tarfs(5): Grammar fix for a source code comment

- s/the the/of the/

MFC after:i 3 days

tarfs: Implement VOP_BMAP

This lets tarfs provide readahead/behind hints to the VFS, which helps
memory-mapped I/O performance, important when running faulting in
executables out of a tarfs mount as one might if tarfs is used to back
the root filesystem, for example. The improvement is particularly
noticeable when the backing tarball is zstd-compressed.

The implementation simply returns the extent of the virtual block
containing the target offset, clamped by the maximum I/O size. This is
perhaps simplistic; it effectively just chooses values that would
correspond to a single VOP_READ call in tarfs_read_file().

Reviewed by: des, kib
MFC after: 1 month
Sponsored by: Klara, Inc.
Differential Revision: https://reviews.freebsd.org/D44626

tarfs: Fix deadlock between descent and ascent in tarfs_lookup().

Sponsored by: Juniper Networks, Inc.
Sponsored by: Klara, Inc.
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D38486

tarfs: Fix issues revealed by static analysis and testing.

* tarfs_alloc_mount(): Remove an unnecessary null check (CID 1504505) and an unused variable.

* tarfs_alloc_one(): Verify that the file size is not negative (CID 1504506). While there, also validate the mode, owner and group.

* tarfs_vget(), tarfs_zio_init(): Explicitly ignore return value from getnewvnode(), which cannot fail (CID 1504508)

* tarfs_lookup_path(): Fix a case where a specially-crafted tarball could trigger a null pointer dereference by first descending into, and then backing out of, a previously unknown directory. (CID 1504515)

* mktar: Construct a tarball that triggers the aforementioned null pointer dereference.

Reported by: Coverity
Sponsored by: Juniper Networks, Inc.
Sponsored by: Klara, Inc.
Reviewed by: imp, kib
Differential Revision: https://reviews.freebsd.org/D38463

tarfs: Remove unnecessary code.

Reported by: kib
Sponsored by: Juniper Networks, Inc.
Sponsored by: Klara, Inc.
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D38401

tarfs: Terminate dirents before copying them out.

Reported by: markj
Sponsored by: Juniper Networks, Inc.
Sponsored bu: Klara, Inc.
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D38400

tarfs: Fix 32-bit build.

Sponsored by: Juniper Networks, Inc.
Sponsored by: Klara, Inc.

Add tarfs, a filesystem backed by tarballs.

Sponsored by: Juniper Networks, Inc.
Sponsored by: Klara, Inc.
Reviewed by: pauamma, imp
Differential Revision: https://reviews.freebsd.org/D37753