[PATCH 02/18] drbd: device->ldev is not guaranteed on an D_ATTACHING disk

From: Philipp Reisner
Date: Mon Jun 30 2014 - 12:02:53 EST

Some parts of the code assumed that get_ldev_if_state(device, D_ATTACHING)
is sufficient to access the ldev member of the device object. That was
wrong. ldev may not be there or might be freed at any time if the device
has a disk state of D_ATTACHING.

bm_rw()
Documented that drbd_bm_read() is only called from drbd_adm_attach.
drbd_bm_write() is only called when a reference is held, and it is
documented that a caller has to hold a reference before calling
drbd_bm_write()

drbd_bm_write_page()
Use get_ldev() instead of get_ldev_if_state(device, D_ATTACHING)

drbd_bmio_set_n_write()
No longer use get_ldev_if_state(device, D_ATTACHING). All callers
hold a reference to ldev now.

drbd_bmio_clear_n_write()
All callers where holding a reference of ldev anyways. Remove the
misleading get_ldev_if_state(device, D_ATTACHING)

drbd_reconsider_max_bio_size()
Removed the get_ldev_if_state(device, D_ATTACHING). All callers
now pass a struct drbd_backing_dev* when they have a proper
reference, or a NULL pointer.
Before this fix, the receiver could trigger a NULL pointer
deref when in drbd_reconsider_max_bio_size()

drbd_bump_write_ordering()
Used get_ldev_if_state(device, D_ATTACHING) with the wrong assumption.
Remove it, and allow the caller to pass in a struct drbd_backing_dev*
when the caller knows that accessing this bdev is safe.

Signed-off-by: Philipp Reisner <philipp.reisner@xxxxxxxxxx>
Signed-off-by: Lars Ellenberg <lars.ellenberg@xxxxxxxxxx>
---
drivers/block/drbd/drbd_bitmap.c | 4 +++-
drivers/block/drbd/drbd_int.h | 9 ++++----
drivers/block/drbd/drbd_main.c | 36 +++++++++++++------------------
drivers/block/drbd/drbd_nl.c | 41 +++++++++++++++++++++++-------------
drivers/block/drbd/drbd_receiver.c | 43 ++++++++++++++++++++++++++------------
include/linux/drbd.h | 2 +-
6 files changed, 79 insertions(+), 56 deletions(-)

diff --git a/drivers/block/drbd/drbd_bitmap.c b/drivers/block/drbd/drbd_bitmap.c
index 1aa29f8..ed31041 100644
--- a/drivers/block/drbd/drbd_bitmap.c
+++ b/drivers/block/drbd/drbd_bitmap.c
@@ -1085,6 +1085,8 @@ static int bm_rw(struct drbd_device *device, int rw, unsigned flags, unsigned la
kfree(ctx);
return -ENODEV;
}
+ /* Here D_ATTACHING is sufficient since drbd_bm_read() is called only from
+ drbd_adm_attach(), after device->ldev was assigned. */

if (!ctx->flags)
WARN_ON(!(BM_LOCKED_MASK & b->bm_flags));
@@ -1260,7 +1262,7 @@ int drbd_bm_write_page(struct drbd_device *device, unsigned int idx) __must_hold
.kref = { ATOMIC_INIT(2) },
};

- if (!get_ldev_if_state(device, D_ATTACHING)) { /* put is in bm_aio_ctx_destroy() */
+ if (!get_ldev(device)) { /* put is in bm_aio_ctx_destroy() */
drbd_err(device, "ASSERT FAILED: get_ldev_if_state() == 1 in drbd_bm_write_page()\n");
kfree(ctx);
return -ENODEV;
diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 1ef2474..c87bc8e 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -984,8 +984,8 @@ extern int drbd_bitmap_io(struct drbd_device *device,
extern int drbd_bitmap_io_from_worker(struct drbd_device *device,
int (*io_fn)(struct drbd_device *),
char *why, enum bm_flag flags);
-extern int drbd_bmio_set_n_write(struct drbd_device *device);
-extern int drbd_bmio_clear_n_write(struct drbd_device *device);
+extern int drbd_bmio_set_n_write(struct drbd_device *device) __must_hold(local);
+extern int drbd_bmio_clear_n_write(struct drbd_device *device) __must_hold(local);
extern void drbd_ldev_destroy(struct drbd_device *device);

/* Meta data layout
@@ -1313,7 +1313,7 @@ enum determine_dev_size {
extern enum determine_dev_size
drbd_determine_dev_size(struct drbd_device *, enum dds_flags, struct resize_parms *) __must_hold(local);
extern void resync_after_online_grow(struct drbd_device *);
-extern void drbd_reconsider_max_bio_size(struct drbd_device *device);
+extern void drbd_reconsider_max_bio_size(struct drbd_device *device, struct drbd_backing_dev *bdev);
extern enum drbd_state_rv drbd_set_role(struct drbd_device *device,
enum drbd_role new_role,
int force);
@@ -1479,7 +1479,8 @@ static inline void drbd_generic_make_request(struct drbd_device *device,
generic_make_request(bio);
}

-void drbd_bump_write_ordering(struct drbd_resource *resource, enum write_ordering_e wo);
+void drbd_bump_write_ordering(struct drbd_resource *resource, struct drbd_backing_dev *bdev,
+ enum write_ordering_e wo);

/* drbd_proc.c */
extern struct proc_dir_entry *drbd_proc;
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 17b9a23..a6af935 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -3466,23 +3466,19 @@ void drbd_uuid_set_bm(struct drbd_device *device, u64 val) __must_hold(local)
*
* Sets all bits in the bitmap and writes the whole bitmap to stable storage.
*/
-int drbd_bmio_set_n_write(struct drbd_device *device)
+int drbd_bmio_set_n_write(struct drbd_device *device) __must_hold(local)
{
int rv = -EIO;

- if (get_ldev_if_state(device, D_ATTACHING)) {
- drbd_md_set_flag(device, MDF_FULL_SYNC);
- drbd_md_sync(device);
- drbd_bm_set_all(device);
-
- rv = drbd_bm_write(device);
+ drbd_md_set_flag(device, MDF_FULL_SYNC);
+ drbd_md_sync(device);
+ drbd_bm_set_all(device);

- if (!rv) {
- drbd_md_clear_flag(device, MDF_FULL_SYNC);
- drbd_md_sync(device);
- }
+ rv = drbd_bm_write(device);

- put_ldev(device);
+ if (!rv) {
+ drbd_md_clear_flag(device, MDF_FULL_SYNC);
+ drbd_md_sync(device);
}

return rv;
@@ -3494,18 +3490,11 @@ int drbd_bmio_set_n_write(struct drbd_device *device)
*
* Clears all bits in the bitmap and writes the whole bitmap to stable storage.
*/
-int drbd_bmio_clear_n_write(struct drbd_device *device)
+int drbd_bmio_clear_n_write(struct drbd_device *device) __must_hold(local)
{
- int rv = -EIO;
-
drbd_resume_al(device);
- if (get_ldev_if_state(device, D_ATTACHING)) {
- drbd_bm_clear_all(device);
- rv = drbd_bm_write(device);
- put_ldev(device);
- }
-
- return rv;
+ drbd_bm_clear_all(device);
+ return drbd_bm_write(device);
}

static int w_bitmap_io(struct drbd_work *w, int unused)
@@ -3603,6 +3592,9 @@ static int w_go_diskless(struct drbd_work *w, int unused)
* that drbd_set_out_of_sync() can not be called. This function MAY ONLY be
* called from worker context. It MUST NOT be used while a previous such
* work is still pending!
+ *
+ * Its worker function encloses the call of io_fn() by get_ldev() and
+ * put_ldev().
*/
void drbd_queue_bitmap_io(struct drbd_device *device,
int (*io_fn)(struct drbd_device *),
diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 43fad2c..25f4b6f 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1110,15 +1110,16 @@ static int drbd_check_al_size(struct drbd_device *device, struct disk_conf *dc)
return 0;
}

-static void drbd_setup_queue_param(struct drbd_device *device, unsigned int max_bio_size)
+static void drbd_setup_queue_param(struct drbd_device *device, struct drbd_backing_dev *bdev,
+ unsigned int max_bio_size)
{
struct request_queue * const q = device->rq_queue;
unsigned int max_hw_sectors = max_bio_size >> 9;
unsigned int max_segments = 0;
struct request_queue *b = NULL;

- if (get_ldev_if_state(device, D_ATTACHING)) {
- b = device->ldev->backing_bdev->bd_disk->queue;
+ if (bdev) {
+ b = bdev->backing_bdev->bd_disk->queue;

max_hw_sectors = min(queue_max_hw_sectors(b), max_bio_size >> 9);
rcu_read_lock();
@@ -1163,11 +1164,10 @@ static void drbd_setup_queue_param(struct drbd_device *device, unsigned int max_
b->backing_dev_info.ra_pages);
q->backing_dev_info.ra_pages = b->backing_dev_info.ra_pages;
}
- put_ldev(device);
}
}

-void drbd_reconsider_max_bio_size(struct drbd_device *device)
+void drbd_reconsider_max_bio_size(struct drbd_device *device, struct drbd_backing_dev *bdev)
{
unsigned int now, new, local, peer;

@@ -1175,10 +1175,9 @@ void drbd_reconsider_max_bio_size(struct drbd_device *device)
local = device->local_max_bio_size; /* Eventually last known value, from volatile memory */
peer = device->peer_max_bio_size; /* Eventually last known value, from meta data */

- if (get_ldev_if_state(device, D_ATTACHING)) {
- local = queue_max_hw_sectors(device->ldev->backing_bdev->bd_disk->queue) << 9;
+ if (bdev) {
+ local = queue_max_hw_sectors(bdev->backing_bdev->bd_disk->queue) << 9;
device->local_max_bio_size = local;
- put_ldev(device);
}
local = min(local, DRBD_MAX_BIO_SIZE);

@@ -1211,7 +1210,7 @@ void drbd_reconsider_max_bio_size(struct drbd_device *device)
if (new != now)
drbd_info(device, "max BIO size = %u\n", new);

- drbd_setup_queue_param(device, new);
+ drbd_setup_queue_param(device, bdev, new);
}

/* Starts the worker thread */
@@ -1399,7 +1398,7 @@ int drbd_adm_disk_opts(struct sk_buff *skb, struct genl_info *info)
else
set_bit(MD_NO_FUA, &device->flags);

- drbd_bump_write_ordering(device->resource, WO_bdev_flush);
+ drbd_bump_write_ordering(device->resource, NULL, WO_bdev_flush);

drbd_md_sync(device);

@@ -1704,7 +1703,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
new_disk_conf = NULL;
new_plan = NULL;

- drbd_bump_write_ordering(device->resource, WO_bdev_flush);
+ drbd_bump_write_ordering(device->resource, device->ldev, WO_bdev_flush);

if (drbd_md_test_flag(device->ldev, MDF_CRASHED_PRIMARY))
set_bit(CRASHED_PRIMARY, &device->flags);
@@ -1720,7 +1719,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
device->read_cnt = 0;
device->writ_cnt = 0;

- drbd_reconsider_max_bio_size(device);
+ drbd_reconsider_max_bio_size(device, device->ldev);

/* If I am currently not R_PRIMARY,
* but meta data primary indicator is set,
@@ -2648,8 +2647,13 @@ int drbd_adm_invalidate(struct sk_buff *skb, struct genl_info *info)
if (retcode != NO_ERROR)
goto out;

- mutex_lock(&adm_ctx.resource->adm_mutex);
device = adm_ctx.device;
+ if (!get_ldev(device)) {
+ retcode = ERR_NO_DISK;
+ goto out;
+ }
+
+ mutex_lock(&adm_ctx.resource->adm_mutex);

/* If there is still bitmap IO pending, probably because of a previous
* resync just being finished, wait for it before requesting a new resync.
@@ -2673,6 +2677,7 @@ int drbd_adm_invalidate(struct sk_buff *skb, struct genl_info *info)
retcode = drbd_request_state(device, NS(conn, C_STARTING_SYNC_T));
drbd_resume_io(device);
mutex_unlock(&adm_ctx.resource->adm_mutex);
+ put_ldev(device);
out:
drbd_adm_finish(&adm_ctx, info, retcode);
return 0;
@@ -2698,7 +2703,7 @@ out:
return 0;
}

-static int drbd_bmio_set_susp_al(struct drbd_device *device)
+static int drbd_bmio_set_susp_al(struct drbd_device *device) __must_hold(local)
{
int rv;

@@ -2719,8 +2724,13 @@ int drbd_adm_invalidate_peer(struct sk_buff *skb, struct genl_info *info)
if (retcode != NO_ERROR)
goto out;

- mutex_lock(&adm_ctx.resource->adm_mutex);
device = adm_ctx.device;
+ if (!get_ldev(device)) {
+ retcode = ERR_NO_DISK;
+ goto out;
+ }
+
+ mutex_lock(&adm_ctx.resource->adm_mutex);

/* If there is still bitmap IO pending, probably because of a previous
* resync just being finished, wait for it before requesting a new resync.
@@ -2747,6 +2757,7 @@ int drbd_adm_invalidate_peer(struct sk_buff *skb, struct genl_info *info)
retcode = drbd_request_state(device, NS(conn, C_STARTING_SYNC_S));
drbd_resume_io(device);
mutex_unlock(&adm_ctx.resource->adm_mutex);
+ put_ldev(device);
out:
drbd_adm_finish(&adm_ctx, info, retcode);
return 0;
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index c708418..be0c376 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -1168,7 +1168,7 @@ static void drbd_flush(struct drbd_connection *connection)
/* would rather check on EOPNOTSUPP, but that is not reliable.
* don't try again for ANY return value != 0
* if (rv == -EOPNOTSUPP) */
- drbd_bump_write_ordering(connection->resource, WO_drain_io);
+ drbd_bump_write_ordering(connection->resource, NULL, WO_drain_io);
}
put_ldev(device);
kref_put(&device->kref, drbd_destroy_device);
@@ -1257,14 +1257,29 @@ static enum finish_epoch drbd_may_finish_epoch(struct drbd_connection *connectio
return rv;
}

+static enum write_ordering_e
+max_allowed_wo(struct drbd_backing_dev *bdev, enum write_ordering_e wo)
+{
+ struct disk_conf *dc;
+
+ dc = rcu_dereference(bdev->disk_conf);
+
+ if (wo == WO_bdev_flush && !dc->disk_flushes)
+ wo = WO_drain_io;
+ if (wo == WO_drain_io && !dc->disk_drain)
+ wo = WO_none;
+
+ return wo;
+}
+
/**
* drbd_bump_write_ordering() - Fall back to an other write ordering method
* @connection: DRBD connection.
* @wo: Write ordering method to try.
*/
-void drbd_bump_write_ordering(struct drbd_resource *resource, enum write_ordering_e wo)
+void drbd_bump_write_ordering(struct drbd_resource *resource, struct drbd_backing_dev *bdev,
+ enum write_ordering_e wo)
{
- struct disk_conf *dc;
struct drbd_device *device;
enum write_ordering_e pwo;
int vnr;
@@ -1278,17 +1293,18 @@ void drbd_bump_write_ordering(struct drbd_resource *resource, enum write_orderin
wo = min(pwo, wo);
rcu_read_lock();
idr_for_each_entry(&resource->devices, device, vnr) {
- if (!get_ldev_if_state(device, D_ATTACHING))
- continue;
- dc = rcu_dereference(device->ldev->disk_conf);
-
- if (wo == WO_bdev_flush && !dc->disk_flushes)
- wo = WO_drain_io;
- if (wo == WO_drain_io && !dc->disk_drain)
- wo = WO_none;
- put_ldev(device);
+ if (get_ldev(device)) {
+ wo = max_allowed_wo(device->ldev, wo);
+ if (device->ldev == bdev)
+ bdev = NULL;
+ put_ldev(device);
+ }
}
rcu_read_unlock();
+
+ if (bdev)
+ wo = max_allowed_wo(bdev, wo);
+
resource->write_ordering = wo;
if (pwo != resource->write_ordering || wo == WO_bdev_flush)
drbd_info(resource, "Method to ensure write ordering: %s\n", write_ordering_str[resource->write_ordering]);
@@ -3709,7 +3725,6 @@ static int receive_sizes(struct drbd_connection *connection, struct packet_info
}

device->peer_max_bio_size = be32_to_cpu(p->max_bio_size);
- drbd_reconsider_max_bio_size(device);
/* Leave drbd_reconsider_max_bio_size() before drbd_determine_dev_size().
In case we cleared the QUEUE_FLAG_DISCARD from our queue in
drbd_reconsider_max_bio_size(), we can be sure that after
@@ -3717,6 +3732,7 @@ static int receive_sizes(struct drbd_connection *connection, struct packet_info

ddsf = be16_to_cpu(p->dds_flags);
if (get_ldev(device)) {
+ drbd_reconsider_max_bio_size(device, device->ldev);
dd = drbd_determine_dev_size(device, ddsf, NULL);
put_ldev(device);
if (dd == DS_ERROR)
@@ -3724,6 +3740,7 @@ static int receive_sizes(struct drbd_connection *connection, struct packet_info
drbd_md_sync(device);
} else {
/* I am diskless, need to accept the peer's size. */
+ drbd_reconsider_max_bio_size(device, NULL);
drbd_set_my_capacity(device, p_size);
}

diff --git a/include/linux/drbd.h b/include/linux/drbd.h
index 3dbe9bd..20ec890 100644
--- a/include/linux/drbd.h
+++ b/include/linux/drbd.h
@@ -245,7 +245,7 @@ enum drbd_disk_state {
D_DISKLESS,
D_ATTACHING, /* In the process of reading the meta-data */
D_FAILED, /* Becomes D_DISKLESS as soon as we told it the peer */
- /* when >= D_FAILED it is legal to access mdev->bc */
+ /* when >= D_FAILED it is legal to access mdev->ldev */
D_NEGOTIATING, /* Late attaching state, we need to talk to the peer */
D_INCONSISTENT,
D_OUTDATED,
--
1.9.1

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