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    Subject[PATCH v21 04/30] splice: Clean up copy_splice_read() a bit
    Date
    Do a couple of cleanups to copy_splice_read():

    (1) Cast to struct page **, not void *.

    (2) Simplify the calculation of the number of pages to keep/reclaim in
    copy_splice_read().

    Suggested-by: Christoph Hellwig <hch@infradead.org>
    Signed-off-by: David Howells <dhowells@redhat.com>
    Reviewed-by: Christoph Hellwig <hch@lst.de>
    cc: Jens Axboe <axboe@kernel.dk>
    cc: Al Viro <viro@zeniv.linux.org.uk>
    cc: David Hildenbrand <david@redhat.com>
    cc: John Hubbard <jhubbard@nvidia.com>
    cc: linux-mm@kvack.org
    cc: linux-block@vger.kernel.org
    cc: linux-fsdevel@vger.kernel.org
    ---

    Notes:
    ver #21)
    - direct_splice_read() got renamed to copy_splice_read().

    fs/splice.c | 19 +++++++------------
    1 file changed, 7 insertions(+), 12 deletions(-)

    diff --git a/fs/splice.c b/fs/splice.c
    index 2478e065bc53..f9a9be797b0c 100644
    --- a/fs/splice.c
    +++ b/fs/splice.c
    @@ -311,7 +311,7 @@ ssize_t copy_splice_read(struct file *in, loff_t *ppos,
    struct kiocb kiocb;
    struct page **pages;
    ssize_t ret;
    - size_t used, npages, chunk, remain, reclaim;
    + size_t used, npages, chunk, remain, keep = 0;
    int i;

    /* Work out how much data we can actually add into the pipe */
    @@ -325,7 +325,7 @@ ssize_t copy_splice_read(struct file *in, loff_t *ppos,
    if (!bv)
    return -ENOMEM;

    - pages = (void *)(bv + npages);
    + pages = (struct page **)(bv + npages);
    npages = alloc_pages_bulk_array(GFP_USER, npages, pages);
    if (!npages) {
    kfree(bv);
    @@ -348,11 +348,8 @@ ssize_t copy_splice_read(struct file *in, loff_t *ppos,
    kiocb.ki_pos = *ppos;
    ret = call_read_iter(in, &kiocb, &to);

    - reclaim = npages * PAGE_SIZE;
    - remain = 0;
    if (ret > 0) {
    - reclaim -= ret;
    - remain = ret;
    + keep = DIV_ROUND_UP(ret, PAGE_SIZE);
    *ppos = kiocb.ki_pos;
    file_accessed(in);
    } else if (ret < 0) {
    @@ -365,14 +362,12 @@ ssize_t copy_splice_read(struct file *in, loff_t *ppos,
    }

    /* Free any pages that didn't get touched at all. */
    - reclaim /= PAGE_SIZE;
    - if (reclaim) {
    - npages -= reclaim;
    - release_pages(pages + npages, reclaim);
    - }
    + if (keep < npages)
    + release_pages(pages + keep, npages - keep);

    /* Push the remaining pages into the pipe. */
    - for (i = 0; i < npages; i++) {
    + remain = ret;
    + for (i = 0; i < keep; i++) {
    struct pipe_buffer *buf = pipe_head_buf(pipe);

    chunk = min_t(size_t, remain, PAGE_SIZE);
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