From f046f89a99ccfd9408b94c653374ff3065c7edb3 Mon Sep 17 00:00:00 2001 From: Joe Thornber Date: Wed, 20 Mar 2013 17:21:24 +0000 Subject: dm thin: fix discard corruption Fix a bug in dm_btree_remove that could leave leaf values with incorrect reference counts. The effect of this was that removal of a shared block could result in the space maps thinking the block was no longer used. More concretely, if you have a thin device and a snapshot of it, sending a discard to a shared region of the thin could corrupt the snapshot. Thinp uses a 2-level nested btree to store it's mappings. This first level is indexed by thin device, and the second level by logical block. Often when we're removing an entry in this mapping tree we need to rebalance nodes, which can involve shadowing them, possibly creating a copy if the block is shared. If we do create a copy then children of that node need to have their reference counts incremented. In this way reference counts percolate down the tree as shared trees diverge. The rebalance functions were incrementing the children at the appropriate time, but they were always assuming the children were internal nodes. This meant the leaf values (in our case packed block/flags entries) were not being incremented. Cc: stable@vger.kernel.org Signed-off-by: Joe Thornber Signed-off-by: Alasdair G Kergon --- drivers/md/dm-thin.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'drivers/md/dm-thin.c') diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c index 009339d62828..ab95e5ff3758 100644 --- a/drivers/md/dm-thin.c +++ b/drivers/md/dm-thin.c @@ -2544,7 +2544,7 @@ static struct target_type pool_target = { .name = "thin-pool", .features = DM_TARGET_SINGLETON | DM_TARGET_ALWAYS_WRITEABLE | DM_TARGET_IMMUTABLE, - .version = {1, 6, 1}, + .version = {1, 7, 0}, .module = THIS_MODULE, .ctr = pool_ctr, .dtr = pool_dtr, @@ -2831,7 +2831,7 @@ static int thin_iterate_devices(struct dm_target *ti, static struct target_type thin_target = { .name = "thin", - .version = {1, 7, 1}, + .version = {1, 8, 0}, .module = THIS_MODULE, .ctr = thin_ctr, .dtr = thin_dtr, -- cgit From 58051b94e05a59c4d34f9f1a441af40894817c59 Mon Sep 17 00:00:00 2001 From: Joe Thornber Date: Wed, 20 Mar 2013 17:21:25 +0000 Subject: dm thin: fix non power of two discard granularity calc Fix a discard granularity calculation to work for non power of 2 block sizes. In order for thinp to passdown discard bios to the underlying data device, the data device must have a discard granularity that is a factor of the thinp block size. Originally this check was done by using bitops since the block_size was known to be a power of two. Introduced by commit f13945d75730081830b6f3360266950e2b7c9067 ("dm thin: support a non power of 2 discard_granularity"). Signed-off-by: Joe Thornber Signed-off-by: Alasdair G Kergon --- drivers/md/dm-thin.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'drivers/md/dm-thin.c') diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c index ab95e5ff3758..004ad1652b73 100644 --- a/drivers/md/dm-thin.c +++ b/drivers/md/dm-thin.c @@ -1577,6 +1577,11 @@ static bool data_dev_supports_discard(struct pool_c *pt) return q && blk_queue_discard(q); } +static bool is_factor(sector_t block_size, uint32_t n) +{ + return !sector_div(block_size, n); +} + /* * If discard_passdown was enabled verify that the data device * supports discards. Disable discard_passdown if not. @@ -1602,7 +1607,7 @@ static void disable_passdown_if_not_supported(struct pool_c *pt) else if (data_limits->discard_granularity > block_size) reason = "discard granularity larger than a block"; - else if (block_size & (data_limits->discard_granularity - 1)) + else if (!is_factor(block_size, data_limits->discard_granularity)) reason = "discard granularity not a factor of block size"; if (reason) { -- cgit