Date: Fri, 13 Mar 2020 19:48:17 -0400 From: Mark Johnston <markj@freebsd.org> To: Chuck Silvers <chs@freebsd.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r358597 - head/sys/kern Message-ID: <20200313234817.GA10027@spy> In-Reply-To: <202003040022.0240Mpm6074186@repo.freebsd.org> References: <202003040022.0240Mpm6074186@repo.freebsd.org>
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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. > Reviewed by: glebius > Approved by: imp (mentor) > Sponsored by: Netflix > > Modified: > head/sys/kern/kern_sendfile.c > > Modified: head/sys/kern/kern_sendfile.c > ============================================================================== > --- head/sys/kern/kern_sendfile.c Tue Mar 3 23:15:30 2020 (r358596) > +++ head/sys/kern/kern_sendfile.c Wed Mar 4 00:22:50 2020 (r358597) > @@ -454,6 +454,7 @@ sendfile_swapin(vm_object_t obj, struct sf_io *sfio, i > __func__, pa, j)); > vm_page_unwire(pa[j], PQ_INACTIVE); > } > + refcount_release(&sfio->nios); > return (EIO); > } >
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