Re: synchronous mounts

[Matthias Andree <matthias.andree@stud.uni-dortmund.de>]

On Fri, 16 Nov 2001, Andrew Morton wrote:

> A `dirsync' option does make sense though, for the reasons which
> Stephen outlined.

So we could then have:

- (no option) == async, which only syncs file + data on fsync() or
   O_SYNC (BSD calls this async, it may corrupt file systems because
   writes are out-of-order)
- dirsync, which syncs directories and metadata and causes ordered
  writes thereof (BSD calls this noasync), no chance of corrupting
  on-disk structure unrecoverably.
- sync, which syncs all filesystem operations (BSD calls this sync
  also), will have at most 1 dirty block at a time on non-journaled file
  systems(?)

I expect sync to be faster on journalled file systems in that case,
because "in-order execution" to journal will probably cause linear
writes, while on ext2, it will involve seeking.

-- 
Matthias Andree

"They that can give up essential liberty to obtain a little temporary
safety deserve neither liberty nor safety."         Benjamin Franklin