From: Jeff Layton <jlayton@redhat.com>
To: Jan Harkes <jaharkes@cs.cmu.edu>, coda@cs.cmu.edu
Cc: codalist@coda.cs.cmu.edu,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
open list <linux-kernel@vger.kernel.org>,
David Howells <dhowells@redhat.com>,
Al Viro <viro@zeniv.linux.org.uk>
Subject: coda's use of file->f_mapping and inode->i_mapping
Date: Wed, 02 Aug 2017 11:05:31 -0400 [thread overview]
Message-ID: <1501686331.4654.6.camel@redhat.com> (raw)
I've been slowly crawling through filesystems to convert them to
errseq_t based error handling for ->fsync operations. I started looking
at coda, but it does some strange things with the f_mapping that I don't
quite understand.
When a file is opened on coda, we call down to userland daemon, which
opens the file and passes the fd back to the kernel. The kernel then
converts that to a struct file pointer and stores that in the
coda_file_info->cfi_container. So far, so good...
The weird bit is that in coda_file_mmap, we then do this:
coda_file->f_mapping = host_file->f_mapping;
if (coda_inode->i_mapping == &coda_inode->i_data)
coda_inode->i_mapping = host_inode->i_mapping;
What is the significance of mmap on coda files? If you want to monkey
around with the i_mapping and f_mapping, wouldn't it make more sense to
do so at open() time?
--
Jeff Layton <jlayton@redhat.com>
next reply other threads:[~2017-08-02 15:05 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-02 15:05 Jeff Layton [this message]
2017-08-02 20:43 ` coda's use of file->f_mapping and inode->i_mapping Jan Harkes
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