dm crypt: use cond_resched

Add cond_resched() to prevent monopolising CPU when processing large bios.

dm-crypt processes encryption of bios in sector units.  If the bio request
is big it can spend a long time in the encryption call.

Signed-off-by: Milan Broz <mbroz@redhat.com>
Tested-by: Yan Li <elliot.li.tech@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 835def11419d..ab6a61db63ce 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -432,6 +432,7 @@ static int crypt_convert(struct crypt_config *cc,
                 case 0:
                         atomic_dec(&ctx->pending);
                         ctx->sector++;
+                        cond_resched();
                         continue;
 
                 /* error */