On Tue, Jun 01, 2010 at 11:39:23PM +1000, Nick Piggin wrote:
> It appears that I've broken inode time modifications on tmpfs/ext2.
> While ftruncate always updates these attributes, truncate must not
> unless size is changed. I hadn't actually understood that until
> Christoph told me.
>
> Confusion is increased because other filesystems get this wrong.
> Those without ->setattr or ->truncate get it wrong by default.
> Others appear to have problems too.
>
> I haven't gone through many yet, but is there any reason not to
> just do it in the vfs?
Doing it in the VFS is fine with me, we still have the the file
pointer in struct iatta to indicate a ftruncate / open O_TRUNC
if any filesystem really cares. But I think you need to audit
all instances if they care about this. And while you're at it
also remove the code handling this and the comments about it in
XFS.
> - if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
> - loff_t newsize = attr->ia_size;
> + if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE) &&
> + newsize != inode->i_size) {
Btw, the S_ISREG is superflous - we only ever set ATTR_SIZE for
regular files from the upper layer code.
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