Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Fix a minor style(9) issue.

Take out the hack to write -1's to non-NAND. Always do a BIO_DELETE on
the ranges we want to erase. This is nicer to SSDs that want TRIMs
anyway.

More properly account for free/reserved segments to avoid deadlock or
worse when filling up a device and then trying to erase files to make
space. Without enough space, you can't do that. Also, ensure that the
metadata writes don't generate ENOSPC. They will be retried later
since the buffers are still dirty...

Submitted by: mjg@

remove duplicate semicolons where possible.

Approved by: cperciva
MFC after: 1 week

Import work done under project/nand (@235533) into head.

The NAND Flash environment consists of several distinct components:
- NAND framework (drivers harness for NAND controllers and NAND chips)
- NAND simulator (NANDsim)
- NAND file system (NAND FS)
- Companion tools and utilities
- Documentation (manual pages)

This work is still experimental. Please use with caution.

Obtained from: Semihalf
Supported by: FreeBSD Foundation, Juniper Networks