Re: fsync_range and O_RDONLY

[David Holland <dholland-tech%netbsd.org@localhost>]

On Wed, Feb 17, 2021 at 01:17:14PM -0500, Greg Troxel wrote:
 > > Last year, fdatasync() was changed to allow syncing files opened
 > > read-only, because that ceased to be prohibited by POSIX and something
 > > apparently depended on it.
 > 
 > I have a dim memory of this and mongodb.
 > 
 > > However, fsync_range() was not also so changed. Should it have been?
 > > It's now inconsistent with fsync and fdatasync and it seems like it's
 > > meant to be a strict superset of them.
 > 
 > It seems like it might as well be.  I would expect this to only really
 > sync the file's metadata, same as the others, but I do not feel like I
 > really understand this.

Well, if you have it open for write and I have it open for read, and I
fsync it, it'll sync your changes.

And report any errors to me, so if you're a database and I'm feeling
nasty I can maybe mess with you that way. So I'm not sure it's a great
idea.

Right now fsync error reporting is a trainwreck though.

-- 
David A. Holland
dholland%netbsd.org@localhost