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[PATCH] md: add write-behind support for md/raid1

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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 <paul.clements@steeleye.com>
Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
NeilBrown
2005-09-09 16:23:47 -07:00
committed by Linus Torvalds
parent 8ddf9efe67
commit 4b6d287f62
5 changed files with 165 additions and 16 deletions
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15
include/linux/raid/bitmap.h
View File

@@ -7,7 +7,7 @@
#define BITMAP_H 1
#define BITMAP_MAJOR 3
#define BITMAP_MINOR 38
#define BITMAP_MINOR 39
/*
* in-memory bitmap:
@@ -147,8 +147,9 @@ typedef struct bitmap_super_s {
__u32 state; /* 48 bitmap state information */
__u32 chunksize; /* 52 the bitmap chunk size in bytes */
__u32 daemon_sleep; /* 56 seconds between disk flushes */
__u32 write_behind; /* 60 number of outstanding write-behind writes */
__u8 pad[256 - 60]; /* set to zero */
__u8 pad[256 - 64]; /* set to zero */
} bitmap_super_t;
/* notes:
@@ -226,6 +227,9 @@ struct bitmap {
unsigned long flags;
unsigned long max_write_behind; /* write-behind mode */
atomic_t behind_writes;
/*
* the bitmap daemon - periodically wakes up and sweeps the bitmap
* file, cleaning up bits and flushing out pages to disk as necessary
@@ -260,9 +264,10 @@ int bitmap_setallbits(struct bitmap *bitmap);
void bitmap_write_all(struct bitmap *bitmap);
/* these are exported */
int bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sectors);
void bitmap_endwrite(struct bitmap *bitmap, sector_t offset, unsigned long sectors,
int success);
int bitmap_startwrite(struct bitmap *bitmap, sector_t offset,
unsigned long sectors, int behind);
void bitmap_endwrite(struct bitmap *bitmap, sector_t offset,
unsigned long sectors, int success, int behind);
int bitmap_start_sync(struct bitmap *bitmap, sector_t offset, int *blocks, int degraded);
void bitmap_end_sync(struct bitmap *bitmap, sector_t offset, int *blocks, int aborted);
void bitmap_close_sync(struct bitmap *bitmap);

3
include/linux/raid/md_k.h
View File

@@ -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

13
include/linux/raid/raid1.h
View File

@@ -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