Posted Dec 28, 2010 16:06 UTC (Tue) by man_ls
In reply to: Ext4 filesystem hits Android, no need to fear data loss (ars technica)
Parent article: Ext4 filesystem hits Android, no need to fear data loss (ars technica)
This particular horse has got its share of postmortem beatings before, but there it goes: what developers usually want is atomicity, not durability. Durability (once written stay written) is a different requirement, but in this particular instance we need atomicity: do the rename in one step, so it's either finished or not done. The same goes for appending to an existing file: either append or do not append, but at no point in the process leave a corrupt file.
The funny part about T'so's fsync obsession is that he considers fsync to be a requirement for good filesystem programming. Instead of solving the atomicity problems and shutting up, he insists on the use of fsync:
it's unlikely that Android devices will routinely run into the kind of system failure that causes data loss for applications that don't properly use fsync.
and proposes "product QA" as a substitute for proper filesystem-level atomicity. Weird.
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