ocfs2: Add readahead support for CoW.

Add a new function ocfs2_readahead_for_cow so that
we start readahead before we start our CoW.

Signed-off-by: Tao Ma <tao.ma@oracle.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/fs/ocfs2/refcounttree.c b/fs/ocfs2/refcounttree.c
index 66dab3c0d49..ad08c1134ba 100644
--- a/fs/ocfs2/refcounttree.c
+++ b/fs/ocfs2/refcounttree.c
@@ -3398,6 +3398,28 @@ static int ocfs2_replace_cow(struct ocfs2_cow_context *context)
         return ret;
 }
 
+static void ocfs2_readahead_for_cow(struct inode *inode,
+                                    struct file *file,
+                                    u32 start, u32 len)
+{
+        struct address_space *mapping;
+        pgoff_t index;
+        unsigned long num_pages;
+        int cs_bits = OCFS2_SB(inode->i_sb)->s_clustersize_bits;
+
+        if (!file)
+                return;
+
+        mapping = file->f_mapping;
+        num_pages = (len << cs_bits) >> PAGE_CACHE_SHIFT;
+        if (!num_pages)
+                num_pages = 1;
+
+        index = ((loff_t)start << cs_bits) >> PAGE_CACHE_SHIFT;
+        page_cache_sync_readahead(mapping, &file->f_ra, file,
+                                  index, num_pages);
+}
+
 /*
  * Starting at cpos, try to CoW write_len clusters.  Don't CoW
  * past max_cpos.  This will stop when it runs into a hole or an
@@ -3433,6 +3455,8 @@ static int ocfs2_refcount_cow_hunk(struct inode *inode,
 
         BUG_ON(cow_len == 0);
 
+        ocfs2_readahead_for_cow(inode, file, cow_start, cow_len);
+
         context = kzalloc(sizeof(struct ocfs2_cow_context), GFP_NOFS);
         if (!context) {
                 ret = -ENOMEM;