+.BI nodiscard
+Do not attempt to discard free blocks and unused inode blocks. This option is
+exactly the opposite of discard option. This is set as default.
+.TP
+.BI no_optimize_extents
+Do not offer to optimize the extent tree by eliminating unnecessary
+width or depth. This can also be enabled in the options section of
+.BR /etc/e2fsck.conf .
+.TP
+.BI optimize_extents
+Offer to optimize the extent tree by eliminating unnecessary
+width or depth. This is the default unless otherwise specified in
+.BR /etc/e2fsck.conf .
+.TP
+.BI inode_count_fullmap
+Trade off using memory for speed when checking a file system with a
+large number of hard-linked files. The amount of memory required is
+proportional to the number of inodes in the file system. For large file
+systems, this can be gigabytes of memory. (For example, a 40TB file system
+with 2.8 billion inodes will consume an additional 5.7 GB memory if this
+optimization is enabled.) This optimization can also be enabled in the
+options section of
+.BR /etc/e2fsck.conf .
+.TP
+.BI no_inode_count_fullmap
+Disable the
+.B inode_count_fullmap
+optimization. This is the default unless otherwise specified in
+.BR /etc/e2fsck.conf .
+.TP
+.BI readahead_kb
+Use this many KiB of memory to pre-fetch metadata in the hopes of reducing
+e2fsck runtime. By default, this is set to the size of two block groups' inode
+tables (typically 4MiB on a regular ext4 file system); if this amount is more
+than 1/50th of total physical memory, readahead is disabled. Set this to zero
+to disable readahead entirely.
+.TP
+.BI bmap2extent
+Convert block-mapped files to extent-mapped files.
+.TP
+.BI fixes_only
+Only fix damaged metadata; do not optimize htree directories or compress
+extent trees. This option is incompatible with the -D and -E bmap2extent
+options.
+.TP
+.BI check_encoding
+Force verification of encoded filenames in case-insensitive directories.
+This is the default mode if the file system has the strict flag enabled.
+.TP
+.BI unshare_blocks
+If the file system has shared blocks, with the shared blocks read-only feature
+enabled, then this will unshare all shared blocks and unset the read-only
+feature bit. If there is not enough free space then the operation will fail.
+If the file system does not have the read-only feature bit, but has shared
+blocks anyway, then this option will have no effect. Note when using this
+option, if there is no free space to clone blocks, there is no prompt to
+delete files and instead the operation will fail.
+.IP
+Note that unshare_blocks implies the "-f" option to ensure that all passes
+are run. Additionally, if "-n" is also specified, e2fsck will simulate trying
+to allocate enough space to deduplicate. If this fails, the exit code will
+be non-zero.
+.RE
+.TP
+.B \-f