On Wed, May 02, 2007 at 09:23:38AM +0100, Anton Altaparmakov wrote:

On a different issue, do you think it would be worth adding an option  
flags like FIEMAP_DONT_RELOCATE or something similar that would be a  
compulsory flag and if set the FS is not allowed to move the file  
around/change the block allocation of the file.

We already have an inode flag in XFS to say this - the defrag
tool checks it and ignores the file if it is set.

Or alternatively a flag like FIEMAP_MAKE_DIRECT or something to tell  
the FS we want to access the actual raw blocks so the FS can make  
sure the data is on block aligned boundaries and if the FS does not  
support this (e.g. ZFS or a compressed or encrypted NTFS file) then  
it can return -ENOTSUP.

Perhaps this is totally the wrong interface and such a "prepare file  
for direct access" API should be a different ioctl() or syscall or  
whatever.  It just seems very simple and appropriate to combine it  
here as people who use FIEMAP are at least sometimes going to be  
wanting to access those blocks directly as well and it feels right to  
be able to communicate this to the FS in the same call, kind of like  
an "open intent" of "I want to use the data directly on disk"...

I think this is wrong interface for this. Sure, use it to get the
mappings (that's what it's for) but what you do with the mappings
after that is not part of FIEMAP....

Cheers,

Dave.
-- 
Dave Chinner
Principal Engineer
SGI Australian Software Group