[PATCH 1/6] rbd: update capacity in rbd_dev_refresh()

[Alex Elder <elder@inktank.com>]

When a mapped image changes size, we change the capacity recorded
for the Linux disk associated with it, in rbd_update_mapping_size().
That function is called in two places--the format 1 and format 2
refresh routines.

There is no need to set the capacity while holding the header
semaphore.  Instead, do it in the common rbd_dev_refresh(), using
the logic that's already there to initiate disk revalidation.

Add handling in the request function, just in case a request
that exceeds the capacity of the device comes in (perhaps one
that was started before a refresh shrunk the device).

Signed-off-by: Alex Elder <elder@inktank.com>
---
 drivers/block/rbd.c |   23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 5d5e3f0..a0f1fe5 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -2874,6 +2874,13 @@ static void rbd_request_fn(struct request_queue *q)
 			goto end_request;	/* Shouldn't happen */
 		}

+		result = -ENOSPC;
+		if (offset + length > rbd_dev->mapping.size) {
+			rbd_warn(rbd_dev, "beyond EOD (%llu~%llu > %llu)\n",
+				offset, length, rbd_dev->mapping.size);
+			goto end_request;
+		}
+
 		result = -ENOMEM;
 		img_request = rbd_img_request_create(rbd_dev, offset, length,
 							write_request, false);
@@ -3116,14 +3123,8 @@ static void rbd_update_mapping_size(struct
rbd_device *rbd_dev)
 	if (rbd_dev->spec->snap_id != CEPH_NOSNAP)
 		return;

-	if (rbd_dev->mapping.size != rbd_dev->header.image_size) {
-		sector_t size;
-
+	if (rbd_dev->mapping.size != rbd_dev->header.image_size)
 		rbd_dev->mapping.size = rbd_dev->header.image_size;
-		size = (sector_t)rbd_dev->mapping.size / SECTOR_SIZE;
-		dout("setting size to %llu sectors", (unsigned long long)size);
-		set_capacity(rbd_dev->disk, size);
-	}
 }

 /*
@@ -3200,8 +3201,14 @@ static int rbd_dev_refresh(struct rbd_device
*rbd_dev)

 	rbd_exists_validate(rbd_dev);
 	mutex_unlock(&ctl_mutex);
-	if (mapping_size != rbd_dev->mapping.size)
+	if (mapping_size != rbd_dev->mapping.size) {
+		sector_t size;
+
+		size = (sector_t)rbd_dev->mapping.size / SECTOR_SIZE;
+		dout("setting size to %llu sectors", (unsigned long long)size);
+		set_capacity(rbd_dev->disk, size);
 		revalidate_disk(rbd_dev->disk);
+	}

 	return ret;
 }
-- 
1.7.9.5