[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>

1 files changed, 10 insertions, 49 deletions

diff --git a/fs/splice.c b/fs/splice.c
index 9f796b1034d1..8b5efcc906dc 100644
--- 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;
 }
 
 /**