[PATCH] splice: cleanup the SPLICE_F_NONBLOCK handling

- generic_file_splice_read() more readable and correct
- Don't bail on page allocation with NONBLOCK set, just don't allow
  direct blocking on IO (eg lock_page).

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

diff --git a/fs/splice.c b/fs/splice.c
index 7e85855..78cd264 100644 (file)
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -279,14 +279,6 @@ find_page:
                page = find_get_page(mapping, index);
                if (!page) {
                        /*
-                        * If in nonblock mode then dont block on
-                        * readpage (we've kicked readahead so there
-                        * will be asynchronous progress):
-                        */
-                       if (flags & SPLICE_F_NONBLOCK)
-                               break;
-
-                       /*
                         * page didn't exist, allocate one
                         */
                        page = page_cache_alloc_cold(mapping);
@@ -307,6 +299,13 @@ find_page:
                 * If the page isn't uptodate, we may need to start io on it
                 */
                if (!PageUptodate(page)) {
+                       /*
+                        * If in nonblock mode then dont block on waiting
+                        * for an in-flight io page
+                        */
+                       if (flags & SPLICE_F_NONBLOCK)
+                               break;
+
                        lock_page(page);
 
                        /*
@@ -400,17 +399,20 @@ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
        while (len) {
                ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
 
-               if (ret <= 0)
+               if (ret < 0)
                        break;
+               else if (!ret) {
+                       if (spliced)
+                               break;
+                       if (flags & SPLICE_F_NONBLOCK) {
+                               ret = -EAGAIN;
+                               break;
+                       }
+               }
 
                *ppos += ret;
                len -= ret;
                spliced += ret;
-
-               if (!(flags & SPLICE_F_NONBLOCK))
-                       continue;
-               ret = -EAGAIN;
-               break;
        }
 
        if (spliced)