ocfs2: Read from an unwritten extent returns zeros

Return an optional extent flags field from our lookup functions and wire up
callers to treat unwritten regions as holes for the purpose of returning
zeros to the user.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

1 files changed, 7 insertions, 4 deletions

diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c
index 0eab0d328289..412a2888a3ed 100644
--- a/fs/ocfs2/alloc.c
+++ b/fs/ocfs2/alloc.c
@@ -3487,6 +3487,7 @@ static int ocfs2_grab_eof_pages(struct inode *inode, loff_t isize, struct page *
 {
         int i, numpages = 0, ret = 0;
         unsigned int csize = OCFS2_SB(inode->i_sb)->s_clustersize;
+        unsigned int ext_flags;
         struct super_block *sb = inode->i_sb;
         struct address_space *mapping = inode->i_mapping;
         unsigned long index;
@@ -3499,7 +3500,7 @@ static int ocfs2_grab_eof_pages(struct inode *inode, loff_t isize, struct page *
                 goto out;
 
         ret = ocfs2_extent_map_get_blocks(inode, isize >> sb->s_blocksize_bits,
-                                          phys, NULL);
+                                          phys, NULL, &ext_flags);
         if (ret) {
                 mlog_errno(ret);
                 goto out;
@@ -3509,6 +3510,11 @@ static int ocfs2_grab_eof_pages(struct inode *inode, loff_t isize, struct page *
         if (*phys == 0)
                 goto out;
 
+        /* Tail is marked as unwritten, we can count on write to zero
+         * in that case. */
+        if (ext_flags & OCFS2_EXT_UNWRITTEN)
+                goto out;
+
         next_cluster_bytes = ocfs2_align_bytes_to_clusters(inode->i_sb, isize);
         index = isize >> PAGE_CACHE_SHIFT;
         do {
@@ -3579,9 +3585,6 @@ int ocfs2_zero_tail_for_truncate(struct inode *inode, handle_t *handle,
                 goto out;
         }
 
-        /*
-         * Truncate on an i_size boundary - nothing more to do.
-         */
         if (numpages == 0)
                 goto out;