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Message-ID: <CAKLKtzeB4vP41FNxUk87KV_d7+KxpYwM33eWYrFspnFN+9TtZw@mail.gmail.com>
Date: Tue, 22 May 2012 09:52:43 +0530
From: Saugata Das <saugata.das@...aro.org>
To: linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org
Cc: arnd.bergmann@...aro.org, venkat@...aro.org,
Deepak Saxena <deepak.saxena@...aro.org>
Subject: Re: [RFC 1/3] block: Context support
Hi Group,
Will you please provide some feedback on the following RFC patches,
[RFC 1/3] block: Context support
[RFC 2/3] ext4: Context support
Regards
Saugata
On 16 May 2012 21:00, Saugata Das <saugata.das@...ricsson.com> wrote:
> From: Saugata Das <saugata.das@...aro.org>
>
> On eMMC and UFS devices there is a new feature of setting context with each
> read or write. The idea is to classify the data from different files and
> apply the realibility on the complete file instead of individual writes,
> which helps in performance. A new address space operation has been a added
> to get the context from file system and set up the bi_context field in bio.
> Then we need to ensure that bio from different contexts are not merged. The
> context is then passed to the underlying driver as part of the read or write
> request. Since the number of MMC contexts is limited, multiple file system
> contexts are mapped to single MMC context.
>
> Signed-off-by: Saugata Das <saugata.das@...aro.org>
> ---
> block/blk-core.c | 1 +
> block/blk-merge.c | 3 +++
> fs/mpage.c | 12 ++++++++++++
> include/linux/blk_types.h | 1 +
> include/linux/blkdev.h | 1 +
> include/linux/buffer_head.h | 2 ++
> include/linux/fs.h | 1 +
> 7 files changed, 21 insertions(+), 0 deletions(-)
>
> diff --git a/block/blk-core.c b/block/blk-core.c
> index 1f61b74..274e05d 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -1309,6 +1309,7 @@ void init_request_from_bio(struct request *req, struct bio *bio)
> req->errors = 0;
> req->__sector = bio->bi_sector;
> req->ioprio = bio_prio(bio);
> + req->context = bio->bi_context;
> blk_rq_bio_prep(req->q, req, bio);
> }
>
> diff --git a/block/blk-merge.c b/block/blk-merge.c
> index 160035f..ed70d56 100644
> --- a/block/blk-merge.c
> +++ b/block/blk-merge.c
> @@ -497,6 +497,9 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
> if (bio_integrity(bio) != blk_integrity_rq(rq))
> return false;
>
> + if (bio->bi_context != rq->bio->bi_context)
> + return false;
> +
> return true;
> }
>
> diff --git a/fs/mpage.c b/fs/mpage.c
> index 0face1c..4889842 100644
> --- a/fs/mpage.c
> +++ b/fs/mpage.c
> @@ -293,6 +293,12 @@ alloc_new:
> goto confused;
> }
>
> + if (page && page->mapping && page->mapping->a_ops &&
> + page->mapping->a_ops->get_context)
> + bio->bi_context = page->mapping->a_ops->get_context(page);
> + else
> + bio->bi_context = 0;
> +
> length = first_hole << blkbits;
> if (bio_add_page(bio, page, length, 0) < length) {
> bio = mpage_bio_submit(READ, bio);
> @@ -581,6 +587,12 @@ alloc_new:
> goto confused;
> }
>
> + if (page && page->mapping && page->mapping->a_ops &&
> + page->mapping->a_ops->get_context)
> + bio->bi_context = page->mapping->a_ops->get_context(page);
> + else
> + bio->bi_context = 0;
> +
> /*
> * Must try to add the page before marking the buffer clean or
> * the confused fail path above (OOM) will be very confused when
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index 4053cbd..f3ac448 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -42,6 +42,7 @@ struct bio {
>
> unsigned short bi_vcnt; /* how many bio_vec's */
> unsigned short bi_idx; /* current index into bvl_vec */
> + unsigned long bi_context; /* context of this bio */
>
> /* Number of segments in this BIO after
> * physical address coalescing is performed.
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 2aa2466..0dd9a08 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -167,6 +167,7 @@ struct request {
> struct list_head timeout_list;
> unsigned int timeout;
> int retries;
> + unsigned long context; /* context of this request */
>
> /*
> * completion callback.
> diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
> index 13bba17..0776564 100644
> --- a/include/linux/buffer_head.h
> +++ b/include/linux/buffer_head.h
> @@ -72,6 +72,8 @@ struct buffer_head {
> struct list_head b_assoc_buffers; /* associated with another mapping */
> struct address_space *b_assoc_map; /* mapping this buffer is
> associated with */
> + unsigned long b_context; /* context for this buffer within the
> + storage device */
> atomic_t b_count; /* users using this buffer_head */
> };
>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 8de6755..4b379d8 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -626,6 +626,7 @@ struct address_space_operations {
> int (*is_partially_uptodate) (struct page *, read_descriptor_t *,
> unsigned long);
> int (*error_remove_page)(struct address_space *, struct page *);
> + int (*get_context)(struct page *);
> };
>
> extern const struct address_space_operations empty_aops;
> --
> 1.7.4.3
>
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