linux-kernel - [PATCH 10/22] mm/hmm: Remove duplicate condition test before wait_event

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Date:   Mon,  1 Jul 2019 08:20:08 +0200
From:   Christoph Hellwig <hch@....de>
To:     Dan Williams <dan.j.williams@...el.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Ben Skeggs <bskeggs@...hat.com>
Cc:     Ira Weiny <ira.weiny@...el.com>, linux-mm@...ck.org,
        nouveau@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-nvdimm@...ts.01.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Ralph Campbell <rcampbell@...dia.com>,
        John Hubbard <jhubbard@...dia.com>,
        Philip Yang <Philip.Yang@....com>
Subject: [PATCH 10/22] mm/hmm: Remove duplicate condition test before wait_event_timeout

From: Jason Gunthorpe <jgg@...lanox.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 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 <jgg@...lanox.com>
Reviewed-by: Ralph Campbell <rcampbell@...dia.com>
Reviewed-by: John Hubbard <jhubbard@...dia.com>
Reviewed-by: Ira Weiny <ira.weiny@...el.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Tested-by: Philip Yang <Philip.Yang@....com>
---
 include/linux/hmm.h | 13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index 1d97b6d62c5b..26e7c477490c 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;
 }
 
 /*
-- 
2.20.1