Hi,
On Fri, 11 May 2012 20:32:56 +0530, Saugata Das wrote:
> From: Saugata Das <saugata.das@xxxxxxxxxx>
>
> Today, storage devices like eMMC has special features like data tagging
> (introduced in MMC-4.5 version) in order to improve performance of some
> specific writes. On MMC stack, data tagging is used for all writes which
> has REQ_META flag set. This patch adds the capability to add REQ_META flag
> during meta data write.
>
AFAIK, the REQ_META is only for marking a bio/req to be recognized when
using blktrace or something. You can use REQ_PRIO for the purpose but it
applies only if your ioscheduler is CFQ.
But I'm not aware how the MMC stack works, so I might be missing something.
Thanks,
Namhyung
> Signed-off-by: Saugata Das <saugata.das@xxxxxxxxxx>
> ---
> fs/buffer.c | 10 ++++++++--
> include/linux/buffer_head.h | 2 ++
> 2 files changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/fs/buffer.c b/fs/buffer.c
> index 36d6665..688b38b 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -1685,7 +1685,10 @@ static int __block_write_full_page(struct inode *inode, struct page *page,
> do {
> struct buffer_head *next = bh->b_this_page;
> if (buffer_async_write(bh)) {
> - submit_bh(write_op, bh);
> + if (buffer_meta(bh))
> + submit_bh(write_op | REQ_META, bh);
> + else
> + submit_bh(write_op, bh);
> nr_underway++;
> }
> bh = next;
> @@ -1739,7 +1742,10 @@ recover:
> struct buffer_head *next = bh->b_this_page;
> if (buffer_async_write(bh)) {
> clear_buffer_dirty(bh);
> - submit_bh(write_op, bh);
> + if (buffer_meta(bh))
> + submit_bh(write_op | REQ_META, bh);
> + else
> + submit_bh(write_op, bh);
> nr_underway++;
> }
> bh = next;
> diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
> index ef26043..0776564 100644
> --- a/include/linux/buffer_head.h
> +++ b/include/linux/buffer_head.h
> @@ -34,6 +34,7 @@ enum bh_state_bits {
> BH_Write_EIO, /* I/O error on write */
> BH_Unwritten, /* Buffer is allocated on disk but not written */
> BH_Quiet, /* Buffer Error Prinks to be quiet */
> + BH_Meta, /* Is meta */
>
> BH_PrivateStart,/* not a state bit, but the first bit available
> * for private allocation by other entities
> @@ -126,6 +127,7 @@ BUFFER_FNS(Delay, delay)
> BUFFER_FNS(Boundary, boundary)
> BUFFER_FNS(Write_EIO, write_io_error)
> BUFFER_FNS(Unwritten, unwritten)
> +BUFFER_FNS(Meta, meta)
>
> #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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