Date: Tue, 31 Aug 2010 01:16:46 +0000 (UTC) From: Rick Macklem <rmacklem@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r212043 - head/sys/fs/nullfs Message-ID: <201008310116.o7V1GkM6013982@svn.freebsd.org>
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Author: rmacklem Date: Tue Aug 31 01:16:45 2010 New Revision: 212043 URL: http://svn.freebsd.org/changeset/base/212043 Log: Add a null_remove() function to nullfs, so that the v_usecount of the lower level vnode is incremented to greater than 1 when the upper level vnode's v_usecount is greater than one. This is necessary for the NFS clients, so that they will do a silly rename of the file instead of actually removing it when the file is still in use. It is "racy", since the v_usecount is incremented in many places in the kernel with minimal synchronization, but an extraneous silly rename is preferred to not doing a silly rename when it is required. The only other file systems that currently check the value of v_usecount in their VOP_REMOVE() functions are nwfs and smbfs. These file systems choose to fail a remove when the v_usecount is greater than 1 and I believe will function more correctly with this patch, as well. Tested by: to.my.trociny at gmail.com Submitted by: to.my.trociny at gmail.com (earlier version) Reviewed by: kib MFC after: 2 weeks Modified: head/sys/fs/nullfs/null_vnops.c Modified: head/sys/fs/nullfs/null_vnops.c ============================================================================== --- head/sys/fs/nullfs/null_vnops.c Tue Aug 31 00:20:10 2010 (r212042) +++ head/sys/fs/nullfs/null_vnops.c Tue Aug 31 01:16:45 2010 (r212043) @@ -499,6 +499,32 @@ null_accessx(struct vop_accessx_args *ap } /* + * Increasing refcount of lower vnode is needed at least for the case + * when lower FS is NFS to do sillyrename if the file is in use. + * Unfortunately v_usecount is incremented in many places in + * the kernel and, as such, there may be races that result in + * the NFS client doing an extraneous silly rename, but that seems + * preferable to not doing a silly rename when it is needed. + */ +static int +null_remove(struct vop_remove_args *ap) +{ + int retval, vreleit; + struct vnode *lvp; + + if (vrefcnt(ap->a_vp) > 1) { + lvp = NULLVPTOLOWERVP(ap->a_vp); + VREF(lvp); + vreleit = 1; + } else + vreleit = 0; + retval = null_bypass(&ap->a_gen); + if (vreleit != 0) + vrele(lvp); + return (retval); +} + +/* * We handle this to eliminate null FS to lower FS * file moving. Don't know why we don't allow this, * possibly we should. @@ -809,6 +835,7 @@ struct vop_vector null_vnodeops = { .vop_open = null_open, .vop_print = null_print, .vop_reclaim = null_reclaim, + .vop_remove = null_remove, .vop_rename = null_rename, .vop_setattr = null_setattr, .vop_strategy = VOP_EOPNOTSUPP,
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