Messages in this thread | | | Subject | Re: vfs: Add MS_FLUSHONFSYNC mount flag | From | Fernando Luis Vázquez Cao <> | Date | Fri, 13 Feb 2009 10:47:02 +0900 |
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On Thu, 2009-02-12 at 15:30 -0600, Eric Sandeen wrote: > Jan Kara wrote: > > On Thu 12-02-09 11:13:37, Eric Sandeen wrote: > > ... > > >> Also that way if you have 8 partitions on a battery-backed blockdev, you > >> can tune it once, instead of needing to mount all 8 filesystems with the > >> new option. > > Yes, but OTOH we should give sysadmin a possibility to enable / disable > > it on just some partitions. I don't see a reasonable use for that but people > > tend to do strange things ;) and here isn't probably a strong reason to not > > allow them. > > > > Honza > > But nobody has asked for that, have they? So why offer it up a this point? > > They could use LD_PRELOAD to make fsync a no-op if they really don't > care for it, I guess... though that's not easily per-fs either. > > But do we really want to go out of our way to enable people to > short-circuit data integrity paths and then file bugs when their files > go missing? :)
Well, it is just a matter of using safe defaults. IMHO, a scenario where the administrator wants to optimize writes to a certain partition and _explicitly_ clears MS_FLUSHONFSYNC on that superblock is not completely unreasonable.
> (I guess the blockdev tunable is similarly dangerous, but it more > clearly meets the explicit need (writecache-safe devices))
If distributions use sane defaults and we document the mount option or bdev tunable properly I guess it might make sense to allow system administrators to shoot themselves in the foot.
(By the way, in this patch-set a patch for mount(8) is included.)
- Fernando
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