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[PATCH] md: support write-mostly device in raid1

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This allows a device in a raid1 to be marked as "write mostly".  Read requests
will only be sent if there is no other option.

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 16:23:45 -07:00
committed by Linus Torvalds
parent 36fa30636f
commit 8ddf9efe67
4 changed files with 82 additions and 26 deletions
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3
include/linux/raid/md_k.h
View File

@@ -181,6 +181,9 @@ struct mdk_rdev_s
int faulty; /* if faulty do not issue IO requests */
int in_sync; /* device is a full member of the array */
unsigned long flags; /* Should include faulty and in_sync here. */
#define WriteMostly 4 /* Avoid reading if at all possible */
int desc_nr; /* descriptor index in the superblock */
int raid_disk; /* role of device in array */
int saved_raid_disk; /* role that device used to have in the

11
include/linux/raid/md_p.h
View File

@@ -79,6 +79,11 @@
#define MD_DISK_SYNC 2 /* disk is in sync with the raid set */
#define MD_DISK_REMOVED 3 /* disk is in sync with the raid set */
#define MD_DISK_WRITEMOSTLY 9 /* disk is "write-mostly" is RAID1 config.
* read requests will only be sent here in
* dire need
*/
typedef struct mdp_device_descriptor_s {
__u32 number; /* 0 Device number in the entire set */
__u32 major; /* 1 Device major number */
@@ -193,7 +198,7 @@ struct mdp_superblock_1 {
__u64 ctime; /* lo 40 bits are seconds, top 24 are microseconds or 0*/
__u32 level; /* -4 (multipath), -1 (linear), 0,1,4,5 */
__u32 layout; /* only for raid5 currently */
__u32 layout; /* only for raid5 and raid10 currently */
__u64 size; /* used size of component devices, in 512byte sectors */
__u32 chunksize; /* in 512byte sectors */
@@ -212,7 +217,9 @@ struct mdp_superblock_1 {
__u32 dev_number; /* permanent identifier of this device - not role in raid */
__u32 cnt_corrected_read; /* number of read errors that were corrected by re-writing */
__u8 device_uuid[16]; /* user-space setable, ignored by kernel */
__u8 pad2[64-56]; /* set to 0 when writing */
__u8 devflags; /* per-device flags. Only one defined...*/
#define WriteMostly1 1 /* mask for writemostly flag in above */
__u8 pad2[64-57]; /* set to 0 when writing */
/* array state information - 64 bytes */
__u64 utime; /* 40 bits second, 24 btes microseconds */