md/bitmap: don't read page from device with Bitmap_sync
The device owns Bitmap_sync flag needs recovery
to become in sync, and read page from this type
device could get stale status.
Also add comments for Bitmap_sync bit per the
suggestion from Shaohua and Neil.
Previous disscussion can be found here:
https://marc.info/?t=149760428900004&r=1&w=2
Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 991f0fe..b50eb4a 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -134,7 +134,9 @@ enum flag_bits {
Faulty, /* device is known to have a fault */
In_sync, /* device is in_sync with rest of array */
Bitmap_sync, /* ..actually, not quite In_sync. Need a
- * bitmap-based recovery to get fully in sync
+ * bitmap-based recovery to get fully in sync.
+ * The bit is only meaningful before device
+ * has been passed to pers->hot_add_disk.
*/
WriteMostly, /* Avoid reading if at all possible */
AutoDetected, /* added by auto-detect */