On Thu, 2008-04-24 at 12:47 -0400, Joe Smith wrote: > Patrick O'Callaghan wrote: > > On Thu, 2008-04-24 at 10:49 -0400, Joe Smith wrote: > >> ... > >> I'm not convinced that using sync(1) would be effective, especially from > >> the desktop environment where who knows what processes have something > >> open on a pluggable device. Sync would be prudent if you were moving raw > >> data blocks to a device, but not for mounted filesystems. > > > > Of course sync is effective for mounted filesystems, why wouldn't it be? > > It means data are now synched *up to this point*. > > By "not effective" I don't mean that it doesn't work, I mean that it > can't guarantee that the device is safe to remove. What's to stop > something from starting a write to the device 10us after the kernel > syncs all the buffers? The sync+unmount has to be atomic in order to > guarantee that the data buffers are flushed and that nothing else can > start a new write. unmount(2) is the logical (only?) place to lock the > two operations together. Correct, but show me where it says that unmount does a sync. If some "official" doc somewhere says that that's what happens, then I'll accept it, but until then it's speculation *even if it's in the source*. This point needs to be stressed. The docs are the only collective memory we have about how things are *supposed* to work. Everything else is written in sand. > > ... > > There is no documentary evidence that unmount calls sync (contrary to > > what many people think, including me up to about yesterday). The > > eject(1) page doesn't mention syncing or flushing buffers. > > A man page is usually an afterthought, not a spec. A unix without > incomplete man pages wouldn't be unix ;-) > > As you yourself pointed out, even a look at the source code won't prove > it. If you have evidence that umount (or eject) alone is not sufficient > to flush all pending i/o for the device, then it should be reported as a > bug. > > Use "sync && umount" if you like, there's no harm in it, but sync alone > is not a substitute for umount. eject(1) can safely substitute for > umount, because eject is designed to unmount the device. Who said sync was a substitute for unmount? The point at issue is whether you need both of them, or just unmount on its own. poc -- fedora-list mailing list fedora-list@xxxxxxxxxx To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list
