From: Matthias Schiffer 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 +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 +Cc: Heiko Carstens +Cc: Christoph Hellwig +Cc: Al Viro +Signed-off-by: Andrew Morton +Signed-off-by: Linus Torvalds +--- + 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;