teach-ext4_ext_find_extent-to-realloc-path-if-necessary

   1 ext4: teach ext4_ext_find_extent() to realloc path if necessary
   2
   3 This adds additional safety in case for some reason we end reusing a
   4 path structure which isn't big enough for current depth of the inode.
   5
   6 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
   7 diff --git a/fs/ext4/ext4_extents.h b/fs/ext4/ext4_extents.h
   8 index a867f5c..3c93815 100644
   9 --- a/fs/ext4/ext4_extents.h
  10 +++ b/fs/ext4/ext4_extents.h
  11 @@ -123,6 +123,7 @@ find_ext4_extent_tail(struct ext4_extent_header *eh)
  12  struct ext4_ext_path {
  13         ext4_fsblk_t                    p_block;
  14         __u16                           p_depth;
  15 +       __u16                           p_maxdepth;
  16         struct ext4_extent              *p_ext;
  17         struct ext4_extent_idx          *p_idx;
  18         struct ext4_extent_header       *p_hdr;
  19 diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
  20 index d3fe3b2..ecd86e0 100644
  21 --- a/fs/ext4/extents.c
  22 +++ b/fs/ext4/extents.c
  23 @@ -861,14 +861,20 @@ ext4_ext_find_extent(struct inode *inode, ext4_lblk_t block,
  24         eh = ext_inode_hdr(inode);
  25         depth = ext_depth(inode);
  26
  27 -       if (path)
  28 +       if (path) {
  29                 ext4_ext_drop_refs(path);
  30 -       else {
  31 +               if (depth > path[0].p_maxdepth) {
  32 +                       kfree(path);
  33 +                       *orig_path = path = NULL;
  34 +               }
  35 +       }
  36 +       if (!path) {
  37                 /* account possible depth increase */
  38                 path = kzalloc(sizeof(struct ext4_ext_path) * (depth + 2),
  39                                 GFP_NOFS);
  40                 if (unlikely(!path))
  41                         return ERR_PTR(-ENOMEM);
  42 +               path[0].p_maxdepth = depth + 1;
  43         }
  44         path[0].p_hdr = eh;
  45         path[0].p_bh = NULL;
  46 @@ -1812,6 +1818,7 @@ static void ext4_ext_try_to_merge_up(handle_t *handle,
  47                 sizeof(struct ext4_extent_idx);
  48         s += sizeof(struct ext4_extent_header);
  49
  50 +       path[1].p_maxdepth = path[0].p_maxdepth;
  51         memcpy(path[0].p_hdr, path[1].p_hdr, s);
  52         path[0].p_depth = 0;
  53         path[0].p_ext = EXT_FIRST_EXTENT(path[0].p_hdr) +
  54 @@ -2142,12 +2149,6 @@ static int ext4_fill_fiemap_extents(struct inode *inode,
  55                 /* find extent for this block */
  56                 down_read(&EXT4_I(inode)->i_data_sem);
  57
  58 -               if (path && ext_depth(inode) != depth) {
  59 -                       /* depth was changed. we have to realloc path */
  60 -                       kfree(path);
  61 -                       path = NULL;
  62 -               }
  63 -
  64                 path = ext4_ext_find_extent(inode, block, &path, 0);
  65                 if (IS_ERR(path)) {
  66                         up_read(&EXT4_I(inode)->i_data_sem);
  67 @@ -2165,7 +2166,6 @@ static int ext4_fill_fiemap_extents(struct inode *inode,
  68                 }
  69                 ex = path[depth].p_ext;
  70                 next = ext4_ext_next_allocated_block(path);
  71 -               ext4_ext_drop_refs(path);
  72
  73                 flags = 0;
  74                 exists = 0;
  75 @@ -2889,7 +2889,7 @@ again:
  76                         ext4_journal_stop(handle);
  77                         return -ENOMEM;
  78                 }
  79 -               path[0].p_depth = depth;
  80 +               path[0].p_maxdepth = path[0].p_depth = depth;
  81                 path[0].p_hdr = ext_inode_hdr(inode);
  82                 i = 0;
  83