add-i_data_sem-sanity-check

   1 ext4: add i_data_sem sanity check
   2
   3 From: Dmitry Monakhov <dmonakhov@openvz.org>
   4
   5 Each caller of ext4_ext_dirty must hold i_data_sem,
   6 The only exception is migration code, let's make it convenient.
   7
   8 Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
   9 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  10 Reviewed-by: Jan Kara <jack@suse.cz>
  11 ---
  12  fs/ext4/extents.c |    2 ++
  13  fs/ext4/migrate.c |    7 +++++++
  14  2 files changed, 9 insertions(+), 0 deletions(-)
  15
  16 diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
  17 index b30172d..ee93f82 100644
  18 --- a/fs/ext4/extents.c
  19 +++ b/fs/ext4/extents.c
  20 @@ -161,6 +161,8 @@ int __ext4_ext_dirty(const char *where, unsigned int line, handle_t *handle,
  21                      struct inode *inode, struct ext4_ext_path *path)
  22  {
  23         int err;
  24 +
  25 +       WARN_ON(!rwsem_is_locked(&EXT4_I(inode)->i_data_sem));
  26         if (path->p_bh) {
  27                 ext4_extent_block_csum_set(inode, ext_block_hdr(path->p_bh));
  28                 /* path points to block */
  29 diff --git a/fs/ext4/migrate.c b/fs/ext4/migrate.c
  30 index ec09243..d3567f2 100644
  31 --- a/fs/ext4/migrate.c
  32 +++ b/fs/ext4/migrate.c
  33 @@ -39,6 +39,8 @@ static int finish_range(handle_t *handle, struct inode *inode,
  34         newext.ee_block = cpu_to_le32(lb->first_block);
  35         newext.ee_len   = cpu_to_le16(lb->last_block - lb->first_block + 1);
  36         ext4_ext_store_pblock(&newext, lb->first_pblock);
  37 +       /* Locking only for convinience since we are operating on temp inode */
  38 +       down_write(&EXT4_I(inode)->i_data_sem);
  39         path = ext4_ext_find_extent(inode, lb->first_block, NULL, 0);
  40
  41         if (IS_ERR(path)) {
  42 @@ -61,7 +63,9 @@ static int finish_range(handle_t *handle, struct inode *inode,
  43          */
  44         if (needed && ext4_handle_has_enough_credits(handle,
  45                                                 EXT4_RESERVE_TRANS_BLOCKS)) {
  46 +               up_write((&EXT4_I(inode)->i_data_sem));
  47                 retval = ext4_journal_restart(handle, needed);
  48 +               down_write((&EXT4_I(inode)->i_data_sem));
  49                 if (retval)
  50                         goto err_out;
  51         } else if (needed) {
  52 @@ -70,13 +74,16 @@ static int finish_range(handle_t *handle, struct inode *inode,
  53                         /*
  54                          * IF not able to extend the journal restart the journal
  55                          */
  56 +                       up_write((&EXT4_I(inode)->i_data_sem));
  57                         retval = ext4_journal_restart(handle, needed);
  58 +                       down_write((&EXT4_I(inode)->i_data_sem));
  59                         if (retval)
  60                                 goto err_out;
  61                 }
  62         }
  63         retval = ext4_ext_insert_extent(handle, inode, path, &newext, 0);
  64  err_out:
  65 +       up_write((&EXT4_I(inode)->i_data_sem));
  66         if (path) {
  67                 ext4_ext_drop_refs(path);
  68                 kfree(path);
  69 --
  70 1.7.1
  71
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