linux/drivers/md/raid10.h
NeilBrown 95af587e95 md/raid10: ensure device failure recorded before write request returns.
When a write to one of the legs of a RAID10 fails, the failure is
recorded in the metadata of the other legs so that after a restart
the data on the failed drive wont be trusted even if that drive seems
to be working again (maybe a cable was unplugged).

Currently there is no interlock between the write request completing
and the metadata update.  So it is possible that the write will
complete, the app will confirm success in some way, and then the
machine will crash before the metadata update completes.

This is an extremely small hole for a racy to fit in, but it is
theoretically possible and so should be closed.

So:
 - set MD_CHANGE_PENDING when requesting a metadata update for a
   failed device, so we can know with certainty when it completes
 - queue requests that experienced an error on a new queue which
   is only processed after the metadata update completes
 - call raid_end_bio_io() on bios in that queue when the time comes.

Signed-off-by: NeilBrown <neilb@suse.com>
2015-08-31 19:43:45 +02:00

160 lines
4.1 KiB
C

#ifndef _RAID10_H
#define _RAID10_H
struct raid10_info {
struct md_rdev *rdev, *replacement;
sector_t head_position;
int recovery_disabled; /* matches
* mddev->recovery_disabled
* when we shouldn't try
* recovering this device.
*/
};
struct r10conf {
struct mddev *mddev;
struct raid10_info *mirrors;
struct raid10_info *mirrors_new, *mirrors_old;
spinlock_t device_lock;
/* geometry */
struct geom {
int raid_disks;
int near_copies; /* number of copies laid out
* raid0 style */
int far_copies; /* number of copies laid out
* at large strides across drives
*/
int far_offset; /* far_copies are offset by 1
* stripe instead of many
*/
sector_t stride; /* distance between far copies.
* This is size / far_copies unless
* far_offset, in which case it is
* 1 stripe.
*/
int far_set_size; /* The number of devices in a set,
* where a 'set' are devices that
* contain far/offset copies of
* each other.
*/
int chunk_shift; /* shift from chunks to sectors */
sector_t chunk_mask;
} prev, geo;
int copies; /* near_copies * far_copies.
* must be <= raid_disks
*/
sector_t dev_sectors; /* temp copy of
* mddev->dev_sectors */
sector_t reshape_progress;
sector_t reshape_safe;
unsigned long reshape_checkpoint;
sector_t offset_diff;
struct list_head retry_list;
/* A separate list of r1bio which just need raid_end_bio_io called.
* This mustn't happen for writes which had any errors if the superblock
* needs to be written.
*/
struct list_head bio_end_io_list;
/* queue pending writes and submit them on unplug */
struct bio_list pending_bio_list;
int pending_count;
spinlock_t resync_lock;
int nr_pending;
int nr_waiting;
int nr_queued;
int barrier;
sector_t next_resync;
int fullsync; /* set to 1 if a full sync is needed,
* (fresh device added).
* Cleared when a sync completes.
*/
int have_replacement; /* There is at least one
* replacement device.
*/
wait_queue_head_t wait_barrier;
mempool_t *r10bio_pool;
mempool_t *r10buf_pool;
struct page *tmppage;
/* When taking over an array from a different personality, we store
* the new thread here until we fully activate the array.
*/
struct md_thread *thread;
};
/*
* this is our 'private' RAID10 bio.
*
* it contains information about what kind of IO operations were started
* for this RAID10 operation, and about their status:
*/
struct r10bio {
atomic_t remaining; /* 'have we finished' count,
* used from IRQ handlers
*/
sector_t sector; /* virtual sector number */
int sectors;
unsigned long state;
struct mddev *mddev;
/*
* original bio going to /dev/mdx
*/
struct bio *master_bio;
/*
* if the IO is in READ direction, then this is where we read
*/
int read_slot;
struct list_head retry_list;
/*
* if the IO is in WRITE direction, then multiple bios are used,
* one for each copy.
* When resyncing we also use one for each copy.
* When reconstructing, we use 2 bios, one for read, one for write.
* We choose the number when they are allocated.
* We sometimes need an extra bio to write to the replacement.
*/
struct r10dev {
struct bio *bio;
union {
struct bio *repl_bio; /* used for resync and
* writes */
struct md_rdev *rdev; /* used for reads
* (read_slot >= 0) */
};
sector_t addr;
int devnum;
} devs[0];
};
/* bits for r10bio.state */
enum r10bio_state {
R10BIO_Uptodate,
R10BIO_IsSync,
R10BIO_IsRecover,
R10BIO_IsReshape,
R10BIO_Degraded,
/* Set ReadError on bios that experience a read error
* so that raid10d knows what to do with them.
*/
R10BIO_ReadError,
/* If a write for this request means we can clear some
* known-bad-block records, we set this flag.
*/
R10BIO_MadeGood,
R10BIO_WriteError,
/* During a reshape we might be performing IO on the
* 'previous' part of the array, in which case this
* flag is set
*/
R10BIO_Previous,
};
#endif