost_while_pending,
  94         read_retry_remote_canceled,
  95         recv_acked_by_peer,
  96         write_acked_by_peer,
  97         write_acked_by_peer_and_sis, /* and set_in_sync */
  98         conflict_discarded_by_peer,
  99         neg_acked,
 100         barrier_acked, /* in protocol A and B */
 101         data_received, /* (remote read) */
 102
 103         read_completed_with_error,
 104         read_ahead_completed_with_error,
 105         write_completed_with_error,
 106         completed_ok,
 107         resend,
 108         fail_frozen_disk_io,
 109         restart_frozen_disk_io,
 110         nothing, /* for tracing only */
 111 };
 112
 113 /* encoding of request states for now.  we don't actually need that many bits.
 114  * we don't need to do atomic bit operations either, since most of the time we
 115  * need to look at the connection state and/or manipulate some lists at the
 116  * same time, so we should hold the request lock anyways.
 117  */
 118 enum drbd_req_state_bits {
 119         /* 210
 120          * 000: no local possible
 121          * 001: to be submitted
 122          *    UNUSED, we could map: 011: submitted, completion still pending
 123          * 110: completed ok
 124          * 010: completed with error
 125          */
 126         __RQ_LOCAL_PENDING,
 127         __RQ_LOCAL_COMPLETED,
 128         __RQ_LOCAL_OK,
 129
 130         /* 76543
 131          * 00000: no network possible
 132          * 00001: to be send
 133          * 00011: to be send, on worker queue
 134          * 00101: sent, expecting recv_ack (B) or write_ack (C)
 135          * 11101: sent,
 136          *        recv_ack (B) or implicit "ack" (A),
 137          *        still waiting for the barrier ack.
 138          *        master_bio may already be completed and invalidated.
 139          * 11100: write_acked (C),
 140          *        data_received (for remote read, any protocol)
 141          *        or finally the barrier ack has arrived (B,A)...
 142          *        request can be freed
 143          * 01100: neg-acked (write, protocol C)
 144          *        or neg-d-acked (read, any protocol)
 145          *        or killed from the transfer log
 146          *        during cleanup after connection loss
 147          *        request can be freed
 148          * 01000: canceled or send failed...
 149          *        request can be freed
 150          */
 151
 152         /* if "SENT" is not set, yet, this can still fail or be canceled.
 153          * if "SENT" is set already, we still wait for an Ack packet.
 154          * when cleared, the master_bio may be completed.
 155          * in (B,A) the request object may still linger on the transaction log
 156          * until the corresponding barrier ack comes in */
 157         __RQ_NET_PENDING,
 158
 159         /* If it is QUEUED, and it is a WRITE, it is also registered in the
 160          * transfer log. Currently we need this flag to avoid conflicts between
 161          * worker canceling the request and tl_clear_barrier killing it from
 162          * transfer log.  We should restructure the code so this conflict does
 163          * no longer occur. */
 164         __RQ_NET_QUEUED,
 165
 166         /* well, actually only "handed over to the network stack".
 167          *
 168          * TODO can potentially be dropped because of the similar meaning
 169          * of RQ_NET_SENT and ~RQ_NET_QUEUED.
 170          * however it is not exactly the same. before we drop it
 171          * we must ensure that we can tell a request with network part
 172          * from a request without, regardless of what happens to it. */
 173         __RQ_NET_SENT,
 174
 175         /* when set, the request may be freed (if RQ_NET_QUEUED is clear).
 176          * basically this means the corresponding P_BARRIER_ACK was received */
 177         __RQ_NET_DONE,
 178
 179         /* whether or not we know (C) or pretend (B,A) that the write
 180          * was successfully written on the peer.
 181          */
 182         __RQ_NET_OK,
 183
 184         /* peer called drbd_set_in_sync() for this write */
 185         __RQ_NET_SIS,
 186
 187         /* keep this last, its for the RQ_NET_MASK */
 188         __RQ_NET_MAX,
 189
 190         /* Set when this is a write, clear for a read */
 191         __RQ_WRITE,
 192
 193         /* Should call drbd_al_complete_io() for this request... */
 194         __RQ_IN_ACT_LOG,
 195 };
 196
 197 #define RQ_LOCAL_PENDING   (1UL << __RQ_LOCAL_PENDING)
 198 #define RQ_LOCAL_COMPLETED (1UL << __RQ_LOCAL_COMPLETED)
 199 #define RQ_LOCAL_OK        (1UL << __RQ_LOCAL_OK)
 200
 201 #define RQ_LOCAL_MASK      ((RQ_LOCAL_OK << 1)-1) /* 0x07 */
 202
 203 #define RQ_NET_PENDING     (1UL << __RQ_NET_PENDING)
 204 #define RQ_NET_QUEUED      (1UL << __RQ_NET_QUEUED)
 205 #define RQ_NET_SENT        (1UL << __RQ_NET_SENT)
 206 #define RQ_NET_DONE        (1UL << __RQ_NET_DONE)
 207 #define RQ_NET_OK          (1UL << __RQ_NET_OK)
 208 #define RQ_NET_SIS         (1UL << __RQ_NET_SIS)
 209
 210 /* 0x1f8 */
 211 #define RQ_NET_MASK        (((1UL << __RQ_NET_MAX)-1) & ~RQ_LOCAL_MASK)
 212
 213 #define RQ_WRITE           (1UL << __RQ_WRITE)
 214 #define RQ_IN_ACT_LOG      (1UL << __RQ_IN_ACT_LOG)
 215
 216 /* For waking up the frozen transfer log mod_req() has to return if the request
 217    should be counted in the epoch object*/
 218 #define MR_WRITE_SHIFT 0
 219 #define MR_WRITE       (1 << MR_WRITE_SHIFT)
 220 #define MR_READ_SHIFT  1
 221 #define MR_READ        (1 << MR_READ_SHIFT)
 222
 223 /* epoch entries */
 224 static inline
 225 struct hlist_head *ee_hash_slot(struct drbd_conf *mdev, sector_t sector)
 226 {
 227         BUG_ON(mdev->ee_hash_s == 0);
 228         return mdev->ee_hash +
 229                 ((unsigned int)(sector>>HT_SHIFT) % mdev->ee_hash_s);
 230 }
 231
 232 /* transfer log (drbd_request objects) */
 233 static inline
 234 struct hlist_head *tl_hash_slot(struct drbd_conf *mdev, sector_t sector)
 235 {
 236         BUG_ON(mdev->tl_hash_s == 0);
 237         return mdev->tl_hash +
 238                 ((unsigned int)(sector>>HT_SHIFT) % mdev->tl_hash_s);
 239 }
 240
 241 /* application reads (drbd_request objects) */
 242 static struct hlist_head *ar_hash_slot(struct drbd_conf *mdev, sector_t sector)
 243 {
 244         return mdev->app_reads_hash
 245                 + ((unsigned int)(sector) % APP_R_HSIZE);
 246 }
 247
 248 /* when we receive the answer for a read request,
 249  * verify that we actually know about it */
 250 static inline struct drbd_request *_ar_id_to_req(struct drbd_conf *mdev,
 251         u64 id, sector_t sector)
 252 {
 253         struct hlist_head *slot = ar_hash_slot(mdev, sector);
 254         struct hlist_node *n;
 255         struct drbd_request *req;
 256
 257         hlist_for_each_entry(req, n, slot, colision) {
 258                 if ((unsigned long)req == (unsigned long)id) {
 259                         D_ASSERT(req->sector == sector);
 260                         return req;
 261                 }
 262         }
 263         return NULL;
 264 }
 265
 266 static inline void drbd_req_make_private_bio(struct drbd_request *req, struct bio *bio_src)
 267 {
 268         struct bio *bio;
 269         bio = bio_clone(bio_src, GFP_NOIO); /* XXX cannot fail?? */
 270
 271         req->private_bio = bio;
 272
 273         bio->bi_private  = req;
 274         bio->bi_end_io   = drbd_endio_pri;
 275         bio->bi_next     = NULL;
 276 }
 277
 278 static inline struct drbd_request *drbd_req_new(struct drbd_conf *mdev,
 279         struct bio *bio_src)
 280 {
 281         struct drbd_request *req =
 282                 mempool_alloc(drbd_request_mempool, GFP_NOIO);
 283         if (likely(req)) {
 284                 drbd_req_make_private_bio(req, bio_src);
 285
 286                 req->rq_state    = bio_data_dir(bio_src) == WRITE ? RQ_WRITE : 0;
 287                 req->mdev        = mdev;
 288                 req->master_bio  = bio_src;
 289                 req->epoch       = 0;
 290                 req->sector      = bio_src->bi_sector;
 291                 req->size        = bio_src->bi_size;
 292                 req->start_time  = jiffies;
 293                 INIT_HLIST_NODE(&req->colision);
 294                 INIT_LIST_HEAD(&req->tl_requests);
 295                 INIT_LIST_HEAD(&req->w.list);
 296         }
 297         return req;
 298 }
 299
 300 static inline void drbd_req_free(struct drbd_request *req)
 301 {
 302         mempool_free(req, drbd_request_mempool);
 303 }
 304
 305 static inline int overlaps(sector_t s1, int l1, sector_t s2, int l2)
 306 {
 307         return !((s1 + (l1>>9) <= s2) || (s1 >= s2 + (l2>>9)));
 308 }
 309
 310 /* Short lived temporary struct on the stack.
 311  * We could squirrel the error to be returned into
 312  * bio->bi_size, or similar. But that would be too ugly. */
 313 struct bio_and_error {
 314         struct bio *bio;
 315         int error;
 316 };
 317
 318 extern void _req_may_be_done(struct drbd_request *req,
 319                 struct bio_and_error *m);
 320 extern int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 321                 struct bio_and_error *m);
 322 extern void complete_master_bio(struct drbd_conf *mdev,
 323                 struct bio_and_error *m);
 324
 325 /* use this if you don't want to deal with calling complete_master_bio()
 326  * outside the spinlock, e.g. when walking some list on cleanup. */
 327 static inline int _req_mod(struct drbd_request *req, enum drbd_req_event what)
 328 {
 329         struct drbd_conf *mdev = req->mdev;
 330         struct bio_and_error m;
 331         int rv;
 332
 333         /* __req_mod possibly frees req, do not touch req after that! */
 334         rv = __req_mod(req, what, &m);
 335         if (m.bio)
 336                 complete_master_bio(mdev, &m);
 337
 338         return rv;
 339 }
 340
 341 /* completion of master bio is outside of spinlock.
 342  * If you need it irqsave, do it your self! */
 343 static inline int req_mod(struct drbd_request *req,
 344                 enum drbd_req_event what)
 345 {
 346         struct drbd_conf *mdev = req->mdev;
 347         struct bio_and_error m;
 348         int rv;
 349
 350         spin_lock_irq(&mdev->req_lock);
 351         rv = __req_mod(req, what, &m);
 352         spin_unlock_irq(&mdev->req_lock);
 353
 354         if (m.bio)
 355                 complete_master_bio(mdev, &m);
 356
 357         return rv;
 358 }
 359 #endif