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md/raid10: add rcu protection to rdev access during reshape. 

mirrors[].rdev can become NULL at any point unless:
   - a counted reference is held
   - ->reconfig_mutex is held, or
   - rcu_read_lock() is held

Reshape isn't always suitably careful as in the past rdev couldn't be
removed during reshape.  It can now, so add protection.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>
hifive-unleashed-5.1
NeilBrown 2016-06-02 16:19:52 +10:00 committed by Shaohua Li
parent f90145f317
commit d094d6860b
1 changed files with 22 additions and 8 deletions
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30
drivers/md/raid10.c
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@ -4361,15 +4361,16 @@ read_more:
blist = read_bio;
read_bio->bi_next = NULL;
rcu_read_lock();
for (s = 0; s < conf->copies*2; s++) {
struct bio *b;
int d = r10_bio->devs[s/2].devnum;
struct md_rdev *rdev2;
if (s&1) {
rdev2 = conf->mirrors[d].replacement;
rdev2 = rcu_dereference(conf->mirrors[d].replacement);
b = r10_bio->devs[s/2].repl_bio;
} else {
rdev2 = conf->mirrors[d].rdev;
rdev2 = rcu_dereference(conf->mirrors[d].rdev);
b = r10_bio->devs[s/2].bio;
}
if (!rdev2 || test_bit(Faulty, &rdev2->flags))
@ -4414,6 +4415,7 @@ read_more:
nr_sectors += len >> 9;
}
bio_full:
rcu_read_unlock();
r10_bio->sectors = nr_sectors;
/* Now submit the read */
@ -4465,16 +4467,20 @@ static void reshape_request_write(struct mddev *mddev, struct r10bio *r10_bio)
struct bio *b;
int d = r10_bio->devs[s/2].devnum;
struct md_rdev *rdev;
rcu_read_lock();
if (s&1) {
rdev = conf->mirrors[d].replacement;
rdev = rcu_dereference(conf->mirrors[d].replacement);
b = r10_bio->devs[s/2].repl_bio;
} else {
rdev = conf->mirrors[d].rdev;
rdev = rcu_dereference(conf->mirrors[d].rdev);
b = r10_bio->devs[s/2].bio;
}
if (!rdev || test_bit(Faulty, &rdev->flags))
if (!rdev || test_bit(Faulty, &rdev->flags)) {
rcu_read_unlock();
continue;
}
atomic_inc(&rdev->nr_pending);
rcu_read_unlock();
md_sync_acct(b->bi_bdev, r10_bio->sectors);
atomic_inc(&r10_bio->remaining);
b->bi_next = NULL;
@ -4535,9 +4541,10 @@ static int handle_reshape_read_error(struct mddev *mddev,
if (s > (PAGE_SIZE >> 9))
s = PAGE_SIZE >> 9;
rcu_read_lock();
while (!success) {
int d = r10b->devs[slot].devnum;
struct md_rdev *rdev = conf->mirrors[d].rdev;
struct md_rdev *rdev = rcu_dereference(conf->mirrors[d].rdev);
sector_t addr;
if (rdev == NULL ||
test_bit(Faulty, &rdev->flags) ||
@ -4545,11 +4552,15 @@ static int handle_reshape_read_error(struct mddev *mddev,
goto failed;
addr = r10b->devs[slot].addr + idx * PAGE_SIZE;
atomic_inc(&rdev->nr_pending);
rcu_read_unlock();
success = sync_page_io(rdev,
addr,
s << 9,
bvec[idx].bv_page,
READ, false);
rdev_dec_pending(rdev, mddev);
rcu_read_lock();
if (success)
break;
failed:
@ -4559,6 +4570,7 @@ static int handle_reshape_read_error(struct mddev *mddev,
if (slot == first_slot)
break;
}
rcu_read_unlock();
if (!success) {
/* couldn't read this block, must give up */
set_bit(MD_RECOVERY_INTR,
@ -4628,16 +4640,18 @@ static void raid10_finish_reshape(struct mddev *mddev)
}
} else {
int d;
rcu_read_lock();
for (d = conf->geo.raid_disks ;
d < conf->geo.raid_disks - mddev->delta_disks;
d++) {
struct md_rdev *rdev = conf->mirrors[d].rdev;
struct md_rdev *rdev = rcu_dereference(conf->mirrors[d].rdev);
if (rdev)
clear_bit(In_sync, &rdev->flags);
rdev = conf->mirrors[d].replacement;
rdev = rcu_dereference(conf->mirrors[d].replacement);
if (rdev)
clear_bit(In_sync, &rdev->flags);
}
rcu_read_unlock();
}
mddev->layout = mddev->new_layout;
mddev->chunk_sectors = 1 << conf->geo.chunk_shift;