[v6] DAX: enable iostat for read/write
diff mbox

Message ID 20170113145406.b1f065fb7fda67fd18830969@linux-foundation.org
State New, archived
Headers show

Commit Message

Andrew Morton Jan. 13, 2017, 10:54 p.m. UTC
On Fri, 13 Jan 2017 16:34:18 -0700 Toshi Kani <toshi.kani@hpe.com> 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).

Comments

Kani, Toshi Jan. 13, 2017, 11:09 p.m. UTC | #1
On Fri, 2017-01-13 at 14:54 -0800, Andrew Morton wrote:
> On Fri, 13 Jan 2017 16:34:18 -0700 Toshi Kani <toshi.kani@hpe.com>

> 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).


It was unclear to me what type I needed to use.  test_bit() is 'bool'
in arch/x86/include/asm/bitops.h but is 'int' in  include/asm-
generic/bitops/non-atomic.h.  So, I used 'int' for safe... 

Thanks,
-Toshi


> 

> --- 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;

> _

>
Andrew Morton Jan. 13, 2017, 11:16 p.m. UTC | #2
On Fri, 13 Jan 2017 23:09:58 +0000 "Kani, Toshimitsu" <toshi.kani@hpe.com> wrote:

> On Fri, 2017-01-13 at 14:54 -0800, Andrew Morton wrote:
> > On Fri, 13 Jan 2017 16:34:18 -0700 Toshi Kani <toshi.kani@hpe.com>
> > 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).
> 
> It was unclear to me what type I needed to use.  test_bit() is 'bool'
> in arch/x86/include/asm/bitops.h but is 'int' in  include/asm-
> generic/bitops/non-atomic.h.  So, I used 'int' for safe... 

Yes, x86 does appear to be an outlier.  Mess.

Patch
diff mbox

--- 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;