On Friday August 18, paul.clements@xxxxxxxxxxxx wrote:
>
> The atomic_add (and any other access to an rdev, for that matter) needs
> to be guarded by a NULL check, I think.
>
> Neil, does that sound right?
Yes. Thanks for doing the analysis.
However after looking closely through the code, I think the atomic_inc
really is in the wrong place.
We are increasing 'corrected_errors' before we try to write out the
good data. We should really wait until after reading back the good
data. So rather than just protecting the atomic_inc with "if(dev)",
I'm going to move it several lines down.
And while I'm at it, there seem to be several place that reference
->rdev that could be cleaned up.
So I'm thinking of something like the following against -mm
I'll make a smaller patch for -stable.
Thanks,
NeilBrown
Signed-off-by: Neil Brown <neilb@xxxxxxx>
### Diffstat output
./drivers/md/raid1.c | 55 +++++++++++++++++++++++++++++++--------------------
1 file changed, 34 insertions(+), 21 deletions(-)
diff .prev/drivers/md/raid1.c ./drivers/md/raid1.c
--- .prev/drivers/md/raid1.c 2006-08-15 13:33:02.000000000 +1000
+++ ./drivers/md/raid1.c 2006-08-21 09:40:41.000000000 +1000
@@ -930,10 +930,13 @@ static void status(struct seq_file *seq,
seq_printf(seq, " [%d/%d] [", conf->raid_disks,
conf->raid_disks - mddev->degraded);
- for (i = 0; i < conf->raid_disks; i++)
+ rcu_read_lock();
+ for (i = 0; i < conf->raid_disks; i++) {
+ mdk_rdev_t *rdev = rcu_dereference(conf->mirrors[i].rdev);
seq_printf(seq, "%s",
- conf->mirrors[i].rdev &&
- test_bit(In_sync, &conf->mirrors[i].rdev->flags) ? "U" : "_");
+ rdev && test_bit(In_sync, &rdev->flags) ? "U" : "_");
+ }
+ rcu_read_unlock();
seq_printf(seq, "]");
}
@@ -976,7 +979,6 @@ static void error(mddev_t *mddev, mdk_rd
static void print_conf(conf_t *conf)
{
int i;
- mirror_info_t *tmp;
printk("RAID1 conf printout:\n");
if (!conf) {
@@ -986,14 +988,17 @@ static void print_conf(conf_t *conf)
printk(" --- wd:%d rd:%d\n", conf->raid_disks - conf->mddev->degraded,
conf->raid_disks);
+ rcu_read_lock();
for (i = 0; i < conf->raid_disks; i++) {
char b[BDEVNAME_SIZE];
- tmp = conf->mirrors + i;
- if (tmp->rdev)
+ mdk_rdev_t *rdev = rcu_dereference(conf->mirrors[i].rdev);
+ if (rdev)
printk(" disk %d, wo:%d, o:%d, dev:%s\n",
- i, !test_bit(In_sync, &tmp->rdev->flags), !test_bit(Faulty, &tmp->rdev->flags),
- bdevname(tmp->rdev->bdev,b));
+ i, !test_bit(In_sync, &rdev->flags),
+ !test_bit(Faulty, &rdev->flags),
+ bdevname(rdev->bdev,b));
}
+ rcu_read_unlock();
}
static void close_sync(conf_t *conf)
@@ -1009,17 +1014,17 @@ static int raid1_spare_active(mddev_t *m
{
int i;
conf_t *conf = mddev->private;
- mirror_info_t *tmp;
/*
* Find all failed disks within the RAID1 configuration
- * and mark them readable
+ * and mark them readable.
+ * Called under mddev lock, so rcu protection not needed.
*/
for (i = 0; i < conf->raid_disks; i++) {
- tmp = conf->mirrors + i;
- if (tmp->rdev
- && !test_bit(Faulty, &tmp->rdev->flags)
- && !test_and_set_bit(In_sync, &tmp->rdev->flags)) {
+ mdk_rdev_t *rdev = conf->mirrors[i].rdev;
+ if (rdev
+ && !test_bit(Faulty, &rdev->flags)
+ && !test_and_set_bit(In_sync, &rdev->flags)) {
unsigned long flags;
spin_lock_irqsave(&conf->device_lock, flags);
mddev->degraded--;
@@ -1239,7 +1244,7 @@ static void sync_request_write(mddev_t *
/* ouch - failed to read all of that.
* Try some synchronous reads of other devices to get
* good data, much like with normal read errors. Only
- * read into the pages we already have so they we don't
+ * read into the pages we already have so we don't
* need to re-issue the read request.
* We don't need to freeze the array, because being in an
* active sync request, there is no normal IO, and
@@ -1259,6 +1264,10 @@ static void sync_request_write(mddev_t *
s = PAGE_SIZE >> 9;
do {
if (r1_bio->bios[d]->bi_end_io == end_sync_read) {
+ /* No rcu protection needed here devices
+ * can only be removed when no resync is
+ * active, and resync is currently active
+ */
rdev = conf->mirrors[d].rdev;
if (sync_page_io(rdev->bdev,
sect + rdev->data_offset,
@@ -1376,6 +1385,11 @@ static void fix_read_error(conf_t *conf,
s = PAGE_SIZE >> 9;
do {
+ /* Note: no rcu protection needed here
+ * as this is synchronous in the raid1d thread
+ * which is the thread that might remove
+ * a device. If raid1d ever becomes multi-threaded....
+ */
rdev = conf->mirrors[d].rdev;
if (rdev &&
test_bit(In_sync, &rdev->flags) &&
@@ -1403,7 +1417,6 @@ static void fix_read_error(conf_t *conf,
d = conf->raid_disks;
d--;
rdev = conf->mirrors[d].rdev;
- atomic_add(s, &rdev->corrected_errors);
if (rdev &&
test_bit(In_sync, &rdev->flags)) {
if (sync_page_io(rdev->bdev,
@@ -1429,7 +1442,8 @@ static void fix_read_error(conf_t *conf,
== 0)
/* Well, this device is dead */
md_error(mddev, rdev);
- else
+ else {
+ atomic_add(s, &rdev->corrected_errors);
printk(KERN_INFO
"raid1:%s: read error corrected "
"(%d sectors at %llu on %s)\n",
@@ -1437,6 +1451,7 @@ static void fix_read_error(conf_t *conf,
(unsigned long long)sect +
rdev->data_offset,
bdevname(rdev->bdev, b));
+ }
}
}
sectors -= s;
@@ -1806,19 +1821,17 @@ static sector_t sync_request(mddev_t *md
for (i=0; i<conf->raid_disks; i++) {
bio = r1_bio->bios[i];
if (bio->bi_end_io == end_sync_read) {
- md_sync_acct(conf->mirrors[i].rdev->bdev, nr_sectors);
+ md_sync_acct(bio->bi_bdev, nr_sectors);
generic_make_request(bio);
}
}
} else {
atomic_set(&r1_bio->remaining, 1);
bio = r1_bio->bios[r1_bio->read_disk];
- md_sync_acct(conf->mirrors[r1_bio->read_disk].rdev->bdev,
- nr_sectors);
+ md_sync_acct(bio->bi_bdev, nr_sectors);
generic_make_request(bio);
}
-
return nr_sectors;
}
-
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
