Commit d6f123a9 authored Jul 03, 2015 by Eryu Guan Committed by Theodore Ts'o Jul 03, 2015

ext4: be more strict when migrating to non-extent based file



Currently the check in ext4_ind_migrate() is not enough before doing the
real conversion:

a) delayed allocated extents could bypass the check on eh->eh_entries
   and eh->eh_depth

This can be demonstrated by this script

  xfs_io -fc "pwrite 0 4k" -c "pwrite 8k 4k" /mnt/ext4/testfile
  chattr -e /mnt/ext4/testfile

where testfile has two extents but still be converted to non-extent
based file format.

b) only extent length is checked but not the offset, which would result
   in data lose (delalloc) or fs corruption (nodelalloc), because
   non-extent based file only supports at most (12 + 2^10 + 2^20 + 2^30)
   blocks

This can be demostrated by

  xfs_io -fc "pwrite 5T 4k" /mnt/ext4/testfile
  chattr -e /mnt/ext4/testfile
  sync

If delalloc is enabled, dmesg prints
  EXT4-fs warning (device dm-4): ext4_block_to_path:105: block 1342177280 > max in inode 53
  EXT4-fs (dm-4): Delayed block allocation failed for inode 53 at logical offset 1342177280 with max blocks 1 with error 5
  EXT4-fs (dm-4): This should not happen!! Data will be lost

If delalloc is disabled, e2fsck -nf shows corruption
  Inode 53, i_size is 5497558142976, should be 4096.  Fix? no

Fix the two issues by

a) forcing all delayed allocation blocks to be allocated before checking
   eh->eh_depth and eh->eh_entries
b) limiting the last logical block of the extent is within direct map

Signed-off-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org

parent 9705acd6

fs/ext4/migrate.c

+11 −1

Original line number	Diff line number	Diff line
		@@ -620,6 +620,7 @@ int ext4_ind_migrate(struct inode *inode)
		struct ext4_inode_info *ei = EXT4_I(inode);
		struct ext4_extent *ex;
		unsigned int i, len;
		ext4_lblk_t end;
		ext4_fsblk_t blk;
		handle_t *handle;
		int ret;
		@@ -633,6 +634,14 @@ int ext4_ind_migrate(struct inode *inode)
		EXT4_FEATURE_RO_COMPAT_BIGALLOC))
		return -EOPNOTSUPP;

		/*
		* In order to get correct extent info, force all delayed allocation
		* blocks to be allocated, otherwise delayed allocation blocks may not
		* be reflected and bypass the checks on extent header.
		*/
		if (test_opt(inode->i_sb, DELALLOC))
		ext4_alloc_da_blocks(inode);

		handle = ext4_journal_start(inode, EXT4_HT_MIGRATE, 1);
		if (IS_ERR(handle))
		return PTR_ERR(handle);
		@@ -654,7 +663,8 @@ int ext4_ind_migrate(struct inode *inode)
		else {
		len = le16_to_cpu(ex->ee_len);
		blk = ext4_ext_pblock(ex);
		if (len > EXT4_NDIR_BLOCKS) {
		end = le32_to_cpu(ex->ee_block) + len - 1;
		if (end >= EXT4_NDIR_BLOCKS) {
		ret = -EOPNOTSUPP;
		goto errout;
		}

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