From 53502592aca32e9908450df3c39c149dc43e9fc8 Mon Sep 17 00:00:00 2001 From: Greg Thelen Date: Thu, 22 Oct 2015 09:03:59 +1100 Subject: [PATCH] fs, seqfile: always allow oom killer Since 5cec38ac866b ("fs, seq_file: fallback to vmalloc instead of oom kill processes") seq_buf_alloc() avoids calling the oom killer for PAGE_SIZE or smaller allocations; but larger allocations can use the oom killer via vmalloc(). Thus reads of small files can return ENOMEM, but larger files use the oom killer to avoid ENOMEM. The effect of this bug is that reads from /proc and other virtual filesystems can return ENOMEM instead of the preferred behavior - oom killing something (possibly the calling process). I don't know of anyone except Google who has noticed the issue. I suspect the fix is more needed in smaller systems where there isn't any reclaimable memory. But these seem like the kinds of systems which probably don't use the oom killer for production situations. Memory overcommit requires use of the oom killer to select a victim regardless of file size. Enable oom killer for small seq_buf_alloc() allocations. Fixes: 5cec38ac866b ("fs, seq_file: fallback to vmalloc instead of oom kill processes") Signed-off-by: David Rientjes Signed-off-by: Greg Thelen Acked-by: Eric Dumazet Cc: Signed-off-by: Andrew Morton --- fs/seq_file.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/fs/seq_file.c b/fs/seq_file.c index 00bbe2bfc634..e85664b7c7d9 100644 --- a/fs/seq_file.c +++ b/fs/seq_file.c @@ -26,12 +26,17 @@ static void seq_set_overflow(struct seq_file *m) static void *seq_buf_alloc(unsigned long size) { void *buf; + gfp_t gfp = GFP_KERNEL; /* - * __GFP_NORETRY to avoid oom-killings with high-order allocations - - * it's better to fall back to vmalloc() than to kill things. + * For high order allocations, use __GFP_NORETRY to avoid oom-killing - + * it's better to fall back to vmalloc() than to kill things. For small + * allocations, just use GFP_KERNEL which will oom kill, thus no need + * for vmalloc fallback. */ - buf = kmalloc(size, GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN); + if (size > PAGE_SIZE) + gfp |= __GFP_NORETRY | __GFP_NOWARN; + buf = kmalloc(size, gfp); if (!buf && size > PAGE_SIZE) buf = vmalloc(size); return buf; -- 2.39.5