[v3,hmm,05/12] mm/hmm: Remove duplicate condition test before wait_event_timeout

Commit Message

Jason Gunthorpe June 14, 2019, 12:44 a.m. UTC

From: Jason Gunthorpe <[e-mail]>

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 now simplify the required condition
test:
 - 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.

Allowing the return value of wait_event_timeout() (along with its internal
barriers) to compute the result of the function.

Signed-off-by: Jason Gunthorpe <[e-mail]>
Reviewed-by: Ralph Campbell <[e-mail]>
Reviewed-by: John Hubbard <[e-mail]>
Reviewed-by: Ira Weiny <[e-mail]>
Tested-by: Philip Yang <[e-mail]>
---
v3
- Simplify the wait_event_timeout to not check valid
---
 include/linux/hmm.h | 13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

Comments

Christoph Hellwig June 15, 2019, 2:12 p.m. UTC | #1

Looks good,

Reviewed-by: Christoph Hellwig <[e-mail]>

Patch

diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index 1d97b6d62c5bcf..26e7c477490c4e 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -209,17 +209,8 @@  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,
-			   msecs_to_jiffies(timeout));
-	/* Return current valid status just in case we get lucky */
-	return range->valid;
+	return wait_event_timeout(range->hmm->wq, range->valid,
+				  msecs_to_jiffies(timeout)) != 0;
 }
 
 /*