On Thu 02-03-17 19:04:48, Tetsuo Handa wrote:
[...]
> So, commit 5d17a73a2ebeb8d1("vmalloc: back off when the current task is
> killed") implemented __GFP_KILLABLE flag and automatically applied that
> flag. As a result, those who are not ready to fail upon SIGKILL are
> confused. ;-)
You are right! The function is documented it might fail but the code
doesn't really allow that. This seems like a bug to me. What do you
think about the following?
---
>From d02cb0285d8ce3344fd64dc7e2912e9a04bef80d Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@xxxxxxxx>
Date: Thu, 2 Mar 2017 11:31:11 +0100
Subject: [PATCH] xfs: allow kmem_zalloc_greedy to fail
Even though kmem_zalloc_greedy is documented it might fail the current
code doesn't really implement this properly and loops on the smallest
allowed size for ever. This is a problem because vzalloc might fail
permanently. Since 5d17a73a2ebe ("vmalloc: back off when the current
task is killed") such a failure is much more probable than it used to
be. Fix this by bailing out if the minimum size request failed.
This has been noticed by a hung generic/269 xfstest by Xiong Zhou.
Reported-by: Xiong Zhou <xzhou@xxxxxxxxxx>
Analyzed-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
---
fs/xfs/kmem.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/fs/xfs/kmem.c b/fs/xfs/kmem.c
index 339c696bbc01..ee95f5c6db45 100644
--- a/fs/xfs/kmem.c
+++ b/fs/xfs/kmem.c
@@ -34,6 +34,8 @@ kmem_zalloc_greedy(size_t *size, size_t minsize, size_t maxsize)
size_t kmsize = maxsize;
while (!(ptr = vzalloc(kmsize))) {
+ if (kmsize == minsize)
+ break;
if ((kmsize >>= 1) <= minsize)
kmsize = minsize;
}
--
2.11.0
--
Michal Hocko
SUSE Labs
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