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drbd: drbd_rs_number_requests: fix unit mismatch in comparison 

We try to limit the number of "in-flight" resync requests.
One condition for that is the amount of requested data should not exceed
half of what can be covered by our "max-buffers" setting.

However we compared number of 4k pages with number of in-flight 512 Byte
sectors, and this extra throttle triggered much earlier than intended.

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 2014-04-22 16:37:16 +02:00 committed by Philipp Reisner
parent f88c5d90cc
commit 7f34f61490
1 changed files with 9 additions and 4 deletions
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13
drivers/block/drbd/drbd_worker.c
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@ -504,9 +504,9 @@ struct fifo_buffer *fifo_alloc(int fifo_size)
static int drbd_rs_controller(struct drbd_device *device, unsigned int sect_in) static int drbd_rs_controller(struct drbd_device *device, unsigned int sect_in)
{ {
struct disk_conf *dc; struct disk_conf *dc;
unsigned int want; /* The number of sectors we want in the proxy */ unsigned int want; /* The number of sectors we want in-flight */
int req_sect; /* Number of sectors to request in this turn */ int req_sect; /* Number of sectors to request in this turn */
int correction; /* Number of sectors more we need in the proxy*/ int correction; /* Number of sectors more we need in-flight */
int cps; /* correction per invocation of drbd_rs_controller() */ int cps; /* correction per invocation of drbd_rs_controller() */
int steps; /* Number of time steps to plan ahead */ int steps; /* Number of time steps to plan ahead */
int curr_corr; int curr_corr;
@ -577,8 +577,13 @@ static int drbd_rs_number_requests(struct drbd_device *device)
* potentially causing a distributed deadlock on congestion during * potentially causing a distributed deadlock on congestion during
* online-verify or (checksum-based) resync, if max-buffers, * online-verify or (checksum-based) resync, if max-buffers,
* socket buffer sizes and resync rate settings are mis-configured. */ * socket buffer sizes and resync rate settings are mis-configured. */
if (mxb - device->rs_in_flight < number)
number = mxb - device->rs_in_flight; /* note that "number" is in units of "BM_BLOCK_SIZE" (which is 4k),
* mxb (as used here, and in drbd_alloc_pages on the peer) is
* "number of pages" (typically also 4k),
* but "rs_in_flight" is in "sectors" (512 Byte). */
if (mxb - device->rs_in_flight/8 < number)
number = mxb - device->rs_in_flight/8;
return number; return number;
} }