ext4: Fix sub-block zeroing for writes into preallocated extents
We need to mark the buffer_head mapping preallocated space as new
during write_begin. Otherwise we don't zero out the page cache content
properly for a partial write. This will cause file corruption with
preallocation.
Now that we mark the buffer_head new we also need to have a valid
buffer_head blocknr so that unmap_underlying_metadata() unmaps the
correct block.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index e91f978..d4b634a 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2323,6 +2323,13 @@
set_buffer_delay(bh_result);
} else if (ret > 0) {
bh_result->b_size = (ret << inode->i_blkbits);
+ /*
+ * With sub-block writes into unwritten extents
+ * we also need to mark the buffer as new so that
+ * the unwritten parts of the buffer gets correctly zeroed.
+ */
+ if (buffer_unwritten(bh_result))
+ set_buffer_new(bh_result);
ret = 0;
}