From 4b6d287f627b5fb6a49f78f9e81649ff98c62bb7 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Fri, 9 Sep 2005 16:23:47 -0700 Subject: [PATCH] md: add write-behind support for md/raid1 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 Signed-off-by: Neil Brown Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/raid/md_k.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include/linux/raid/md_k.h') diff --git a/include/linux/raid/md_k.h b/include/linux/raid/md_k.h index 7ef78e15ce0..2514e5fcda7 100644 --- a/include/linux/raid/md_k.h +++ b/include/linux/raid/md_k.h @@ -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 -- cgit v1.2.3-70-g09d2