Btrfs: zero page past end of inline file items

When btrfs_get_extent is reading inline file items for readpage,
it needs to copy the inline extent into the page.  If the
inline extent doesn't cover all of the page, that means there
is a hole in the file, or that our file is smaller than one
page.

readpage does zeroing for the case where the file is smaller than one
page, but nobody is currently zeroing for the case where there is
a hole after the inline item.

This commit changes btrfs_get_extent to zero fill the page past
the end of the inline item.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index c846482e79850ff2ba3a7eb97bfb23932fa44782..88f9df7bfdaee77dcc65b223b8afbc0b61ee35d2 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -4233,6 +4233,11 @@ again:
                                map = kmap(page);
                                read_extent_buffer(leaf, map + pg_offset, ptr,
                                                   copy_size);
+                               if (pg_offset + copy_size < PAGE_CACHE_SIZE) {
+                                       memset(map + pg_offset + copy_size, 0,
+                                              PAGE_CACHE_SIZE - pg_offset -
+                                              copy_size);
+                               }
                                kunmap(page);
                        }
                        flush_dcache_page(page);