[PATCH] md: add write-intent-bitmap support to raid5
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@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index ed859e0..4683ca2 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -24,6 +24,8 @@
#include <linux/bitops.h>
#include <asm/atomic.h>
+#include <linux/raid/bitmap.h>
+
/*
* Stripe cache
*/
@@ -79,8 +81,13 @@
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 @@
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 @@
{
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 @@
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 @@
(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 @@
* 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 @@
/* 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 @@
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 @@
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 @@
}
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 @@
}
}
/* 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 @@
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 @@
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 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 @@
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 @@
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 @@
*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);
@@ -1525,6 +1594,7 @@
set_current_state(TASK_UNINTERRUPTIBLE);
schedule_timeout(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);
@@ -1558,6 +1628,13 @@
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) &&
@@ -1591,7 +1668,7 @@
PRINTK("--- raid5d inactive\n");
}
-static int run (mddev_t *mddev)
+static int run(mddev_t *mddev)
{
raid5_conf_t *conf;
int raid_disk, memory;
@@ -1621,6 +1698,7 @@
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);
@@ -1732,6 +1810,9 @@
/* 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;
@@ -1912,6 +1993,8 @@
rdev->in_sync = 0;
rdev->raid_disk = disk;
found = 1;
+ if (rdev->saved_raid_disk != disk)
+ conf->fullsync = 1;
p->rdev = rdev;
break;
}
@@ -1941,6 +2024,35 @@
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",
@@ -1955,6 +2067,7 @@
.spare_active = raid5_spare_active,
.sync_request = sync_request,
.resize = raid5_resize,
+ .quiesce = raid5_quiesce,
};
static int __init raid5_init (void)