1 files changed, 14 insertions, 0 deletions

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index e0a793113ea9..0479c32c5eb1 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -1344,6 +1344,14 @@ __xfs_get_blocks(
         /*
          * If this is O_DIRECT or the mpage code calling tell them how large
          * the mapping is, so that we can avoid repeated get_blocks calls.
+         *
+         * If the mapping spans EOF, then we have to break the mapping up as the
+         * mapping for blocks beyond EOF must be marked new so that sub block
+         * regions can be correctly zeroed. We can't do this for mappings within
+         * EOF unless the mapping was just allocated or is unwritten, otherwise
+         * the callers would overwrite existing data with zeros. Hence we have
+         * to split the mapping into a range up to and including EOF, and a
+         * second mapping for beyond EOF.
          */
         if (direct || size > (1 << inode->i_blkbits)) {
                 xfs_off_t               mapping_size;
@@ -1354,6 +1362,12 @@ __xfs_get_blocks(
                 ASSERT(mapping_size > 0);
                 if (mapping_size > size)
                         mapping_size = size;
+                if (offset < i_size_read(inode) &&
+                    offset + mapping_size >= i_size_read(inode)) {
+                        /* limit mapping to block that spans EOF */
+                        mapping_size = roundup_64(i_size_read(inode) - offset,
+                                                  1 << inode->i_blkbits);
+                }
                 if (mapping_size > LONG_MAX)
                         mapping_size = LONG_MAX;