dm: support non power of two target max_io_len
Remove the restriction that limits a target's specified maximum incoming
I/O size to be a power of 2.
Rename this setting from 'split_io' to the less-ambiguous 'max_io_len'.
Change it from sector_t to uint32_t, which is plenty big enough, and
introduce a wrapper function dm_set_target_max_io_len() to set it.
Use sector_div() to process it now that it is not necessarily a power of 2.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index e24143c..415c280 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -968,22 +968,41 @@
static sector_t max_io_len(sector_t sector, struct dm_target *ti)
{
sector_t len = max_io_len_target_boundary(sector, ti);
+ sector_t offset, max_len;
/*
- * Does the target need to split even further ?
+ * Does the target need to split even further?
*/
- if (ti->split_io) {
- sector_t boundary;
- sector_t offset = dm_target_offset(ti, sector);
- boundary = ((offset + ti->split_io) & ~(ti->split_io - 1))
- - offset;
- if (len > boundary)
- len = boundary;
+ if (ti->max_io_len) {
+ offset = dm_target_offset(ti, sector);
+ if (unlikely(ti->max_io_len & (ti->max_io_len - 1)))
+ max_len = sector_div(offset, ti->max_io_len);
+ else
+ max_len = offset & (ti->max_io_len - 1);
+ max_len = ti->max_io_len - max_len;
+
+ if (len > max_len)
+ len = max_len;
}
return len;
}
+int dm_set_target_max_io_len(struct dm_target *ti, sector_t len)
+{
+ if (len > UINT_MAX) {
+ DMERR("Specified maximum size of target IO (%llu) exceeds limit (%u)",
+ (unsigned long long)len, UINT_MAX);
+ ti->error = "Maximum size of target IO is too large";
+ return -EINVAL;
+ }
+
+ ti->max_io_len = (uint32_t) len;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(dm_set_target_max_io_len);
+
static void __map_bio(struct dm_target *ti, struct bio *clone,
struct dm_target_io *tio)
{