Il 04/03/2011 09:17, Marco Stornelli ha scritto:

Hi Dave,

Il 03/03/2011 22:39, Dave Chinner ha scritto:

quoted

WTF?  Why does append mode have any effect on whether we can punch
holes in a file or not? There's no justification for adding this in
the commit message. Why is it even in a patch that is for checking
immutable inodes? What is the point of adding it, when all that will
happen is people will switch to XFS_IOC_UNRESVSP which has never had
this limitation?

So according to you, it's legal to do an "unreserve" operation on an
append-only file. It's not the same for me, but if the community said
that this is the right behavior then ok.

quoted

And this asks bigger questions - why would you allow preallocate
anywhere but at or beyond EOF on an append mode inode? You can only
append to the file, so if you're going to add limitations based on
the append flag, you need to think this through a bit more....

I don't understand this point. The theory of operation was:

1) we don't allow any operation (reserve/unreserve) on a immutable file;
2) we don't allow *unreserve* operation on an append-only file (this
check makes sense only for fs that support the unreserve operation).

quoted

Also, like Christoph said, these checks belong in the generic code,
not in every filesystem. The same checks have to be made for every
filesystem, so they should be done before calling out the
filesystems regardless of what functionality the filesystem actually
supports.

This was related to the first point, if we remove it then it's ok to
check in a common code. Even if I think we should do the check under the
inode lock to avoid race between fallocate and setattr, isn't it?

Oops, I meant setflags in ioctl path, sorry. At this point I'm waiting
for response about how to manage the append flag and how to manage the
lock on the flags. Ted pointed out that a proper fix would be to avoid
the lock and use bit operation but it requires a deep modification on
several fs and it could be a separate patch and code review, so I think
we can choice to use lock/unlock in do_fallocate. I'll resend the patch.

Marco