4.4-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit 45c815f06b80031659c63d7b93e580015d6024dd ]
We are currently using asynchronous deallocation in the error path in AUX mmap code, which is unnecessary and also presents a problem for users that wish to probe for the biggest possible buffer size they can get: they'll get -EINVAL on all subsequent attemts to allocate a smaller buffer before the asynchronous deallocation callback frees up the pages from the previous unsuccessful attempt.
Currently, gdb does that for allocating AUX buffers for Intel PT traces. More specifically, overwrite mode of AUX pmus that don't support hardware sg (some implementations of Intel PT, for instance) is limited to only one contiguous high order allocation for its buffer and there is no way of knowing its size without trying.
This patch changes error path freeing to be synchronous as there won't be any contenders for the AUX pages at that point.
Reported-by: Markus Metzger markus.t.metzger@intel.com Signed-off-by: Alexander Shishkin alexander.shishkin@linux.intel.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Cc: Arnaldo Carvalho de Melo acme@infradead.org Cc: Arnaldo Carvalho de Melo acme@redhat.com Cc: David Ahern dsahern@gmail.com Cc: Jiri Olsa jolsa@redhat.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Namhyung Kim namhyung@kernel.org Cc: Peter Zijlstra peterz@infradead.org Cc: Stephane Eranian eranian@google.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Vince Weaver vincent.weaver@maine.edu Cc: vince@deater.net Link: http://lkml.kernel.org/r/1453216469-9509-1-git-send-email-alexander.shishkin... Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/events/ring_buffer.c | 40 ++++++++++++++++++------------------- 1 file changed, 20 insertions(+), 20 deletions(-)
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index 358bb53c1e74..94dc6b0763ab 100644 --- a/kernel/events/ring_buffer.c +++ b/kernel/events/ring_buffer.c @@ -468,6 +468,25 @@ static void rb_free_aux_page(struct ring_buffer *rb, int idx) __free_page(page); }
+static void __rb_free_aux(struct ring_buffer *rb) +{ + int pg; + + if (rb->aux_priv) { + rb->free_aux(rb->aux_priv); + rb->free_aux = NULL; + rb->aux_priv = NULL; + } + + if (rb->aux_nr_pages) { + for (pg = 0; pg < rb->aux_nr_pages; pg++) + rb_free_aux_page(rb, pg); + + kfree(rb->aux_pages); + rb->aux_nr_pages = 0; + } +} + int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event, pgoff_t pgoff, int nr_pages, long watermark, int flags) { @@ -556,30 +575,11 @@ int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event, if (!ret) rb->aux_pgoff = pgoff; else - rb_free_aux(rb); + __rb_free_aux(rb);
return ret; }
-static void __rb_free_aux(struct ring_buffer *rb) -{ - int pg; - - if (rb->aux_priv) { - rb->free_aux(rb->aux_priv); - rb->free_aux = NULL; - rb->aux_priv = NULL; - } - - if (rb->aux_nr_pages) { - for (pg = 0; pg < rb->aux_nr_pages; pg++) - rb_free_aux_page(rb, pg); - - kfree(rb->aux_pages); - rb->aux_nr_pages = 0; - } -} - void rb_free_aux(struct ring_buffer *rb) { if (atomic_dec_and_test(&rb->aux_refcount))