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/raid1.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'include/linux/raid/raid1.h') diff --git a/include/linux/raid/raid1.h b/include/linux/raid/raid1.h index 9d93cf12e89..60e19b66754 100644 --- a/include/linux/raid/raid1.h +++ b/include/linux/raid/raid1.h @@ -80,6 +80,9 @@ struct r1bio_s { atomic_t remaining; /* 'have we finished' count, * used from IRQ handlers */ + atomic_t behind_remaining; /* number of write-behind ios remaining + * in this BehindIO request + */ sector_t sector; int sectors; unsigned long state; @@ -107,4 +110,14 @@ struct r1bio_s { #define R1BIO_Uptodate 0 #define R1BIO_IsSync 1 #define R1BIO_Degraded 2 +#define R1BIO_BehindIO 3 +/* For write-behind requests, we call bi_end_io when + * the last non-write-behind device completes, providing + * any write was successful. Otherwise we call when + * any write-behind write succeeds, otherwise we call + * with failure when last write completes (and all failed). + * Record that bi_end_io was called with this flag... + */ +#define R1BIO_Returned 4 + #endif -- cgit v1.2.3