Re: + readahead-commentary.patch added to -mm tree

[Coywolf Qi Hunt]

On 03/11/05, akpm@xxxxxxxx <akpm@xxxxxxxx> wrote:
>
> The patch titled
>
>      readahead commentary
>
> has been added to the -mm tree.  Its filename is
>
>      readahead-commentary.patch
>
>
> From: Andrew Morton <akpm@xxxxxxxx>
>
> Add a few comments surrounding thr generic readahead API.
>
> Also convert some ulongs into pgoff_t: the identifier for PAGE_CACHE_SIZE
> offsets into pagecache.
>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
> ---
>
>  include/linux/mm.h |    8 ++++----
>  mm/readahead.c     |   31 ++++++++++++++++++++++---------
>  2 files changed, 26 insertions(+), 13 deletions(-)
>
> diff -puN mm/readahead.c~readahead-commentary mm/readahead.c
> --- 25/mm/readahead.c~readahead-commentary      2005-11-03 08:06:16.000000000 +1100
> +++ 25-akpm/mm/readahead.c      2005-11-03 08:16:16.000000000 +1100
> @@ -254,7 +254,7 @@ out:
>   */
>  static int
>  __do_page_cache_readahead(struct address_space *mapping, struct file *filp,
> -                       unsigned long offset, unsigned long nr_to_read)
> +                       pgoff_t offset, unsigned long nr_to_read)
>  {
>         struct inode *inode = mapping->host;
>         struct page *page;
> @@ -274,7 +274,7 @@ __do_page_cache_readahead(struct address
>          */
>         read_lock_irq(&mapping->tree_lock);
>         for (page_idx = 0; page_idx < nr_to_read; page_idx++) {
> -               unsigned long page_offset = offset + page_idx;
> +               pgoff_t page_offset = offset + page_idx;
>
>                 if (page_offset > end_index)
>                         break;
> @@ -311,7 +311,7 @@ out:
>   * memory at once.
>   */
>  int force_page_cache_readahead(struct address_space *mapping, struct file *filp,
> -               unsigned long offset, unsigned long nr_to_read)
> +               pgoff_t offset, unsigned long nr_to_read)
>  {
>         int ret = 0;
>
> @@ -368,7 +368,7 @@ static inline int check_ra_success(struc
>   * request queues.
>   */
>  int do_page_cache_readahead(struct address_space *mapping, struct file *filp,
> -                       unsigned long offset, unsigned long nr_to_read)
> +                       pgoff_t offset, unsigned long nr_to_read)
>  {
>         if (bdi_read_congested(mapping->backing_dev_info))
>                 return -1;
> @@ -385,7 +385,7 @@ int do_page_cache_readahead(struct addre
>   */
>  static int
>  blockable_page_cache_readahead(struct address_space *mapping, struct file *filp,
> -                       unsigned long offset, unsigned long nr_to_read,
> +                       pgoff_t offset, unsigned long nr_to_read,
>                         struct file_ra_state *ra, int block)
>  {
>         int actual;
> @@ -430,14 +430,27 @@ static int make_ahead_window(struct addr
>         return ret;
>  }
>
> -/*
> - * page_cache_readahead is the main function.  If performs the adaptive
> +/**
> + * page_cache_readahead - generic adaptive readahead
> + * @mapping: address_space which holds te pagecache and I/O vectors

typo. s/te/the/

> + * @ra: file_ra_state which holds the readahead state
> + * @filp: passed on to ->readpage() and ->readpages()
> + * @offset: start offset into @mapping, in PAGE_CACHE_SIZE units
> + * @req_size: hint: total size of the read which the caller is performing in
> + *            PAGE_CACHE_SIZE units
> + *
> + * page_cache_readahead() is the main function.  If performs the adaptive
>   * readahead window size management and submits the readahead I/O.
> + *
> + * Note that @filp is purely used for passing on to the ->readpage[s]()
> + * handler: it may refer to a different file from @mapping (so we may not use
> + * @filp->f_mapping or @filp->f_dentry->d_inode here).
> + * Also, @ra may not be equal to &@filp->f_ra.
> + *
>   */
>  unsigned long
>  page_cache_readahead(struct address_space *mapping, struct file_ra_state *ra,
> -                    struct file *filp, unsigned long offset,
> -                    unsigned long req_size)
> +                    struct file *filp, pgoff_t offset, unsigned long req_size)
>  {
>         unsigned long max, newsize;
>         int sequential;

--
Coywolf Qi Hunt
http://sosdg.org/~coywolf/
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