resize2fs: move bitmaps if shrinking would orphan them

It is possible to have a flex_bg filesystem with block groups
which have inode & block bitmaps at some point well past the
start of the group.

If an offline shrink puts the new size somewhere between
the start of the block group and the (old) location of
the bitmaps, they can be left beyond the end of the filesystem,
i.e. result in fs corruption.

Check each remaining block group for whether its bitmaps
are beyond the end of the new filesystem, and reallocate
them in a new location if needed.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/resize/resize2fs.c b/resize/resize2fs.c
index 7c4f86a..204b10a 100644 (file)
--- a/resize/resize2fs.c
+++ b/resize/resize2fs.c
@@ -856,6 +856,7 @@ static errcode_t blocks_to_move(ext2_resize_t rfs)
        dgrp_t          i, max_groups, g;
        blk64_t         blk, group_blk;
        blk64_t         old_blocks, new_blocks;
+       blk64_t         new_size;
        unsigned int    meta_bg, meta_bg_size;
        errcode_t       retval;
        ext2_filsys     fs, old_fs;
@@ -884,6 +885,32 @@ static errcode_t blocks_to_move(ext2_resize_t rfs)
        fs = rfs->new_fs;
 
        /*
+        * If we're shrinking the filesystem, we need to move any group's
+        * bitmaps which are beyond the end of the new filesystem.
+        */
+       new_size = ext2fs_blocks_count(fs->super);
+       if (new_size < ext2fs_blocks_count(old_fs->super)) {
+               for (g = 0; g < fs->group_desc_count; g++) {
+                       /*
+                        * ext2fs_allocate_group_table re-allocates bitmaps
+                        * which are set to block 0.
+                        */
+                       if (ext2fs_block_bitmap_loc(fs, g) >= new_size) {
+                               ext2fs_block_bitmap_loc_set(fs, g, 0);
+                               retval = ext2fs_allocate_group_table(fs, g, 0);
+                               if (retval)
+                                       return retval;
+                       }
+                       if (ext2fs_inode_bitmap_loc(fs, g) >= new_size) {
+                               ext2fs_inode_bitmap_loc_set(fs, g, 0);
+                               retval = ext2fs_allocate_group_table(fs, g, 0);
+                               if (retval)
+                                       return retval;
+                       }
+               }
+       }
+
+       /*
         * If we're shrinking the filesystem, we need to move all of
         * the blocks that don't fit any more
         */