char: add aio_{read,write} to /dev/{null,zero}

These are handy for measuring the cost of the aio infrastructure with
operations that do very little and complete immediately.

Signed-off-by: Zach Brown <zab@redhat.com>
Signed-off-by: Kent Overstreet <koverstreet@google.com>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Asai Thambi S P <asamymuthupa@micron.com>
Cc: Selvan Mani <smani@micron.com>
Cc: Sam Bradshaw <sbradshaw@micron.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 2c644afbcdd4561d2fc7810aafd2ef9502ecf0e6..e49265f18f86bc9b2c22603db340381c3ff057bd 100644 (file)
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -627,6 +627,18 @@ static ssize_t write_null(struct file *file, const char __user *buf,
        return count;
 }
 
+static ssize_t aio_read_null(struct kiocb *iocb, const struct iovec *iov,
+                            unsigned long nr_segs, loff_t pos)
+{
+       return 0;
+}
+
+static ssize_t aio_write_null(struct kiocb *iocb, const struct iovec *iov,
+                             unsigned long nr_segs, loff_t pos)
+{
+       return iov_length(iov, nr_segs);
+}
+
 static int pipe_to_null(struct pipe_inode_info *info, struct pipe_buffer *buf,
                        struct splice_desc *sd)
 {
@@ -670,6 +682,24 @@ static ssize_t read_zero(struct file *file, char __user *buf,
        return written ? written : -EFAULT;
 }
 
+static ssize_t aio_read_zero(struct kiocb *iocb, const struct iovec *iov,
+                            unsigned long nr_segs, loff_t pos)
+{
+       size_t written = 0;
+       unsigned long i;
+       ssize_t ret;
+
+       for (i = 0; i < nr_segs; i++) {
+               ret = read_zero(iocb->ki_filp, iov[i].iov_base, iov[i].iov_len,
+                               &pos);
+               if (ret < 0)
+                       break;
+               written += ret;
+       }
+
+       return written ? written : -EFAULT;
+}
+
 static int mmap_zero(struct file *file, struct vm_area_struct *vma)
 {
 #ifndef CONFIG_MMU
@@ -738,6 +768,7 @@ static int open_port(struct inode *inode, struct file *filp)
 #define full_lseek      null_lseek
 #define write_zero     write_null
 #define read_full       read_zero
+#define aio_write_zero aio_write_null
 #define open_mem       open_port
 #define open_kmem      open_mem
 #define open_oldmem    open_mem
@@ -766,6 +797,8 @@ static const struct file_operations null_fops = {
        .llseek         = null_lseek,
        .read           = read_null,
        .write          = write_null,
+       .aio_read       = aio_read_null,
+       .aio_write      = aio_write_null,
        .splice_write   = splice_write_null,
 };
 
@@ -782,6 +815,8 @@ static const struct file_operations zero_fops = {
        .llseek         = zero_lseek,
        .read           = read_zero,
        .write          = write_zero,
+       .aio_read       = aio_read_zero,
+       .aio_write      = aio_write_zero,
        .mmap           = mmap_zero,
 };