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authorNeilBrown <neilb@suse.de>2011-12-23 10:17:54 +1100
committerNeilBrown <neilb@suse.de>2011-12-23 10:17:54 +1100
commitabbf098e6e1e23d5d247b9eaaf325e67f67b0328 (patch)
treee2d8dc88c99ecc14d6d87596d95b3de9b9dc87c9
parent96c3fd1f3802371610c620cff03f9d825707e80e (diff)
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md/raid10: preferentially read from replacement device if possible.
When reading (for array reads, not for recovery etc) we read from the replacement device if it has recovered far enough. This requires storing the chosen rdev in the 'r10_bio' so we can make sure to drop the ref on the right device when the read finishes. Signed-off-by: NeilBrown <neilb@suse.de>
-rw-r--r--drivers/md/raid10.c36
1 files changed, 23 insertions, 13 deletions
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 70356c13027..5b886218110 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -324,11 +324,13 @@ static void raid10_end_read_request(struct bio *bio, int error)
int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
struct r10bio *r10_bio = bio->bi_private;
int slot, dev;
+ struct md_rdev *rdev;
struct r10conf *conf = r10_bio->mddev->private;
slot = r10_bio->read_slot;
dev = r10_bio->devs[slot].devnum;
+ rdev = r10_bio->devs[slot].rdev;
/*
* this branch is our 'one mirror IO has finished' event handler:
*/
@@ -346,7 +348,7 @@ static void raid10_end_read_request(struct bio *bio, int error)
*/
set_bit(R10BIO_Uptodate, &r10_bio->state);
raid_end_bio_io(r10_bio);
- rdev_dec_pending(conf->mirrors[dev].rdev, conf->mddev);
+ rdev_dec_pending(rdev, conf->mddev);
} else {
/*
* oops, read error - keep the refcount on the rdev
@@ -355,7 +357,7 @@ static void raid10_end_read_request(struct bio *bio, int error)
printk_ratelimited(KERN_ERR
"md/raid10:%s: %s: rescheduling sector %llu\n",
mdname(conf->mddev),
- bdevname(conf->mirrors[dev].rdev->bdev, b),
+ bdevname(rdev->bdev, b),
(unsigned long long)r10_bio->sector);
set_bit(R10BIO_ReadError, &r10_bio->state);
reschedule_retry(r10_bio);
@@ -599,7 +601,7 @@ static struct md_rdev *read_balance(struct r10conf *conf,
int sectors = r10_bio->sectors;
int best_good_sectors;
sector_t new_distance, best_dist;
- struct md_rdev *rdev;
+ struct md_rdev *rdev, *best_rdev;
int do_balance;
int best_slot;
@@ -608,6 +610,7 @@ static struct md_rdev *read_balance(struct r10conf *conf,
retry:
sectors = r10_bio->sectors;
best_slot = -1;
+ best_rdev = NULL;
best_dist = MaxSector;
best_good_sectors = 0;
do_balance = 1;
@@ -629,10 +632,16 @@ retry:
if (r10_bio->devs[slot].bio == IO_BLOCKED)
continue;
disk = r10_bio->devs[slot].devnum;
- rdev = rcu_dereference(conf->mirrors[disk].rdev);
+ rdev = rcu_dereference(conf->mirrors[disk].replacement);
+ if (rdev == NULL || test_bit(Faulty, &rdev->flags) ||
+ r10_bio->devs[slot].addr + sectors > rdev->recovery_offset)
+ rdev = rcu_dereference(conf->mirrors[disk].rdev);
if (rdev == NULL)
continue;
- if (!test_bit(In_sync, &rdev->flags))
+ if (test_bit(Faulty, &rdev->flags))
+ continue;
+ if (!test_bit(In_sync, &rdev->flags) &&
+ r10_bio->devs[slot].addr + sectors > rdev->recovery_offset)
continue;
dev_sector = r10_bio->devs[slot].addr;
@@ -657,6 +666,7 @@ retry:
if (good_sectors > best_good_sectors) {
best_good_sectors = good_sectors;
best_slot = slot;
+ best_rdev = rdev;
}
if (!do_balance)
/* Must read from here */
@@ -685,16 +695,15 @@ retry:
if (new_distance < best_dist) {
best_dist = new_distance;
best_slot = slot;
+ best_rdev = rdev;
}
}
- if (slot == conf->copies)
+ if (slot >= conf->copies) {
slot = best_slot;
+ rdev = best_rdev;
+ }
if (slot >= 0) {
- disk = r10_bio->devs[slot].devnum;
- rdev = rcu_dereference(conf->mirrors[disk].rdev);
- if (!rdev)
- goto retry;
atomic_inc(&rdev->nr_pending);
if (test_bit(Faulty, &rdev->flags)) {
/* Cannot risk returning a device that failed
@@ -990,6 +999,7 @@ read_again:
max_sectors);
r10_bio->devs[slot].bio = read_bio;
+ r10_bio->devs[slot].rdev = rdev;
read_bio->bi_sector = r10_bio->devs[slot].addr +
rdev->data_offset;
@@ -2088,10 +2098,9 @@ static int narrow_write_error(struct r10bio *r10_bio, int i)
static void handle_read_error(struct mddev *mddev, struct r10bio *r10_bio)
{
int slot = r10_bio->read_slot;
- int mirror = r10_bio->devs[slot].devnum;
struct bio *bio;
struct r10conf *conf = mddev->private;
- struct md_rdev *rdev;
+ struct md_rdev *rdev = r10_bio->devs[slot].rdev;
char b[BDEVNAME_SIZE];
unsigned long do_sync;
int max_sectors;
@@ -2109,7 +2118,7 @@ static void handle_read_error(struct mddev *mddev, struct r10bio *r10_bio)
fix_read_error(conf, mddev, r10_bio);
unfreeze_array(conf);
}
- rdev_dec_pending(conf->mirrors[mirror].rdev, mddev);
+ rdev_dec_pending(rdev, mddev);
bio = r10_bio->devs[slot].bio;
bdevname(bio->bi_bdev, b);
@@ -2144,6 +2153,7 @@ read_more:
r10_bio->sector - bio->bi_sector,
max_sectors);
r10_bio->devs[slot].bio = bio;
+ r10_bio->devs[slot].rdev = rdev;
bio->bi_sector = r10_bio->devs[slot].addr
+ rdev->data_offset;
bio->bi_bdev = rdev->bdev;