1 files changed, 6 insertions, 2 deletions

diff --git a/mm/readahead.c b/mm/readahead.c
index e4ed04149785..7cdbb44aa90b 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -401,6 +401,7 @@ ondemand_readahead(struct address_space *mapping,
                    unsigned long req_size)
 {
         unsigned long max = max_sane_readahead(ra->ra_pages);
+        pgoff_t prev_offset;
 
         /*
          * start of file
@@ -452,8 +453,11 @@ ondemand_readahead(struct address_space *mapping,
 
         /*
          * sequential cache miss
+         * trivial case: (offset - prev_offset) == 1
+         * unaligned reads: (offset - prev_offset) == 0
          */
-        if (offset - (ra->prev_pos >> PAGE_CACHE_SHIFT) <= 1UL)
+        prev_offset = (unsigned long long)ra->prev_pos >> PAGE_CACHE_SHIFT;
+        if (offset - prev_offset <= 1UL)
                 goto initial_readahead;
 
         /*
@@ -569,7 +573,7 @@ static ssize_t
 do_readahead(struct address_space *mapping, struct file *filp,
              pgoff_t index, unsigned long nr)
 {
-        if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
+        if (!mapping || !mapping->a_ops)
                 return -EINVAL;
 
         force_page_cache_readahead(mapping, filp, index, nr);