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fsync loose objects before moving into place

When we write a loose object to disk, we simply close the
file object before moving it into place. If the machine
crashes shortly after our write, the contents may not have
been committed to disk (depending your filesystem, usually
the metadata is, and you end up with a corrupt, zero-length
loose object file).

This is especially bad because we report that the object is
successfully written, which means we may have updated refs
to point to it. A corrupt object at that point means not
only does the operation fail, but the repository is left in
a corrupted and unusable state.

We can fix this by calling fsync on the object file before
linking it into place. Between this and the previous commit,
our object writing should now behave exactly like git's
internal routines.
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1 parent 00a0054 commit cdf0fdb3e19237a2fe8a2667d774a25b5fa46e76 @peff peff committed Feb 22, 2013
Showing with 1 addition and 0 deletions.
  1. +1 −0 lib/grit/git-ruby/internal/loose.rb
1 lib/grit/git-ruby/internal/loose.rb
@@ -66,6 +66,7 @@ def get_raw_object(buf)
def safe_write(path, content)"tmp_obj_", File.dirname(path), :opt => "wb") do |f|
f.write content
+ f.fsync
begin, path)

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