2.6.32-stable review patch. If anyone has any objections, please let us know.
------------------
From: NeilBrown <neilb@suse.de>
commit e555190d82c0f58e825e3cbd9e6ebe2e7ac713bd upstream.
When a raid1 array is configured to support write-behind
on some devices, it normally only reads from other devices.
If all devices are write-behind (because the rest have failed)
it is possible for a read request to be serviced before a
behind-write request, which would appear as data corruption.
So when forced to read from a WriteMostly device, wait for any
write-behind to complete, and don't start any more behind-writes.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
drivers/md/bitmap.c | 4 +++-
drivers/md/bitmap.h | 3 +++
drivers/md/raid1.c | 25 ++++++++++++++++++-------
3 files changed, 24 insertions(+), 8 deletions(-)
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -1317,7 +1317,8 @@ void bitmap_endwrite(struct bitmap *bitm
{
if (!bitmap) return;
if (behind) {
- atomic_dec(&bitmap->behind_writes);
+ if (atomic_dec_and_test(&bitmap->behind_writes))
+ wake_up(&bitmap->behind_wait);
PRINTK(KERN_DEBUG "dec write-behind count %d/%d\n",
atomic_read(&bitmap->behind_writes), bitmap->max_write_behind);
}
@@ -1629,6 +1630,7 @@ int bitmap_create(mddev_t *mddev)
atomic_set(&bitmap->pending_writes, 0);
init_waitqueue_head(&bitmap->write_wait);
init_waitqueue_head(&bitmap->overflow_wait);
+ init_waitqueue_head(&bitmap->behind_wait);
bitmap->mddev = mddev;
--- a/drivers/md/bitmap.h
+++ b/drivers/md/bitmap.h
@@ -254,6 +254,9 @@ struct bitmap {
wait_queue_head_t write_wait;
wait_queue_head_t overflow_wait;
+#ifndef __GENKSYMS__
+ wait_queue_head_t behind_wait;
+#endif
};
/* the bitmap API */
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -845,6 +845,15 @@ static int make_request(struct request_q
}
mirror = conf->mirrors + rdisk;
+ if ...
