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raid1.c
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/*
* raid1.c : Multiple Devices driver for Linux
*
* Copyright (C) 1999, 2000, 2001 Ingo Molnar, Red Hat
*
* Copyright (C) 1996, 1997, 1998 Ingo Molnar, Miguel de Icaza, Gadi Oxman
*
* RAID-1 management functions.
*
* Better read-balancing code written by Mika Kuoppala <miku@iki.fi>, 2000
*
* Fixes to reconstruction by Jakob Østergaard" <jakob@ostenfeld.dk>
* Various fixes by Neil Brown <neilb@cse.unsw.edu.au>
*
* Changes by Peter T. Breuer <ptb@it.uc3m.es> 31/1/2003 to support
* bitmapped intelligence in resync:
*
* - bitmap marked during normal i/o
* - bitmap used to skip nondirty blocks during sync
*
* Additions to bitmap code, (C) 2003-2004 Paul Clements, SteelEye Technology:
* - persistent bitmap code
*
* This program 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.
*
* You should have received a copy of the GNU General Public License
* (for example /usr/src/linux/COPYING); if not, write to the Free
* Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <linux/slab.h>
#include <linux/delay.h>
#include <linux/blkdev.h>
#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/ratelimit.h>
#include <linux/sched/signal.h>
#include <trace/events/block.h>
#include "md.h"
#include "raid1.h"
#include "bitmap.h"
#define UNSUPPORTED_MDDEV_FLAGS \
((1L << MD_HAS_JOURNAL) | \
(1L << MD_JOURNAL_CLEAN) | \
(1L << MD_HAS_PPL))
/*
* Number of guaranteed r1bios in case of extreme VM load:
*/
#define NR_RAID1_BIOS 256
/* when we get a read error on a read-only array, we redirect to another
* device without failing the first device, or trying to over-write to
* correct the read error. To keep track of bad blocks on a per-bio
* level, we store IO_BLOCKED in the appropriate 'bios' pointer
*/
#define IO_BLOCKED ((struct bio *)1)
/* When we successfully write to a known bad-block, we need to remove the
* bad-block marking which must be done from process context. So we record
* the success by setting devs[n].bio to IO_MADE_GOOD
*/
#define IO_MADE_GOOD ((struct bio *)2)
#define BIO_SPECIAL(bio) ((unsigned long)bio <= 2)
/* When there are this many requests queue to be written by
* the raid1 thread, we become 'congested' to provide back-pressure
* for writeback.
*/
static int max_queued_requests = 1024;
static void allow_barrier(struct r1conf *conf, sector_t sector_nr);
static void lower_barrier(struct r1conf *conf, sector_t sector_nr);
#define raid1_log(md, fmt, args...) \
do { if ((md)->queue) blk_add_trace_msg((md)->queue, "raid1 " fmt, ##args); } while (0)
/*
* 'strct resync_pages' stores actual pages used for doing the resync
* IO, and it is per-bio, so make .bi_private points to it.
*/
static inline struct resync_pages *get_resync_pages(struct bio *bio)
{
return bio->bi_private;
}
/*
* for resync bio, r1bio pointer can be retrieved from the per-bio
* 'struct resync_pages'.
*/
static inline struct r1bio *get_resync_r1bio(struct bio *bio)
{
return get_resync_pages(bio)->raid_bio;
}
static void * r1bio_pool_alloc(gfp_t gfp_flags, void *data)
{
struct pool_info *pi = data;
int size = offsetof(struct r1bio, bios[pi->raid_disks]);
/* allocate a r1bio with room for raid_disks entries in the bios array */
return kzalloc(size, gfp_flags);
}
static void r1bio_pool_free(void *r1_bio, void *data)
{
kfree(r1_bio);
}
#define RESYNC_DEPTH 32
#define RESYNC_SECTORS (RESYNC_BLOCK_SIZE >> 9)
#define RESYNC_WINDOW (RESYNC_BLOCK_SIZE * RESYNC_DEPTH)
#define RESYNC_WINDOW_SECTORS (RESYNC_WINDOW >> 9)
#define CLUSTER_RESYNC_WINDOW (16 * RESYNC_WINDOW)
#define CLUSTER_RESYNC_WINDOW_SECTORS (CLUSTER_RESYNC_WINDOW >> 9)
static void * r1buf_pool_alloc(gfp_t gfp_flags, void *data)
{
struct pool_info *pi = data;
struct r1bio *r1_bio;
struct bio *bio;
int need_pages;
int j;
struct resync_pages *rps;
r1_bio = r1bio_pool_alloc(gfp_flags, pi);
if (!r1_bio)
return NULL;
rps = kmalloc(sizeof(struct resync_pages) * pi->raid_disks,
gfp_flags);
if (!rps)
goto out_free_r1bio;
/*
* Allocate bios : 1 for reading, n-1 for writing
*/
for (j = pi->raid_disks ; j-- ; ) {
bio = bio_kmalloc(gfp_flags, RESYNC_PAGES);
if (!bio)
goto out_free_bio;
r1_bio->bios[j] = bio;
}
/*
* Allocate RESYNC_PAGES data pages and attach them to
* the first bio.
* If this is a user-requested check/repair, allocate
* RESYNC_PAGES for each bio.
*/
if (test_bit(MD_RECOVERY_REQUESTED, &pi->mddev->recovery))
need_pages = pi->raid_disks;
else
need_pages = 1;
for (j = 0; j < pi->raid_disks; j++) {
struct resync_pages *rp = &rps[j];
bio = r1_bio->bios[j];
if (j < need_pages) {
if (resync_alloc_pages(rp, gfp_flags))
goto out_free_pages;
} else {
memcpy(rp, &rps[0], sizeof(*rp));
resync_get_all_pages(rp);
}
rp->idx = 0;
rp->raid_bio = r1_bio;
bio->bi_private = rp;
}
r1_bio->master_bio = NULL;
return r1_bio;
out_free_pages:
while (--j >= 0)
resync_free_pages(&rps[j]);
out_free_bio:
while (++j < pi->raid_disks)
bio_put(r1_bio->bios[j]);
kfree(rps);
out_free_r1bio:
r1bio_pool_free(r1_bio, data);
return NULL;
}
static void r1buf_pool_free(void *__r1_bio, void *data)
{
struct pool_info *pi = data;
int i;
struct r1bio *r1bio = __r1_bio;
struct resync_pages *rp = NULL;
for (i = pi->raid_disks; i--; ) {
rp = get_resync_pages(r1bio->bios[i]);
resync_free_pages(rp);
bio_put(r1bio->bios[i]);
}
/* resync pages array stored in the 1st bio's .bi_private */
kfree(rp);
r1bio_pool_free(r1bio, data);
}
static void put_all_bios(struct r1conf *conf, struct r1bio *r1_bio)
{
int i;
for (i = 0; i < conf->raid_disks * 2; i++) {
struct bio **bio = r1_bio->bios + i;
if (!BIO_SPECIAL(*bio))
bio_put(*bio);
*bio = NULL;
}
}
static void free_r1bio(struct r1bio *r1_bio)
{
struct r1conf *conf = r1_bio->mddev->private;
put_all_bios(conf, r1_bio);
mempool_free(r1_bio, conf->r1bio_pool);
}
static void put_buf(struct r1bio *r1_bio)
{
struct r1conf *conf = r1_bio->mddev->private;
sector_t sect = r1_bio->sector;
int i;
for (i = 0; i < conf->raid_disks * 2; i++) {
struct bio *bio = r1_bio->bios[i];
if (bio->bi_end_io)
rdev_dec_pending(conf->mirrors[i].rdev, r1_bio->mddev);
}
mempool_free(r1_bio, conf->r1buf_pool);
lower_barrier(conf, sect);
}
static void reschedule_retry(struct r1bio *r1_bio)
{
unsigned long flags;
struct mddev *mddev = r1_bio->mddev;
struct r1conf *conf = mddev->private;
int idx;
idx = sector_to_idx(r1_bio->sector);
spin_lock_irqsave(&conf->device_lock, flags);
list_add(&r1_bio->retry_list, &conf->retry_list);
atomic_inc(&conf->nr_queued[idx]);
spin_unlock_irqrestore(&conf->device_lock, flags);
wake_up(&conf->wait_barrier);
md_wakeup_thread(mddev->thread);
}
/*
* raid_end_bio_io() is called when we have finished servicing a mirrored
* operation and are ready to return a success/failure code to the buffer
* cache layer.
*/
static void call_bio_endio(struct r1bio *r1_bio)
{
struct bio *bio = r1_bio->master_bio;
struct r1conf *conf = r1_bio->mddev->private;
if (!test_bit(R1BIO_Uptodate, &r1_bio->state))
bio->bi_error = -EIO;
bio_endio(bio);
/*
* Wake up any possible resync thread that waits for the device
* to go idle.
*/
allow_barrier(conf, r1_bio->sector);
}
static void raid_end_bio_io(struct r1bio *r1_bio)
{
struct bio *bio = r1_bio->master_bio;
/* if nobody has done the final endio yet, do it now */
if (!test_and_set_bit(R1BIO_Returned, &r1_bio->state)) {
pr_debug("raid1: sync end %s on sectors %llu-%llu\n",
(bio_data_dir(bio) == WRITE) ? "write" : "read",
(unsigned long long) bio->bi_iter.bi_sector,
(unsigned long long) bio_end_sector(bio) - 1);
call_bio_endio(r1_bio);
}
free_r1bio(r1_bio);
}
/*
* Update disk head position estimator based on IRQ completion info.
*/
static inline void update_head_pos(int disk, struct r1bio *r1_bio)
{
struct r1conf *conf = r1_bio->mddev->private;
conf->mirrors[disk].head_position =
r1_bio->sector + (r1_bio->sectors);
}
/*
* Find the disk number which triggered given bio
*/
static int find_bio_disk(struct r1bio *r1_bio, struct bio *bio)
{
int mirror;
struct r1conf *conf = r1_bio->mddev->private;
int raid_disks = conf->raid_disks;
for (mirror = 0; mirror < raid_disks * 2; mirror++)
if (r1_bio->bios[mirror] == bio)
break;
BUG_ON(mirror == raid_disks * 2);
update_head_pos(mirror, r1_bio);
return mirror;
}
static void raid1_end_read_request(struct bio *bio)
{
int uptodate = !bio->bi_error;
struct r1bio *r1_bio = bio->bi_private;
struct r1conf *conf = r1_bio->mddev->private;
struct md_rdev *rdev = conf->mirrors[r1_bio->read_disk].rdev;
/*
* this branch is our 'one mirror IO has finished' event handler:
*/
update_head_pos(r1_bio->read_disk, r1_bio);
if (uptodate)
set_bit(R1BIO_Uptodate, &r1_bio->state);
else if (test_bit(FailFast, &rdev->flags) &&
test_bit(R1BIO_FailFast, &r1_bio->state))
/* This was a fail-fast read so we definitely
* want to retry */
;
else {
/* If all other devices have failed, we want to return
* the error upwards rather than fail the last device.
* Here we redefine "uptodate" to mean "Don't want to retry"
*/
unsigned long flags;
spin_lock_irqsave(&conf->device_lock, flags);
if (r1_bio->mddev->degraded == conf->raid_disks ||
(r1_bio->mddev->degraded == conf->raid_disks-1 &&
test_bit(In_sync, &rdev->flags)))
uptodate = 1;
spin_unlock_irqrestore(&conf->device_lock, flags);
}
if (uptodate) {
raid_end_bio_io(r1_bio);
rdev_dec_pending(rdev, conf->mddev);
} else {
/*
* oops, read error:
*/
char b[BDEVNAME_SIZE];
pr_err_ratelimited("md/raid1:%s: %s: rescheduling sector %llu\n",
mdname(conf->mddev),
bdevname(rdev->bdev, b),
(unsigned long long)r1_bio->sector);
set_bit(R1BIO_ReadError, &r1_bio->state);
reschedule_retry(r1_bio);
/* don't drop the reference on read_disk yet */
}
}
static void close_write(struct r1bio *r1_bio)
{
/* it really is the end of this request */
if (test_bit(R1BIO_BehindIO, &r1_bio->state)) {
bio_free_pages(r1_bio->behind_master_bio);
bio_put(r1_bio->behind_master_bio);
r1_bio->behind_master_bio = NULL;
}
/* clear the bitmap if all writes complete successfully */
bitmap_endwrite(r1_bio->mddev->bitmap, r1_bio->sector,
r1_bio->sectors,
!test_bit(R1BIO_Degraded, &r1_bio->state),
test_bit(R1BIO_BehindIO, &r1_bio->state));
md_write_end(r1_bio->mddev);
}
static void r1_bio_write_done(struct r1bio *r1_bio)
{
if (!atomic_dec_and_test(&r1_bio->remaining))
return;
if (test_bit(R1BIO_WriteError, &r1_bio->state))
reschedule_retry(r1_bio);
else {
close_write(r1_bio);
if (test_bit(R1BIO_MadeGood, &r1_bio->state))
reschedule_retry(r1_bio);
else
raid_end_bio_io(r1_bio);
}
}
static void raid1_end_write_request(struct bio *bio)
{
struct r1bio *r1_bio = bio->bi_private;
int behind = test_bit(R1BIO_BehindIO, &r1_bio->state);
struct r1conf *conf = r1_bio->mddev->private;
struct bio *to_put = NULL;
int mirror = find_bio_disk(r1_bio, bio);
struct md_rdev *rdev = conf->mirrors[mirror].rdev;
bool discard_error;
discard_error = bio->bi_error && bio_op(bio) == REQ_OP_DISCARD;
/*
* 'one mirror IO has finished' event handler:
*/
if (bio->bi_error && !discard_error) {
set_bit(WriteErrorSeen, &rdev->flags);
if (!test_and_set_bit(WantReplacement, &rdev->flags))
set_bit(MD_RECOVERY_NEEDED, &
conf->mddev->recovery);
if (test_bit(FailFast, &rdev->flags) &&
(bio->bi_opf & MD_FAILFAST) &&
/* We never try FailFast to WriteMostly devices */
!test_bit(WriteMostly, &rdev->flags)) {
md_error(r1_bio->mddev, rdev);
if (!test_bit(Faulty, &rdev->flags))
/* This is the only remaining device,
* We need to retry the write without
* FailFast
*/
set_bit(R1BIO_WriteError, &r1_bio->state);
else {
/* Finished with this branch */
r1_bio->bios[mirror] = NULL;
to_put = bio;
}
} else
set_bit(R1BIO_WriteError, &r1_bio->state);
} else {
/*
* Set R1BIO_Uptodate in our master bio, so that we
* will return a good error code for to the higher
* levels even if IO on some other mirrored buffer
* fails.
*
* The 'master' represents the composite IO operation
* to user-side. So if something waits for IO, then it
* will wait for the 'master' bio.
*/
sector_t first_bad;
int bad_sectors;
r1_bio->bios[mirror] = NULL;
to_put = bio;
/*
* Do not set R1BIO_Uptodate if the current device is
* rebuilding or Faulty. This is because we cannot use
* such device for properly reading the data back (we could
* potentially use it, if the current write would have felt
* before rdev->recovery_offset, but for simplicity we don't
* check this here.
*/
if (test_bit(In_sync, &rdev->flags) &&
!test_bit(Faulty, &rdev->flags))
set_bit(R1BIO_Uptodate, &r1_bio->state);
/* Maybe we can clear some bad blocks. */
if (is_badblock(rdev, r1_bio->sector, r1_bio->sectors,
&first_bad, &bad_sectors) && !discard_error) {
r1_bio->bios[mirror] = IO_MADE_GOOD;
set_bit(R1BIO_MadeGood, &r1_bio->state);
}
}
if (behind) {
/* we release behind master bio when all write are done */
if (r1_bio->behind_master_bio == bio)
to_put = NULL;
if (test_bit(WriteMostly, &rdev->flags))
atomic_dec(&r1_bio->behind_remaining);
/*
* In behind mode, we ACK the master bio once the I/O
* has safely reached all non-writemostly
* disks. Setting the Returned bit ensures that this
* gets done only once -- we don't ever want to return
* -EIO here, instead we'll wait
*/
if (atomic_read(&r1_bio->behind_remaining) >= (atomic_read(&r1_bio->remaining)-1) &&
test_bit(R1BIO_Uptodate, &r1_bio->state)) {
/* Maybe we can return now */
if (!test_and_set_bit(R1BIO_Returned, &r1_bio->state)) {
struct bio *mbio = r1_bio->master_bio;
pr_debug("raid1: behind end write sectors"
" %llu-%llu\n",
(unsigned long long) mbio->bi_iter.bi_sector,
(unsigned long long) bio_end_sector(mbio) - 1);
call_bio_endio(r1_bio);
}
}
}
if (r1_bio->bios[mirror] == NULL)
rdev_dec_pending(rdev, conf->mddev);
/*
* Let's see if all mirrored write operations have finished
* already.
*/
r1_bio_write_done(r1_bio);
if (to_put)
bio_put(to_put);
}
static sector_t align_to_barrier_unit_end(sector_t start_sector,
sector_t sectors)
{
sector_t len;
WARN_ON(sectors == 0);
/*
* len is the number of sectors from start_sector to end of the
* barrier unit which start_sector belongs to.
*/
len = round_up(start_sector + 1, BARRIER_UNIT_SECTOR_SIZE) -
start_sector;
if (len > sectors)
len = sectors;
return len;
}
/*
* This routine returns the disk from which the requested read should
* be done. There is a per-array 'next expected sequential IO' sector
* number - if this matches on the next IO then we use the last disk.
* There is also a per-disk 'last know head position' sector that is
* maintained from IRQ contexts, both the normal and the resync IO
* completion handlers update this position correctly. If there is no
* perfect sequential match then we pick the disk whose head is closest.
*
* If there are 2 mirrors in the same 2 devices, performance degrades
* because position is mirror, not device based.
*
* The rdev for the device selected will have nr_pending incremented.
*/
static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sectors)
{
const sector_t this_sector = r1_bio->sector;
int sectors;
int best_good_sectors;
int best_disk, best_dist_disk, best_pending_disk;
int has_nonrot_disk;
int disk;
sector_t best_dist;
unsigned int min_pending;
struct md_rdev *rdev;
int choose_first;
int choose_next_idle;
rcu_read_lock();
/*
* Check if we can balance. We can balance on the whole
* device if no resync is going on, or below the resync window.
* We take the first readable disk when above the resync window.
*/
retry:
sectors = r1_bio->sectors;
best_disk = -1;
best_dist_disk = -1;
best_dist = MaxSector;
best_pending_disk = -1;
min_pending = UINT_MAX;
best_good_sectors = 0;
has_nonrot_disk = 0;
choose_next_idle = 0;
clear_bit(R1BIO_FailFast, &r1_bio->state);
if ((conf->mddev->recovery_cp < this_sector + sectors) ||
(mddev_is_clustered(conf->mddev) &&
md_cluster_ops->area_resyncing(conf->mddev, READ, this_sector,
this_sector + sectors)))
choose_first = 1;
else
choose_first = 0;
for (disk = 0 ; disk < conf->raid_disks * 2 ; disk++) {
sector_t dist;
sector_t first_bad;
int bad_sectors;
unsigned int pending;
bool nonrot;
rdev = rcu_dereference(conf->mirrors[disk].rdev);
if (r1_bio->bios[disk] == IO_BLOCKED
|| rdev == NULL
|| test_bit(Faulty, &rdev->flags))
continue;
if (!test_bit(In_sync, &rdev->flags) &&
rdev->recovery_offset < this_sector + sectors)
continue;
if (test_bit(WriteMostly, &rdev->flags)) {
/* Don't balance among write-mostly, just
* use the first as a last resort */
if (best_dist_disk < 0) {
if (is_badblock(rdev, this_sector, sectors,
&first_bad, &bad_sectors)) {
if (first_bad <= this_sector)
/* Cannot use this */
continue;
best_good_sectors = first_bad - this_sector;
} else
best_good_sectors = sectors;
best_dist_disk = disk;
best_pending_disk = disk;
}
continue;
}
/* This is a reasonable device to use. It might
* even be best.
*/
if (is_badblock(rdev, this_sector, sectors,
&first_bad, &bad_sectors)) {
if (best_dist < MaxSector)
/* already have a better device */
continue;
if (first_bad <= this_sector) {
/* cannot read here. If this is the 'primary'
* device, then we must not read beyond
* bad_sectors from another device..
*/
bad_sectors -= (this_sector - first_bad);
if (choose_first && sectors > bad_sectors)
sectors = bad_sectors;
if (best_good_sectors > sectors)
best_good_sectors = sectors;
} else {
sector_t good_sectors = first_bad - this_sector;
if (good_sectors > best_good_sectors) {
best_good_sectors = good_sectors;
best_disk = disk;
}
if (choose_first)
break;
}
continue;
} else
best_good_sectors = sectors;
if (best_disk >= 0)
/* At least two disks to choose from so failfast is OK */
set_bit(R1BIO_FailFast, &r1_bio->state);
nonrot = blk_queue_nonrot(bdev_get_queue(rdev->bdev));
has_nonrot_disk |= nonrot;
pending = atomic_read(&rdev->nr_pending);
dist = abs(this_sector - conf->mirrors[disk].head_position);
if (choose_first) {
best_disk = disk;
break;
}
/* Don't change to another disk for sequential reads */
if (conf->mirrors[disk].next_seq_sect == this_sector
|| dist == 0) {
int opt_iosize = bdev_io_opt(rdev->bdev) >> 9;
struct raid1_info *mirror = &conf->mirrors[disk];
best_disk = disk;
/*
* If buffered sequential IO size exceeds optimal
* iosize, check if there is idle disk. If yes, choose
* the idle disk. read_balance could already choose an
* idle disk before noticing it's a sequential IO in
* this disk. This doesn't matter because this disk
* will idle, next time it will be utilized after the
* first disk has IO size exceeds optimal iosize. In
* this way, iosize of the first disk will be optimal
* iosize at least. iosize of the second disk might be
* small, but not a big deal since when the second disk
* starts IO, the first disk is likely still busy.
*/
if (nonrot && opt_iosize > 0 &&
mirror->seq_start != MaxSector &&
mirror->next_seq_sect > opt_iosize &&
mirror->next_seq_sect - opt_iosize >=
mirror->seq_start) {
choose_next_idle = 1;
continue;
}
break;
}
if (choose_next_idle)
continue;
if (min_pending > pending) {
min_pending = pending;
best_pending_disk = disk;
}
if (dist < best_dist) {
best_dist = dist;
best_dist_disk = disk;
}
}
/*
* If all disks are rotational, choose the closest disk. If any disk is
* non-rotational, choose the disk with less pending request even the
* disk is rotational, which might/might not be optimal for raids with
* mixed ratation/non-rotational disks depending on workload.
*/
if (best_disk == -1) {
if (has_nonrot_disk || min_pending == 0)
best_disk = best_pending_disk;
else
best_disk = best_dist_disk;
}
if (best_disk >= 0) {
rdev = rcu_dereference(conf->mirrors[best_disk].rdev);
if (!rdev)
goto retry;
atomic_inc(&rdev->nr_pending);
sectors = best_good_sectors;
if (conf->mirrors[best_disk].next_seq_sect != this_sector)
conf->mirrors[best_disk].seq_start = this_sector;
conf->mirrors[best_disk].next_seq_sect = this_sector + sectors;
}
rcu_read_unlock();
*max_sectors = sectors;
return best_disk;
}
static int raid1_congested(struct mddev *mddev, int bits)
{
struct r1conf *conf = mddev->private;
int i, ret = 0;
if ((bits & (1 << WB_async_congested)) &&
conf->pending_count >= max_queued_requests)
return 1;
rcu_read_lock();
for (i = 0; i < conf->raid_disks * 2; i++) {
struct md_rdev *rdev = rcu_dereference(conf->mirrors[i].rdev);
if (rdev && !test_bit(Faulty, &rdev->flags)) {
struct request_queue *q = bdev_get_queue(rdev->bdev);
BUG_ON(!q);
/* Note the '|| 1' - when read_balance prefers
* non-congested targets, it can be removed
*/
if ((bits & (1 << WB_async_congested)) || 1)
ret |= bdi_congested(q->backing_dev_info, bits);
else
ret &= bdi_congested(q->backing_dev_info, bits);
}
}
rcu_read_unlock();
return ret;
}
static void flush_bio_list(struct r1conf *conf, struct bio *bio)
{
/* flush any pending bitmap writes to disk before proceeding w/ I/O */
bitmap_unplug(conf->mddev->bitmap);
wake_up(&conf->wait_barrier);
while (bio) { /* submit pending writes */
struct bio *next = bio->bi_next;
struct md_rdev *rdev = (void*)bio->bi_bdev;
bio->bi_next = NULL;
bio->bi_bdev = rdev->bdev;
if (test_bit(Faulty, &rdev->flags)) {
bio->bi_error = -EIO;
bio_endio(bio);
} else if (unlikely((bio_op(bio) == REQ_OP_DISCARD) &&
!blk_queue_discard(bdev_get_queue(bio->bi_bdev))))
/* Just ignore it */
bio_endio(bio);
else
generic_make_request(bio);
bio = next;
}
}
static void flush_pending_writes(struct r1conf *conf)
{
/* Any writes that have been queued but are awaiting
* bitmap updates get flushed here.
*/
spin_lock_irq(&conf->device_lock);
if (conf->pending_bio_list.head) {
struct bio *bio;
bio = bio_list_get(&conf->pending_bio_list);
conf->pending_count = 0;
spin_unlock_irq(&conf->device_lock);
flush_bio_list(conf, bio);
} else
spin_unlock_irq(&conf->device_lock);
}
/* Barriers....
* Sometimes we need to suspend IO while we do something else,
* either some resync/recovery, or reconfigure the array.
* To do this we raise a 'barrier'.
* The 'barrier' is a counter that can be raised multiple times
* to count how many activities are happening which preclude
* normal IO.
* We can only raise the barrier if there is no pending IO.
* i.e. if nr_pending == 0.
* We choose only to raise the barrier if no-one is waiting for the
* barrier to go down. This means that as soon as an IO request
* is ready, no other operations which require a barrier will start
* until the IO request has had a chance.
*
* So: regular IO calls 'wait_barrier'. When that returns there
* is no backgroup IO happening, It must arrange to call
* allow_barrier when it has finished its IO.
* backgroup IO calls must call raise_barrier. Once that returns
* there is no normal IO happeing. It must arrange to call
* lower_barrier when the particular background IO completes.
*/
static void raise_barrier(struct r1conf *conf, sector_t sector_nr)
{
int idx = sector_to_idx(sector_nr);
spin_lock_irq(&conf->resync_lock);
/* Wait until no block IO is waiting */
wait_event_lock_irq(conf->wait_barrier,
!atomic_read(&conf->nr_waiting[idx]),
conf->resync_lock);
/* block any new IO from starting */
atomic_inc(&conf->barrier[idx]);
/*
* In raise_barrier() we firstly increase conf->barrier[idx] then
* check conf->nr_pending[idx]. In _wait_barrier() we firstly
* increase conf->nr_pending[idx] then check conf->barrier[idx].
* A memory barrier here to make sure conf->nr_pending[idx] won't
* be fetched before conf->barrier[idx] is increased. Otherwise
* there will be a race between raise_barrier() and _wait_barrier().
*/
smp_mb__after_atomic();
/* For these conditions we must wait:
* A: while the array is in frozen state
* B: while conf->nr_pending[idx] is not 0, meaning regular I/O
* existing in corresponding I/O barrier bucket.
* C: while conf->barrier[idx] >= RESYNC_DEPTH, meaning reaches
* max resync count which allowed on current I/O barrier bucket.
*/
wait_event_lock_irq(conf->wait_barrier,
!conf->array_frozen &&
!atomic_read(&conf->nr_pending[idx]) &&
atomic_read(&conf->barrier[idx]) < RESYNC_DEPTH,
conf->resync_lock);
atomic_inc(&conf->nr_sync_pending);
spin_unlock_irq(&conf->resync_lock);
}
static void lower_barrier(struct r1conf *conf, sector_t sector_nr)
{
int idx = sector_to_idx(sector_nr);
BUG_ON(atomic_read(&conf->barrier[idx]) <= 0);
atomic_dec(&conf->barrier[idx]);
atomic_dec(&conf->nr_sync_pending);
wake_up(&conf->wait_barrier);
}
static void _wait_barrier(struct r1conf *conf, int idx)
{
/*
* We need to increase conf->nr_pending[idx] very early here,
* then raise_barrier() can be blocked when it waits for
* conf->nr_pending[idx] to be 0. Then we can avoid holding
* conf->resync_lock when there is no barrier raised in same
* barrier unit bucket. Also if the array is frozen, I/O
* should be blocked until array is unfrozen.
*/
atomic_inc(&conf->nr_pending[idx]);
/*
* In _wait_barrier() we firstly increase conf->nr_pending[idx], then
* check conf->barrier[idx]. In raise_barrier() we firstly increase
* conf->barrier[idx], then check conf->nr_pending[idx]. A memory
* barrier is necessary here to make sure conf->barrier[idx] won't be
* fetched before conf->nr_pending[idx] is increased. Otherwise there
* will be a race between _wait_barrier() and raise_barrier().
*/
smp_mb__after_atomic();
/*
* Don't worry about checking two atomic_t variables at same time
* here. If during we check conf->barrier[idx], the array is
* frozen (conf->array_frozen is 1), and chonf->barrier[idx] is
* 0, it is safe to return and make the I/O continue. Because the
* array is frozen, all I/O returned here will eventually complete
* or be queued, no race will happen. See code comment in
* frozen_array().
*/
if (!READ_ONCE(conf->array_frozen) &&
!atomic_read(&conf->barrier[idx]))
return;
/*
* After holding conf->resync_lock, conf->nr_pending[idx]
* should be decreased before waiting for barrier to drop.
* Otherwise, we may encounter a race condition because
* raise_barrer() might be waiting for conf->nr_pending[idx]
* to be 0 at same time.
*/
spin_lock_irq(&conf->resync_lock);
atomic_inc(&conf->nr_waiting[idx]);
atomic_dec(&conf->nr_pending[idx]);
/*
* In case freeze_array() is waiting for
* get_unqueued_pending() == extra
*/
wake_up(&conf->wait_barrier);
/* Wait for the barrier in same barrier unit bucket to drop. */
wait_event_lock_irq(conf->wait_barrier,
!conf->array_frozen &&
!atomic_read(&conf->barrier[idx]),
conf->resync_lock);
atomic_inc(&conf->nr_pending[idx]);
atomic_dec(&conf->nr_waiting[idx]);
spin_unlock_irq(&conf->resync_lock);
}
static void wait_read_barrier(struct r1conf *conf, sector_t sector_nr)
{
int idx = sector_to_idx(sector_nr);
/*
* Very similar to _wait_barrier(). The difference is, for read
* I/O we don't need wait for sync I/O, but if the whole array
* is frozen, the read I/O still has to wait until the array is
* unfrozen. Since there is no ordering requirement with
* conf->barrier[idx] here, memory barrier is unnecessary as well.
*/
atomic_inc(&conf->nr_pending[idx]);
if (!READ_ONCE(conf->array_frozen))
return;
spin_lock_irq(&conf->resync_lock);
atomic_inc(&conf->nr_waiting[idx]);
atomic_dec(&conf->nr_pending[idx]);
/*
* In case freeze_array() is waiting for
* get_unqueued_pending() == extra
*/
wake_up(&conf->wait_barrier);
/* Wait for array to be unfrozen */
wait_event_lock_irq(conf->wait_barrier,
!conf->array_frozen,
conf->resync_lock);
atomic_inc(&conf->nr_pending[idx]);
atomic_dec(&conf->nr_waiting[idx]);
spin_unlock_irq(&conf->resync_lock);
}
static void wait_barrier(struct r1conf *conf, sector_t sector_nr)
{
int idx = sector_to_idx(sector_nr);
_wait_barrier(conf, idx);
}