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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 <>.
Copyright (C) 2006-2008, Philipp Reisner <>.
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
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 successfully 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 {
/* XXX yes, now I am inconsistent...
* these two are not "events" but "actions"
* oh, well... */
write_acked_by_peer_and_sis, /* and set_in_sync */
barrier_acked, /* in protocol A and B */
data_received, /* (remote read) */
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
/* 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 */
/* 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. */
/* well, actually only "handed over to the network stack".
* TODO can potentially be dropped because of the similar meaning
* 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. */
/* when set, the request may be freed (if RQ_NET_QUEUED is clear).
* basically this means the corresponding P_BARRIER_ACK was received */
/* whether or not we know (C) or pretend (B,A) that the write
* was successfully written on the peer.
/* peer called drbd_set_in_sync() for this write */
/* keep this last, its for the RQ_NET_MASK */
#define RQ_LOCAL_OK (1UL << __RQ_LOCAL_OK)
#define RQ_LOCAL_MASK ((RQ_LOCAL_OK << 1)-1) /* 0x07 */
#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;
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 (
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;
__req_mod(req, what, &m);
if (
complete_master_bio(mdev, &m);