[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>

1 files changed, 1 insertions, 2 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index be7873c61b3c..dbf540a7fccc 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -645,7 +645,7 @@ static int super_90_validate(mddev_t *mddev, mdk_rdev_t *rdev)
 
                 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 blocks, int ok)
  */
 void md_write_start(mddev_t *mddev, struct bio *bi)
 {
-        DEFINE_WAIT(w);
         if (bio_data_dir(bi) != WRITE)
                 return;