blktrace: split out relaying a blktrace event

Split out the code relaying a blktrace event to user-space using relayfs.

This enables adding a second version supporting a new version of the
protocol.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index 25a0a1b09747e6043868f0ec897b2a5b477f2d9f..51745832c713c41730768364a7c8b227d335c5b1 100644 (file)
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -91,6 +91,26 @@ static void record_blktrace_event(struct blk_io_trace *t, pid_t pid, int cpu,
                memcpy((void *)t + sizeof(*t) + cgid_len, pdu_data, pdu_len);
 }
 
+static void relay_blktrace_event(struct blk_trace *bt, unsigned long sequence,
+                                pid_t pid, int cpu, sector_t sector, int bytes,
+                                u32 what, int error, u64 cgid,
+                                ssize_t cgid_len, void *pdu_data, int pdu_len)
+{
+       struct blk_io_trace *t;
+       size_t trace_len = sizeof(*t) + pdu_len + cgid_len;
+
+       t = relay_reserve(bt->rchan, trace_len);
+       if (!t)
+               return;
+
+       t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
+       t->sequence = sequence;
+       t->time = ktime_to_ns(ktime_get());
+
+       record_blktrace_event(t, pid, cpu, sector, bytes, what, bt->dev, error,
+                             cgid, cgid_len, pdu_data, pdu_len);
+}
+
 /*
  * Send out a notify message.
  */
@@ -126,16 +146,9 @@ static void trace_note(struct blk_trace *bt, pid_t pid, int action,
        if (!bt->rchan)
                return;
 
-       t = relay_reserve(bt->rchan, trace_len);
-       if (t) {
-               t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
-               t->time = ktime_to_ns(ktime_get());
-
-               record_blktrace_event(t, pid, cpu, 0, 0,
-                                     action | (cgid ? __BLK_TN_CGROUP : 0),
-                                     bt->dev, 0, cgid, cgid_len, (void *)data,
-                                     len);
-       }
+       relay_blktrace_event(bt, 0, pid, cpu, 0, 0,
+                            action | (cgid ? __BLK_TN_CGROUP : 0), 0, cgid,
+                            cgid_len, (void *)data, len);
 }
 
 /*
@@ -246,7 +259,6 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
        struct task_struct *tsk = current;
        struct ring_buffer_event *event = NULL;
        struct trace_buffer *buffer = NULL;
-       struct blk_io_trace *t;
        unsigned long flags = 0;
        unsigned long *sequence;
        unsigned int trace_ctx = 0;
@@ -278,20 +290,21 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
                return;
        cpu = raw_smp_processor_id();
 
-       trace_len = sizeof(*t) + pdu_len + cgid_len;
        if (blk_tracer) {
                tracing_record_cmdline(current);
 
                buffer = blk_tr->array_buffer.buffer;
                trace_ctx = tracing_gen_ctx_flags(0);
+               trace_len = sizeof(struct blk_io_trace) + pdu_len + cgid_len;
                event = trace_buffer_lock_reserve(buffer, TRACE_BLK,
                                                  trace_len, trace_ctx);
                if (!event)
                        return;
-               t = ring_buffer_event_data(event);
 
-               record_blktrace_event(t, pid, cpu, sector, bytes, what, bt->dev,
-                                     error, cgid, cgid_len, pdu_data, pdu_len);
+               record_blktrace_event(ring_buffer_event_data(event),
+                                     pid, cpu, sector, bytes, what, bt->dev,
+                                     error, cgid, cgid_len, pdu_data,
+                                     pdu_len);
 
                trace_buffer_unlock_commit(blk_tr, buffer, event, trace_ctx);
                return;
@@ -306,19 +319,10 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
         * from coming in and stepping on our toes.
         */
        local_irq_save(flags);
-       t = relay_reserve(bt->rchan, trace_len);
-       if (t) {
-               sequence = per_cpu_ptr(bt->sequence, cpu);
-
-               t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
-               t->sequence = ++(*sequence);
-               t->time = ktime_to_ns(ktime_get());
-
-               record_blktrace_event(t, pid, cpu, sector, bytes, what,
-                                     bt->dev, error, cgid, cgid_len,
-                                     pdu_data, pdu_len);
-       }
-
+       sequence = per_cpu_ptr(bt->sequence, cpu);
+       (*sequence)++;
+       relay_blktrace_event(bt, *sequence, pid, cpu, sector, bytes, what,
+                            error, cgid, cgid_len, pdu_data, pdu_len);
        local_irq_restore(flags);
 }