[Linux-cachefs] [PATCH 5/5] ceph: fold ceph_update_writeable_page into ceph_write_begin

[Jeff Layton]

On Fri, 2021-06-11 at 10:14 -0400, Andrew W Elble wrote:
> We're seeing file corruption while running 5.10, bisected to 1cc1699070bd:
> 
> > > +static int ceph_write_begin(struct file *file, struct address_space *mapping,
> > > +			    loff_t pos, unsigned len, unsigned flags,
> > > +			    struct page **pagep, void **fsdata)
> 
> <snip>
> 
> > > +		/*
> > > +		 * In some cases we don't need to read at all:
> > > +		 * - full page write
> > > +		 * - write that lies completely beyond EOF
> > > +		 * - write that covers the the page from start to EOF or beyond it
> > > +		 */
> > > +		if ((pos_in_page == 0 && len == PAGE_SIZE) ||
> > > +		    (pos >= i_size_read(inode)) ||
> 
> Shouldn't this be '((pos & PAGE_MASK) >= i_size_read(inode)) ||' ?
> 
> Seems like fs/netfs/read_helper.c currently has the same issue?
> 

Yeah...I think you may be right. Have you tried a patch that does that
and does it fix the issue?

Also, do you happen to have a testcase that we could stick in xfstests
for this? If not, we can probably write one, but if you already have one
that'd be great.



> > > +		    (pos_in_page == 0 && (pos + len) >= i_size_read(inode))) {
> > > +			zero_user_segments(page, 0, pos_in_page,
> > > +					   pos_in_page + len, PAGE_SIZE);
> > > +			break;
> > > +		}
> 

-- 
Jeff Layton <jlayton at kernel.org>