1 files changed, 17 insertions, 7 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 8c88e186a773..870971e20967 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1917,9 +1917,8 @@ static void shrink_readahead_size_eio(struct file *filp,
 }
 
 /**
- * do_generic_file_read - generic file read routine
- * @filp:       the file to read
- * @ppos:       current file position
+ * generic_file_buffered_read - generic file read routine
+ * @iocb:       the iocb to read
  * @iter:       data destination
  * @written:    already copied
  *
@@ -1929,12 +1928,14 @@ static void shrink_readahead_size_eio(struct file *filp,
  * This is really ugly. But the goto's actually try to clarify some
  * of the logic when it comes to error handling etc.
  */
-static ssize_t do_generic_file_read(struct file *filp, loff_t *ppos,
+static ssize_t generic_file_buffered_read(struct kiocb *iocb,
                 struct iov_iter *iter, ssize_t written)
 {
+        struct file *filp = iocb->ki_filp;
         struct address_space *mapping = filp->f_mapping;
         struct inode *inode = mapping->host;
         struct file_ra_state *ra = &filp->f_ra;
+        loff_t *ppos = &iocb->ki_pos;
         pgoff_t index;
         pgoff_t last_index;
         pgoff_t prev_index;
@@ -1967,6 +1968,8 @@ find_page:
 
                 page = find_get_page(mapping, index);
                 if (!page) {
+                        if (iocb->ki_flags & IOCB_NOWAIT)
+                                goto would_block;
                         page_cache_sync_readahead(mapping,
                                         ra, filp,
                                         index, last_index - index);
@@ -1980,6 +1983,11 @@ find_page:
                                         index, last_index - index);
                 }
                 if (!PageUptodate(page)) {
+                        if (iocb->ki_flags & IOCB_NOWAIT) {
+                                put_page(page);
+                                goto would_block;
+                        }
+
                         /*
                          * See comment in do_read_cache_page on why
                          * wait_on_page_locked is used to avoid unnecessarily
@@ -2161,6 +2169,8 @@ no_cached_page:
                 goto readpage;
         }
 
+would_block:
+        error = -EAGAIN;
 out:
         ra->prev_pos = prev_index;
         ra->prev_pos <<= PAGE_SHIFT;
@@ -2182,14 +2192,14 @@ out:
 ssize_t
 generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 {
-        struct file *file = iocb->ki_filp;
-        ssize_t retval = 0;
         size_t count = iov_iter_count(iter);
+        ssize_t retval = 0;
 
         if (!count)
                 goto out; /* skip atime */
 
         if (iocb->ki_flags & IOCB_DIRECT) {
+                struct file *file = iocb->ki_filp;
                 struct address_space *mapping = file->f_mapping;
                 struct inode *inode = mapping->host;
                 loff_t size;
@@ -2230,7 +2240,7 @@ generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
                         goto out;
         }
 
-        retval = do_generic_file_read(file, &iocb->ki_pos, iter, retval);
+        retval = generic_file_buffered_read(iocb, iter, retval);
 out:
         return retval;
 }