fs: only inc/dec inode->i_dio_count for file systems

We don't need truncate protection for block devices, so add a flag
bypassing this cache line dirtying for every IO.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/block_dev.c b/fs/block_dev.c
index aae187a7f94a661edb82189496242fdac4c33fcf..00a6f9efce51ed260adbd8fcd00164e228fe66f7 100644 (file)
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -164,7 +164,8 @@ blkdev_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
        struct inode *inode = file->f_mapping->host;
 
        return __blockdev_direct_IO(rw, iocb, inode, I_BDEV(inode), iov, offset,
-                                   nr_segs, blkdev_get_block, NULL, NULL, 0);
+                                   nr_segs, blkdev_get_block, NULL, NULL,
+                                   DIO_IGNORE_TRUNCATE);
 }
 
 int __sync_blockdev(struct block_device *bdev, int wait)

diff --git a/fs/direct-io.c b/fs/direct-io.c
index 9e639f0edf5c2d91fa942c1a20725ee6bb5ebb03..f66555cdf203115693e751344ea7664e9733bcdc 100644 (file)
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -266,7 +266,11 @@ static ssize_t dio_complete(struct dio *dio, loff_t offset, ssize_t ret, bool is
                dio->end_io(dio->iocb, offset, transferred,
                            dio->private, ret, is_async);
        } else {
-               inode_dio_done(dio->inode);
+               if (dio->flags & DIO_IGNORE_TRUNCATE)
+                       __inode_dio_done(dio->inode);
+               else
+                       inode_dio_done(dio->inode);
+
                if (is_async)
                        aio_complete(dio->iocb, ret, 0);
        }
@@ -1125,9 +1129,12 @@ do_blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
        }
 
        /*
-        * Will be decremented at I/O completion time.
+        * Will be decremented at I/O completion time. For a block device
+        * we don't need to protect against truncate, so don't increment
+        * the inode direct IO count.
         */
-       atomic_inc(&inode->i_dio_count);
+       if (!(dio->flags & DIO_IGNORE_TRUNCATE))
+               atomic_inc(&inode->i_dio_count);
 
        /*
         * For file extending writes updating i_size before data

diff --git a/fs/inode.c b/fs/inode.c
index a898b3d43ccf3990986d51be3305bdc3e6d665ef..6878ba8979ff5bd1d06310da2282d6ffadcf0517 100644 (file)
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1883,6 +1883,11 @@ void inode_dio_wait(struct inode *inode)
 }
 EXPORT_SYMBOL(inode_dio_wait);
 
+void __inode_dio_done(struct inode *inode)
+{
+       wake_up_bit(&inode->i_state, __I_DIO_WAKEUP);
+}
+
 /*
  * inode_dio_done - signal finish of a direct I/O requests
  * @inode: inode the direct I/O happens on
@@ -1893,6 +1898,6 @@ EXPORT_SYMBOL(inode_dio_wait);
 void inode_dio_done(struct inode *inode)
 {
        if (atomic_dec_and_test(&inode->i_dio_count))
-               wake_up_bit(&inode->i_state, __I_DIO_WAKEUP);
+               __inode_dio_done(inode);
 }
 EXPORT_SYMBOL(inode_dio_done);

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 2c28271ab9d40a834c50931084cb15e8860cd765..db36094768ea1911452a65d1b9021cc17bb15554 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2433,6 +2433,9 @@ enum {
 
        /* filesystem does not support filling holes */
        DIO_SKIP_HOLES  = 0x02,
+
+       /* inode/fs/bdev does not need truncate protection */
+       DIO_IGNORE_TRUNCATE = 0x04,
 };
 
 void dio_end_io(struct bio *bio, int error);
@@ -2453,6 +2456,7 @@ static inline ssize_t blockdev_direct_IO(int rw, struct kiocb *iocb,
 #endif
 
 void inode_dio_wait(struct inode *inode);
+void __inode_dio_done(struct inode *inode);
 void inode_dio_done(struct inode *inode);
 
 extern const struct file_operations generic_ro_fops;