relay: Use per CPU constructs for the relay channel buffer pointers

[linux-block.git] / include / linux / relay.h

diff --git a/include/linux/relay.h b/include/linux/relay.h
index d7c8359693c6e19cdf57c52316f2e223581f14b2..eb295e373b90cee3103ae0519c34c38baff8dd48 100644 (file)
--- a/include/linux/relay.h
+++ b/include/linux/relay.h
@@ -19,6 +19,7 @@
 #include <linux/fs.h>
 #include <linux/poll.h>
 #include <linux/kref.h>
+#include <linux/percpu.h>
 
 /*
  * Tracks changes to rchan/rchan_buf structs
@@ -63,7 +64,7 @@ struct rchan
        struct kref kref;               /* channel refcount */
        void *private_data;             /* for user-defined data */
        size_t last_toobig;             /* tried to log event > subbuf size */
-       struct rchan_buf *buf[NR_CPUS]; /* per-cpu channel buffers */
+       struct rchan_buf ** __percpu buf; /* per-cpu channel buffers */
        int is_global;                  /* One global buffer ? */
        struct list_head list;          /* for channel list */
        struct dentry *parent;          /* parent dentry passed to open */
@@ -204,7 +205,7 @@ static inline void relay_write(struct rchan *chan,
        struct rchan_buf *buf;
 
        local_irq_save(flags);
-       buf = chan->buf[smp_processor_id()];
+       buf = *this_cpu_ptr(chan->buf);
        if (unlikely(buf->offset + length > chan->subbuf_size))
                length = relay_switch_subbuf(buf, length);
        memcpy(buf->data + buf->offset, data, length);
@@ -230,12 +231,12 @@ static inline void __relay_write(struct rchan *chan,
 {
        struct rchan_buf *buf;
 
-       buf = chan->buf[get_cpu()];
+       buf = *get_cpu_ptr(chan->buf);
        if (unlikely(buf->offset + length > buf->chan->subbuf_size))
                length = relay_switch_subbuf(buf, length);
        memcpy(buf->data + buf->offset, data, length);
        buf->offset += length;
-       put_cpu();
+       put_cpu_ptr(chan->buf);
 }
 
 /**
@@ -251,17 +252,19 @@ static inline void __relay_write(struct rchan *chan,
  */
 static inline void *relay_reserve(struct rchan *chan, size_t length)
 {
-       void *reserved;
-       struct rchan_buf *buf = chan->buf[smp_processor_id()];
+       void *reserved = NULL;
+       struct rchan_buf *buf = *get_cpu_ptr(chan->buf);
 
        if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {
                length = relay_switch_subbuf(buf, length);
                if (!length)
-                       return NULL;
+                       goto end;
        }
        reserved = buf->data + buf->offset;
        buf->offset += length;
 
+end:
+       put_cpu_ptr(chan->buf);
        return reserved;
 }