Several months ago I reported a problem with NFS corruption from three
simultaneous NFS users of ccache on the same file; two writers to the cache
and one reader.
I believe I have tracked this issue down to a race related to the use of
unlink. On NFS, unlink() is NOT atomic; so what seemed to be happening was
the second writer unlink()ed the first's object, then the reader got the
partially unlinked (truncated) object.
The following patch fixes this issue by always calling rename before a
unlink - a new x_unlink function. There are some places where temp files
are being unlinked; for performance these can remain as the ordinary
unlink.
projects / thirdparty / ccache.git / commit
