On Wednesday October 5, [email protected] wrote:
> Please consider the following patch submittal
> to insert rcu_dereference() to make explicit
> the object of the rcu read-side critical sections.
> Thank you.
Thank for the patch and detailed explanations.
I agree with all the places where you add rcu_dereference.
I do not agree with the place you added rcu_assign_pointer.
rdev->mddev is of no relevance to the rcu usage. However I think it
is appropriate to use rcu_assign_pointer when setting the pointer that
rcu_dereference dereferences. I had made appropriate changes.
The place where you put the comment about incrementing new_disk does
*not* require an increment. That loop actually runs backwards, and
new_disk is decremented in the body of the loop.
You moved 'rcu_read_unlock' down several lines in raid5.c, but didn't
make an equivalent change in similar code in raid6main.c. I'm
confident that this change isn't needed. After nr_pending has been
incremented, there is no longer a need to hold the rcu read lock.
I have improved the code in raid10.c so that the rcu_dereference'd
pointer is held in a temporary variable, which is much cleaner than
the existing code.
My revised patch follows. I will submit it to Andrew if I hear
nothing negative.
Thanks,
NeilBrown
-----
Provide proper rcu_dereference / rcu_assign_pointer annotations in md
Acked-by: <[email protected]>
Signed-off-by: <[email protected]>
Signed-off-by: Neil Brown <[email protected]>
### Diffstat output
./drivers/md/multipath.c | 8 ++++----
./drivers/md/raid1.c | 20 ++++++++++----------
./drivers/md/raid10.c | 30 ++++++++++++++++--------------
./drivers/md/raid5.c | 8 ++++----
./drivers/md/raid6main.c | 8 ++++----
5 files changed, 38 insertions(+), 36 deletions(-)
diff ./drivers/md/multipath.c~current~ ./drivers/md/multipath.c
--- ./drivers/md/multipath.c~current~ 2005-10-13 13:42:05.000000000 +1000
+++ ./drivers/md/multipath.c 2005-10-13 13:49:39.000000000 +1000
@@ -63,7 +63,7 @@ static int multipath_map (multipath_conf
rcu_read_lock();
for (i = 0; i < disks; i++) {
- mdk_rdev_t *rdev = conf->multipaths[i].rdev;
+ mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
if (rdev && rdev->in_sync) {
atomic_inc(&rdev->nr_pending);
rcu_read_unlock();
@@ -139,7 +139,7 @@ static void unplug_slaves(mddev_t *mddev
rcu_read_lock();
for (i=0; i<mddev->raid_disks; i++) {
- mdk_rdev_t *rdev = conf->multipaths[i].rdev;
+ mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
if (rdev && !rdev->faulty && atomic_read(&rdev->nr_pending)) {
request_queue_t *r_queue = bdev_get_queue(rdev->bdev);
@@ -228,7 +228,7 @@ static int multipath_issue_flush(request
rcu_read_lock();
for (i=0; i<mddev->raid_disks && ret == 0; i++) {
- mdk_rdev_t *rdev = conf->multipaths[i].rdev;
+ mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
if (rdev && !rdev->faulty) {
struct block_device *bdev = rdev->bdev;
request_queue_t *r_queue = bdev_get_queue(bdev);
@@ -335,7 +335,7 @@ static int multipath_add_disk(mddev_t *m
conf->working_disks++;
rdev->raid_disk = path;
rdev->in_sync = 1;
- p->rdev = rdev;
+ rcu_assign_pointer(p->rdev, rdev);
found = 1;
}
diff ./drivers/md/raid1.c~current~ ./drivers/md/raid1.c
--- ./drivers/md/raid1.c~current~ 2005-10-13 13:42:05.000000000 +1000
+++ ./drivers/md/raid1.c 2005-10-13 13:50:32.000000000 +1000
@@ -416,10 +416,10 @@ static int read_balance(conf_t *conf, r1
/* Choose the first operation device, for consistancy */
new_disk = 0;
- for (rdev = conf->mirrors[new_disk].rdev;
+ for (rdev = rcu_dereference(conf->mirrors[new_disk].rdev);
!rdev || !rdev->in_sync
|| test_bit(WriteMostly, &rdev->flags);
- rdev = conf->mirrors[++new_disk].rdev) {
+ rdev = rcu_dereference(conf->mirrors[++new_disk].rdev)) {
if (rdev && rdev->in_sync)
wonly_disk = new_disk;
@@ -434,10 +434,10 @@ static int read_balance(conf_t *conf, r1
/* make sure the disk is operational */
- for (rdev = conf->mirrors[new_disk].rdev;
+ for (rdev = rcu_dereference(conf->mirrors[new_disk].rdev);
!rdev || !rdev->in_sync ||
test_bit(WriteMostly, &rdev->flags);
- rdev = conf->mirrors[new_disk].rdev) {
+ rdev = rcu_dereference(conf->mirrors[new_disk].rdev)) {
if (rdev && rdev->in_sync)
wonly_disk = new_disk;
@@ -474,7 +474,7 @@ static int read_balance(conf_t *conf, r1
disk = conf->raid_disks;
disk--;
- rdev = conf->mirrors[disk].rdev;
+ rdev = rcu_dereference(conf->mirrors[disk].rdev);
if (!rdev ||
!rdev->in_sync ||
@@ -496,7 +496,7 @@ static int read_balance(conf_t *conf, r1
if (new_disk >= 0) {
- rdev = conf->mirrors[new_disk].rdev;
+ rdev = rcu_dereference(conf->mirrors[new_disk].rdev);
if (!rdev)
goto retry;
atomic_inc(&rdev->nr_pending);
@@ -522,7 +522,7 @@ static void unplug_slaves(mddev_t *mddev
rcu_read_lock();
for (i=0; i<mddev->raid_disks; i++) {
- mdk_rdev_t *rdev = conf->mirrors[i].rdev;
+ mdk_rdev_t *rdev = rcu_dereference(conf->mirrors[i].rdev);
if (rdev && !rdev->faulty && atomic_read(&rdev->nr_pending)) {
request_queue_t *r_queue = bdev_get_queue(rdev->bdev);
@@ -556,7 +556,7 @@ static int raid1_issue_flush(request_que
rcu_read_lock();
for (i=0; i<mddev->raid_disks && ret == 0; i++) {
- mdk_rdev_t *rdev = conf->mirrors[i].rdev;
+ mdk_rdev_t *rdev = rcu_dereference(conf->mirrors[i].rdev);
if (rdev && !rdev->faulty) {
struct block_device *bdev = rdev->bdev;
request_queue_t *r_queue = bdev_get_queue(bdev);
@@ -732,7 +732,7 @@ static int make_request(request_queue_t
#endif
rcu_read_lock();
for (i = 0; i < disks; i++) {
- if ((rdev=conf->mirrors[i].rdev) != NULL &&
+ if ((rdev=rcu_dereference(conf->mirrors[i].rdev)) != NULL &&
!rdev->faulty) {
atomic_inc(&rdev->nr_pending);
if (rdev->faulty) {
@@ -958,7 +958,7 @@ static int raid1_add_disk(mddev_t *mddev
found = 1;
if (rdev->saved_raid_disk != mirror)
conf->fullsync = 1;
- p->rdev = rdev;
+ rcu_assign_pointer(p->rdev, rdev);
break;
}
diff ./drivers/md/raid10.c~current~ ./drivers/md/raid10.c
--- ./drivers/md/raid10.c~current~ 2005-10-13 13:42:05.000000000 +1000
+++ ./drivers/md/raid10.c 2005-10-13 14:09:29.000000000 +1000
@@ -496,6 +496,7 @@ static int read_balance(conf_t *conf, r1
int disk, slot, nslot;
const int sectors = r10_bio->sectors;
sector_t new_distance, current_distance;
+ mdk_rdev_t *rdev;
raid10_find_phys(conf, r10_bio);
rcu_read_lock();
@@ -510,8 +511,8 @@ static int read_balance(conf_t *conf, r1
slot = 0;
disk = r10_bio->devs[slot].devnum;
- while (!conf->mirrors[disk].rdev ||
- !conf->mirrors[disk].rdev->in_sync) {
+ while ((rdev = rcu_dereference(conf->mirrors[disk].rdev)) == NULL ||
+ !rdev->in_sync) {
slot++;
if (slot == conf->copies) {
slot = 0;
@@ -527,8 +528,8 @@ static int read_balance(conf_t *conf, r1
/* make sure the disk is operational */
slot = 0;
disk = r10_bio->devs[slot].devnum;
- while (!conf->mirrors[disk].rdev ||
- !conf->mirrors[disk].rdev->in_sync) {
+ while ((rdev=rcu_dereference(conf->mirrors[disk].rdev)) == NULL ||
+ !rdev->in_sync) {
slot ++;
if (slot == conf->copies) {
disk = -1;
@@ -547,11 +548,11 @@ static int read_balance(conf_t *conf, r1
int ndisk = r10_bio->devs[nslot].devnum;
- if (!conf->mirrors[ndisk].rdev ||
- !conf->mirrors[ndisk].rdev->in_sync)
+ if ((rdev=rcu_dereference(conf->mirrors[ndisk].rdev)) == NULL ||
+ !rdev->in_sync)
continue;
- if (!atomic_read(&conf->mirrors[ndisk].rdev->nr_pending)) {
+ if (!atomic_read(&rdev->nr_pending)) {
disk = ndisk;
slot = nslot;
break;
@@ -569,7 +570,7 @@ rb_out:
r10_bio->read_slot = slot;
/* conf->next_seq_sect = this_sector + sectors;*/
- if (disk >= 0 && conf->mirrors[disk].rdev)
+ if (disk >= 0 && (rdev=rcu_dereference(conf->mirrors[disk].rdev))!= NULL)
atomic_inc(&conf->mirrors[disk].rdev->nr_pending);
rcu_read_unlock();
@@ -583,7 +584,7 @@ static void unplug_slaves(mddev_t *mddev
rcu_read_lock();
for (i=0; i<mddev->raid_disks; i++) {
- mdk_rdev_t *rdev = conf->mirrors[i].rdev;
+ mdk_rdev_t *rdev = rcu_dereference(conf->mirrors[i].rdev);
if (rdev && !rdev->faulty && atomic_read(&rdev->nr_pending)) {
request_queue_t *r_queue = bdev_get_queue(rdev->bdev);
@@ -614,7 +615,7 @@ static int raid10_issue_flush(request_qu
rcu_read_lock();
for (i=0; i<mddev->raid_disks && ret == 0; i++) {
- mdk_rdev_t *rdev = conf->mirrors[i].rdev;
+ mdk_rdev_t *rdev = rcu_dereference(conf->mirrors[i].rdev);
if (rdev && !rdev->faulty) {
struct block_device *bdev = rdev->bdev;
request_queue_t *r_queue = bdev_get_queue(bdev);
@@ -772,9 +773,10 @@ static int make_request(request_queue_t
rcu_read_lock();
for (i = 0; i < conf->copies; i++) {
int d = r10_bio->devs[i].devnum;
- if (conf->mirrors[d].rdev &&
- !conf->mirrors[d].rdev->faulty) {
- atomic_inc(&conf->mirrors[d].rdev->nr_pending);
+ mdk_rdev_t *rdev = rcu_dereference(conf->mirrors[d].rdev);
+ if (rdev &&
+ !rdev->faulty) {
+ atomic_inc(&rdev->nr_pending);
r10_bio->devs[i].bio = bio;
} else
r10_bio->devs[i].bio = NULL;
@@ -984,7 +986,7 @@ static int raid10_add_disk(mddev_t *mdde
p->head_position = 0;
rdev->raid_disk = mirror;
found = 1;
- p->rdev = rdev;
+ rcu_assign_pointer(p->rdev, rdev);
break;
}
diff ./drivers/md/raid5.c~current~ ./drivers/md/raid5.c
--- ./drivers/md/raid5.c~current~ 2005-10-13 13:42:05.000000000 +1000
+++ ./drivers/md/raid5.c 2005-10-13 14:00:38.000000000 +1000
@@ -1383,7 +1383,7 @@ static void handle_stripe(struct stripe_
bi->bi_end_io = raid5_end_read_request;
rcu_read_lock();
- rdev = conf->disks[i].rdev;
+ rdev = rcu_dereference(conf->disks[i].rdev);
if (rdev && rdev->faulty)
rdev = NULL;
if (rdev)
@@ -1457,7 +1457,7 @@ static void unplug_slaves(mddev_t *mddev
rcu_read_lock();
for (i=0; i<mddev->raid_disks; i++) {
- mdk_rdev_t *rdev = conf->disks[i].rdev;
+ mdk_rdev_t *rdev = rcu_dereference(conf->disks[i].rdev);
if (rdev && !rdev->faulty && atomic_read(&rdev->nr_pending)) {
request_queue_t *r_queue = bdev_get_queue(rdev->bdev);
@@ -1502,7 +1502,7 @@ static int raid5_issue_flush(request_que
rcu_read_lock();
for (i=0; i<mddev->raid_disks && ret == 0; i++) {
- mdk_rdev_t *rdev = conf->disks[i].rdev;
+ mdk_rdev_t *rdev = rcu_dereference(conf->disks[i].rdev);
if (rdev && !rdev->faulty) {
struct block_device *bdev = rdev->bdev;
request_queue_t *r_queue = bdev_get_queue(bdev);
@@ -2178,7 +2178,7 @@ static int raid5_add_disk(mddev_t *mddev
found = 1;
if (rdev->saved_raid_disk != disk)
conf->fullsync = 1;
- p->rdev = rdev;
+ rcu_assign_pointer(p->rdev, rdev);
break;
}
print_raid5_conf(conf);
diff ./drivers/md/raid6main.c~current~ ./drivers/md/raid6main.c
--- ./drivers/md/raid6main.c~current~ 2005-10-13 13:42:05.000000000 +1000
+++ ./drivers/md/raid6main.c 2005-10-13 13:57:08.000000000 +1000
@@ -1464,7 +1464,7 @@ static void handle_stripe(struct stripe_
bi->bi_end_io = raid6_end_read_request;
rcu_read_lock();
- rdev = conf->disks[i].rdev;
+ rdev = rcu_dereference(conf->disks[i].rdev);
if (rdev && rdev->faulty)
rdev = NULL;
if (rdev)
@@ -1538,7 +1538,7 @@ static void unplug_slaves(mddev_t *mddev
rcu_read_lock();
for (i=0; i<mddev->raid_disks; i++) {
- mdk_rdev_t *rdev = conf->disks[i].rdev;
+ mdk_rdev_t *rdev = rcu_dereference(conf->disks[i].rdev);
if (rdev && !rdev->faulty && atomic_read(&rdev->nr_pending)) {
request_queue_t *r_queue = bdev_get_queue(rdev->bdev);
@@ -1583,7 +1583,7 @@ static int raid6_issue_flush(request_que
rcu_read_lock();
for (i=0; i<mddev->raid_disks && ret == 0; i++) {
- mdk_rdev_t *rdev = conf->disks[i].rdev;
+ mdk_rdev_t *rdev = rcu_dereference(conf->disks[i].rdev);
if (rdev && !rdev->faulty) {
struct block_device *bdev = rdev->bdev;
request_queue_t *r_queue = bdev_get_queue(bdev);
@@ -2158,7 +2158,7 @@ static int raid6_add_disk(mddev_t *mddev
found = 1;
if (rdev->saved_raid_disk != disk)
conf->fullsync = 1;
- p->rdev = rdev;
+ rcu_assign_pointer(p->rdev, rdev);
break;
}
print_raid6_conf(conf);
-
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