On Fri, Nov 11, 2011 at 10:48:33AM +0000, Steven Whitehouse wrote:
> Hi,
>
> On Thu, 2011-11-10 at 18:34 +0800, Zheng Liu wrote:
> > From: Zheng Liu <wenqing.lz@xxxxxxxxxx>
> >
> > 'Issue' flag is added into buffer_head to indicate that a request is issued
> > to the disk. When an io doesn't hit page cache, 'Issue' flag will be set in
> > submit_bh(). Filesystem can understand request is sent to the disk according
> > to whether or not this flag is set. This flag will be cleared after filesystem
> > tests it. If filesystem doesn't want to count the io type, it can ignore this
> > flag.
> >
> > Signed-off-by: Zheng Liu <wenqing.lz@xxxxxxxxxx>
> > Signed-off-by: Wang Shaoyan <wangshaoyan.pt@xxxxxxxxxx>
> > ---
> > fs/buffer.c | 3 +++
> > include/linux/buffer_head.h | 5 +++++
> > 2 files changed, 8 insertions(+), 0 deletions(-)
> >
> > diff --git a/fs/buffer.c b/fs/buffer.c
> > index 70a1974..f681caa 100644
> > --- a/fs/buffer.c
> > +++ b/fs/buffer.c
> > @@ -2920,6 +2920,9 @@ int submit_bh(int rw, struct buffer_head * bh)
> > BUG_ON(buffer_delay(bh));
> > BUG_ON(buffer_unwritten(bh));
> >
> > + /* set issue flag for indicating a request is issued to the disk */
> > + set_buffer_issue(bh);
> > +
> > /*
> > * Only clear out a write error when rewriting
> > */
> > diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
> > index 458f497..2bccdb4 100644
> > --- a/include/linux/buffer_head.h
> > +++ b/include/linux/buffer_head.h
> > @@ -38,6 +38,10 @@ enum bh_state_bits {
> > BH_PrivateStart,/* not a state bit, but the first bit available
> > * for private allocation by other entities
> > */
> > +
> > + BH_Issue, /* Issue a request to the disk when this request
> > + * doesn't hit cache
> > + */
> > };
> This looks like it will collide with any fs using more than one private
> flag, for example, ext4.
I will put this flag on the top of BH_PrivateStart.
Regards,
Zheng
>
>
> Steve.
>
>
>
> >
> > #define MAX_BUF_PER_PAGE (PAGE_CACHE_SIZE / 512)
> > @@ -124,6 +128,7 @@ BUFFER_FNS(Delay, delay)
> > BUFFER_FNS(Boundary, boundary)
> > BUFFER_FNS(Write_EIO, write_io_error)
> > BUFFER_FNS(Unwritten, unwritten)
> > +BUFFER_FNS(Issue, issue)
> >
> > #define bh_offset(bh) ((unsigned long)(bh)->b_data & ~PAGE_MASK)
> > #define touch_buffer(bh) mark_page_accessed(bh->b_page)
>
>
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