On Sun, Feb 07, 2016 at 12:38:14AM -0800, Christoph Hellwig wrote: > On Fri, Feb 05, 2016 at 03:25:00PM -0700, Ross Zwisler wrote: > > According to the standard specification (e.g., POSIX.1-2001), sync() > > schedules the writes, but may return before the actual writing > > is done. However, since version 1.3.20 Linux does actually wait. > > (This still does not guarantee data integrity: modern disks have large > > caches.) > > > > Based on this I don't believe that it is a requirement that sync and syncfs > > actually flush the data durably to media before they return - they just need > > to make sure it has been sent to the device, which is always true for all > > writes PMEM via DAX, even without any calls to > > dax_writeback_mapping_range(). > > For Linux there is a requirement to not return before the data is on disk, > and our users rely on it. The man page is rather confusing, and I'll see > if I can fix it up.
Okay, thank you for the clarification. :)
