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linux/drivers/block/drbd/drbd_req.c

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/*
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@linbit.com>.
Copyright (C) 2002-2008, Lars Ellenberg <lars.ellenberg@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/module.h>
#include <linux/slab.h>
#include <linux/drbd.h>
#include "drbd_int.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_inc_in_flight(&mdev->vdisk->part0, rw);
part_stat_unlock();
}
/* 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_dec_in_flight(&mdev->vdisk->part0, rw);
part_stat_unlock();
}
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
* initialized 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);
}
}
}
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
}
void complete_master_bio(struct drbd_conf *mdev,
struct bio_and_error *m)
{
bio_endio(m->bio, m->error);
dec_ap_bio(mdev);
}
/* Helper for __req_mod().
* Set m->bio to the master bio, if it is fit to be completed,
* or leave it alone (it is initialized to NULL in __req_mod),
* if it has already been completed, or cannot be completed yet.
* If m->bio is set, the error status to be returned is placed in m->error.
*/
void _req_may_be_done(struct drbd_request *req, struct bio_and_error *m)
{
const unsigned long s = req->rq_state;
struct drbd_conf *mdev = req->mdev;
/* only WRITES may end up here without a master bio (on barrier ack) */
int rw = req->master_bio ? bio_data_dir(req->master_bio) : WRITE;
/* 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 succeeded.
* 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.
*
* local completion error, if any, has been stored as ERR_PTR
* in private_bio within drbd_endio_pri.
*/
int ok = (s & RQ_LOCAL_OK) || (s & RQ_NET_OK);
int error = PTR_ERR(req->private_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);
m->error = ok ? 0 : (error ?: -EIO);
m->bio = req->master_bio;
req->master_bio = NULL;
}
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,
struct bio_and_error *m)
{
struct drbd_conf *mdev = req->mdev;
m->bio = NULL;
switch (what) {
default:
dev_err(DEV, "LOGIC BUG in %s:%u\n", __FILE__ , __LINE__);
break;
/* 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->master_bio) == WRITE)
mdev->writ_cnt += req->size>>9;
else
mdev->read_cnt += req->size>>9;
req->rq_state |= (RQ_LOCAL_COMPLETED|RQ_LOCAL_OK);
req->rq_state &= ~RQ_LOCAL_PENDING;
_req_may_be_done(req, m);
put_ldev(mdev);
break;
case write_completed_with_error:
req->rq_state |= RQ_LOCAL_COMPLETED;
req->rq_state &= ~RQ_LOCAL_PENDING;
__drbd_chk_io_error(mdev, FALSE);
_req_may_be_done(req, m);
put_ldev(mdev);
break;
case read_ahead_completed_with_error:
/* it is legal to fail READA */
req->rq_state |= RQ_LOCAL_COMPLETED;
req->rq_state &= ~RQ_LOCAL_PENDING;
_req_may_be_done(req, m);
put_ldev(mdev);
break;
case read_completed_with_error:
drbd_set_out_of_sync(mdev, req->sector, req->size);
req->rq_state |= RQ_LOCAL_COMPLETED;
req->rq_state &= ~RQ_LOCAL_PENDING;
D_ASSERT(!(req->rq_state & RQ_NET_MASK));
__drbd_chk_io_error(mdev, FALSE);
put_ldev(mdev);
/* no point in retrying if there is no good remote data,
* or we have no connection. */
if (mdev->state.pdsk != D_UP_TO_DATE) {
_req_may_be_done(req, m);
break;
}
/* _req_mod(req,to_be_send); oops, recursion... */
req->rq_state |= RQ_NET_PENDING;
inc_ap_pending(mdev);
/* 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);
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). */
/* otherwise we may lose an unplug, which may cause some remote
* io-scheduler timeout to expire, increasing maximum latency,
* hurting performance. */
set_bit(UNPLUG_REMOTE, &mdev->flags);
/* 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, m);
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 successfully 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, m);
break;
case read_retry_remote_canceled:
req->rq_state &= ~RQ_NET_QUEUED;
/* fall through, in case we raced with drbd_disconnect */
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, m);
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 primaries,
* there is no need to keep anything in the tl, potential
* node crashes are covered by the activity log. */
if (what == conflict_discarded_by_peer)
dev_alert(DEV, "Got DiscardAck packet %llus +%u!"
" DRBD is not a random data generator!\n",
(unsigned long long)req->sector, req->size);
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 unnecessary optimization. */
/* this makes it effectively the same as for: */
case recv_acked_by_peer:
/* protocol B; pretends to be successfully 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, m);
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, m);
/* 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");
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, m);
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, m);
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;
int ret = 0;
/* 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, that's not our business. */
dev_err(DEV, "could not kmalloc() req\n");
bio_endio(bio, -ENOMEM);
return 0;
}
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) && !mdev->state.susp) {
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 (mdev->state.susp) {
/* If we got suspended, use the retry mechanism of
generic_make_request() to restart processing of this
bio. In the next call to drbd_make_request_26
we sleep in inc_ap_bio() */
ret = 1;
spin_unlock_irq(&mdev->req_lock);
goto fail_free_complete;
}
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 defers 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);
if (local)
_req_mod(req, to_be_submitted);
/* check this request on the collision 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.
*/
_req_mod(req, (rw == WRITE)
? queue_for_net_write
: queue_for_net_read);
}
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;
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);
}
if (!ret)
bio_endio(bio, err);
drbd_req_free(req);
dec_ap_bio(mdev);
kfree(b);
return ret;
}
/* 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)
{
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?) somewhere
* 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->bi_rw & REQ_HARDBARRIER) && 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 alignment 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 three references
* atomically, otherwise we might deadlock when trying to submit the
* second one! */
inc_ap_bio(mdev, 3);
D_ASSERT(e_enr == s_enr + 1);
while (drbd_make_request_common(mdev, &bp->bio1))
inc_ap_bio(mdev, 1);
while (drbd_make_request_common(mdev, &bp->bio2))
inc_ap_bio(mdev, 1);
dec_ap_bio(mdev);
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 empty 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) {
backing_limit = b->merge_bvec_fn(b, bvm, bvec);
limit = min(limit, backing_limit);
}
put_ldev(mdev);
}
return limit;
}
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