splice: fix infinite loop in generic_file_splice_read()

There's a quirky loop in generic_file_splice_read() that could go
on indefinitely, if the file splice returns 0 permanently (and not
just as a temporary condition). Get rid of the loop and pass
back -EAGAIN correctly from __generic_file_splice_read(), so we
handle that condition properly as well.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 6 insertions, 25 deletions

diff --git a/fs/splice.c b/fs/splice.c
index a861bb318ac8..eeb1a86a7014 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -370,8 +370,10 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
                          * for an in-flight io page
                          */
                         if (flags & SPLICE_F_NONBLOCK) {
-                                if (TestSetPageLocked(page))
+                                if (TestSetPageLocked(page)) {
+                                        error = -EAGAIN;
                                         break;
+                                }
                         } else
                                 lock_page(page);
 
@@ -479,9 +481,8 @@ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
                                  struct pipe_inode_info *pipe, size_t len,
                                  unsigned int flags)
 {
-        ssize_t spliced;
-        int ret;
         loff_t isize, left;
+        int ret;
 
         isize = i_size_read(in->f_mapping->host);
         if (unlikely(*ppos >= isize))
@@ -491,29 +492,9 @@ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
         if (unlikely(left < len))
                 len = left;
 
-        ret = 0;
-        spliced = 0;
-        while (len && !spliced) {
-                ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
-
-                if (ret < 0)
-                        break;
-                else if (!ret) {
-                        if (spliced)
-                                break;
-                        if (flags & SPLICE_F_NONBLOCK) {
-                                ret = -EAGAIN;
-                                break;
-                        }
-                }
-
+        ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
+        if (ret > 0)
                 *ppos += ret;
-                len -= ret;
-                spliced += ret;
-        }
-
-        if (spliced)
-                return spliced;
 
         return ret;
 }