On Thu, Jun 06, 2019 at 12:58:55PM +0200, Jan Kara wrote: > On Wed 05-06-19 18:45:40, ira.weiny@xxxxxxxxx wrote: > > From: Ira Weiny <ira.weiny@xxxxxxxxx> > > > > If pages are actively gup pinned fail the truncate operation. > > > > Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx> > > --- > > fs/ext4/inode.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > > index 75f543f384e4..1ded83ec08c0 100644 > > --- a/fs/ext4/inode.c > > +++ b/fs/ext4/inode.c > > @@ -4250,6 +4250,9 @@ int ext4_break_layouts(struct inode *inode, loff_t offset, loff_t len) > > if (!page) > > return 0; > > > > + if (page_gup_pinned(page)) > > + return -ETXTBSY; > > + > > error = ___wait_var_event(&page->_refcount, > > atomic_read(&page->_refcount) == 1, > > TASK_INTERRUPTIBLE, 0, 0, > > This caught my eye. Does this mean that now truncate for a file which has > temporary gup users (such buffers for DIO) can fail with ETXTBUSY? I thought about that before and I _thought_ I had accounted for it. But I think you are right... > > That > doesn't look desirable. No not desirable at all... Ah it just dawned on my why I thought it was ok... I was wrong. :-/ > If we would mandate layout lease while pages are > pinned as I suggested, this could be dealt with by checking for leases with > pins (breaking such lease would return error and not break it) and if > breaking leases succeeds (i.e., there are no long-term pinned pages), we'd > just wait for the remaining references as we do now. Agreed. But I'm going to respond with some of the challenges of this (and ideas I had) when replying to your other email. Ira > > Honza > -- > Jan Kara <jack@xxxxxxxx> > SUSE Labs, CR
