On Fri, 2007-03-02 at 09:16 -0600, Eric Sandeen wrote:

Badari Pulavarty wrote:

quoted

Amit K. Arora wrote:

quoted

This is to give a heads up on few patches that we will be soon coming up
with. These patches implement a new system call sys_fallocate() and a
new inode operation "fallocate", for persistent preallocation. The new
system call, as Andrew suggested, will look like:

 asmlinkage long sys_fallocate(int fd, loff_t offset, loff_t len);

I am wondering about return values from this syscall ? Is it supposed to 
return the
number of bytes allocated ? What about partial allocations ? 

If you don't have enough blocks to cover the request, you should 
probably just return -ENOSPC, not a partial allocation.

That could be challenging, when multiple writers are working in
parallel. You may not be able to return -ENOSPC, till you fail the
allocation (for filesystems which alllocates a block at a time).

quoted

What about 
if the
blocks already exists ? What would be return values in those cases ?

0 on success, other normal errors oetherwise..

If asked for a range that includes already-allocated blocks, you just 
allocate any non-allocated blocks in the range, I think.

Yes. What I was trying to figure out is, if there is a requirement that
interface need to return exact number of bytes it *really* allocated
(like write() or read()). I can't think of any, but just wanted to
through it out..

BTW, what is the interface for finding out what is the size of the
pre-allocated file ? 

Thanks,
Badari