diff options
Diffstat (limited to 'fs/xfs/libxfs/xfs_format.h')
| -rw-r--r-- | fs/xfs/libxfs/xfs_format.h | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h index 82b404c99b80..43de892d0305 100644 --- a/fs/xfs/libxfs/xfs_format.h +++ b/fs/xfs/libxfs/xfs_format.h @@ -915,6 +915,19 @@ enum xfs_dinode_fmt { * * Rounding up 47 to the nearest multiple of bits-per-byte results in 48. Hence * 2^48 was chosen as the maximum data fork extent count. + * + * The maximum file size that can be represented by the data fork extent counter + * in the worst case occurs when all extents are 1 block in length and each + * block is 1KB in size. + * + * With XFS_MAX_EXTCNT_DATA_FORK_SMALL representing maximum extent count and + * with 1KB sized blocks, a file can reach upto, + * 1KB * (2^31) = 2TB + * + * This is much larger than the theoretical maximum size of a directory + * i.e. XFS_DIR2_SPACE_SIZE * XFS_DIR2_MAX_SPACES = ~96GB. + * + * Hence, a directory inode can never overflow its data fork extent counter. */ #define XFS_MAX_EXTCNT_DATA_FORK_LARGE ((xfs_extnum_t)((1ULL << 48) - 1)) #define XFS_MAX_EXTCNT_ATTR_FORK_LARGE ((xfs_extnum_t)((1ULL << 32) - 1)) |