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>
Acked-by: Jeff Moyer <jmoyer@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Reviewed-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 35 insertions, 0 deletions

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 2c644afbcdd4..e49265f18f86 100644
--- 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,
 };