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One of the fixes in PipeFS 0.25 was to fix the fsfile_ReadInfo operation to block until the pipe is no longer open for write (instead of failing with a "file not found" error, as it had done previously). This fix had some knock-ons for FileSwitch, since the contemporary version (2.89) only made use of fsfile_ReadInfo. E.g. trying to open a pipe for read while it's open for write would block due to TopPath_DoBusinessToPath using fsfile_ReadInfo when FileSwitch is checking whether the file exists. This specific issue was fixed in FileSwitch 2.90 by changing some areas of FileSwitch to use fsfile_ReadInfoNoLen instead.

Further testing has revealed a few more areas which are making unnecessary use of fsfile_ReadInfo and have the potential to break programs. Specifically, with FileSwitch 2.90 & PipeFS 0.25, programs which use GCC's UnixLib will get stuck if they try to open a PipeFS file for write while running in a taskwindow. E.g. the call to GNU.gawk in Env.!Common. This happens because after opening the file, UnixLib attempts to set its attributes using OS_File 4, which in turn causes FileSwitch to attempt to examine the file using fsfile_ReadInfo.

This MR fixes that above issue and a few other potential issues by changing several more areas of FileSwitch to use fsfile_ReadInfoNoLen where possible:

• OS_File (most operations)
• OS_FSControl (CanonicalisePathEntry & RenameEntry) and ChangeDirectory helper routine
• TopPath_DoBusinessForDirectoryRead