<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> </head> <body> <div class="moz-cite-prefix">On 7/13/21 1:26 PM, Steven Whitehouse wrote: </div> <blockquote type="cite" cite="mid:34e7b795c97d781b8788d965dd7caf48d8b8ec24.camel@redhat.com"> <pre class="moz-quote-pre" wrap="">Hi, On Tue, 2021-07-13 at 13:09 -0500, Bob Peterson wrote: </pre> <blockquote type="cite"> <pre class="moz-quote-pre" wrap="">Before this patch, gfs2 kept its own address space for rgrps, but this caused a lockdep problem because vfs assumes a 1:1 relationship between address spaces and their inode. One problematic area is this: </pre> </blockquote> <pre class="moz-quote-pre" wrap="">I don't think that is the case. The reason that the address space is a separate structure in the first place is to allow them to exist without an inode. Maybe that has changed, but we should see why that is, in that case rather than just making this change immediately. I can't see any reason why if we have to have an inode here that it needs to be hashed... what would need to look it up via the hashes? Steve. </pre> </blockquote> Hi, The actual use case, which is easily demonstrated with lockdep, is given in the patch text shortly after where you placed your comment. This goes back to this discussion from April 2018: <a class="moz-txt-link-freetext" href="https://listman.redhat.com/archives/cluster-devel/2018-April/msg00017.html">https://listman.redhat.com/archives/cluster-devel/2018-April/msg00017.html</a> in which Jan Kara pointed out that: <pre>"The problem is we really do expect mapping->host->i_mapping == mapping as we pass mapping and inode interchangebly in the mm code. The address_space and inodes are separate structures because you can have many inodes pointing to one address space (block devices). However it is not allowed for several address_spaces to point to one inode!"</pre> Regards, Bob Peterson </body> </html>