On Mon, 14 Mar 2011 02:56:52 +0100 (CET) "Indan Zupancic" <indan@xxxxxx> wrote: > On Sat, March 12, 2011 18:32, Greg KH wrote: > > On Fri, Mar 11, 2011 at 08:10:01PM -0600, Jonathan Nieder wrote: > >> Indan Zupancic wrote: > >> > >> > I'm not pushing for any official convention, just what seems good taste. > >> > >> In cases like this, conventions (consistency and best practices) are > >> very important. > >> > >> > Less code added, less bloat. Architecture independent, no need to update > >> > all system call tables everywhere (all archs, libc versions and strace). > >> > Two files changed, instead of 7 (which only hooks up x86). > >> > >> Thanks for explaining. Those do seem like good reasons to use a ioctl > >> instead of a new syscall. > > > > No, make it a syscall, it's more obvious and will be documented much > > better. > > There is no such guarantee. Everyone seems to want to add this new syncfs, > but it's not even defined what it does. "Same as sync, but only on one fs" > is IMHO not good enough, because sync's behaviour is pretty badly documented, > and that's a system call. The sync_file_range argument effects are quite > well defined, on the other hand, unlike sync behaviour. You're right for > ioctls though. I think the semantics of sync are easily enough defined, even if they're not well-defined in the documentation: all data which was dirty at the time sync() was called will be written back and accessible when the sync() returns. I do agree that this should be a standalone syscall, not grafted into sync_file_range() or into an ioctl. That being said, we have two similar-looking-but-quite-different "sync" concepts in the kernel. One is "sync for data integrity" and the other is "sync to reduce the dirty memory load". The latter is not a data integrity thing - it is a resource management thing. There might one day be a requirement to be able to initiate a resource-management-style writeback against a whole filesystem. When that happens, we'll regret not having added a "mode" argument to sys_syncfs(). Or maybe not - given that we're syncing the entire fs and that sync_filesystem() does the two-pass "write for data cleaning then write for data integrity" thing, it could be that a syncfs-for-data-cleaning operation has little performance benefit over a syncfs-for-data-integrity operation. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
