Most awkward part of this is delaying write requests until bitmap
updates have been flushed.
To achieve this, we have a sequence number (seq_flush) which is incremented
each time the raid5 is unplugged.
If the raid thread notices that this has changed, it flushes
bitmap changes, and assigned the value of seq_flush to seq_write.
When a write request arrives, it is given the number from seq_write, and
that write request may not complete until seq_flush is larger than the saved
seq number.
We have a new queue for storing stripes which are waiting for a bitmap
flush and an extra flag for stripes to record if the write was 'degraded'
and so should not clear the a bit in the bitmap.
Signed-off-by: Neil Brown <neilb@xxxxxxxxxxxxxxx>
### Diffstat output
./drivers/md/md.c | 3
./drivers/md/raid5.c | 133 +++++++++++++++++++++++++++++++++++++++----
./include/linux/raid/raid5.h | 14 ++++
3 files changed, 137 insertions(+), 13 deletions(-)
diff ./drivers/md/md.c~current~ ./drivers/md/md.c
--- ./drivers/md/md.c~current~ 2005-08-29 16:32:20.000000000 +1000
+++ ./drivers/md/md.c 2005-08-29 16:32:24.000000000 +1000
@@ -645,7 +645,7 @@ static int super_90_validate(mddev_t *md
if (sb->state & (1<<MD_SB_BITMAP_PRESENT) &&
mddev->bitmap_file == NULL) {
- if (mddev->level != 1) {
+ if (mddev->level != 1 && mddev->level != 5) {
/* FIXME use a better test */
printk(KERN_WARNING "md: bitmaps only support for raid1\n");
return -EINVAL;
@@ -3517,7 +3517,6 @@ void md_done_sync(mddev_t *mddev, int bl
*/
void md_write_start(mddev_t *mddev, struct bio *bi)
{
- DEFINE_WAIT(w);
if (bio_data_dir(bi) != WRITE)
return;
diff ./drivers/md/raid5.c~current~ ./drivers/md/raid5.c
--- ./drivers/md/raid5.c~current~ 2005-08-29 16:32:20.000000000 +1000
+++ ./drivers/md/raid5.c 2005-08-29 16:32:24.000000000 +1000
@@ -24,6 +24,8 @@
#include <linux/bitops.h>
#include <asm/atomic.h>
+#include <linux/raid/bitmap.h>
+
/*
* Stripe cache
*/
@@ -79,8 +81,13 @@ static inline void __release_stripe(raid
if (test_bit(STRIPE_HANDLE, &sh->state)) {
if (test_bit(STRIPE_DELAYED, &sh->state))
list_add_tail(&sh->lru, &conf->delayed_list);
- else
+ else if (test_bit(STRIPE_BIT_DELAY, &sh->state) &&
+ conf->seq_write == sh->bm_seq)
+ list_add_tail(&sh->lru, &conf->bitmap_list);
+ else {
+ clear_bit(STRIPE_BIT_DELAY, &sh->state);
list_add_tail(&sh->lru, &conf->handle_list);
+ }
md_wakeup_thread(conf->mddev->thread);
} else {
if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
@@ -244,6 +251,9 @@ static struct stripe_head *get_active_st
spin_lock_irq(&conf->device_lock);
do {
+ wait_event_lock_irq(conf->wait_for_stripe,
+ conf->quiesce == 0,
+ conf->device_lock, /* nothing */);
sh = __find_stripe(conf, sector);
if (!sh) {
if (!conf->inactive_blocked)
@@ -803,6 +813,7 @@ static int add_stripe_bio(struct stripe_
{
struct bio **bip;
raid5_conf_t *conf = sh->raid_conf;
+ int firstwrite=0;
PRINTK("adding bh b#%llu to stripe s#%llu\n",
(unsigned long long)bi->bi_sector,
@@ -811,9 +822,11 @@ static int add_stripe_bio(struct stripe_
spin_lock(&sh->lock);
spin_lock_irq(&conf->device_lock);
- if (forwrite)
+ if (forwrite) {
bip = &sh->dev[dd_idx].towrite;
- else
+ if (*bip == NULL && sh->dev[dd_idx].written == NULL)
+ firstwrite = 1;
+ } else
bip = &sh->dev[dd_idx].toread;
while (*bip && (*bip)->bi_sector < bi->bi_sector) {
if ((*bip)->bi_sector + ((*bip)->bi_size >> 9) > bi->bi_sector)
@@ -836,6 +849,13 @@ static int add_stripe_bio(struct stripe_
(unsigned long long)bi->bi_sector,
(unsigned long long)sh->sector, dd_idx);
+ if (conf->mddev->bitmap && firstwrite) {
+ sh->bm_seq = conf->seq_write;
+ bitmap_startwrite(conf->mddev->bitmap, sh->sector,
+ STRIPE_SECTORS, 0);
+ set_bit(STRIPE_BIT_DELAY, &sh->state);
+ }
+
if (forwrite) {
/* check if page is covered */
sector_t sector = sh->dev[dd_idx].sector;
@@ -958,12 +978,13 @@ static void handle_stripe(struct stripe_
* need to be failed
*/
if (failed > 1 && to_read+to_write+written) {
- spin_lock_irq(&conf->device_lock);
for (i=disks; i--; ) {
+ int bitmap_end = 0;
+ spin_lock_irq(&conf->device_lock);
/* fail all writes first */
bi = sh->dev[i].towrite;
sh->dev[i].towrite = NULL;
- if (bi) to_write--;
+ if (bi) { to_write--; bitmap_end = 1; }
if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
wake_up(&conf->wait_for_overlap);
@@ -981,6 +1002,7 @@ static void handle_stripe(struct stripe_
/* and fail all 'written' */
bi = sh->dev[i].written;
sh->dev[i].written = NULL;
+ if (bi) bitmap_end = 1;
while (bi && bi->bi_sector < sh->dev[i].sector + STRIPE_SECTORS) {
struct bio *bi2 = r5_next_bio(bi, sh->dev[i].sector);
clear_bit(BIO_UPTODATE, &bi->bi_flags);
@@ -1009,8 +1031,11 @@ static void handle_stripe(struct stripe_
bi = nextbi;
}
}
+ spin_unlock_irq(&conf->device_lock);
+ if (bitmap_end)
+ bitmap_endwrite(conf->mddev->bitmap, sh->sector,
+ STRIPE_SECTORS, 0, 0);
}
- spin_unlock_irq(&conf->device_lock);
}
if (failed > 1 && syncing) {
md_done_sync(conf->mddev, STRIPE_SECTORS,0);
@@ -1038,6 +1063,7 @@ static void handle_stripe(struct stripe_
test_bit(R5_UPTODATE, &dev->flags) ) {
/* We can return any write requests */
struct bio *wbi, *wbi2;
+ int bitmap_end = 0;
PRINTK("Return write for disc %d\n", i);
spin_lock_irq(&conf->device_lock);
wbi = dev->written;
@@ -1051,7 +1077,13 @@ static void handle_stripe(struct stripe_
}
wbi = wbi2;
}
+ if (dev->towrite == NULL)
+ bitmap_end = 1;
spin_unlock_irq(&conf->device_lock);
+ if (bitmap_end)
+ bitmap_endwrite(conf->mddev->bitmap, sh->sector,
+ STRIPE_SECTORS,
+ !test_bit(STRIPE_DEGRADED, &sh->state), 0);
}
}
}
@@ -1175,7 +1207,8 @@ static void handle_stripe(struct stripe_
}
}
/* now if nothing is locked, and if we have enough data, we can start a write request */
- if (locked == 0 && (rcw == 0 ||rmw == 0)) {
+ if (locked == 0 && (rcw == 0 ||rmw == 0) &&
+ !test_bit(STRIPE_BIT_DELAY, &sh->state)) {
PRINTK("Computing parity...\n");
compute_parity(sh, rcw==0 ? RECONSTRUCT_WRITE : READ_MODIFY_WRITE);
/* now every locked buffer is ready to be written */
@@ -1231,6 +1264,7 @@ static void handle_stripe(struct stripe_
dev = &sh->dev[failed_num];
set_bit(R5_LOCKED, &dev->flags);
set_bit(R5_Wantwrite, &dev->flags);
+ clear_bit(STRIPE_DEGRADED, &sh->state);
locked++;
set_bit(STRIPE_INSYNC, &sh->state);
set_bit(R5_Syncio, &dev->flags);
@@ -1298,6 +1332,8 @@ static void handle_stripe(struct stripe_
bi->bi_next = NULL;
generic_make_request(bi);
} else {
+ if (rw == 1)
+ set_bit(STRIPE_DEGRADED, &sh->state);
PRINTK("skip op %ld on disc %d for sector %llu\n",
bi->bi_rw, i, (unsigned long long)sh->sector);
clear_bit(R5_LOCKED, &sh->dev[i].flags);
@@ -1322,6 +1358,20 @@ static inline void raid5_activate_delaye
}
}
+static inline void activate_bit_delay(raid5_conf_t *conf)
+{
+ /* device_lock is held */
+ struct list_head head;
+ list_add(&head, &conf->bitmap_list);
+ list_del_init(&conf->bitmap_list);
+ while (!list_empty(&head)) {
+ struct stripe_head *sh = list_entry(head.next, struct stripe_head, lru);
+ list_del_init(&sh->lru);
+ atomic_inc(&sh->count);
+ __release_stripe(conf, sh);
+ }
+}
+
static void unplug_slaves(mddev_t *mddev)
{
raid5_conf_t *conf = mddev_to_conf(mddev);
@@ -1354,8 +1404,10 @@ static void raid5_unplug_device(request_
spin_lock_irqsave(&conf->device_lock, flags);
- if (blk_remove_plug(q))
+ if (blk_remove_plug(q)) {
+ conf->seq_flush++;
raid5_activate_delayed(conf);
+ }
md_wakeup_thread(mddev->thread);
spin_unlock_irqrestore(&conf->device_lock, flags);
@@ -1493,10 +1545,20 @@ static sector_t sync_request(mddev_t *md
sector_t first_sector;
int raid_disks = conf->raid_disks;
int data_disks = raid_disks-1;
+ sector_t max_sector = mddev->size << 1;
+ int sync_blocks;
- if (sector_nr >= mddev->size <<1) {
+ if (sector_nr >= max_sector) {
/* just being told to finish up .. nothing much to do */
unplug_slaves(mddev);
+
+ if (mddev->curr_resync < max_sector) /* aborted */
+ bitmap_end_sync(mddev->bitmap, mddev->curr_resync,
+ &sync_blocks, 1);
+ else /* compelted sync */
+ conf->fullsync = 0;
+ bitmap_close_sync(mddev->bitmap);
+
return 0;
}
/* if there is 1 or more failed drives and we are trying
@@ -1508,6 +1570,13 @@ static sector_t sync_request(mddev_t *md
*skipped = 1;
return rv;
}
+ if (!bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, 1) &&
+ !conf->fullsync && sync_blocks >= STRIPE_SECTORS) {
+ /* we can skip this block, and probably more */
+ sync_blocks /= STRIPE_SECTORS;
+ *skipped = 1;
+ return sync_blocks * STRIPE_SECTORS; /* keep things rounded to whole stripes */
+ }
x = sector_nr;
chunk_offset = sector_div(x, sectors_per_chunk);
@@ -1524,6 +1593,7 @@ static sector_t sync_request(mddev_t *md
*/
schedule_timeout_uninterruptible(1);
}
+ bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, 0);
spin_lock(&sh->lock);
set_bit(STRIPE_SYNCING, &sh->state);
clear_bit(STRIPE_INSYNC, &sh->state);
@@ -1557,6 +1627,13 @@ static void raid5d (mddev_t *mddev)
while (1) {
struct list_head *first;
+ if (conf->seq_flush - conf->seq_write > 0) {
+ int seq = conf->seq_flush;
+ bitmap_unplug(mddev->bitmap);
+ conf->seq_write = seq;
+ activate_bit_delay(conf);
+ }
+
if (list_empty(&conf->handle_list) &&
atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD &&
!blk_queue_plugged(mddev->queue) &&
@@ -1590,7 +1667,7 @@ static void raid5d (mddev_t *mddev)
PRINTK("--- raid5d inactive\n");
}
-static int run (mddev_t *mddev)
+static int run(mddev_t *mddev)
{
raid5_conf_t *conf;
int raid_disk, memory;
@@ -1620,6 +1697,7 @@ static int run (mddev_t *mddev)
init_waitqueue_head(&conf->wait_for_overlap);
INIT_LIST_HEAD(&conf->handle_list);
INIT_LIST_HEAD(&conf->delayed_list);
+ INIT_LIST_HEAD(&conf->bitmap_list);
INIT_LIST_HEAD(&conf->inactive_list);
atomic_set(&conf->active_stripes, 0);
atomic_set(&conf->preread_active_stripes, 0);
@@ -1731,6 +1809,9 @@ memory = conf->max_nr_stripes * (sizeof(
/* Ok, everything is just fine now */
+ if (mddev->bitmap)
+ mddev->thread->timeout = mddev->bitmap->daemon_sleep * HZ;
+
mddev->queue->unplug_fn = raid5_unplug_device;
mddev->queue->issue_flush_fn = raid5_issue_flush;
@@ -1911,6 +1992,8 @@ static int raid5_add_disk(mddev_t *mddev
rdev->in_sync = 0;
rdev->raid_disk = disk;
found = 1;
+ if (rdev->saved_raid_disk != disk)
+ conf->fullsync = 1;
p->rdev = rdev;
break;
}
@@ -1940,6 +2023,35 @@ static int raid5_resize(mddev_t *mddev,
return 0;
}
+static void raid5_quiesce(mddev_t *mddev, int state)
+{
+ raid5_conf_t *conf = mddev_to_conf(mddev);
+
+ switch(state) {
+ case 1: /* stop all writes */
+ spin_lock_irq(&conf->device_lock);
+ conf->quiesce = 1;
+ wait_event_lock_irq(conf->wait_for_stripe,
+ atomic_read(&conf->active_stripes) == 0,
+ conf->device_lock, /* nothing */);
+ spin_unlock_irq(&conf->device_lock);
+ break;
+
+ case 0: /* re-enable writes */
+ spin_lock_irq(&conf->device_lock);
+ conf->quiesce = 0;
+ wake_up(&conf->wait_for_stripe);
+ spin_unlock_irq(&conf->device_lock);
+ break;
+ }
+ if (mddev->thread) {
+ if (mddev->bitmap)
+ mddev->thread->timeout = mddev->bitmap->daemon_sleep * HZ;
+ else
+ mddev->thread->timeout = MAX_SCHEDULE_TIMEOUT;
+ md_wakeup_thread(mddev->thread);
+ }
+}
static mdk_personality_t raid5_personality=
{
.name = "raid5",
@@ -1954,6 +2066,7 @@ static mdk_personality_t raid5_personali
.spare_active = raid5_spare_active,
.sync_request = sync_request,
.resize = raid5_resize,
+ .quiesce = raid5_quiesce,
};
static int __init raid5_init (void)
diff ./include/linux/raid/raid5.h~current~ ./include/linux/raid/raid5.h
--- ./include/linux/raid/raid5.h~current~ 2005-08-29 16:32:20.000000000 +1000
+++ ./include/linux/raid/raid5.h 2005-08-29 16:32:24.000000000 +1000
@@ -134,6 +134,7 @@ struct stripe_head {
unsigned long state; /* state flags */
atomic_t count; /* nr of active thread/requests */
spinlock_t lock;
+ int bm_seq; /* sequence number for bitmap flushes */
struct r5dev {
struct bio req;
struct bio_vec vec;
@@ -165,12 +166,13 @@ struct stripe_head {
/*
* Stripe state
*/
-#define STRIPE_ERROR 1
#define STRIPE_HANDLE 2
#define STRIPE_SYNCING 3
#define STRIPE_INSYNC 4
#define STRIPE_PREREAD_ACTIVE 5
#define STRIPE_DELAYED 6
+#define STRIPE_DEGRADED 7
+#define STRIPE_BIT_DELAY 8
/*
* Plugging:
@@ -210,10 +212,20 @@ struct raid5_private_data {
struct list_head handle_list; /* stripes needing handling */
struct list_head delayed_list; /* stripes that have plugged requests */
+ struct list_head bitmap_list; /* stripes delaying awaiting bitmap update */
atomic_t preread_active_stripes; /* stripes with scheduled io */
char cache_name[20];
kmem_cache_t *slab_cache; /* for allocating stripes */
+
+ int seq_flush, seq_write;
+ int quiesce;
+
+ int fullsync; /* set to 1 if a full sync is needed,
+ * (fresh device added).
+ * Cleared when a sync completes.
+ */
+
/*
* Free stripes pool
*/
-
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