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From: | Jamie Lokier |
Subject: | Re: [Qemu-devel] [PATCH 2/4] block: use fdatasync instead of fsync |
Date: | Mon, 31 Aug 2009 22:51:38 +0100 |
User-agent: | Mutt/1.5.13 (2006-08-11) |
Christoph Hellwig wrote: > > If we are flushing the caches for our image files we only care about the > data (including the metadata required for accessing it) but not things > like timestamp updates. So use fdatasync instead of fsync to implement > the flush operations. > - fsync(s->fd); > + fdatasync(s->fd); I believe fsync was used because of uncertainty about whether fdatasync reliably flushes the necessary metadata to access the data on all hosts, after things like writing to holes and extending a file. I'm still not sure if fdatasync provides that guarantee on Linux. -- Jamie
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