The MD personnality

The structure “struct md_personality” is the one which contains information about a RAID level. It is defined in md.h . You’ll find below some explanations about each member of the structure.

char *name; //Name of the level
int level; //Number related to the level, negative level are for "special one", for example the linear level is -1
struct list_head l i s t ; //Linked list of all MD personnalities.
struct module *owner; //Pointer to the Linux module managing this level

/∗* Do a block I/O operation
 * @param mddev structure representing the array
 * @param bio Bock I/O representing the operation to do
 */
void (*make_request)(struct mddev *mddev, struct bio* bio);

/** Build and assemble a RAID array
 * @param mddev structure representing the array
 */
int (*run)(struct mddev *mddev);

/** Disassemble an array
 * @param mddev structure representing the array
 */
int (*stop)(struct mddev *mddev);

/** Write some status informations to a file
 * @param seq virtual file
 * @param mddev structure representing the array
 */
void (*status)(struct seq_file *seq, struct mddev *mddev);

/** Function called when an error occur in the MD subsystem.
 * The usual way to run it is to call md_error() inside a md module, which will set some flags and start the recovery thread, and call this error_handler
 * @param mddev structure representing the array
 * @param rdev The physical drive responsible for the failure if applicable
void (*error_handler)(struct mddev *mddev, struct md_rdev *rdev);

/** Add a disk while the array is still running
 * @param mddev structure representing the array
 * @param rdev the physical disk to add
 */
int (*hot_add_disk) (struct mddev *mddev, struct md_rdev *rdev);

/** Remove a disk while the array is still running
 * @param mddev structure representing the array
 * @param number index of the disk to remove
 */
int (*hot_remove_disk) (struct mddev *mddev, int number);

/** Return the number of active spare drive.
 * @param mddev structure representing the array
 */
int (*spare_active) (struct mddev *mddev);

/** Handle a re-synchronization request for some sector
 * @param mddev structure representing the array
 * @param sector_nr Sector to synchronize
 * @param skipped Will be set to 1 if the sync was skipped
 * @param go_faster If false, will sleep interruptible to throttle resync
 */ 
sector_t (*sync_request)(struct mddev *mddev, sector_t sector_nr, int *skipped, int go_faster);

/** Resize an array
 * @param mddev structure representing the array
 * @param sectors new size
 */
int (*resize) (struct mddev *mddev, sector_t sectors);

/** Return the size of the array. If sectors and raid_disks are not zero, size is computed using those numbers instead of the real ones.
 */
sector_t (*size) (struct mddev *mddev, sector_t sectors, int raid_disks);

/** Check_reshape Reshape an array after adding or removing some disks
 */
int (*check_reshape) (struct mddev *mddev);

// unused
int (*start_reshape) (struct mddev *mddev);
void (*finish_reshape) (struct mddev *mddev);

/** quiesce moves between quiescence states
 * 0 - fully active
 * 1 - no new requests allowed
 * others - reserved
 */
void (*quiesce) (struct mddev *mddev, int state);

/** takeover is used to transition an array from one
 * personality to another.  The new personality must be able
 * to handle the data in the current layout.
 * e.g. 2drive raid1 -> 2drive raid5
 *      ndrive raid5 -> degraded n+1drive raid6 with special layout
 * If the takeover succeeds, a new 'private' structure is returned.
 * This needs to be installed and then ->run used to activate the
 * array.
 */
void *(*takeover) (struct mddev *mddev);

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