linux-kernel - [PATCH] x86/Hyper-V: Balloon up according to request page number

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Date:   Tue, 14 Jan 2020 15:44:35 +0800
From:   lantianyu1986@...il.com
To:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        x86@...nel.org, dave.hansen@...ux.intel.com, luto@...nel.org,
        peterz@...radead.org, kys@...rosoft.com, haiyangz@...rosoft.com,
        sthemmin@...rosoft.com, sashal@...nel.org,
        akpm@...ux-foundation.org, michael.h.kelley@...rosoft.com,
        decui@...rosoft.com
Cc:     Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        linux-kernel@...r.kernel.org, linux-hyperv@...r.kernel.org,
        linux-mm@...ck.org, vkuznets@...hat.com, stable@...r.kernel.org
Subject: [PATCH] x86/Hyper-V: Balloon up according to request page number

From: Tianyu Lan <Tianyu.Lan@...rosoft.com>

Current code has assumption that balloon request memory size aligns
with 2MB. But actually Hyper-V doesn't guarantee such alignment. When
balloon driver receives non-aligned balloon request, it produces warning
and balloon up more memory than requested in order to keep 2MB alignment.
Remove the warning and balloon up memory according to actual requested
memory size.

Fixes: f6712238471a ("hv: hv_balloon: avoid memory leak on alloc_error of 2MB memory block")
Cc: stable@...r.kernel.org
Signed-off-by: Tianyu Lan <Tianyu.Lan@...rosoft.com>
---
 drivers/hv/hv_balloon.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index 7f3e7ab22d5d..38ad0e44e927 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -1684,7 +1684,7 @@ static unsigned int alloc_balloon_pages(struct hv_dynmem_device *dm,
 	if (num_pages < alloc_unit)
 		return 0;
 
-	for (i = 0; (i * alloc_unit) < num_pages; i++) {
+	for (i = 0; i < num_pages / alloc_unit; i++) {
 		if (bl_resp->hdr.size + sizeof(union dm_mem_page_range) >
 			HV_HYP_PAGE_SIZE)
 			return i * alloc_unit;
@@ -1722,7 +1722,7 @@ static unsigned int alloc_balloon_pages(struct hv_dynmem_device *dm,
 
 	}
 
-	return num_pages;
+	return i * alloc_unit;
 }
 
 static void balloon_up(union dm_msg_info *msg_info)
@@ -1737,9 +1737,6 @@ static void balloon_up(union dm_msg_info *msg_info)
 	long avail_pages;
 	unsigned long floor;
 
-	/* The host balloons pages in 2M granularity. */
-	WARN_ON_ONCE(num_pages % PAGES_IN_2M != 0);
-
 	/*
 	 * We will attempt 2M allocations. However, if we fail to
 	 * allocate 2M chunks, we will go back to PAGE_SIZE allocations.
-- 
2.14.5