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SubjectRe: Zero length files - an alternative approach?
Graham Murray wrote:
> Just a thought on the ongoing discussion of dataloss with ext4 vs ext3.
> Taking the common scenario:
> Read oldfile
> create newfile file
> write newfile data
> close newfile
> rename newfile to oldfile
> When using this scenario, the application writer wants to ensure that
> either the old or new content are present. With delayed allocation, this
> can lead to zero length files. Most of the suggestions on how to address
> this have involved syncing the data either before the rename or making
> the rename sync the data.
> What about, instead of 'bringing forward' the allocation and flushing of
> the data, would it be possible to instead delay the rename until after
> the blocks for newfile have been allocated and the data buffers flushed?
> This would keep the performance benefits of delayed allocation etc and
> also satisfy the applications developers' apparent dislike of using
> fsync(). It would give better performance that syncing the data at
> rename time (either using fsync() or automatically) and satisfy the
> requirements that either the old or new content is present.
> I am not a filesystem developer, so do not know how feasible this would
> be.

This has been suggested, I believe. In filesystem terms, it means
inserting a barrier before the rename operation, meaning that any write
operations needed to carry out the rename must not take place until all
write operations from the previous calls have completed.

error compiling committee.c: too many arguments to function

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