[PATCH] splice: cleanup __generic_file_splice_read()

The whole shadow/pages logic got overly complex, and this simpler
approach is actually faster in testing.

Signed-off-by: Jens Axboe <axboe@suse.de>

diff --git a/fs/splice.c b/fs/splice.c
index 9f796b1..8b5efcc 100644 (file)
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -220,10 +220,10 @@ static int __generic_file_splice_read(struct file *in, struct inode *pipe,
 {
        struct address_space *mapping = in->f_mapping;
        unsigned int offset, nr_pages;
-       struct page *pages[PIPE_BUFFERS], *shadow[PIPE_BUFFERS];
+       struct page *pages[PIPE_BUFFERS];
        struct page *page;
-       pgoff_t index, pidx;
-       int i, j;
+       pgoff_t index;
+       int i;
 
        index = in->f_pos >> PAGE_CACHE_SHIFT;
        offset = in->f_pos & ~PAGE_CACHE_MASK;
@@ -238,41 +238,13 @@ static int __generic_file_splice_read(struct file *in, struct inode *pipe,
        do_page_cache_readahead(mapping, in, index, nr_pages);
 
        /*
-        * Get as many pages from the page cache as possible..
-        * Start IO on the page cache entries we create (we
-        * can assume that any pre-existing ones we find have
-        * already had IO started on them).
-        */
-       i = find_get_pages(mapping, index, nr_pages, pages);
-
-       /*
-        * common case - we found all pages and they are contiguous,
-        * kick them off
-        */
-       if (i && (pages[i - 1]->index == index + i - 1))
-               goto splice_them;
-
-       /*
-        * fill shadow[] with pages at the right locations, so we only
-        * have to fill holes
-        */
-       memset(shadow, 0, nr_pages * sizeof(struct page *));
-       for (j = 0; j < i; j++)
-               shadow[pages[j]->index - index] = pages[j];
-
-       /*
         * now fill in the holes
         */
-       for (i = 0, pidx = index; i < nr_pages; pidx++, i++) {
-               int error;
-
-               if (shadow[i])
-                       continue;
-
+       for (i = 0; i < nr_pages; i++, index++) {
                /*
                 * no page there, look one up / create it
                 */
-               page = find_or_create_page(mapping, pidx,
+               page = find_or_create_page(mapping, index,
                                                   mapping_gfp_mask(mapping));
                if (!page)
                        break;
@@ -280,31 +252,20 @@ static int __generic_file_splice_read(struct file *in, struct inode *pipe,
                if (PageUptodate(page))
                        unlock_page(page);
                else {
-                       error = mapping->a_ops->readpage(in, page);
+                       int error = mapping->a_ops->readpage(in, page);
 
                        if (unlikely(error)) {
                                page_cache_release(page);
                                break;
                        }
                }
-               shadow[i] = page;
-       }
-
-       if (!i) {
-               for (i = 0; i < nr_pages; i++) {
-                        if (shadow[i])
-                               page_cache_release(shadow[i]);
-               }
-               return 0;
+               pages[i] = page;
        }
 
-       memcpy(pages, shadow, i * sizeof(struct page *));
+       if (i)
+               return move_to_pipe(pipe, pages, i, offset, len, flags);
 
-       /*
-        * Now we splice them into the pipe..
-        */
-splice_them:
-       return move_to_pipe(pipe, pages, i, offset, len, flags);
+       return 0;
 }
 
 /**