[PATCH v2 hmm 05/11] mm/hmm: Remove duplicate condition test before wait_event_timeout

Jason Gunthorpe jgg at ziepe.ca
Thu Jun 6 18:44:32 UTC 2019

From: Jason Gunthorpe <jgg at mellanox.com>

The wait_event_timeout macro already tests the condition as its first
action, so there is no reason to open code another version of this, all
that does is skip the might_sleep() debugging in common cases, which is
not helpful.

Further, based on prior patches, we can no simplify the required condition
 - If range is valid memory then so is range->hmm
 - If hmm_release() has run then range->valid is set to false
   at the same time as dead, so no reason to check both.
 - A valid hmm has a valid hmm->mm.

Also, add the READ_ONCE for range->valid as there is no lock held here.

Signed-off-by: Jason Gunthorpe <jgg at mellanox.com>
Reviewed-by: Jérôme Glisse <jglisse at redhat.com>
 include/linux/hmm.h | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index 4ee3acabe5ed22..2ab35b40992b24 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -218,17 +218,9 @@ static inline unsigned long hmm_range_page_size(const struct hmm_range *range)
 static inline bool hmm_range_wait_until_valid(struct hmm_range *range,
 					      unsigned long timeout)
-	/* Check if mm is dead ? */
-	if (range->hmm == NULL || range->hmm->dead || range->hmm->mm == NULL) {
-		range->valid = false;
-		return false;
-	}
-	if (range->valid)
-		return true;
-	wait_event_timeout(range->hmm->wq, range->valid || range->hmm->dead,
+	wait_event_timeout(range->hmm->wq, range->valid,
-	/* Return current valid status just in case we get lucky */
-	return range->valid;
+	return READ_ONCE(range->valid);

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