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authorNeilBrown <neilb@suse.de>2010-03-31 02:21:44 +0200
committerNeilBrown <neilb@suse.de>2010-05-18 07:27:57 +0200
commite555190d82c0f58e825e3cbd9e6ebe2e7ac713bd (patch)
treeea9c8e548c4d5eb5fc903bab05af3bda4192ed00 /drivers/md/bitmap.c
parentmd/raid1: fix confusing 'redirect sector' message. (diff)
downloadlinux-e555190d82c0f58e825e3cbd9e6ebe2e7ac713bd.tar.xz
linux-e555190d82c0f58e825e3cbd9e6ebe2e7ac713bd.zip
md/raid1: delay reads that could overtake behind-writes.
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>
Diffstat (limited to 'drivers/md/bitmap.c')
-rw-r--r--drivers/md/bitmap.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 49d6080387c8..c9c6a345e17b 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -1356,7 +1356,8 @@ void bitmap_endwrite(struct bitmap *bitmap, sector_t offset, unsigned long secto
{
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);
}
@@ -1680,6 +1681,7 @@ 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;