fix hard-coded disk header chunk size for persistent snapshot
(2010/05/12 13:58), Mikulas Patocka wrote:
On Wed, 12 May 2010, Alasdair G Kergon wrote:
On Wed, May 12, 2010 at 10:29:22AM +0900, Tomohiro Kusumi wrote:
This patch fixes hard-coded value for the size of a chunk that includes
disk header for persistent snapshot. It should be changed to existing
macro NUM_SNAPSHOT_HDR_CHUNKS instead of using hard-coded value 1.
Any more places too? (E.g. persistent_commit_merge)
I think the expression in persistent_commit_merge should be changed to:
ps->next_free = area_location(ps, ps->current_area) +
ps->current_committed + 1;
It is numerically the same, but will avoid trouble if
NUM_SNAPSHOT_HDR_CHUNKS is increased.
a single chunk is large enough to contain 16byte disk header
which does not seem necessary to increase NUM_SNAPSHOT_HDR_CHUNKS in the future
(unless whole structure get totally changed),
but it should also get fixed to avoid trouble.
I merged it to the patch with your names signed off.
Signed-off-by: Tomohiro Kusumi <firstname.lastname@example.org>
Signed-off-by: Alasdair G Kergon <email@example.com>
Signed-off-by: Mikulas Patocka <firstname.lastname@example.org>
diff -aNur linux-2.6.34-rc7.org/drivers/md/dm-snap-persistent.c linux-2.6.34-rc7/drivers/md/dm-snap-persistent.c
--- linux-2.6.34-rc7.org/drivers/md/dm-snap-persistent.c 2010-05-10 10:36:28.000000000 +0900
+++ linux-2.6.34-rc7/drivers/md/dm-snap-persistent.c 2010-05-12 14:49:13.000000000 +0900
@@ -266,7 +266,7 @@
static chunk_t area_location(struct pstore *ps, chunk_t area)
- return 1 + ((ps->exceptions_per_area + 1) * area);
+ return NUM_SNAPSHOT_HDR_CHUNKS + ((ps->exceptions_per_area + 1) * area);
@@ -780,8 +780,8 @@
* ps->current_area does not get reduced by prepare_merge() until
* after commit_merge() has removed the nr_merged previous exceptions.
- ps->next_free = (area_location(ps, ps->current_area) - 1) +
- (ps->current_committed + 1) + NUM_SNAPSHOT_HDR_CHUNKS;
+ ps->next_free = area_location(ps, ps->current_area) +
+ ps->current_committed + 1;
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