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drbd: don't implicitly resize Diskless node beyond end of device 

During handshake, we compare backend sizes, and user set limits,
and agree on what device size we are going to expose.

We remember that last-agreed-size in our meta data.

But if we come up diskless, we have to accept what the peer
presents us with. We used to accept the peers maximum potential
capacity (backend size), which is wrong, and could lead to IO errors
due to access beyond end of device.

Instead, we need to accept the peer's current size.
Unless that is communicated as 0, in which case we
accept the backend size, or the user set limit, if set.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
This commit is contained in:
Lars Ellenberg 2014-03-18 12:22:14 +01:00 committed by Philipp Reisner
parent a5655dac75
commit 6a8d68b187
1 changed files with 16 additions and 3 deletions
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19
drivers/block/drbd/drbd_receiver.c
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@ -3657,7 +3657,7 @@ static int receive_sizes(struct drbd_connection *connection, struct packet_info
struct drbd_device *device; struct drbd_device *device;
struct p_sizes *p = pi->data; struct p_sizes *p = pi->data;
enum determine_dev_size dd = DS_UNCHANGED; enum determine_dev_size dd = DS_UNCHANGED;
sector_t p_size, p_usize, my_usize; sector_t p_size, p_usize, p_csize, my_usize;
int ldsc = 0; /* local disk size changed */ int ldsc = 0; /* local disk size changed */
enum dds_flags ddsf; enum dds_flags ddsf;
@ -3668,6 +3668,7 @@ static int receive_sizes(struct drbd_connection *connection, struct packet_info
p_size = be64_to_cpu(p->d_size); p_size = be64_to_cpu(p->d_size);
p_usize = be64_to_cpu(p->u_size); p_usize = be64_to_cpu(p->u_size);
p_csize = be64_to_cpu(p->c_size);
/* just store the peer's disk size for now. /* just store the peer's disk size for now.
* we still need to figure out whether we accept that. */ * we still need to figure out whether we accept that. */
@ -3742,9 +3743,21 @@ static int receive_sizes(struct drbd_connection *connection, struct packet_info
return -EIO; return -EIO;
drbd_md_sync(device); drbd_md_sync(device);
} else { } else {
/* I am diskless, need to accept the peer's size. */ /*
* I am diskless, need to accept the peer's *current* size.
* I must NOT accept the peers backing disk size,
* it may have been larger than mine all along...
*
* At this point, the peer knows more about my disk, or at
* least about what we last agreed upon, than myself.
* So if his c_size is less than his d_size, the most likely
* reason is that *my* d_size was smaller last time we checked.
*
* However, if he sends a zero current size,
* take his (user-capped or) backing disk size anyways.
*/
drbd_reconsider_max_bio_size(device, NULL); drbd_reconsider_max_bio_size(device, NULL);
drbd_set_my_capacity(device, p_size); drbd_set_my_capacity(device, p_csize ?: p_usize ?: p_size);
} }
if (get_ldev(device)) { if (get_ldev(device)) {