On Wed, Jul 11, 2007 at 10:03:12AM +0100, Christoph Hellwig wrote:

On Tue, Jul 03, 2007 at 05:16:50PM +0530, Amit K. Arora wrote:

quoted

Well, if you see the modes proposed using above flags :

#define FA_ALLOCATE	0
#define FA_DEALLOCATE	FA_FL_DEALLOC
#define FA_RESV_SPACE	FA_FL_KEEP_SIZE
#define FA_UNRESV_SPACE	(FA_FL_DEALLOC | FA_FL_KEEP_SIZE | FA_FL_DEL_DATA)

FA_FL_DEL_DATA is _not_ being used for preallocation. We have two modes
for preallocation FA_ALLOCATE and FA_RESV_SPACE, which do not use this
flag. Hence prealloction will never delete data.
This mode is required only for FA_UNRESV_SPACE, which is a deallocation
mode, to support any existing XFS aware applications/usage-scenarios.

Sorry, but this doesn't make any sense.  There is no need to put every
feature in the XFS ioctls in the syscalls.  The XFS ioctls will need to
be supported forever anyway - as I suggested before they really should
be moved to generic code.

What needs to be supported is what makes sense as an interface.
A punch a hole interface does make sense, but trying to hack this into
a preallocation system call is just madness.  We're not IRIX or windows
that fit things into random subcall just because there was some space
left to squeeze them in.

quoted

quoted

quoted

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FA_FL_NO_MTIME	0x10 /* keep same mtime (default change on size, data change) */
FA_FL_NO_CTIME	0x20 /* keep same ctime (default change on size, data change) */

NACK to these aswell.  If i_size changes c/mtime need updates, if the size
doesn't chamge they don't.  No need to add more flags for this.

This requirement was from the point of view of HSM applications. Hope
you saw Andreas previous post and are keeping that in mind.

HSMs needs this basically for every system call, which screams for an
open flag like O_INVISIBLE anyway.  Adding this in a generic way is
a good idea, but hacking bits and pieces that won't fit into the global
design is completely wrong.

Why don't we just merge the interface for preallocation (essentially
enough to satisfy posix_fallocate() and the simple XFS requirement for 
space reservation without changing file size), which there is clear agreement
on (I hope :)).  After all, this was all that we set out to do when we
started.

And leave all the dealloc/punch/hsm type features for separate future patches/
debates, those really shouldn't hold up the basic fallocate interface.
I agree with Christoph that we are just diverging too much in trying to
club those decisions here.

Dave, Andreas, Ted ?

Regards
Suparna

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-- 
Suparna Bhattacharya (suparna@in.ibm.com)
Linux Technology Center
IBM Software Lab, India