Commit 671488cc authored by NeilBrown's avatar NeilBrown
Browse files

md/raid5: allow each slot to have an extra replacement device 



Just enhance data structures to record a second device per slot to be
used as a 'replacement' device, replacing the original.
We also have a second bio in each slot in each stripe_head.  This will
only be used when writing to the array - we need to write to both the
original and the replacement at the same time, so will need two bios.

For now, only try using the replacement drive for aligned-reads.
In this case, we prefer the replacement if it has been recovered far
enough, otherwise use the original.

This includes a small enhancement.  Previously we would only do
aligned reads if the target device was fully recovered.  Now we also
do them if it has recovered far enough.

Reviewed-by: default avatarDan Williams <dan.j.williams@intel.com>
Signed-off-by: default avatarNeilBrown <neilb@suse.de>
parent 2d78f8c4

drivers/md/raid5.c

+13 −2
Original line number Diff line number Diff line
@@ -3594,6 +3594,7 @@ static int chunk_aligned_read(struct mddev *mddev, struct bio * raid_bio) 
	int dd_idx;

	struct bio* align_bi;

	struct md_rdev *rdev;

	sector_t end_sector;



	if (!in_chunk_boundary(mddev, raid_bio)) {

		pr_debug("chunk_aligned_read : non aligned\n");
@@ -3618,9 +3619,19 @@ static int chunk_aligned_read(struct mddev *mddev, struct bio * raid_bio) 
						    0,

						    &dd_idx, NULL);



	end_sector = align_bi->bi_sector + (align_bi->bi_size >> 9);

	rcu_read_lock();

	rdev = rcu_dereference(conf->disks[dd_idx].replacement);

	if (!rdev || test_bit(Faulty, &rdev->flags) ||

	    rdev->recovery_offset < end_sector) {

		rdev = rcu_dereference(conf->disks[dd_idx].rdev);

	if (rdev && test_bit(In_sync, &rdev->flags)) {

		if (rdev &&

		    (test_bit(Faulty, &rdev->flags) ||

		    !(test_bit(In_sync, &rdev->flags) ||

		      rdev->recovery_offset >= end_sector)))

			rdev = NULL;

	}

	if (rdev) {

		sector_t first_bad;

		int bad_sectors;

drivers/md/raid5.h

+33 −24
Original line number Diff line number Diff line
@@ -226,8 +226,11 @@ struct stripe_head { 
		#endif

	} ops;

	struct r5dev {

		struct bio	req;

		struct bio_vec	vec;

		/* rreq and rvec are used for the replacement device when

		 * writing data to both devices.

		 */

		struct bio	req, rreq;

		struct bio_vec	vec, rvec;

		struct page	*page;

		struct bio	*toread, *read, *towrite, *written;

		sector_t	sector;			/* sector of this page */
@@ -252,29 +255,35 @@ struct stripe_head_state { 
	int handle_bad_blocks;

};



/* Flags */

#define	R5_UPTODATE	0	/* page contains current data */

#define	R5_LOCKED	1	/* IO has been submitted on "req" */

#define	R5_OVERWRITE	2	/* towrite covers whole page */

/* Flags for struct r5dev.flags */

enum r5dev_flags {

	R5_UPTODATE,	/* page contains current data */

	R5_LOCKED,	/* IO has been submitted on "req" */

	R5_OVERWRITE,	/* towrite covers whole page */

/* and some that are internal to handle_stripe */

#define	R5_Insync	3	/* rdev && rdev->in_sync at start */

#define	R5_Wantread	4	/* want to schedule a read */

#define	R5_Wantwrite	5

#define	R5_Overlap	7	/* There is a pending overlapping request on this block */

#define	R5_ReadError	8	/* seen a read error here recently */

#define	R5_ReWrite	9	/* have tried to over-write the readerror */

	R5_Insync,	/* rdev && rdev->in_sync at start */

	R5_Wantread,	/* want to schedule a read */

	R5_Wantwrite,

	R5_Overlap,	/* There is a pending overlapping request

			 * on this block */

	R5_ReadError,	/* seen a read error here recently */

	R5_ReWrite,	/* have tried to over-write the readerror */



#define	R5_Expanded	10	/* This block now has post-expand data */

#define	R5_Wantcompute	11	/* compute_block in progress treat as

	R5_Expanded,	/* This block now has post-expand data */

	R5_Wantcompute,	/* compute_block in progress treat as

			 * uptodate

			 */

#define	R5_Wantfill	12	/* dev->toread contains a bio that needs

	R5_Wantfill,	/* dev->toread contains a bio that needs

			 * filling

			 */

#define	R5_Wantdrain	13	/* dev->towrite needs to be drained */

#define	R5_WantFUA	14	/* Write should be FUA */

#define	R5_WriteError	15	/* got a write error - need to record it */

#define	R5_MadeGood	16	/* A bad block has been fixed by writing to it*/

	R5_Wantdrain,	/* dev->towrite needs to be drained */

	R5_WantFUA,	/* Write should be FUA */

	R5_WriteError,	/* got a write error - need to record it */

	R5_MadeGood,	/* A bad block has been fixed by writing to it */

	R5_ReadRepl,	/* Will/did read from replacement rather than orig */

	R5_MadeGoodRepl,/* A bad block on the replacement device has been

			 * fixed by writing to it */

};

/*

 * Write method

 */
@@ -344,7 +353,7 @@ enum { 




struct disk_info {

	struct md_rdev	*rdev;

	struct md_rdev	*rdev, *replacement;

};



struct r5conf {

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