On Fri, 13 Jan 2017 16:34:18 -0700 Toshi Kani <toshi.kani@xxxxxxx> wrote:
> DAX IO path does not support iostat, but its metadata IO path does.
> Therefore, iostat shows metadata IO statistics only, which has been
> confusing to users.
>
> Add iostat support to the DAX read/write path.
>
> Note, iostat still does not support the DAX mmap path as it allows
> user applications to access directly.
>
> ...
>
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -1058,12 +1058,24 @@ dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
> {
> struct address_space *mapping = iocb->ki_filp->f_mapping;
> struct inode *inode = mapping->host;
> + struct gendisk *disk = inode->i_sb->s_bdev->bd_disk;
> loff_t pos = iocb->ki_pos, ret = 0, done = 0;
> unsigned flags = 0;
> + unsigned long start = 0;
> + int do_acct = blk_queue_io_stat(disk->queue);
(The poorly named) blk_queue_io_stat() actually returns a bool. This
is well concealed because blk_queue_io_stat() is unnecessarily
implemented as a macro (why oh why).
--- a/fs/dax.c~dax-enable-iostat-for-read-write-fix
+++ a/fs/dax.c
@@ -1085,7 +1085,7 @@ dax_iomap_rw(struct kiocb *iocb, struct
loff_t pos = iocb->ki_pos, ret = 0, done = 0;
unsigned flags = 0;
unsigned long start = 0;
- int do_acct = blk_queue_io_stat(disk->queue);
+ bool do_acct = blk_queue_io_stat(disk->queue);
if (iov_iter_rw(iter) == WRITE)
flags |= IOMAP_WRITE;
_
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