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kernel: fs, seq_file: fallback to vmalloc instead of oom kill processes 

Fixes #177
This commit is contained in:
Matthias Schiffer 2016-01-04 10:26:40 +01:00
parent 7b6f3fed70
commit 0bd0df6f93
1 changed files with 63 additions and 0 deletions
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patches/openwrt/0047-kernel-fs-seq_file-fallback-to-vmalloc-instead-of-oom-kill-processes.patch Normal file
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@ -0,0 +1,63 @@
From: Matthias Schiffer <mschiffer@universe-factory.net>
Date: Mon, 4 Jan 2016 10:22:52 +0100
Subject: kernel: fs, seq_file: fallback to vmalloc instead of oom kill processes
diff --git a/target/linux/generic/patches-3.18/089-fs-seq_file-fallback-to-vmalloc-instead-of-oom-kill-.patch b/target/linux/generic/patches-3.18/089-fs-seq_file-fallback-to-vmalloc-instead-of-oom-kill-.patch
new file mode 100644
index 0000000..cad56f4
--- /dev/null
+++ b/target/linux/generic/patches-3.18/089-fs-seq_file-fallback-to-vmalloc-instead-of-oom-kill-.patch
@@ -0,0 +1,53 @@
+From 5cec38ac866bfb8775638e71a86e4d8cac30caae Mon Sep 17 00:00:00 2001
+Message-Id: <5cec38ac866bfb8775638e71a86e4d8cac30caae.1451899087.git.mschiffer@universe-factory.net>
+From: David Rientjes <rientjes@google.com>
+Date: Fri, 12 Dec 2014 16:56:16 -0800
+Subject: [PATCH] fs, seq_file: fallback to vmalloc instead of oom kill
+ processes
+
+Since commit 058504edd026 ("fs/seq_file: fallback to vmalloc allocation"),
+seq_buf_alloc() falls back to vmalloc() when the kmalloc() for contiguous
+memory fails. This was done to address order-4 slab allocations for
+reading /proc/stat on large machines and noticed because
+PAGE_ALLOC_COSTLY_ORDER < 4, so there is no infinite loop in the page
+allocator when allocating new slab for such high-order allocations.
+
+Contiguous memory isn't necessary for caller of seq_buf_alloc(), however.
+Other GFP_KERNEL high-order allocations that are <=
+PAGE_ALLOC_COSTLY_ORDER will simply loop forever in the page allocator and
+oom kill processes as a result.
+
+We don't want to kill processes so that we can allocate contiguous memory
+in situations when contiguous memory isn't necessary.
+
+This patch does the kmalloc() allocation with __GFP_NORETRY for high-order
+allocations. This still utilizes memory compaction and direct reclaim in
+the allocation path, the only difference is that it will fail immediately
+instead of oom kill processes when out of memory.
+
+[akpm@linux-foundation.org: add comment]
+Signed-off-by: David Rientjes <rientjes@google.com>
+Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
+Cc: Christoph Hellwig <hch@infradead.org>
+Cc: Al Viro <viro@zeniv.linux.org.uk>
+Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
+Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
+---
+ fs/seq_file.c | 6 +++++-
+ 1 file changed, 5 insertions(+), 1 deletion(-)
+
+--- a/fs/seq_file.c
++++ b/fs/seq_file.c
+@@ -36,7 +36,11 @@ static void *seq_buf_alloc(unsigned long
+ {
+ void *buf;
+
+- buf = kmalloc(size, GFP_KERNEL | __GFP_NOWARN);
++ /*
++ * __GFP_NORETRY to avoid oom-killings with high-order allocations -
++ * it's better to fall back to vmalloc() than to kill things.
++ */
++ buf = kmalloc(size, GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN);
+ if (!buf && size > PAGE_SIZE)
+ buf = vmalloc(size);
+ return buf;