This issue MAY be related to CORE-18247 as some code is shared between cygwin1.dll and setup.
Cygwin setup gets ERROR_ACCESS_DENIED on btrfs volumes when trying to move into
the local package directory.
Detected on 0.4.14-release-15
Tested on 0.4.15-dev-4920
Windows 2003 btrfs: https://github.com/maharmstone/btrfs/releases/tag/v1.7
Attempting to install Cygwin on btrfs results in ERROR_ACCESS_DENIED when setup
tries to change working directory, only on btrfs volumes. This error does not
happen on Windows Server 2003.
1. Have a btrfs volume. Only the local package directory needs to go here.
Note that it cannot be the root of the drive but must be a folder in it.
2. Edit and run install-Cygwin-to-D.bat in the attached zip-file to intall
Cygwin on the btrfs volume
3. After clicking Yes to the "error" in "choose local package directory"
the ACCESS_DENIED error appears. This does not happen on Windows Server
(On my VM D:\ is a btrfs volume, that's also shared with a Windows 2003 VM.)
Note: installation can not continue much past this point due to some other (hopefully related) issue and CORE-18247.
Source code for setup is (probably):
git://sourceware.org/git/cygwin-apps/setup.git (checkout release_2.874)