Impose necessary and sufficient conditions on a devices's table such
that any incoming bio which respects its logical_block_size can be
processed successfully.
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Alasdair G Kergon <agk@xxxxxxxxxx>
---
drivers/md/dm-table.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 69 insertions(+)
Index: linux-2.6/drivers/md/dm-table.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-table.c
+++ linux-2.6/drivers/md/dm-table.c
@@ -726,6 +726,71 @@ static void check_for_valid_limits(struc
rs->bounce_pfn = -1;
}
+/*
+ * Impose necessary and sufficient conditions on a devices's table such
+ * that any incoming bio which respects its logical_block_size can be
+ * processed successfully. If it falls across the boundary between
+ * two or more targets, the size of each piece it gets split into must
+ * be compatible with the logical_block_size of the target processing it.
+ */
+static int validate_hardware_logical_block_alignment(struct dm_table *table)
+{
+ /*
+ * This function uses arithmetic modulo the logical_block_size
+ * (in units of 512-byte sectors).
+ */
+ unsigned short device_logical_block_size_sects =
+ table->limits.logical_block_size >> SECTOR_SHIFT;
+
+ /*
+ * Offset of the start of the next table entry, mod logical_block_size.
+ */
+ unsigned short next_target_start = 0;
+
+ /*
+ * Given an aligned bio that extends beyond the end of a
+ * target, how many sectors must the next target handle?
+ */
+ unsigned short remaining = 0;
+
+ struct dm_target *uninitialized_var(ti);
+ unsigned i = 0;
+
+ /*
+ * Check each entry in the table in turn.
+ */
+ while (i < dm_table_get_num_targets(table)) {
+ ti = dm_table_get_target(table, i++);
+
+ /*
+ * If the remaining sectors fall entirely within this
+ * table entry are they compatible with its logical_block_size?
+ */
+ if (remaining < ti->len &&
+ remaining & ((ti->limits.logical_block_size >>
+ SECTOR_SHIFT) - 1))
+ break; /* Error */
+
+ next_target_start =
+ (unsigned short) ((next_target_start + ti->len) &
+ (device_logical_block_size_sects - 1));
+ remaining = next_target_start ?
+ device_logical_block_size_sects - next_target_start : 0;
+ }
+
+ if (remaining) {
+ DMWARN("%s: table line %u (start sect %llu len %llu) "
+ "not aligned to h/w logical_block_size %hu",
+ dm_device_name(table->md), i,
+ (unsigned long long) ti->begin,
+ (unsigned long long) ti->len,
+ table->limits.logical_block_size);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
int dm_table_add_target(struct dm_table *t, const char *type,
sector_t start, sector_t len, char *params)
{
@@ -825,6 +890,10 @@ int dm_table_complete(struct dm_table *t
check_for_valid_limits(&t->limits);
+ r = validate_hardware_logical_block_alignment(t);
+ if (r)
+ return r;
+
/* how many indexes will the btree have ? */
leaf_nodes = dm_div_up(t->num_targets, KEYS_PER_NODE);
t->depth = 1 + int_log(leaf_nodes, CHILDREN_PER_NODE);
--
dm-devel mailing list
dm-devel@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/dm-devel
