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raid10.c
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/*
* raid10.c : Multiple Devices driver for Linux
*
* Copyright (C) 2000-2004 Neil Brown
*
* RAID-10 support for md.
*
* Base on code in raid1.c. See raid1.c for further copyright information.
*
*
* 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/kthread.h>
#include <trace/events/block.h>
#include "md.h"
#include "raid10.h"
#include "raid0.h"
#include "bitmap.h"
/*
* RAID10 provides a combination of RAID0 and RAID1 functionality.
* The layout of data is defined by
* chunk_size
* raid_disks
* near_copies (stored in low byte of layout)
* far_copies (stored in second byte of layout)
* far_offset (stored in bit 16 of layout )
* use_far_sets (stored in bit 17 of layout )
* use_far_sets_bugfixed (stored in bit 18 of layout )
*
* The data to be stored is divided into chunks using chunksize. Each device
* is divided into far_copies sections. In each section, chunks are laid out
* in a style similar to raid0, but near_copies copies of each chunk is stored
* (each on a different drive). The starting device for each section is offset
* near_copies from the starting device of the previous section. Thus there
* are (near_copies * far_copies) of each chunk, and each is on a different
* drive. near_copies and far_copies must be at least one, and their product
* is at most raid_disks.
*
* If far_offset is true, then the far_copies are handled a bit differently.
* The copies are still in different stripes, but instead of being very far
* apart on disk, there are adjacent stripes.
*
* The far and offset algorithms are handled slightly differently if
* 'use_far_sets' is true. In this case, the array's devices are grouped into
* sets that are (near_copies * far_copies) in size. The far copied stripes
* are still shifted by 'near_copies' devices, but this shifting stays confined
* to the set rather than the entire array. This is done to improve the number
* of device combinations that can fail without causing the array to fail.
* Example 'far' algorithm w/o 'use_far_sets' (each letter represents a chunk
* on a device):
* A B C D A B C D E
* ... ...
* D A B C E A B C D
* Example 'far' algorithm w/ 'use_far_sets' enabled (sets illustrated w/ []'s):
* [A B] [C D] [A B] [C D E]
* |...| |...| |...| | ... |
* [B A] [D C] [B A] [E C D]
*/
/*
* Number of guaranteed r10bios in case of extreme VM load:
*/
#define NR_RAID10_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 queued to be written by
* the raid10 thread, we become 'congested' to provide back-pressure
* for writeback.
*/
static int max_queued_requests = 1024;
static void allow_barrier(struct r10conf *conf);
static void lower_barrier(struct r10conf *conf);
static int _enough(struct r10conf *conf, int previous, int ignore);
static int enough(struct r10conf *conf, int ignore);
static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr,
int *skipped);
static void reshape_request_write(struct mddev *mddev, struct r10bio *r10_bio);
static void end_reshape_write(struct bio *bio);
static void end_reshape(struct r10conf *conf);
#define raid10_log(md, fmt, args...) \
do { if ((md)->queue) blk_add_trace_msg((md)->queue, "raid10 " 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, r10bio pointer can be retrieved from the per-bio
* 'struct resync_pages'.
*/
static inline struct r10bio *get_resync_r10bio(struct bio *bio)
{
return get_resync_pages(bio)->raid_bio;
}
static void * r10bio_pool_alloc(gfp_t gfp_flags, void *data)
{
struct r10conf *conf = data;
int size = offsetof(struct r10bio, devs[conf->copies]);
/* allocate a r10bio with room for raid_disks entries in the
* bios array */
return kzalloc(size, gfp_flags);
}
static void r10bio_pool_free(void *r10_bio, void *data)
{
kfree(r10_bio);
}
/* amount of memory to reserve for resync requests */
#define RESYNC_WINDOW (1024*1024)
/* maximum number of concurrent requests, memory permitting */
#define RESYNC_DEPTH (32*1024*1024/RESYNC_BLOCK_SIZE)
/*
* When performing a resync, we need to read and compare, so
* we need as many pages are there are copies.
* When performing a recovery, we need 2 bios, one for read,
* one for write (we recover only one drive per r10buf)
*
*/
static void * r10buf_pool_alloc(gfp_t gfp_flags, void *data)
{
struct r10conf *conf = data;
struct r10bio *r10_bio;
struct bio *bio;
int j;
int nalloc, nalloc_rp;
struct resync_pages *rps;
r10_bio = r10bio_pool_alloc(gfp_flags, conf);
if (!r10_bio)
return NULL;
if (test_bit(MD_RECOVERY_SYNC, &conf->mddev->recovery) ||
test_bit(MD_RECOVERY_RESHAPE, &conf->mddev->recovery))
nalloc = conf->copies; /* resync */
else
nalloc = 2; /* recovery */
/* allocate once for all bios */
if (!conf->have_replacement)
nalloc_rp = nalloc;
else
nalloc_rp = nalloc * 2;
rps = kmalloc(sizeof(struct resync_pages) * nalloc_rp, gfp_flags);
if (!rps)
goto out_free_r10bio;
/*
* Allocate bios.
*/
for (j = nalloc ; j-- ; ) {
bio = bio_kmalloc(gfp_flags, RESYNC_PAGES);
if (!bio)
goto out_free_bio;
r10_bio->devs[j].bio = bio;
if (!conf->have_replacement)
continue;
bio = bio_kmalloc(gfp_flags, RESYNC_PAGES);
if (!bio)
goto out_free_bio;
r10_bio->devs[j].repl_bio = bio;
}
/*
* Allocate RESYNC_PAGES data pages and attach them
* where needed.
*/
for (j = 0; j < nalloc; j++) {
struct bio *rbio = r10_bio->devs[j].repl_bio;
struct resync_pages *rp, *rp_repl;
rp = &rps[j];
if (rbio)
rp_repl = &rps[nalloc + j];
bio = r10_bio->devs[j].bio;
if (!j || test_bit(MD_RECOVERY_SYNC,
&conf->mddev->recovery)) {
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 = r10_bio;
bio->bi_private = rp;
if (rbio) {
memcpy(rp_repl, rp, sizeof(*rp));
rbio->bi_private = rp_repl;
}
}
return r10_bio;
out_free_pages:
while (--j >= 0)
resync_free_pages(&rps[j * 2]);
j = 0;
out_free_bio:
for ( ; j < nalloc; j++) {
if (r10_bio->devs[j].bio)
bio_put(r10_bio->devs[j].bio);
if (r10_bio->devs[j].repl_bio)
bio_put(r10_bio->devs[j].repl_bio);
}
kfree(rps);
out_free_r10bio:
r10bio_pool_free(r10_bio, conf);
return NULL;
}
static void r10buf_pool_free(void *__r10_bio, void *data)
{
struct r10conf *conf = data;
struct r10bio *r10bio = __r10_bio;
int j;
struct resync_pages *rp = NULL;
for (j = conf->copies; j--; ) {
struct bio *bio = r10bio->devs[j].bio;
rp = get_resync_pages(bio);
resync_free_pages(rp);
bio_put(bio);
bio = r10bio->devs[j].repl_bio;
if (bio)
bio_put(bio);
}
/* resync pages array stored in the 1st bio's .bi_private */
kfree(rp);
r10bio_pool_free(r10bio, conf);
}
static void put_all_bios(struct r10conf *conf, struct r10bio *r10_bio)
{
int i;
for (i = 0; i < conf->copies; i++) {
struct bio **bio = & r10_bio->devs[i].bio;
if (!BIO_SPECIAL(*bio))
bio_put(*bio);
*bio = NULL;
bio = &r10_bio->devs[i].repl_bio;
if (r10_bio->read_slot < 0 && !BIO_SPECIAL(*bio))
bio_put(*bio);
*bio = NULL;
}
}
static void free_r10bio(struct r10bio *r10_bio)
{
struct r10conf *conf = r10_bio->mddev->private;
put_all_bios(conf, r10_bio);
mempool_free(r10_bio, conf->r10bio_pool);
}
static void put_buf(struct r10bio *r10_bio)
{
struct r10conf *conf = r10_bio->mddev->private;
mempool_free(r10_bio, conf->r10buf_pool);
lower_barrier(conf);
}
static void reschedule_retry(struct r10bio *r10_bio)
{
unsigned long flags;
struct mddev *mddev = r10_bio->mddev;
struct r10conf *conf = mddev->private;
spin_lock_irqsave(&conf->device_lock, flags);
list_add(&r10_bio->retry_list, &conf->retry_list);
conf->nr_queued ++;
spin_unlock_irqrestore(&conf->device_lock, flags);
/* wake up frozen array... */
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 raid_end_bio_io(struct r10bio *r10_bio)
{
struct bio *bio = r10_bio->master_bio;
struct r10conf *conf = r10_bio->mddev->private;
if (!test_bit(R10BIO_Uptodate, &r10_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);
free_r10bio(r10_bio);
}
/*
* Update disk head position estimator based on IRQ completion info.
*/
static inline void update_head_pos(int slot, struct r10bio *r10_bio)
{
struct r10conf *conf = r10_bio->mddev->private;
conf->mirrors[r10_bio->devs[slot].devnum].head_position =
r10_bio->devs[slot].addr + (r10_bio->sectors);
}
/*
* Find the disk number which triggered given bio
*/
static int find_bio_disk(struct r10conf *conf, struct r10bio *r10_bio,
struct bio *bio, int *slotp, int *replp)
{
int slot;
int repl = 0;
for (slot = 0; slot < conf->copies; slot++) {
if (r10_bio->devs[slot].bio == bio)
break;
if (r10_bio->devs[slot].repl_bio == bio) {
repl = 1;
break;
}
}
BUG_ON(slot == conf->copies);
update_head_pos(slot, r10_bio);
if (slotp)
*slotp = slot;
if (replp)
*replp = repl;
return r10_bio->devs[slot].devnum;
}
static void raid10_end_read_request(struct bio *bio)
{
int uptodate = !bio->bi_error;
struct r10bio *r10_bio = bio->bi_private;
int slot, dev;
struct md_rdev *rdev;
struct r10conf *conf = r10_bio->mddev->private;
slot = r10_bio->read_slot;
dev = r10_bio->devs[slot].devnum;
rdev = r10_bio->devs[slot].rdev;
/*
* this branch is our 'one mirror IO has finished' event handler:
*/
update_head_pos(slot, r10_bio);
if (uptodate) {
/*
* Set R10BIO_Uptodate in our master bio, so that
* we will return a good error code 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.
*/
set_bit(R10BIO_Uptodate, &r10_bio->state);
} else {
/* If all other devices that store this block 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"
*/
if (!_enough(conf, test_bit(R10BIO_Previous, &r10_bio->state),
rdev->raid_disk))
uptodate = 1;
}
if (uptodate) {
raid_end_bio_io(r10_bio);
rdev_dec_pending(rdev, conf->mddev);
} else {
/*
* oops, read error - keep the refcount on the rdev
*/
char b[BDEVNAME_SIZE];
pr_err_ratelimited("md/raid10:%s: %s: rescheduling sector %llu\n",
mdname(conf->mddev),
bdevname(rdev->bdev, b),
(unsigned long long)r10_bio->sector);
set_bit(R10BIO_ReadError, &r10_bio->state);
reschedule_retry(r10_bio);
}
}
static void close_write(struct r10bio *r10_bio)
{
/* clear the bitmap if all writes complete successfully */
bitmap_endwrite(r10_bio->mddev->bitmap, r10_bio->sector,
r10_bio->sectors,
!test_bit(R10BIO_Degraded, &r10_bio->state),
0);
md_write_end(r10_bio->mddev);
}
static void one_write_done(struct r10bio *r10_bio)
{
if (atomic_dec_and_test(&r10_bio->remaining)) {
if (test_bit(R10BIO_WriteError, &r10_bio->state))
reschedule_retry(r10_bio);
else {
close_write(r10_bio);
if (test_bit(R10BIO_MadeGood, &r10_bio->state))
reschedule_retry(r10_bio);
else
raid_end_bio_io(r10_bio);
}
}
}
static void raid10_end_write_request(struct bio *bio)
{
struct r10bio *r10_bio = bio->bi_private;
int dev;
int dec_rdev = 1;
struct r10conf *conf = r10_bio->mddev->private;
int slot, repl;
struct md_rdev *rdev = NULL;
struct bio *to_put = NULL;
bool discard_error;
discard_error = bio->bi_error && bio_op(bio) == REQ_OP_DISCARD;
dev = find_bio_disk(conf, r10_bio, bio, &slot, &repl);
if (repl)
rdev = conf->mirrors[dev].replacement;
if (!rdev) {
smp_rmb();
repl = 0;
rdev = conf->mirrors[dev].rdev;
}
/*
* this branch is our 'one mirror IO has finished' event handler:
*/
if (bio->bi_error && !discard_error) {
if (repl)
/* Never record new bad blocks to replacement,
* just fail it.
*/
md_error(rdev->mddev, rdev);
else {
set_bit(WriteErrorSeen, &rdev->flags);
if (!test_and_set_bit(WantReplacement, &rdev->flags))
set_bit(MD_RECOVERY_NEEDED,
&rdev->mddev->recovery);
dec_rdev = 0;
if (test_bit(FailFast, &rdev->flags) &&
(bio->bi_opf & MD_FAILFAST)) {
md_error(rdev->mddev, rdev);
if (!test_bit(Faulty, &rdev->flags))
/* This is the only remaining device,
* We need to retry the write without
* FailFast
*/
set_bit(R10BIO_WriteError, &r10_bio->state);
else {
r10_bio->devs[slot].bio = NULL;
to_put = bio;
dec_rdev = 1;
}
} else
set_bit(R10BIO_WriteError, &r10_bio->state);
}
} else {
/*
* Set R10BIO_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;
/*
* Do not set R10BIO_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(R10BIO_Uptodate, &r10_bio->state);
/* Maybe we can clear some bad blocks. */
if (is_badblock(rdev,
r10_bio->devs[slot].addr,
r10_bio->sectors,
&first_bad, &bad_sectors) && !discard_error) {
bio_put(bio);
if (repl)
r10_bio->devs[slot].repl_bio = IO_MADE_GOOD;
else
r10_bio->devs[slot].bio = IO_MADE_GOOD;
dec_rdev = 0;
set_bit(R10BIO_MadeGood, &r10_bio->state);
}
}
/*
*
* Let's see if all mirrored write operations have finished
* already.
*/
one_write_done(r10_bio);
if (dec_rdev)
rdev_dec_pending(rdev, conf->mddev);
if (to_put)
bio_put(to_put);
}
/*
* RAID10 layout manager
* As well as the chunksize and raid_disks count, there are two
* parameters: near_copies and far_copies.
* near_copies * far_copies must be <= raid_disks.
* Normally one of these will be 1.
* If both are 1, we get raid0.
* If near_copies == raid_disks, we get raid1.
*
* Chunks are laid out in raid0 style with near_copies copies of the
* first chunk, followed by near_copies copies of the next chunk and
* so on.
* If far_copies > 1, then after 1/far_copies of the array has been assigned
* as described above, we start again with a device offset of near_copies.
* So we effectively have another copy of the whole array further down all
* the drives, but with blocks on different drives.
* With this layout, and block is never stored twice on the one device.
*
* raid10_find_phys finds the sector offset of a given virtual sector
* on each device that it is on.
*
* raid10_find_virt does the reverse mapping, from a device and a
* sector offset to a virtual address
*/
static void __raid10_find_phys(struct geom *geo, struct r10bio *r10bio)
{
int n,f;
sector_t sector;
sector_t chunk;
sector_t stripe;
int dev;
int slot = 0;
int last_far_set_start, last_far_set_size;
last_far_set_start = (geo->raid_disks / geo->far_set_size) - 1;
last_far_set_start *= geo->far_set_size;
last_far_set_size = geo->far_set_size;
last_far_set_size += (geo->raid_disks % geo->far_set_size);
/* now calculate first sector/dev */
chunk = r10bio->sector >> geo->chunk_shift;
sector = r10bio->sector & geo->chunk_mask;
chunk *= geo->near_copies;
stripe = chunk;
dev = sector_div(stripe, geo->raid_disks);
if (geo->far_offset)
stripe *= geo->far_copies;
sector += stripe << geo->chunk_shift;
/* and calculate all the others */
for (n = 0; n < geo->near_copies; n++) {
int d = dev;
int set;
sector_t s = sector;
r10bio->devs[slot].devnum = d;
r10bio->devs[slot].addr = s;
slot++;
for (f = 1; f < geo->far_copies; f++) {
set = d / geo->far_set_size;
d += geo->near_copies;
if ((geo->raid_disks % geo->far_set_size) &&
(d > last_far_set_start)) {
d -= last_far_set_start;
d %= last_far_set_size;
d += last_far_set_start;
} else {
d %= geo->far_set_size;
d += geo->far_set_size * set;
}
s += geo->stride;
r10bio->devs[slot].devnum = d;
r10bio->devs[slot].addr = s;
slot++;
}
dev++;
if (dev >= geo->raid_disks) {
dev = 0;
sector += (geo->chunk_mask + 1);
}
}
}
static void raid10_find_phys(struct r10conf *conf, struct r10bio *r10bio)
{
struct geom *geo = &conf->geo;
if (conf->reshape_progress != MaxSector &&
((r10bio->sector >= conf->reshape_progress) !=
conf->mddev->reshape_backwards)) {
set_bit(R10BIO_Previous, &r10bio->state);
geo = &conf->prev;
} else
clear_bit(R10BIO_Previous, &r10bio->state);
__raid10_find_phys(geo, r10bio);
}
static sector_t raid10_find_virt(struct r10conf *conf, sector_t sector, int dev)
{
sector_t offset, chunk, vchunk;
/* Never use conf->prev as this is only called during resync
* or recovery, so reshape isn't happening
*/
struct geom *geo = &conf->geo;
int far_set_start = (dev / geo->far_set_size) * geo->far_set_size;
int far_set_size = geo->far_set_size;
int last_far_set_start;
if (geo->raid_disks % geo->far_set_size) {
last_far_set_start = (geo->raid_disks / geo->far_set_size) - 1;
last_far_set_start *= geo->far_set_size;
if (dev >= last_far_set_start) {
far_set_size = geo->far_set_size;
far_set_size += (geo->raid_disks % geo->far_set_size);
far_set_start = last_far_set_start;
}
}
offset = sector & geo->chunk_mask;
if (geo->far_offset) {
int fc;
chunk = sector >> geo->chunk_shift;
fc = sector_div(chunk, geo->far_copies);
dev -= fc * geo->near_copies;
if (dev < far_set_start)
dev += far_set_size;
} else {
while (sector >= geo->stride) {
sector -= geo->stride;
if (dev < (geo->near_copies + far_set_start))
dev += far_set_size - geo->near_copies;
else
dev -= geo->near_copies;
}
chunk = sector >> geo->chunk_shift;
}
vchunk = chunk * geo->raid_disks + dev;
sector_div(vchunk, geo->near_copies);
return (vchunk << geo->chunk_shift) + offset;
}
/*
* 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.
*/
/*
* FIXME: possibly should rethink readbalancing and do it differently
* depending on near_copies / far_copies geometry.
*/
static struct md_rdev *read_balance(struct r10conf *conf,
struct r10bio *r10_bio,
int *max_sectors)
{
const sector_t this_sector = r10_bio->sector;
int disk, slot;
int sectors = r10_bio->sectors;
int best_good_sectors;
sector_t new_distance, best_dist;
struct md_rdev *best_rdev, *rdev = NULL;
int do_balance;
int best_slot;
struct geom *geo = &conf->geo;
raid10_find_phys(conf, r10_bio);
rcu_read_lock();
sectors = r10_bio->sectors;
best_slot = -1;
best_rdev = NULL;
best_dist = MaxSector;
best_good_sectors = 0;
do_balance = 1;
clear_bit(R10BIO_FailFast, &r10_bio->state);
/*
* Check if we can balance. We can balance on the whole
* device if no resync is going on (recovery is ok), or below
* the resync window. We take the first readable disk when
* above the resync window.
*/
if (conf->mddev->recovery_cp < MaxSector
&& (this_sector + sectors >= conf->next_resync))
do_balance = 0;
for (slot = 0; slot < conf->copies ; slot++) {
sector_t first_bad;
int bad_sectors;
sector_t dev_sector;
if (r10_bio->devs[slot].bio == IO_BLOCKED)
continue;
disk = r10_bio->devs[slot].devnum;
rdev = rcu_dereference(conf->mirrors[disk].replacement);
if (rdev == NULL || test_bit(Faulty, &rdev->flags) ||
r10_bio->devs[slot].addr + sectors > rdev->recovery_offset)
rdev = rcu_dereference(conf->mirrors[disk].rdev);
if (rdev == NULL ||
test_bit(Faulty, &rdev->flags))
continue;
if (!test_bit(In_sync, &rdev->flags) &&
r10_bio->devs[slot].addr + sectors > rdev->recovery_offset)
continue;
dev_sector = r10_bio->devs[slot].addr;
if (is_badblock(rdev, dev_sector, sectors,
&first_bad, &bad_sectors)) {
if (best_dist < MaxSector)
/* Already have a better slot */
continue;
if (first_bad <= dev_sector) {
/* Cannot read here. If this is the
* 'primary' device, then we must not read
* beyond 'bad_sectors' from another device.
*/
bad_sectors -= (dev_sector - first_bad);
if (!do_balance && sectors > bad_sectors)
sectors = bad_sectors;
if (best_good_sectors > sectors)
best_good_sectors = sectors;
} else {
sector_t good_sectors =
first_bad - dev_sector;
if (good_sectors > best_good_sectors) {
best_good_sectors = good_sectors;
best_slot = slot;
best_rdev = rdev;
}
if (!do_balance)
/* Must read from here */
break;
}
continue;
} else
best_good_sectors = sectors;
if (!do_balance)
break;
if (best_slot >= 0)
/* At least 2 disks to choose from so failfast is OK */
set_bit(R10BIO_FailFast, &r10_bio->state);
/* This optimisation is debatable, and completely destroys
* sequential read speed for 'far copies' arrays. So only
* keep it for 'near' arrays, and review those later.
*/
if (geo->near_copies > 1 && !atomic_read(&rdev->nr_pending))
new_distance = 0;
/* for far > 1 always use the lowest address */
else if (geo->far_copies > 1)
new_distance = r10_bio->devs[slot].addr;
else
new_distance = abs(r10_bio->devs[slot].addr -
conf->mirrors[disk].head_position);
if (new_distance < best_dist) {
best_dist = new_distance;
best_slot = slot;
best_rdev = rdev;
}
}
if (slot >= conf->copies) {
slot = best_slot;
rdev = best_rdev;
}
if (slot >= 0) {
atomic_inc(&rdev->nr_pending);
r10_bio->read_slot = slot;
} else
rdev = NULL;
rcu_read_unlock();
*max_sectors = best_good_sectors;
return rdev;
}
static int raid10_congested(struct mddev *mddev, int bits)
{
struct r10conf *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->geo.raid_disks || i < conf->prev.raid_disks)
&& ret == 0;
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);
ret |= bdi_congested(q->backing_dev_info, bits);
}
}
rcu_read_unlock();
return ret;
}
static void flush_pending_writes(struct r10conf *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 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;
}
} 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 r10conf *conf, int force)
{
BUG_ON(force && !conf->barrier);
spin_lock_irq(&conf->resync_lock);
/* Wait until no block IO is waiting (unless 'force') */
wait_event_lock_irq(conf->wait_barrier, force || !conf->nr_waiting,
conf->resync_lock);
/* block any new IO from starting */
conf->barrier++;
/* Now wait for all pending IO to complete */
wait_event_lock_irq(conf->wait_barrier,
!atomic_read(&conf->nr_pending) && conf->barrier < RESYNC_DEPTH,
conf->resync_lock);
spin_unlock_irq(&conf->resync_lock);
}
static void lower_barrier(struct r10conf *conf)
{
unsigned long flags;
spin_lock_irqsave(&conf->resync_lock, flags);
conf->barrier--;
spin_unlock_irqrestore(&conf->resync_lock, flags);
wake_up(&conf->wait_barrier);
}
static void wait_barrier(struct r10conf *conf)
{
spin_lock_irq(&conf->resync_lock);
if (conf->barrier) {
conf->nr_waiting++;
/* Wait for the barrier to drop.
* However if there are already pending
* requests (preventing the barrier from
* rising completely), and the
* pre-process bio queue isn't empty,
* then don't wait, as we need to empty
* that queue to get the nr_pending
* count down.
*/
raid10_log(conf->mddev, "wait barrier");
wait_event_lock_irq(conf->wait_barrier,
!conf->barrier ||
(atomic_read(&conf->nr_pending) &&
current->bio_list &&
(!bio_list_empty(¤t->bio_list[0]) ||