[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>

1 files changed, 16 insertions, 14 deletions

diff --git a/fs/splice.c b/fs/splice.c
index 7e8585574726..78cd264340f2 100644
--- 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)