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[PATCH] md: add write-behind support for md/raid1

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If a device is flagged 'WriteMostly' and the array has a bitmap, and the
bitmap superblock indicates that write_behind is allowed, then write_behind is
enabled for WriteMostly devices.

Write requests will be acknowledges as complete to the caller (via b_end_io)
when all non-WriteMostly devices have completed the write, but will not be
cleared from the bitmap until all devices complete.

This requires memory allocation to make a local copy of the data being
written.  If there is insufficient memory, then we fall-back on normal write
semantics.

Signed-Off-By: Paul Clements <paul.clements@steeleye.com>
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>
This commit is contained in:
NeilBrown 2005-09-09 16:23:47 -07:00 committed by Linus Torvalds
parent 8ddf9efe67
commit 4b6d287f62
5 changed files with 165 additions and 16 deletions
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26
drivers/md/bitmap.c
View File

@ -437,6 +437,7 @@ void bitmap_print_sb(struct bitmap *bitmap)
printk(KERN_DEBUG " daemon sleep: %ds\n", le32_to_cpu(sb->daemon_sleep));
printk(KERN_DEBUG " sync size: %llu KB\n",
(unsigned long long)le64_to_cpu(sb->sync_size)/2);
printk(KERN_DEBUG "max write behind: %d\n", le32_to_cpu(sb->write_behind));
kunmap(bitmap->sb_page);
}
@ -445,7 +446,7 @@ static int bitmap_read_sb(struct bitmap *bitmap)
{
char *reason = NULL;
bitmap_super_t *sb;
unsigned long chunksize, daemon_sleep;
unsigned long chunksize, daemon_sleep, write_behind;
unsigned long bytes_read;
unsigned long long events;
int err = -EINVAL;
@ -474,6 +475,7 @@ static int bitmap_read_sb(struct bitmap *bitmap)
chunksize = le32_to_cpu(sb->chunksize);
daemon_sleep = le32_to_cpu(sb->daemon_sleep);
write_behind = le32_to_cpu(sb->write_behind);
/* verify that the bitmap-specific fields are valid */
if (sb->magic != cpu_to_le32(BITMAP_MAGIC))
@ -485,7 +487,9 @@ static int bitmap_read_sb(struct bitmap *bitmap)
else if ((1 << ffz(~chunksize)) != chunksize)
reason = "bitmap chunksize not a power of 2";
else if (daemon_sleep < 1 || daemon_sleep > 15)
reason = "daemon sleep period out of range";
reason = "daemon sleep period out of range (1-15s)";
else if (write_behind > COUNTER_MAX)
reason = "write-behind limit out of range (0 - 16383)";
if (reason) {
printk(KERN_INFO "%s: invalid bitmap file superblock: %s\n",
bmname(bitmap), reason);
@ -518,6 +522,7 @@ success:
/* assign fields using values from superblock */
bitmap->chunksize = chunksize;
bitmap->daemon_sleep = daemon_sleep;
bitmap->max_write_behind = write_behind;
bitmap->flags |= sb->state;
bitmap->events_cleared = le64_to_cpu(sb->events_cleared);
if (sb->state & BITMAP_STALE)
@ -1282,9 +1287,16 @@ static bitmap_counter_t *bitmap_get_counter(struct bitmap *bitmap,
}
}
int bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sectors)
int bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sectors, int behind)
{
if (!bitmap) return 0;
if (behind) {
atomic_inc(&bitmap->behind_writes);
PRINTK(KERN_DEBUG "inc write-behind count %d/%d\n",
atomic_read(&bitmap->behind_writes), bitmap->max_write_behind);
}
while (sectors) {
int blocks;
bitmap_counter_t *bmc;
@ -1319,9 +1331,15 @@ int bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sect
}
void bitmap_endwrite(struct bitmap *bitmap, sector_t offset, unsigned long sectors,
int success)
int success, int behind)
{
if (!bitmap) return;
if (behind) {
atomic_dec(&bitmap->behind_writes);
PRINTK(KERN_DEBUG "dec write-behind count %d/%d\n",
atomic_read(&bitmap->behind_writes), bitmap->max_write_behind);
}
while (sectors) {
int blocks;
unsigned long flags;

124
drivers/md/raid1.c
View File

@ -222,8 +222,17 @@ static void raid_end_bio_io(r1bio_t *r1_bio)
{
struct bio *bio = r1_bio->master_bio;
bio_endio(bio, bio->bi_size,
test_bit(R1BIO_Uptodate, &r1_bio->state) ? 0 : -EIO);
/* if nobody has done the final endio yet, do it now */
if (!test_and_set_bit(R1BIO_Returned, &r1_bio->state)) {
PRINTK(KERN_DEBUG "raid1: sync end %s on sectors %llu-%llu\n",
(bio_data_dir(bio) == WRITE) ? "write" : "read",
(unsigned long long) bio->bi_sector,
(unsigned long long) bio->bi_sector +
(bio->bi_size >> 9) - 1);
bio_endio(bio, bio->bi_size,
test_bit(R1BIO_Uptodate, &r1_bio->state) ? 0 : -EIO);
}
free_r1bio(r1_bio);
}
@ -292,7 +301,7 @@ static int raid1_end_write_request(struct bio *bio, unsigned int bytes_done, int
{
int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
r1bio_t * r1_bio = (r1bio_t *)(bio->bi_private);
int mirror;
int mirror, behind;
conf_t *conf = mddev_to_conf(r1_bio->mddev);
if (bio->bi_size)
@ -323,16 +332,46 @@ static int raid1_end_write_request(struct bio *bio, unsigned int bytes_done, int
update_head_pos(mirror, r1_bio);
behind = test_bit(R1BIO_BehindIO, &r1_bio->state);
if (behind) {
if (test_bit(WriteMostly, &conf->mirrors[mirror].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;
PRINTK(KERN_DEBUG "raid1: behind end write sectors %llu-%llu\n",
(unsigned long long) mbio->bi_sector,
(unsigned long long) mbio->bi_sector +
(mbio->bi_size >> 9) - 1);
bio_endio(mbio, mbio->bi_size, 0);
}
}
}
/*
*
* Let's see if all mirrored write operations have finished
* already.
*/
if (atomic_dec_and_test(&r1_bio->remaining)) {
if (test_bit(R1BIO_BehindIO, &r1_bio->state)) {
/* free extra copy of the data pages */
int i = bio->bi_vcnt;
while (i--)
__free_page(bio->bi_io_vec[i].bv_page);
}
/* 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_Degraded, &r1_bio->state),
behind);
md_write_end(r1_bio->mddev);
raid_end_bio_io(r1_bio);
}
@ -562,6 +601,39 @@ static void device_barrier(conf_t *conf, sector_t sect)
spin_unlock_irq(&conf->resync_lock);
}
/* duplicate the data pages for behind I/O */
static struct page **alloc_behind_pages(struct bio *bio)
{
int i;
struct bio_vec *bvec;
struct page **pages = kmalloc(bio->bi_vcnt * sizeof(struct page *),
GFP_NOIO);
if (unlikely(!pages))
goto do_sync_io;
memset(pages, 0, bio->bi_vcnt * sizeof(struct page *));
bio_for_each_segment(bvec, bio, i) {
pages[i] = alloc_page(GFP_NOIO);
if (unlikely(!pages[i]))
goto do_sync_io;
memcpy(kmap(pages[i]) + bvec->bv_offset,
kmap(bvec->bv_page) + bvec->bv_offset, bvec->bv_len);
kunmap(pages[i]);
kunmap(bvec->bv_page);
}
return pages;
do_sync_io:
if (pages)
for (i = 0; i < bio->bi_vcnt && pages[i]; i++)
__free_page(pages[i]);
kfree(pages);
PRINTK("%dB behind alloc failed, doing sync I/O\n", bio->bi_size);
return NULL;
}
static int make_request(request_queue_t *q, struct bio * bio)
{
mddev_t *mddev = q->queuedata;
@ -574,6 +646,7 @@ static int make_request(request_queue_t *q, struct bio * bio)
struct bitmap *bitmap = mddev->bitmap;
unsigned long flags;
struct bio_list bl;
struct page **behind_pages = NULL;
if (unlikely(bio_barrier(bio))) {
bio_endio(bio, bio->bi_size, -EOPNOTSUPP);
@ -613,8 +686,6 @@ static int make_request(request_queue_t *q, struct bio * bio)
r1_bio->mddev = mddev;
r1_bio->sector = bio->bi_sector;
r1_bio->state = 0;
if (bio_data_dir(bio) == READ) {
/*
* read balancing logic:
@ -675,13 +746,22 @@ static int make_request(request_queue_t *q, struct bio * bio)
}
rcu_read_unlock();
BUG_ON(targets == 0); /* we never fail the last device */
if (targets < conf->raid_disks) {
/* array is degraded, we will not clear the bitmap
* on I/O completion (see raid1_end_write_request) */
set_bit(R1BIO_Degraded, &r1_bio->state);
}
/* do behind I/O ? */
if (bitmap &&
atomic_read(&bitmap->behind_writes) < bitmap->max_write_behind &&
(behind_pages = alloc_behind_pages(bio)) != NULL)
set_bit(R1BIO_BehindIO, &r1_bio->state);
atomic_set(&r1_bio->remaining, 0);
atomic_set(&r1_bio->behind_remaining, 0);
bio_list_init(&bl);
for (i = 0; i < disks; i++) {
@ -698,12 +778,31 @@ static int make_request(request_queue_t *q, struct bio * bio)
mbio->bi_rw = WRITE;
mbio->bi_private = r1_bio;
if (behind_pages) {
struct bio_vec *bvec;
int j;
/* Yes, I really want the '__' version so that
* we clear any unused pointer in the io_vec, rather
* than leave them unchanged. This is important
* because when we come to free the pages, we won't
* know the originial bi_idx, so we just free
* them all
*/
__bio_for_each_segment(bvec, mbio, j, 0)
bvec->bv_page = behind_pages[j];
if (test_bit(WriteMostly, &conf->mirrors[i].rdev->flags))
atomic_inc(&r1_bio->behind_remaining);
}
atomic_inc(&r1_bio->remaining);
bio_list_add(&bl, mbio);
}
kfree(behind_pages); /* the behind pages are attached to the bios now */
bitmap_startwrite(bitmap, bio->bi_sector, r1_bio->sectors);
bitmap_startwrite(bitmap, bio->bi_sector, r1_bio->sectors,
test_bit(R1BIO_BehindIO, &r1_bio->state));
spin_lock_irqsave(&conf->device_lock, flags);
bio_list_merge(&conf->pending_bio_list, &bl);
bio_list_init(&bl);
@ -1471,6 +1570,17 @@ out:
static int stop(mddev_t *mddev)
{
conf_t *conf = mddev_to_conf(mddev);
struct bitmap *bitmap = mddev->bitmap;
int behind_wait = 0;
/* wait for behind writes to complete */
while (bitmap && atomic_read(&bitmap->behind_writes) > 0) {
behind_wait++;
printk(KERN_INFO "raid1: behind writes in progress on device %s, waiting to stop (%d)\n", mdname(mddev), behind_wait);
set_current_state(TASK_UNINTERRUPTIBLE);
schedule_timeout(HZ); /* wait a second */
/* need to kick something here to make sure I/O goes? */
}
md_unregister_thread(mddev->thread);
mddev->thread = NULL;

15
include/linux/raid/bitmap.h
View File

@ -7,7 +7,7 @@
#define BITMAP_H 1
#define BITMAP_MAJOR 3
#define BITMAP_MINOR 38
#define BITMAP_MINOR 39
/*
* in-memory bitmap:
@ -147,8 +147,9 @@ typedef struct bitmap_super_s {
__u32 state; /* 48 bitmap state information */
__u32 chunksize; /* 52 the bitmap chunk size in bytes */
__u32 daemon_sleep; /* 56 seconds between disk flushes */
__u32 write_behind; /* 60 number of outstanding write-behind writes */
__u8 pad[256 - 60]; /* set to zero */
__u8 pad[256 - 64]; /* set to zero */
} bitmap_super_t;
/* notes:
@ -226,6 +227,9 @@ struct bitmap {
unsigned long flags;
unsigned long max_write_behind; /* write-behind mode */
atomic_t behind_writes;
/*
* the bitmap daemon - periodically wakes up and sweeps the bitmap
* file, cleaning up bits and flushing out pages to disk as necessary
@ -260,9 +264,10 @@ int bitmap_setallbits(struct bitmap *bitmap);
void bitmap_write_all(struct bitmap *bitmap);
/* these are exported */
int bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sectors);
void bitmap_endwrite(struct bitmap *bitmap, sector_t offset, unsigned long sectors,
int success);
int bitmap_startwrite(struct bitmap *bitmap, sector_t offset,
unsigned long sectors, int behind);
void bitmap_endwrite(struct bitmap *bitmap, sector_t offset,
unsigned long sectors, int success, int behind);
int bitmap_start_sync(struct bitmap *bitmap, sector_t offset, int *blocks, int degraded);
void bitmap_end_sync(struct bitmap *bitmap, sector_t offset, int *blocks, int aborted);
void bitmap_close_sync(struct bitmap *bitmap);

3
include/linux/raid/md_k.h
View File

@ -275,6 +275,9 @@ struct mddev_s
atomic_t writes_pending;
request_queue_t *queue; /* for plugging ... */
atomic_t write_behind; /* outstanding async IO */
unsigned int max_write_behind; /* 0 = sync */
struct bitmap *bitmap; /* the bitmap for the device */
struct file *bitmap_file; /* the bitmap file */
long bitmap_offset; /* offset from superblock of

13
include/linux/raid/raid1.h
View File

@ -80,6 +80,9 @@ struct r1bio_s {
atomic_t remaining; /* 'have we finished' count,
* used from IRQ handlers
*/
atomic_t behind_remaining; /* number of write-behind ios remaining
* in this BehindIO request
*/
sector_t sector;
int sectors;
unsigned long state;
@ -107,4 +110,14 @@ struct r1bio_s {
#define R1BIO_Uptodate 0
#define R1BIO_IsSync 1
#define R1BIO_Degraded 2
#define R1BIO_BehindIO 3
/* For write-behind requests, we call bi_end_io when
* the last non-write-behind device completes, providing
* any write was successful. Otherwise we call when
* any write-behind write succeeds, otherwise we call
* with failure when last write completes (and all failed).
* Record that bi_end_io was called with this flag...
*/
#define R1BIO_Returned 4
#endif