On Tue, Dec 27 2016 at 10:56am -0500,
Ming Lei [off-list ref] wrote:
quoted hunk ↗ jump to hunk
For BIO based DM, some targets aren't ready for dealing with
bigger incoming bio than 1Mbyte, such as crypt target.
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
drivers/md/dm.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 3086da5664f3..6139bf7623f7 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -899,7 +899,16 @@ int dm_set_target_max_io_len(struct dm_target *ti, sector_t len)
return -EINVAL;
}
- ti->max_io_len = (uint32_t) len;
+ /*
+ * BIO based queue uses its own splitting. When multipage bvecs
+ * is switched on, size of the incoming bio may be too big to
+ * be handled in some targets, such as crypt.
+ *
+ * When these targets are ready for the big bio, we can remove
+ * the limit.
+ */
+ ti->max_io_len = min_t(uint32_t, len,
+ (BIO_MAX_PAGES * PAGE_SIZE));
return 0;
}
--
2.7.4
dm_set_target_max_io_len() is already meant to be called by the .ctr
hook for each DM target. So why not just have the dm-crypt target (and
other targets if needed) pass your reduced $len?
That way only targets that need to be fixed (e.g. dm-crypt) impose this
limit.