[PATCH] splice: close i_size truncate races on read

We need to check i_size after doing a blocking readpage.

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

1 files changed, 37 insertions, 6 deletions

diff --git a/fs/splice.c b/fs/splice.c
index 8d57e89924a6..7e8585574726 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -145,8 +145,8 @@ static struct pipe_buf_operations page_cache_pipe_buf_ops = {
  * pipe buffer operations. Otherwise very similar to the regular pipe_writev().
  */
 static ssize_t move_to_pipe(struct pipe_inode_info *pipe, struct page **pages,
-                            int nr_pages, unsigned long offset,
-                            unsigned long len, unsigned int flags)
+                            int nr_pages, unsigned long len,
+                            unsigned int offset, unsigned int flags)
 {
         int ret, do_wakeup, i;
 
@@ -243,14 +243,16 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
                            unsigned int flags)
 {
         struct address_space *mapping = in->f_mapping;
-        unsigned int offset, nr_pages;
+        unsigned int loff, offset, nr_pages;
         struct page *pages[PIPE_BUFFERS];
         struct page *page;
-        pgoff_t index;
+        pgoff_t index, end_index;
+        loff_t isize;
+        size_t bytes;
         int i, error;
 
         index = *ppos >> PAGE_CACHE_SHIFT;
-        offset = *ppos & ~PAGE_CACHE_MASK;
+        loff = offset = *ppos & ~PAGE_CACHE_MASK;
         nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 
         if (nr_pages > PIPE_BUFFERS)
@@ -268,6 +270,7 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
          * Now fill in the holes:
          */
         error = 0;
+        bytes = 0;
         for (i = 0; i < nr_pages; i++, index++) {
 find_page:
                 /*
@@ -336,13 +339,41 @@ readpage:
                                         goto find_page;
                                 break;
                         }
+
+                        /*
+                         * i_size must be checked after ->readpage().
+                         */
+                        isize = i_size_read(mapping->host);
+                        end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
+                        if (unlikely(!isize || index > end_index)) {
+                                page_cache_release(page);
+                                break;
+                        }
+
+                        /*
+                         * if this is the last page, see if we need to shrink
+                         * the length and stop
+                         */
+                        if (end_index == index) {
+                                loff = PAGE_CACHE_SIZE - (isize & ~PAGE_CACHE_MASK);
+                                if (bytes + loff > isize) {
+                                        page_cache_release(page);
+                                        break;
+                                }
+                                /*
+                                 * force quit after adding this page
+                                 */
+                                nr_pages = i;
+                        }
                 }
 fill_it:
                 pages[i] = page;
+                bytes += PAGE_CACHE_SIZE - loff;
+                loff = 0;
         }
 
         if (i)
-                return move_to_pipe(pipe, pages, i, offset, len, flags);
+                return move_to_pipe(pipe, pages, i, bytes, offset, flags);
 
         return error;
 }