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@xxxxxxxxxxxx>
Signed-off-by: Neil Brown <neilb@xxxxxxxxxxxxxxx>
### Diffstat output
./drivers/md/bitmap.c | 26 +++++++-
./drivers/md/raid1.c | 124 +++++++++++++++++++++++++++++++++++++++---
./include/linux/raid/bitmap.h | 15 +++--
./include/linux/raid/md_k.h | 3 +
./include/linux/raid/raid1.h | 13 ++++
5 files changed, 165 insertions(+), 16 deletions(-)
diff ./drivers/md/bitmap.c~current~ ./drivers/md/bitmap.c
--- ./drivers/md/bitmap.c~current~ 2005-08-11 16:17:06.000000000 +1000
+++ ./drivers/md/bitmap.c 2005-08-11 16:04:11.000000000 +1000
@@ -437,6 +437,7 @@ void bitmap_print_sb(struct bitmap *bitm
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
{
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
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
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_coun
}
}
-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 *bit
}
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;
diff ./drivers/md/raid1.c~current~ ./drivers/md/raid1.c
--- ./drivers/md/raid1.c~current~ 2005-08-11 16:17:06.000000000 +1000
+++ ./drivers/md/raid1.c 2005-08-11 16:22:45.000000000 +1000
@@ -222,8 +222,17 @@ static void raid_end_bio_io(r1bio_t *r1_
{
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(struc
{
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(struc
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,
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
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
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
}
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
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;
diff ./include/linux/raid/bitmap.h~current~ ./include/linux/raid/bitmap.h
--- ./include/linux/raid/bitmap.h~current~ 2005-08-11 16:17:06.000000000 +1000
+++ ./include/linux/raid/bitmap.h 2005-08-11 16:04:11.000000000 +1000
@@ -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 *bi
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);
diff ./include/linux/raid/md_k.h~current~ ./include/linux/raid/md_k.h
--- ./include/linux/raid/md_k.h~current~ 2005-08-11 16:17:06.000000000 +1000
+++ ./include/linux/raid/md_k.h 2005-08-11 16:04:11.000000000 +1000
@@ -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
diff ./include/linux/raid/raid1.h~current~ ./include/linux/raid/raid1.h
--- ./include/linux/raid/raid1.h~current~ 2005-08-11 16:17:06.000000000 +1000
+++ ./include/linux/raid/raid1.h 2005-08-11 16:04:11.000000000 +1000
@@ -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
-
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