On Fri, Jul 21, 2017 at 04:49:27PM -0600, Andreas Dilger wrote:

The dir_nlink feature has been enabled by default for new ext4
filesystems since e2fsprogs-1.41 in 2008, and was automatically
enabled by the kernel for older ext4 filesystems since the
dir_nlink feature was added with ext4 in kernel 2.6.28+ when
the subdirectory count exceeded EXT4_LINK_MAX.

We shouldn't really be enabling filesystem features automatically,
as this prevents the administrator from disabling the feature at
format time, or via tune2fs.  This should not affect many users by
this point, but allows limiting subdirectory counts to those that
can strictly fit into i_links_count rather than using "1" to
indicate that the number of links on the directory is not tracked.
This avoids a bug in glibc fts_read() that incorrectly optimizes
the directory traversal for such directories.

This also addresses a minor bug in ext4_inc_count() where i_nlinks
was wrapped at (EXT4_LINK_MAX - 1) links rather than allowing the
full EXT4_LINK_MAX links on the parent directory (including "."
and "..") before storing i_links_count = 1.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=196405
Signed-off-by: Andreas Dilger <redacted>

Thanks, applied.

					- Ted