1 files changed, 22 insertions, 1 deletions

diff --git a/mm/swap_state.c b/mm/swap_state.c
index fd2f21e1c60a..85245fdec8d9 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -523,7 +523,7 @@ static unsigned long swapin_nr_pages(unsigned long offset)
  * This has been extended to use the NUMA policies from the mm triggering
  * the readahead.
  *
- * Caller must hold down_read on the vma->vm_mm if vmf->vma is not NULL.
+ * Caller must hold read mmap_sem if vmf->vma is not NULL.
  */
 struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
                                 struct vm_fault *vmf)
@@ -543,6 +543,13 @@ struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
         if (!mask)
                 goto skip;
 
+        /* Test swap type to make sure the dereference is safe */
+        if (likely(si->flags & (SWP_BLKDEV | SWP_FS))) {
+                struct inode *inode = si->swap_file->f_mapping->host;
+                if (inode_read_congested(inode))
+                        goto skip;
+        }
+
         do_poll = false;
         /* Read a page_cluster sized and aligned cluster around offset. */
         start_offset = offset & ~mask;
@@ -691,6 +698,20 @@ static void swap_ra_info(struct vm_fault *vmf,
         pte_unmap(orig_pte);
 }
 
+/**
+ * swap_vma_readahead - swap in pages in hope we need them soon
+ * @entry: swap entry of this memory
+ * @gfp_mask: memory allocation flags
+ * @vmf: fault information
+ *
+ * Returns the struct page for entry and addr, after queueing swapin.
+ *
+ * Primitive swap readahead code. We simply read in a few pages whoes
+ * virtual addresses are around the fault address in the same vma.
+ *
+ * Caller must hold read mmap_sem if vmf->vma is not NULL.
+ *
+ */
 static struct page *swap_vma_readahead(swp_entry_t fentry, gfp_t gfp_mask,
                                        struct vm_fault *vmf)
 {