[Drbd-dev] [PATCH 05/16] drbd: request state processing
Philipp Reisner
philipp.reisner at linbit.com
Mon Jul 6 17:39:24 CEST 2009
Describes the states an IO request issued to DRBD can be in. As well as
all the state transitions that a request can go through.
In here is also the make_request() function, we register in the block
layer of the kernel to pass IO requests to DRBD.
Signed-off-by: Philipp Reisner <philipp.reisner at linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg at linbit.com>
---
diff --git a/drivers/block/drbd/drbd_req.h b/drivers/block/drbd/drbd_req.h
new file mode 100644
index 0000000..81393ff
--- /dev/null
+++ b/drivers/block/drbd/drbd_req.h
@@ -0,0 +1,299 @@
+/*
+ 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 at linbit.com>.
+ Copyright (C) 2006-2008, Philipp Reisner <philipp.reisner at 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/autoconf.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,
+ 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)));
+}
+
+/* aparently too large to be inlined...
+ * moved to drbd_req.c */
+extern void _req_may_be_done(struct drbd_request *req, int error);
+extern void _req_mod(struct drbd_request *req,
+ enum drbd_req_event what, int error);
+
+/* If you need it irqsave, do it your self! */
+static inline void req_mod(struct drbd_request *req,
+ enum drbd_req_event what, int error)
+{
+ struct drbd_conf *mdev = req->mdev;
+ spin_lock_irq(&mdev->req_lock);
+ _req_mod(req, what, error);
+ spin_unlock_irq(&mdev->req_lock);
+}
+#endif
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
new file mode 100644
index 0000000..d2b941c
--- /dev/null
+++ b/drivers/block/drbd/drbd_req.c
@@ -0,0 +1,1130 @@
+/*
+ drbd_req.c
+
+ This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+ Copyright (C) 2001-2008, LINBIT Information Technologies GmbH.
+ Copyright (C) 1999-2008, Philipp Reisner <philipp.reisner at linbit.com>.
+ Copyright (C) 2002-2008, Lars Ellenberg <lars.ellenberg at 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.
+
+ */
+
+#include <linux/autoconf.h>
+#include <linux/module.h>
+
+#include <linux/slab.h>
+#include <linux/drbd.h>
+#include "drbd_int.h"
+#include "drbd_tracing.h"
+#include "drbd_req.h"
+
+
+/* Update disk stats at start of I/O request */
+static void _drbd_start_io_acct(struct drbd_conf *mdev, struct drbd_request *req, struct bio *bio)
+{
+ const int rw = bio_data_dir(bio);
+ int cpu;
+ cpu = part_stat_lock();
+ part_stat_inc(cpu, &mdev->vdisk->part0, ios[rw]);
+ part_stat_add(cpu, &mdev->vdisk->part0, sectors[rw], bio_sectors(bio));
+ part_stat_unlock();
+ mdev->vdisk->part0.in_flight++;
+}
+
+/* Update disk stats when completing request upwards */
+static void _drbd_end_io_acct(struct drbd_conf *mdev, struct drbd_request *req)
+{
+ int rw = bio_data_dir(req->master_bio);
+ unsigned long duration = jiffies - req->start_time;
+ int cpu;
+ cpu = part_stat_lock();
+ part_stat_add(cpu, &mdev->vdisk->part0, ticks[rw], duration);
+ part_round_stats(cpu, &mdev->vdisk->part0);
+ part_stat_unlock();
+ mdev->vdisk->part0.in_flight--;
+}
+
+static void _req_is_done(struct drbd_conf *mdev, struct drbd_request *req, const int rw)
+{
+ const unsigned long s = req->rq_state;
+ /* if it was a write, we may have to set the corresponding
+ * bit(s) out-of-sync first. If it had a local part, we need to
+ * release the reference to the activity log. */
+ if (rw == WRITE) {
+ /* remove it from the transfer log.
+ * well, only if it had been there in the first
+ * place... if it had not (local only or conflicting
+ * and never sent), it should still be "empty" as
+ * initialised in drbd_req_new(), so we can list_del() it
+ * here unconditionally */
+ list_del(&req->tl_requests);
+ /* Set out-of-sync unless both OK flags are set
+ * (local only or remote failed).
+ * Other places where we set out-of-sync:
+ * READ with local io-error */
+ if (!(s & RQ_NET_OK) || !(s & RQ_LOCAL_OK))
+ drbd_set_out_of_sync(mdev, req->sector, req->size);
+
+ if ((s & RQ_NET_OK) && (s & RQ_LOCAL_OK) && (s & RQ_NET_SIS))
+ drbd_set_in_sync(mdev, req->sector, req->size);
+
+ /* one might be tempted to move the drbd_al_complete_io
+ * to the local io completion callback drbd_endio_pri.
+ * but, if this was a mirror write, we may only
+ * drbd_al_complete_io after this is RQ_NET_DONE,
+ * otherwise the extent could be dropped from the al
+ * before it has actually been written on the peer.
+ * if we crash before our peer knows about the request,
+ * but after the extent has been dropped from the al,
+ * we would forget to resync the corresponding extent.
+ */
+ if (s & RQ_LOCAL_MASK) {
+ if (get_ldev_if_state(mdev, D_FAILED)) {
+ drbd_al_complete_io(mdev, req->sector);
+ put_ldev(mdev);
+ } else if (__ratelimit(&drbd_ratelimit_state)) {
+ dev_warn(DEV, "Should have called drbd_al_complete_io(, %llu), "
+ "but my Disk seems to have failed :(\n",
+ (unsigned long long) req->sector);
+ }
+ }
+ }
+
+ /* if it was a local io error, we want to notify our
+ * peer about that, and see if we need to
+ * detach the disk and stuff.
+ * to avoid allocating some special work
+ * struct, reuse the request. */
+
+ /* THINK
+ * why do we do this not when we detect the error,
+ * but delay it until it is "done", i.e. possibly
+ * until the next barrier ack? */
+
+ if (rw == WRITE &&
+ ((s & RQ_LOCAL_MASK) && !(s & RQ_LOCAL_OK))) {
+ if (!(req->w.list.next == LIST_POISON1 ||
+ list_empty(&req->w.list))) {
+ /* DEBUG ASSERT only; if this triggers, we
+ * probably corrupt the worker list here */
+ dev_err(DEV, "req->w.list.next = %p\n", req->w.list.next);
+ dev_err(DEV, "req->w.list.prev = %p\n", req->w.list.prev);
+ }
+ req->w.cb = w_io_error;
+ drbd_queue_work(&mdev->data.work, &req->w);
+ /* drbd_req_free() is done in w_io_error */
+ } else {
+ drbd_req_free(req);
+ }
+}
+
+static void queue_barrier(struct drbd_conf *mdev)
+{
+ struct drbd_tl_epoch *b;
+
+ /* We are within the req_lock. Once we queued the barrier for sending,
+ * we set the CREATE_BARRIER bit. It is cleared as soon as a new
+ * barrier/epoch object is added. This is the only place this bit is
+ * set. It indicates that the barrier for this epoch is already queued,
+ * and no new epoch has been created yet. */
+ if (test_bit(CREATE_BARRIER, &mdev->flags))
+ return;
+
+ b = mdev->newest_tle;
+ b->w.cb = w_send_barrier;
+ /* inc_ap_pending done here, so we won't
+ * get imbalanced on connection loss.
+ * dec_ap_pending will be done in got_BarrierAck
+ * or (on connection loss) in tl_clear. */
+ inc_ap_pending(mdev);
+ drbd_queue_work(&mdev->data.work, &b->w);
+ set_bit(CREATE_BARRIER, &mdev->flags);
+}
+
+static void _about_to_complete_local_write(struct drbd_conf *mdev,
+ struct drbd_request *req)
+{
+ const unsigned long s = req->rq_state;
+ struct drbd_request *i;
+ struct drbd_epoch_entry *e;
+ struct hlist_node *n;
+ struct hlist_head *slot;
+
+ /* before we can signal completion to the upper layers,
+ * we may need to close the current epoch */
+ if (mdev->state.conn >= C_CONNECTED &&
+ req->epoch == mdev->newest_tle->br_number)
+ queue_barrier(mdev);
+
+ /* we need to do the conflict detection stuff,
+ * if we have the ee_hash (two_primaries) and
+ * this has been on the network */
+ if ((s & RQ_NET_DONE) && mdev->ee_hash != NULL) {
+ const sector_t sector = req->sector;
+ const int size = req->size;
+
+ /* ASSERT:
+ * there must be no conflicting requests, since
+ * they must have been failed on the spot */
+#define OVERLAPS overlaps(sector, size, i->sector, i->size)
+ slot = tl_hash_slot(mdev, sector);
+ hlist_for_each_entry(i, n, slot, colision) {
+ if (OVERLAPS) {
+ dev_alert(DEV, "LOGIC BUG: completed: %p %llus +%u; "
+ "other: %p %llus +%u\n",
+ req, (unsigned long long)sector, size,
+ i, (unsigned long long)i->sector, i->size);
+ }
+ }
+
+ /* maybe "wake" those conflicting epoch entries
+ * that wait for this request to finish.
+ *
+ * currently, there can be only _one_ such ee
+ * (well, or some more, which would be pending
+ * P_DISCARD_ACK not yet sent by the asender...),
+ * since we block the receiver thread upon the
+ * first conflict detection, which will wait on
+ * misc_wait. maybe we want to assert that?
+ *
+ * anyways, if we found one,
+ * we just have to do a wake_up. */
+#undef OVERLAPS
+#define OVERLAPS overlaps(sector, size, e->sector, e->size)
+ slot = ee_hash_slot(mdev, req->sector);
+ hlist_for_each_entry(e, n, slot, colision) {
+ if (OVERLAPS) {
+ wake_up(&mdev->misc_wait);
+ break;
+ }
+ }
+ }
+#undef OVERLAPS
+}
+
+static void _complete_master_bio(struct drbd_conf *mdev,
+ struct drbd_request *req, int error)
+{
+ trace_drbd_bio(mdev, "Rq", req->master_bio, 1, req);
+ bio_endio(req->master_bio, error);
+ req->master_bio = NULL;
+ dec_ap_bio(mdev);
+}
+
+void _req_may_be_done(struct drbd_request *req, int error)
+{
+ const unsigned long s = req->rq_state;
+ struct drbd_conf *mdev = req->mdev;
+ int rw;
+
+ trace_drbd_req(req, nothing, "_req_may_be_done");
+
+ /* we must not complete the master bio, while it is
+ * still being processed by _drbd_send_zc_bio (drbd_send_dblock)
+ * not yet acknowledged by the peer
+ * not yet completed by the local io subsystem
+ * these flags may get cleared in any order by
+ * the worker,
+ * the receiver,
+ * the bio_endio completion callbacks.
+ */
+ if (s & RQ_NET_QUEUED)
+ return;
+ if (s & RQ_NET_PENDING)
+ return;
+ if (s & RQ_LOCAL_PENDING)
+ return;
+
+ if (req->master_bio) {
+ /* this is data_received (remote read)
+ * or protocol C P_WRITE_ACK
+ * or protocol B P_RECV_ACK
+ * or protocol A "handed_over_to_network" (SendAck)
+ * or canceled or failed,
+ * or killed from the transfer log due to connection loss.
+ */
+
+ /*
+ * figure out whether to report success or failure.
+ *
+ * report success when at least one of the operations suceeded.
+ * or, to put the other way,
+ * only report failure, when both operations failed.
+ *
+ * what to do about the failures is handled elsewhere.
+ * what we need to do here is just: complete the master_bio.
+ */
+ int ok = (s & RQ_LOCAL_OK) || (s & RQ_NET_OK);
+ rw = bio_data_dir(req->master_bio);
+
+ /* remove the request from the conflict detection
+ * respective block_id verification hash */
+ if (!hlist_unhashed(&req->colision))
+ hlist_del(&req->colision);
+ else
+ D_ASSERT((s & RQ_NET_MASK) == 0);
+
+ /* for writes we need to do some extra housekeeping */
+ if (rw == WRITE)
+ _about_to_complete_local_write(mdev, req);
+
+ /* Update disk stats */
+ _drbd_end_io_acct(mdev, req);
+
+ _complete_master_bio(mdev, req,
+ ok ? 0 : (error ? error : -EIO));
+ } else {
+ /* only WRITE requests can end up here without a master_bio */
+ rw = WRITE;
+ }
+
+ if ((s & RQ_NET_MASK) == 0 || (s & RQ_NET_DONE)) {
+ /* this is disconnected (local only) operation,
+ * or protocol C P_WRITE_ACK,
+ * or protocol A or B P_BARRIER_ACK,
+ * or killed from the transfer log due to connection loss. */
+ _req_is_done(mdev, req, rw);
+ }
+ /* else: network part and not DONE yet. that is
+ * protocol A or B, barrier ack still pending... */
+}
+
+/*
+ * checks whether there was an overlapping request
+ * or ee already registered.
+ *
+ * if so, return 1, in which case this request is completed on the spot,
+ * without ever being submitted or send.
+ *
+ * return 0 if it is ok to submit this request.
+ *
+ * NOTE:
+ * paranoia: assume something above us is broken, and issues different write
+ * requests for the same block simultaneously...
+ *
+ * To ensure these won't be reordered differently on both nodes, resulting in
+ * diverging data sets, we discard the later one(s). Not that this is supposed
+ * to happen, but this is the rationale why we also have to check for
+ * conflicting requests with local origin, and why we have to do so regardless
+ * of whether we allowed multiple primaries.
+ *
+ * BTW, in case we only have one primary, the ee_hash is empty anyways, and the
+ * second hlist_for_each_entry becomes a noop. This is even simpler than to
+ * grab a reference on the net_conf, and check for the two_primaries flag...
+ */
+static int _req_conflicts(struct drbd_request *req)
+{
+ struct drbd_conf *mdev = req->mdev;
+ const sector_t sector = req->sector;
+ const int size = req->size;
+ struct drbd_request *i;
+ struct drbd_epoch_entry *e;
+ struct hlist_node *n;
+ struct hlist_head *slot;
+
+ D_ASSERT(hlist_unhashed(&req->colision));
+
+ if (!get_net_conf(mdev))
+ return 0;
+
+ /* BUG_ON */
+ ERR_IF (mdev->tl_hash_s == 0)
+ goto out_no_conflict;
+ BUG_ON(mdev->tl_hash == NULL);
+
+#define OVERLAPS overlaps(i->sector, i->size, sector, size)
+ slot = tl_hash_slot(mdev, sector);
+ hlist_for_each_entry(i, n, slot, colision) {
+ if (OVERLAPS) {
+ dev_alert(DEV, "%s[%u] Concurrent local write detected! "
+ "[DISCARD L] new: %llus +%u; "
+ "pending: %llus +%u\n",
+ current->comm, current->pid,
+ (unsigned long long)sector, size,
+ (unsigned long long)i->sector, i->size);
+ goto out_conflict;
+ }
+ }
+
+ if (mdev->ee_hash_s) {
+ /* now, check for overlapping requests with remote origin */
+ BUG_ON(mdev->ee_hash == NULL);
+#undef OVERLAPS
+#define OVERLAPS overlaps(e->sector, e->size, sector, size)
+ slot = ee_hash_slot(mdev, sector);
+ hlist_for_each_entry(e, n, slot, colision) {
+ if (OVERLAPS) {
+ dev_alert(DEV, "%s[%u] Concurrent remote write detected!"
+ " [DISCARD L] new: %llus +%u; "
+ "pending: %llus +%u\n",
+ current->comm, current->pid,
+ (unsigned long long)sector, size,
+ (unsigned long long)e->sector, e->size);
+ goto out_conflict;
+ }
+ }
+ }
+#undef OVERLAPS
+
+out_no_conflict:
+ /* this is like it should be, and what we expected.
+ * our users do behave after all... */
+ put_net_conf(mdev);
+ return 0;
+
+out_conflict:
+ put_net_conf(mdev);
+ return 1;
+}
+
+/* obviously this could be coded as many single functions
+ * instead of one huge switch,
+ * or by putting the code directly in the respective locations
+ * (as it has been before).
+ *
+ * but having it this way
+ * enforces that it is all in this one place, where it is easier to audit,
+ * it makes it obvious that whatever "event" "happens" to a request should
+ * happen "atomically" within the req_lock,
+ * and it enforces that we have to think in a very structured manner
+ * about the "events" that may happen to a request during its life time ...
+ */
+void _req_mod(struct drbd_request *req, enum drbd_req_event what, int error)
+{
+ struct drbd_conf *mdev = req->mdev;
+
+ if (error && (bio_rw(req->master_bio) != READA))
+ dev_err(DEV, "got an _req_mod() errno of %d\n", error);
+
+ trace_drbd_req(req, what, NULL);
+
+ switch (what) {
+ default:
+ dev_err(DEV, "LOGIC BUG in %s:%u\n", __FILE__ , __LINE__);
+ return;
+
+ /* does not happen...
+ * initialization done in drbd_req_new
+ case created:
+ break;
+ */
+
+ case to_be_send: /* via network */
+ /* reached via drbd_make_request_common
+ * and from w_read_retry_remote */
+ D_ASSERT(!(req->rq_state & RQ_NET_MASK));
+ req->rq_state |= RQ_NET_PENDING;
+ inc_ap_pending(mdev);
+ break;
+
+ case to_be_submitted: /* locally */
+ /* reached via drbd_make_request_common */
+ D_ASSERT(!(req->rq_state & RQ_LOCAL_MASK));
+ req->rq_state |= RQ_LOCAL_PENDING;
+ break;
+
+ case completed_ok:
+ if (bio_data_dir(req->private_bio) == WRITE)
+ mdev->writ_cnt += req->size>>9;
+ else
+ mdev->read_cnt += req->size>>9;
+
+ bio_put(req->private_bio);
+ req->private_bio = NULL;
+
+ req->rq_state |= (RQ_LOCAL_COMPLETED|RQ_LOCAL_OK);
+ req->rq_state &= ~RQ_LOCAL_PENDING;
+
+ _req_may_be_done(req, error);
+ put_ldev(mdev);
+ break;
+
+ case write_completed_with_error:
+ req->rq_state |= RQ_LOCAL_COMPLETED;
+ req->rq_state &= ~RQ_LOCAL_PENDING;
+
+ bio_put(req->private_bio);
+ req->private_bio = NULL;
+ dev_alert(DEV, "Local WRITE failed sec=%llus size=%u\n",
+ (unsigned long long)req->sector, req->size);
+ /* and now: check how to handle local io error. */
+ __drbd_chk_io_error(mdev, FALSE);
+ _req_may_be_done(req, error);
+ put_ldev(mdev);
+ break;
+
+ case read_completed_with_error:
+ if (bio_rw(req->master_bio) != READA)
+ drbd_set_out_of_sync(mdev, req->sector, req->size);
+
+ req->rq_state |= RQ_LOCAL_COMPLETED;
+ req->rq_state &= ~RQ_LOCAL_PENDING;
+
+ bio_put(req->private_bio);
+ req->private_bio = NULL;
+ if (bio_rw(req->master_bio) == READA) {
+ /* it is legal to fail READA */
+ _req_may_be_done(req, error);
+ put_ldev(mdev);
+ break;
+ }
+ /* else */
+ dev_alert(DEV, "Local READ failed sec=%llus size=%u\n",
+ (unsigned long long)req->sector, req->size);
+ /* _req_mod(req,to_be_send); oops, recursion... */
+ D_ASSERT(!(req->rq_state & RQ_NET_MASK));
+ req->rq_state |= RQ_NET_PENDING;
+ inc_ap_pending(mdev);
+
+ __drbd_chk_io_error(mdev, FALSE);
+ put_ldev(mdev);
+ /* NOTE: if we have no connection,
+ * or know the peer has no good data either,
+ * then we don't actually need to "queue_for_net_read",
+ * but we do so anyways, since the drbd_io_error()
+ * and the potential state change to "Diskless"
+ * needs to be done from process context */
+
+ /* fall through: _req_mod(req,queue_for_net_read); */
+
+ case queue_for_net_read:
+ /* READ or READA, and
+ * no local disk,
+ * or target area marked as invalid,
+ * or just got an io-error. */
+ /* from drbd_make_request_common
+ * or from bio_endio during read io-error recovery */
+
+ /* so we can verify the handle in the answer packet
+ * corresponding hlist_del is in _req_may_be_done() */
+ hlist_add_head(&req->colision, ar_hash_slot(mdev, req->sector));
+
+ set_bit(UNPLUG_REMOTE, &mdev->flags); /* why? */
+
+ D_ASSERT(req->rq_state & RQ_NET_PENDING);
+ req->rq_state |= RQ_NET_QUEUED;
+ req->w.cb = (req->rq_state & RQ_LOCAL_MASK)
+ ? w_read_retry_remote
+ : w_send_read_req;
+ drbd_queue_work(&mdev->data.work, &req->w);
+ break;
+
+ case queue_for_net_write:
+ /* assert something? */
+ /* from drbd_make_request_common only */
+
+ hlist_add_head(&req->colision, tl_hash_slot(mdev, req->sector));
+ /* corresponding hlist_del is in _req_may_be_done() */
+
+ /* NOTE
+ * In case the req ended up on the transfer log before being
+ * queued on the worker, it could lead to this request being
+ * missed during cleanup after connection loss.
+ * So we have to do both operations here,
+ * within the same lock that protects the transfer log.
+ *
+ * _req_add_to_epoch(req); this has to be after the
+ * _maybe_start_new_epoch(req); which happened in
+ * drbd_make_request_common, because we now may set the bit
+ * again ourselves to close the current epoch.
+ *
+ * Add req to the (now) current epoch (barrier). */
+
+ /* see drbd_make_request_common,
+ * just after it grabs the req_lock */
+ D_ASSERT(test_bit(CREATE_BARRIER, &mdev->flags) == 0);
+
+ req->epoch = mdev->newest_tle->br_number;
+ list_add_tail(&req->tl_requests,
+ &mdev->newest_tle->requests);
+
+ /* increment size of current epoch */
+ mdev->newest_tle->n_req++;
+
+ /* queue work item to send data */
+ D_ASSERT(req->rq_state & RQ_NET_PENDING);
+ req->rq_state |= RQ_NET_QUEUED;
+ req->w.cb = w_send_dblock;
+ drbd_queue_work(&mdev->data.work, &req->w);
+
+ /* close the epoch, in case it outgrew the limit */
+ if (mdev->newest_tle->n_req >= mdev->net_conf->max_epoch_size)
+ queue_barrier(mdev);
+
+ break;
+
+ case send_canceled:
+ /* treat it the same */
+ case send_failed:
+ /* real cleanup will be done from tl_clear. just update flags
+ * so it is no longer marked as on the worker queue */
+ req->rq_state &= ~RQ_NET_QUEUED;
+ /* if we did it right, tl_clear should be scheduled only after
+ * this, so this should not be necessary! */
+ _req_may_be_done(req, error);
+ break;
+
+ case handed_over_to_network:
+ /* assert something? */
+ if (bio_data_dir(req->master_bio) == WRITE &&
+ mdev->net_conf->wire_protocol == DRBD_PROT_A) {
+ /* this is what is dangerous about protocol A:
+ * pretend it was sucessfully written on the peer. */
+ if (req->rq_state & RQ_NET_PENDING) {
+ dec_ap_pending(mdev);
+ req->rq_state &= ~RQ_NET_PENDING;
+ req->rq_state |= RQ_NET_OK;
+ } /* else: neg-ack was faster... */
+ /* it is still not yet RQ_NET_DONE until the
+ * corresponding epoch barrier got acked as well,
+ * so we know what to dirty on connection loss */
+ }
+ req->rq_state &= ~RQ_NET_QUEUED;
+ req->rq_state |= RQ_NET_SENT;
+ /* because _drbd_send_zc_bio could sleep, and may want to
+ * dereference the bio even after the "write_acked_by_peer" and
+ * "completed_ok" events came in, once we return from
+ * _drbd_send_zc_bio (drbd_send_dblock), we have to check
+ * whether it is done already, and end it. */
+ _req_may_be_done(req, error);
+ break;
+
+ case connection_lost_while_pending:
+ /* transfer log cleanup after connection loss */
+ /* assert something? */
+ if (req->rq_state & RQ_NET_PENDING)
+ dec_ap_pending(mdev);
+ req->rq_state &= ~(RQ_NET_OK|RQ_NET_PENDING);
+ req->rq_state |= RQ_NET_DONE;
+ /* if it is still queued, we may not complete it here.
+ * it will be canceled soon. */
+ if (!(req->rq_state & RQ_NET_QUEUED))
+ _req_may_be_done(req, error);
+ break;
+
+ case write_acked_by_peer_and_sis:
+ req->rq_state |= RQ_NET_SIS;
+ case conflict_discarded_by_peer:
+ /* for discarded conflicting writes of multiple primarys,
+ * there is no need to keep anything in the tl, potential
+ * node crashes are covered by the activity log. */
+ req->rq_state |= RQ_NET_DONE;
+ /* fall through */
+ case write_acked_by_peer:
+ /* protocol C; successfully written on peer.
+ * Nothing to do here.
+ * We want to keep the tl in place for all protocols, to cater
+ * for volatile write-back caches on lower level devices.
+ *
+ * A barrier request is expected to have forced all prior
+ * requests onto stable storage, so completion of a barrier
+ * request could set NET_DONE right here, and not wait for the
+ * P_BARRIER_ACK, but that is an unecessary optimisation. */
+
+ /* this makes it effectively the same as for: */
+ case recv_acked_by_peer:
+ /* protocol B; pretends to be sucessfully written on peer.
+ * see also notes above in handed_over_to_network about
+ * protocol != C */
+ req->rq_state |= RQ_NET_OK;
+ D_ASSERT(req->rq_state & RQ_NET_PENDING);
+ dec_ap_pending(mdev);
+ req->rq_state &= ~RQ_NET_PENDING;
+ _req_may_be_done(req, error);
+ break;
+
+ case neg_acked:
+ /* assert something? */
+ if (req->rq_state & RQ_NET_PENDING)
+ dec_ap_pending(mdev);
+ req->rq_state &= ~(RQ_NET_OK|RQ_NET_PENDING);
+
+ req->rq_state |= RQ_NET_DONE;
+ _req_may_be_done(req, error);
+ /* else: done by handed_over_to_network */
+ break;
+
+ case barrier_acked:
+ if (req->rq_state & RQ_NET_PENDING) {
+ /* barrier came in before all requests have been acked.
+ * this is bad, because if the connection is lost now,
+ * we won't be able to clean them up... */
+ dev_err(DEV, "FIXME (barrier_acked but pending)\n");
+ trace_drbd_req(req, nothing, "FIXME (barrier_acked but pending)");
+ list_move(&req->tl_requests, &mdev->out_of_sequence_requests);
+ }
+ D_ASSERT(req->rq_state & RQ_NET_SENT);
+ req->rq_state |= RQ_NET_DONE;
+ _req_may_be_done(req, error);
+ break;
+
+ case data_received:
+ D_ASSERT(req->rq_state & RQ_NET_PENDING);
+ dec_ap_pending(mdev);
+ req->rq_state &= ~RQ_NET_PENDING;
+ req->rq_state |= (RQ_NET_OK|RQ_NET_DONE);
+ _req_may_be_done(req, error);
+ break;
+ };
+}
+
+/* we may do a local read if:
+ * - we are consistent (of course),
+ * - or we are generally inconsistent,
+ * BUT we are still/already IN SYNC for this area.
+ * since size may be bigger than BM_BLOCK_SIZE,
+ * we may need to check several bits.
+ */
+static int drbd_may_do_local_read(struct drbd_conf *mdev, sector_t sector, int size)
+{
+ unsigned long sbnr, ebnr;
+ sector_t esector, nr_sectors;
+
+ if (mdev->state.disk == D_UP_TO_DATE)
+ return 1;
+ if (mdev->state.disk >= D_OUTDATED)
+ return 0;
+ if (mdev->state.disk < D_INCONSISTENT)
+ return 0;
+ /* state.disk == D_INCONSISTENT We will have a look at the BitMap */
+ nr_sectors = drbd_get_capacity(mdev->this_bdev);
+ esector = sector + (size >> 9) - 1;
+
+ D_ASSERT(sector < nr_sectors);
+ D_ASSERT(esector < nr_sectors);
+
+ sbnr = BM_SECT_TO_BIT(sector);
+ ebnr = BM_SECT_TO_BIT(esector);
+
+ return 0 == drbd_bm_count_bits(mdev, sbnr, ebnr);
+}
+
+static int drbd_make_request_common(struct drbd_conf *mdev, struct bio *bio)
+{
+ const int rw = bio_rw(bio);
+ const int size = bio->bi_size;
+ const sector_t sector = bio->bi_sector;
+ struct drbd_tl_epoch *b = NULL;
+ struct drbd_request *req;
+ int local, remote;
+ int err = -EIO;
+
+ /* allocate outside of all locks; */
+ req = drbd_req_new(mdev, bio);
+ if (!req) {
+ dec_ap_bio(mdev);
+ /* only pass the error to the upper layers.
+ * if user cannot handle io errors, thats not our business. */
+ dev_err(DEV, "could not kmalloc() req\n");
+ bio_endio(bio, -ENOMEM);
+ return 0;
+ }
+
+ trace_drbd_bio(mdev, "Rq", bio, 0, req);
+
+ local = get_ldev(mdev);
+ if (!local) {
+ bio_put(req->private_bio); /* or we get a bio leak */
+ req->private_bio = NULL;
+ }
+ if (rw == WRITE) {
+ remote = 1;
+ } else {
+ /* READ || READA */
+ if (local) {
+ if (!drbd_may_do_local_read(mdev, sector, size)) {
+ /* we could kick the syncer to
+ * sync this extent asap, wait for
+ * it, then continue locally.
+ * Or just issue the request remotely.
+ */
+ local = 0;
+ bio_put(req->private_bio);
+ req->private_bio = NULL;
+ put_ldev(mdev);
+ }
+ }
+ remote = !local && mdev->state.pdsk >= D_UP_TO_DATE;
+ }
+
+ /* If we have a disk, but a READA request is mapped to remote,
+ * we are R_PRIMARY, D_INCONSISTENT, SyncTarget.
+ * Just fail that READA request right here.
+ *
+ * THINK: maybe fail all READA when not local?
+ * or make this configurable...
+ * if network is slow, READA won't do any good.
+ */
+ if (rw == READA && mdev->state.disk >= D_INCONSISTENT && !local) {
+ err = -EWOULDBLOCK;
+ goto fail_and_free_req;
+ }
+
+ /* For WRITES going to the local disk, grab a reference on the target
+ * extent. This waits for any resync activity in the corresponding
+ * resync extent to finish, and, if necessary, pulls in the target
+ * extent into the activity log, which involves further disk io because
+ * of transactional on-disk meta data updates. */
+ if (rw == WRITE && local)
+ drbd_al_begin_io(mdev, sector);
+
+ remote = remote && (mdev->state.pdsk == D_UP_TO_DATE ||
+ (mdev->state.pdsk == D_INCONSISTENT &&
+ mdev->state.conn >= C_CONNECTED));
+
+ if (!(local || remote)) {
+ dev_err(DEV, "IO ERROR: neither local nor remote disk\n");
+ goto fail_free_complete;
+ }
+
+ /* For WRITE request, we have to make sure that we have an
+ * unused_spare_tle, in case we need to start a new epoch.
+ * I try to be smart and avoid to pre-allocate always "just in case",
+ * but there is a race between testing the bit and pointer outside the
+ * spinlock, and grabbing the spinlock.
+ * if we lost that race, we retry. */
+ if (rw == WRITE && remote &&
+ mdev->unused_spare_tle == NULL &&
+ test_bit(CREATE_BARRIER, &mdev->flags)) {
+allocate_barrier:
+ b = kmalloc(sizeof(struct drbd_tl_epoch), GFP_NOIO);
+ if (!b) {
+ dev_err(DEV, "Failed to alloc barrier.\n");
+ err = -ENOMEM;
+ goto fail_free_complete;
+ }
+ }
+
+ /* GOOD, everything prepared, grab the spin_lock */
+ spin_lock_irq(&mdev->req_lock);
+
+ if (remote) {
+ remote = (mdev->state.pdsk == D_UP_TO_DATE ||
+ (mdev->state.pdsk == D_INCONSISTENT &&
+ mdev->state.conn >= C_CONNECTED));
+ if (!remote)
+ dev_warn(DEV, "lost connection while grabbing the req_lock!\n");
+ if (!(local || remote)) {
+ dev_err(DEV, "IO ERROR: neither local nor remote disk\n");
+ spin_unlock_irq(&mdev->req_lock);
+ goto fail_free_complete;
+ }
+ }
+
+ if (b && mdev->unused_spare_tle == NULL) {
+ mdev->unused_spare_tle = b;
+ b = NULL;
+ }
+ if (rw == WRITE && remote &&
+ mdev->unused_spare_tle == NULL &&
+ test_bit(CREATE_BARRIER, &mdev->flags)) {
+ /* someone closed the current epoch
+ * while we were grabbing the spinlock */
+ spin_unlock_irq(&mdev->req_lock);
+ goto allocate_barrier;
+ }
+
+
+ /* Update disk stats */
+ _drbd_start_io_acct(mdev, req, bio);
+
+ /* _maybe_start_new_epoch(mdev);
+ * If we need to generate a write barrier packet, we have to add the
+ * new epoch (barrier) object, and queue the barrier packet for sending,
+ * and queue the req's data after it _within the same lock_, otherwise
+ * we have race conditions were the reorder domains could be mixed up.
+ *
+ * Even read requests may start a new epoch and queue the corresponding
+ * barrier packet. To get the write ordering right, we only have to
+ * make sure that, if this is a write request and it triggered a
+ * barrier packet, this request is queued within the same spinlock. */
+ if (remote && mdev->unused_spare_tle &&
+ test_and_clear_bit(CREATE_BARRIER, &mdev->flags)) {
+ _tl_add_barrier(mdev, mdev->unused_spare_tle);
+ mdev->unused_spare_tle = NULL;
+ } else {
+ D_ASSERT(!(remote && rw == WRITE &&
+ test_bit(CREATE_BARRIER, &mdev->flags)));
+ }
+
+ /* NOTE
+ * Actually, 'local' may be wrong here already, since we may have failed
+ * to write to the meta data, and may become wrong anytime because of
+ * local io-error for some other request, which would lead to us
+ * "detaching" the local disk.
+ *
+ * 'remote' may become wrong any time because the network could fail.
+ *
+ * This is a harmless race condition, though, since it is handled
+ * correctly at the appropriate places; so it just deferres the failure
+ * of the respective operation.
+ */
+
+ /* mark them early for readability.
+ * this just sets some state flags. */
+ if (remote)
+ _req_mod(req, to_be_send, 0);
+ if (local)
+ _req_mod(req, to_be_submitted, 0);
+
+ /* check this request on the colison detection hash tables.
+ * if we have a conflict, just complete it here.
+ * THINK do we want to check reads, too? (I don't think so...) */
+ if (rw == WRITE && _req_conflicts(req)) {
+ /* this is a conflicting request.
+ * even though it may have been only _partially_
+ * overlapping with one of the currently pending requests,
+ * without even submitting or sending it, we will
+ * pretend that it was successfully served right now.
+ */
+ if (local) {
+ bio_put(req->private_bio);
+ req->private_bio = NULL;
+ drbd_al_complete_io(mdev, req->sector);
+ put_ldev(mdev);
+ local = 0;
+ }
+ if (remote)
+ dec_ap_pending(mdev);
+ _drbd_end_io_acct(mdev, req);
+ /* THINK: do we want to fail it (-EIO), or pretend success? */
+ bio_endio(req->master_bio, 0);
+ req->master_bio = NULL;
+ dec_ap_bio(mdev);
+ drbd_req_free(req);
+ remote = 0;
+ }
+
+ /* NOTE remote first: to get the concurrent write detection right,
+ * we must register the request before start of local IO. */
+ if (remote) {
+ /* either WRITE and C_CONNECTED,
+ * or READ, and no local disk,
+ * or READ, but not in sync.
+ */
+ if (rw == WRITE)
+ _req_mod(req, queue_for_net_write, 0);
+ else
+ _req_mod(req, queue_for_net_read, 0);
+ }
+ spin_unlock_irq(&mdev->req_lock);
+ kfree(b); /* if someone else has beaten us to it... */
+
+ if (local) {
+ req->private_bio->bi_bdev = mdev->ldev->backing_bdev;
+
+ trace_drbd_bio(mdev, "Pri", req->private_bio, 0, NULL);
+
+ if (FAULT_ACTIVE(mdev, rw == WRITE ? DRBD_FAULT_DT_WR
+ : rw == READ ? DRBD_FAULT_DT_RD
+ : DRBD_FAULT_DT_RA))
+ bio_endio(req->private_bio, -EIO);
+ else
+ generic_make_request(req->private_bio);
+ }
+
+ /* we need to plug ALWAYS since we possibly need to kick lo_dev.
+ * we plug after submit, so we won't miss an unplug event */
+ drbd_plug_device(mdev);
+
+ return 0;
+
+fail_free_complete:
+ if (rw == WRITE && local)
+ drbd_al_complete_io(mdev, sector);
+fail_and_free_req:
+ if (local) {
+ bio_put(req->private_bio);
+ req->private_bio = NULL;
+ put_ldev(mdev);
+ }
+ bio_endio(bio, err);
+ drbd_req_free(req);
+ dec_ap_bio(mdev);
+ kfree(b);
+
+ return 0;
+}
+
+/* helper function for drbd_make_request
+ * if we can determine just by the mdev (state) that this request will fail,
+ * return 1
+ * otherwise return 0
+ */
+static int drbd_fail_request_early(struct drbd_conf *mdev, int is_write)
+{
+ /* Unconfigured */
+ if (mdev->state.conn == C_DISCONNECTING &&
+ mdev->state.disk == D_DISKLESS)
+ return 1;
+
+ if (mdev->state.role != R_PRIMARY &&
+ (!allow_oos || is_write)) {
+ if (__ratelimit(&drbd_ratelimit_state)) {
+ dev_err(DEV, "Process %s[%u] tried to %s; "
+ "since we are not in Primary state, "
+ "we cannot allow this\n",
+ current->comm, current->pid,
+ is_write ? "WRITE" : "READ");
+ }
+ return 1;
+ }
+
+ /*
+ * Paranoia: we might have been primary, but sync target, or
+ * even diskless, then lost the connection.
+ * This should have been handled (panic? suspend?) somehwere
+ * else. But maybe it was not, so check again here.
+ * Caution: as long as we do not have a read/write lock on mdev,
+ * to serialize state changes, this is racy, since we may lose
+ * the connection *after* we test for the cstate.
+ */
+ if (mdev->state.disk < D_UP_TO_DATE && mdev->state.pdsk < D_UP_TO_DATE) {
+ if (__ratelimit(&drbd_ratelimit_state))
+ dev_err(DEV, "Sorry, I have no access to good data anymore.\n");
+ return 1;
+ }
+
+ return 0;
+}
+
+int drbd_make_request_26(struct request_queue *q, struct bio *bio)
+{
+ unsigned int s_enr, e_enr;
+ struct drbd_conf *mdev = (struct drbd_conf *) q->queuedata;
+
+ if (drbd_fail_request_early(mdev, bio_data_dir(bio) & WRITE)) {
+ bio_endio(bio, -EPERM);
+ return 0;
+ }
+
+ /* Reject barrier requests if we know the underlying device does
+ * not support them.
+ * XXX: Need to get this info from peer as well some how so we
+ * XXX: reject if EITHER side/data/metadata area does not support them.
+ *
+ * because of those XXX, this is not yet enabled,
+ * i.e. in drbd_init_set_defaults we set the NO_BARRIER_SUPP bit.
+ */
+ if (unlikely(bio_barrier(bio) && test_bit(NO_BARRIER_SUPP, &mdev->flags))) {
+ /* dev_warn(DEV, "Rejecting barrier request as underlying device does not support\n"); */
+ bio_endio(bio, -EOPNOTSUPP);
+ return 0;
+ }
+
+ /*
+ * what we "blindly" assume:
+ */
+ D_ASSERT(bio->bi_size > 0);
+ D_ASSERT((bio->bi_size & 0x1ff) == 0);
+ D_ASSERT(bio->bi_idx == 0);
+
+ /* to make some things easier, force allignment of requests within the
+ * granularity of our hash tables */
+ s_enr = bio->bi_sector >> HT_SHIFT;
+ e_enr = (bio->bi_sector+(bio->bi_size>>9)-1) >> HT_SHIFT;
+
+ if (likely(s_enr == e_enr)) {
+ inc_ap_bio(mdev, 1);
+ return drbd_make_request_common(mdev, bio);
+ }
+
+ /* can this bio be split generically?
+ * Maybe add our own split-arbitrary-bios function. */
+ if (bio->bi_vcnt != 1 || bio->bi_idx != 0 || bio->bi_size > DRBD_MAX_SEGMENT_SIZE) {
+ /* rather error out here than BUG in bio_split */
+ dev_err(DEV, "bio would need to, but cannot, be split: "
+ "(vcnt=%u,idx=%u,size=%u,sector=%llu)\n",
+ bio->bi_vcnt, bio->bi_idx, bio->bi_size,
+ (unsigned long long)bio->bi_sector);
+ bio_endio(bio, -EINVAL);
+ } else {
+ /* This bio crosses some boundary, so we have to split it. */
+ struct bio_pair *bp;
+ /* works for the "do not cross hash slot boundaries" case
+ * e.g. sector 262269, size 4096
+ * s_enr = 262269 >> 6 = 4097
+ * e_enr = (262269+8-1) >> 6 = 4098
+ * HT_SHIFT = 6
+ * sps = 64, mask = 63
+ * first_sectors = 64 - (262269 & 63) = 3
+ */
+ const sector_t sect = bio->bi_sector;
+ const int sps = 1 << HT_SHIFT; /* sectors per slot */
+ const int mask = sps - 1;
+ const sector_t first_sectors = sps - (sect & mask);
+ bp = bio_split(bio,
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,28)
+ bio_split_pool,
+#endif
+ first_sectors);
+
+ /* we need to get a "reference count" (ap_bio_cnt)
+ * to avoid races with the disconnect/reconnect/suspend code.
+ * In case we need to split the bio here, we need to get two references
+ * atomically, otherwise we might deadlock when trying to submit the
+ * second one! */
+ inc_ap_bio(mdev, 2);
+
+ D_ASSERT(e_enr == s_enr + 1);
+
+ drbd_make_request_common(mdev, &bp->bio1);
+ drbd_make_request_common(mdev, &bp->bio2);
+ bio_pair_release(bp);
+ }
+ return 0;
+}
+
+/* This is called by bio_add_page(). With this function we reduce
+ * the number of BIOs that span over multiple DRBD_MAX_SEGMENT_SIZEs
+ * units (was AL_EXTENTs).
+ *
+ * we do the calculation within the lower 32bit of the byte offsets,
+ * since we don't care for actual offset, but only check whether it
+ * would cross "activity log extent" boundaries.
+ *
+ * As long as the BIO is emtpy we have to allow at least one bvec,
+ * regardless of size and offset. so the resulting bio may still
+ * cross extent boundaries. those are dealt with (bio_split) in
+ * drbd_make_request_26.
+ */
+int drbd_merge_bvec(struct request_queue *q, struct bvec_merge_data *bvm, struct bio_vec *bvec)
+{
+ struct drbd_conf *mdev = (struct drbd_conf *) q->queuedata;
+ unsigned int bio_offset =
+ (unsigned int)bvm->bi_sector << 9; /* 32 bit */
+ unsigned int bio_size = bvm->bi_size;
+ int limit, backing_limit;
+
+ limit = DRBD_MAX_SEGMENT_SIZE
+ - ((bio_offset & (DRBD_MAX_SEGMENT_SIZE-1)) + bio_size);
+ if (limit < 0)
+ limit = 0;
+ if (bio_size == 0) {
+ if (limit <= bvec->bv_len)
+ limit = bvec->bv_len;
+ } else if (limit && get_ldev(mdev)) {
+ struct request_queue * const b =
+ mdev->ldev->backing_bdev->bd_disk->queue;
+ if (b->merge_bvec_fn && mdev->ldev->dc.use_bmbv) {
+ backing_limit = b->merge_bvec_fn(b, bvm, bvec);
+ limit = min(limit, backing_limit);
+ }
+ put_ldev(mdev);
+ }
+ return limit;
+}
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