On Fri, Mar 13, 2020 at 07:48:17PM -0400, Mark Johnston wrote: > On Wed, Mar 04, 2020 at 12:22:51AM +0000, Chuck Silvers wrote: > > Author: chs > > Date: Wed Mar 4 00:22:50 2020 > > New Revision: 358597 > > URL: https://svnweb.freebsd.org/changeset/base/358597 > > > > Log: > > if vm_pager_get_pages_async() returns an error, release the sfio->nios > > refcount that we took earlier that represents the I/O that ended up > > not being started. > > I think a larger bug is that getpages_async is not consistent about > whether it invokes the completion callback in synchronous error cases. > For instance, vop_stdgetpages_async() always calls it, as does > ffs_getpages_async() when the filesystem fragment size is larger than > the page size. But vnode_pager_generic_getpages() does not. So if one > is using sendfile on a filesystem that does not implement > getpages_async, an error will cause sendfile_swapin() to unbusy the > input pages multiple times, and release the sfio refcount twice when it > should be done just once.
ah yes, you're right. I was only looking at the path we actually hit. I think the simplest way to resolve this would be to change vnode_pager_generic_getpages() in the async case to always call the iodone callback and always return 0. (in the sync case vnode_pager_generic_getpages() would continue to return an error code if an error is encountered.) vm_pager_get_pages_async() could then be changed to return void since after the avoid changes it would always return 0. swap_pager_getpages_async() already always calls the iodone callback but it would return void too after the above changes. If that is agreeable to you and Gleb then I'll make the changes. -Chuck _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
