fix-flag-aliasing-in-ext4.h

   1 ext4: fix accidental flag aliasing in ext4_map_blocks flags
   2
   3 Commit b8a8684502a0f introduced an accidental flag aliasing between
   4 EXT4_EX_NOCACHE and EXT4_GET_BLOCKS_CONVERT_UNWRITTEN.
   5
   6 Fortunately, this didn't introduce any untorward side effects --- we
   7 got lucky.  Nevertheless, fix this and leave a warning to hopefully
   8 avoid this from happening in the future.
   9
  10 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  11 ---
  12  fs/ext4/ext4.h | 5 +++--
  13  1 file changed, 3 insertions(+), 2 deletions(-)
  14
  15 diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
  16 index cf3ad75..550b4f9 100644
  17 --- a/fs/ext4/ext4.h
  18 +++ b/fs/ext4/ext4.h
  19 @@ -569,6 +569,7 @@ enum {
  20  #define EXT4_GET_BLOCKS_NO_PUT_HOLE            0x0200
  21         /* Convert written extents to unwritten */
  22  #define EXT4_GET_BLOCKS_CONVERT_UNWRITTEN      0x0400
  23 +/* DO NOT ASSIGN ADDITIONAL FLAG VALUES WITHOUT ADJUSTING THE FLAGS BELOW */
  24
  25  /*
  26   * The bit position of these flags must not overlap with any of the
  27 @@ -579,8 +580,8 @@ enum {
  28   * caching the extents when reading from the extent tree while a
  29   * truncate or punch hole operation is in progress.
  30   */
  31 -#define EXT4_EX_NOCACHE                                0x0400
  32 -#define EXT4_EX_FORCE_CACHE                    0x0800
  33 +#define EXT4_EX_NOCACHE                                0x0800
  34 +#define EXT4_EX_FORCE_CACHE                    0x1000
  35
  36  /*
  37   * Flags used by ext4_free_blocks