adulau/aha
1
0
Fork 0
mirror of https://github.com/adulau/aha.git synced 2024-12-27 19:26:25 +00:00
Code Issues Projects Releases Packages Wiki Activity

md linear: Protecting mddev with rcu locks to avoid races

Browse source 
Due to the lack of memory ordering guarantees, we may have races around
mddev->conf.

In particular, the correct contents of the structure we get from
dereferencing ->private might not be visible to this CPU yet, and
they might not be correct w.r.t mddev->raid_disks.

This patch addresses the problem using rcu protection to avoid
such race conditions.

Signed-off-by: SandeepKsinha <sandeepksinha@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>
This commit is contained in:
SandeepKsinha 2009-06-18 08:49:35 +10:00 committed by NeilBrown
parent 0894cc3066
commit af11c397fd
1 changed files with 38 additions and 9 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

47
drivers/md/linear.c
View file

@ -28,10 +28,11 @@
static inline dev_info_t *which_dev(mddev_t *mddev, sector_t sector)
{
int lo, mid, hi;
linear_conf_t *conf = mddev->private;
linear_conf_t *conf;
lo = 0;
hi = mddev->raid_disks - 1;
conf = rcu_dereference(mddev->private);
/*
* Binary Search
@ -66,8 +67,10 @@ static int linear_mergeable_bvec(struct request_queue *q,
unsigned long maxsectors, bio_sectors = bvm->bi_size >> 9;
sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
rcu_read_lock();
dev0 = which_dev(mddev, sector);
maxsectors = dev0->end_sector - sector;
rcu_read_unlock();
if (maxsectors < bio_sectors)
maxsectors = 0;
@ -86,36 +89,50 @@ static int linear_mergeable_bvec(struct request_queue *q,
static void linear_unplug(struct request_queue *q)
{
mddev_t *mddev = q->queuedata;
linear_conf_t *conf = mddev->private;
linear_conf_t *conf;
int i;
rcu_read_lock();
conf = rcu_dereference(mddev->private);
for (i=0; i < mddev->raid_disks; i++) {
struct request_queue *r_queue = bdev_get_queue(conf->disks[i].rdev->bdev);
blk_unplug(r_queue);
}
rcu_read_unlock();
}
static int linear_congested(void *data, int bits)
{
mddev_t *mddev = data;
linear_conf_t *conf = mddev->private;
linear_conf_t *conf;
int i, ret = 0;
rcu_read_lock();
conf = rcu_dereference(mddev->private);
for (i = 0; i < mddev->raid_disks && !ret ; i++) {
struct request_queue *q = bdev_get_queue(conf->disks[i].rdev->bdev);
ret |= bdi_congested(&q->backing_dev_info, bits);
}
rcu_read_unlock();
return ret;
}
static sector_t linear_size(mddev_t *mddev, sector_t sectors, int raid_disks)
{
linear_conf_t *conf = mddev->private;
linear_conf_t *conf;
sector_t array_sectors;
rcu_read_lock();
conf = rcu_dereference(mddev->private);
WARN_ONCE(sectors || raid_disks,
"%s does not support generic reshape\n", __func__);
array_sectors = conf->array_sectors;
rcu_read_unlock();
return conf->array_sectors;
return array_sectors;
}
static linear_conf_t *linear_conf(mddev_t *mddev, int raid_disks)
@ -229,8 +246,8 @@ static int linear_add(mddev_t *mddev, mdk_rdev_t *rdev)
return -ENOMEM;
newconf->prev = mddev->private;
mddev->private = newconf;
mddev->raid_disks++;
rcu_assign_pointer(mddev->private, newconf);
md_set_array_sectors(mddev, linear_size(mddev, 0, 0));
set_capacity(mddev->gendisk, mddev->array_sectors);
return 0;
@ -239,7 +256,13 @@ static int linear_add(mddev_t *mddev, mdk_rdev_t *rdev)
static int linear_stop (mddev_t *mddev)
{
linear_conf_t *conf = mddev->private;
/*
* We do not require rcu protection here since
* we hold reconfig_mutex for both linear_add and
* linear_stop, so they cannot race.
*/
blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
do {
linear_conf_t *t = conf->prev;
@ -269,9 +292,11 @@ static int linear_make_request (struct request_queue *q, struct bio *bio)
bio_sectors(bio));
part_stat_unlock();
rcu_read_lock();
tmp_dev = which_dev(mddev, bio->bi_sector);
start_sector = tmp_dev->end_sector - tmp_dev->rdev->sectors;
if (unlikely(bio->bi_sector >= (tmp_dev->end_sector)
|| (bio->bi_sector < start_sector))) {
char b[BDEVNAME_SIZE];
@ -282,6 +307,7 @@ static int linear_make_request (struct request_queue *q, struct bio *bio)
bdevname(tmp_dev->rdev->bdev, b),
(unsigned long long)tmp_dev->rdev->sectors,
(unsigned long long)start_sector);
rcu_read_unlock();
bio_io_error(bio);
return 0;
}
@ -291,9 +317,11 @@ static int linear_make_request (struct request_queue *q, struct bio *bio)
* split it.
*/
struct bio_pair *bp;
sector_t end_sector = tmp_dev->end_sector;
bp = bio_split(bio,
tmp_dev->end_sector - bio->bi_sector);
rcu_read_unlock();
bp = bio_split(bio, end_sector - bio->bi_sector);
if (linear_make_request(q, &bp->bio1))
generic_make_request(&bp->bio1);
@ -306,6 +334,7 @@ static int linear_make_request (struct request_queue *q, struct bio *bio)
bio->bi_bdev = tmp_dev->rdev->bdev;
bio->bi_sector = bio->bi_sector - start_sector
+ tmp_dev->rdev->data_offset;
rcu_read_unlock();
return 1;
}