Date: Sat, 12 May 2012 12:10:12 GMT From: dfilter@FreeBSD.ORG (dfilter service) To: freebsd-fs@FreeBSD.org Subject: Re: kern/165923: commit references a PR Message-ID: <201205121210.q4CCACtL043066@freefall.freebsd.org>
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The following reply was made to PR kern/165923; it has been noted by GNATS. From: dfilter@FreeBSD.ORG (dfilter service) To: bug-followup@FreeBSD.org Cc: Subject: Re: kern/165923: commit references a PR Date: Sat, 12 May 2012 12:03:08 +0000 (UTC) Author: rmacklem Date: Sat May 12 12:02:51 2012 New Revision: 235332 URL: http://svn.freebsd.org/changeset/base/235332 Log: PR# 165923 reported intermittent write failures for dirty memory mapped pages being written back on an NFS mount. Since any thread can call VOP_PUTPAGES() to write back a dirty page, the credentials of that thread may not have write access to the file on an NFS server. (Often the uid is 0, which may be mapped to "nobody" in the NFS server.) Although there is no completely correct fix for this (NFS servers check access on every write RPC instead of at open/mmap time), this patch avoids the common cases by holding onto a credential that recently opened the file for writing and uses that credential for the write RPCs being done by VOP_PUTPAGES() for both NFS clients. Tested by: Joel Ray Holveck (joelh at juniper.net) PR: kern/165923 Reviewed by: kib MFC after: 2 weeks Modified: head/sys/fs/nfsclient/nfs_clbio.c head/sys/fs/nfsclient/nfs_clnode.c head/sys/fs/nfsclient/nfs_clvnops.c head/sys/fs/nfsclient/nfsnode.h head/sys/nfsclient/nfs_bio.c head/sys/nfsclient/nfs_node.c head/sys/nfsclient/nfs_vnops.c head/sys/nfsclient/nfsnode.h Modified: head/sys/fs/nfsclient/nfs_clbio.c ============================================================================== --- head/sys/fs/nfsclient/nfs_clbio.c Sat May 12 10:53:49 2012 (r235331) +++ head/sys/fs/nfsclient/nfs_clbio.c Sat May 12 12:02:51 2012 (r235332) @@ -281,7 +281,11 @@ ncl_putpages(struct vop_putpages_args *a vp = ap->a_vp; np = VTONFS(vp); td = curthread; /* XXX */ - cred = curthread->td_ucred; /* XXX */ + /* Set the cred to n_writecred for the write rpcs. */ + if (np->n_writecred != NULL) + cred = crhold(np->n_writecred); + else + cred = crhold(curthread->td_ucred); /* XXX */ nmp = VFSTONFS(vp->v_mount); pages = ap->a_m; count = ap->a_count; @@ -345,6 +349,7 @@ ncl_putpages(struct vop_putpages_args *a iomode = NFSWRITE_FILESYNC; error = ncl_writerpc(vp, &uio, cred, &iomode, &must_commit, 0); + crfree(cred); pmap_qremove(kva, npages); relpbuf(bp, &ncl_pbuf_freecnt); Modified: head/sys/fs/nfsclient/nfs_clnode.c ============================================================================== --- head/sys/fs/nfsclient/nfs_clnode.c Sat May 12 10:53:49 2012 (r235331) +++ head/sys/fs/nfsclient/nfs_clnode.c Sat May 12 12:02:51 2012 (r235332) @@ -300,6 +300,8 @@ ncl_reclaim(struct vop_reclaim_args *ap) FREE((caddr_t)dp2, M_NFSDIROFF); } } + if (np->n_writecred != NULL) + crfree(np->n_writecred); FREE((caddr_t)np->n_fhp, M_NFSFH); if (np->n_v4 != NULL) FREE((caddr_t)np->n_v4, M_NFSV4NODE); Modified: head/sys/fs/nfsclient/nfs_clvnops.c ============================================================================== --- head/sys/fs/nfsclient/nfs_clvnops.c Sat May 12 10:53:49 2012 (r235331) +++ head/sys/fs/nfsclient/nfs_clvnops.c Sat May 12 12:02:51 2012 (r235332) @@ -513,6 +513,7 @@ nfs_open(struct vop_open_args *ap) struct vattr vattr; int error; int fmode = ap->a_mode; + struct ucred *cred; if (vp->v_type != VREG && vp->v_type != VDIR && vp->v_type != VLNK) return (EOPNOTSUPP); @@ -604,7 +605,22 @@ nfs_open(struct vop_open_args *ap) } np->n_directio_opens++; } + + /* + * If this is an open for writing, capture a reference to the + * credentials, so they can be used by ncl_putpages(). Using + * these write credentials is preferable to the credentials of + * whatever thread happens to be doing the VOP_PUTPAGES() since + * the write RPCs are less likely to fail with EACCES. + */ + if ((fmode & FWRITE) != 0) { + cred = np->n_writecred; + np->n_writecred = crhold(ap->a_cred); + } else + cred = NULL; mtx_unlock(&np->n_mtx); + if (cred != NULL) + crfree(cred); vnode_create_vobject(vp, vattr.va_size, ap->a_td); return (0); } Modified: head/sys/fs/nfsclient/nfsnode.h ============================================================================== --- head/sys/fs/nfsclient/nfsnode.h Sat May 12 10:53:49 2012 (r235331) +++ head/sys/fs/nfsclient/nfsnode.h Sat May 12 12:02:51 2012 (r235332) @@ -123,6 +123,7 @@ struct nfsnode { int n_directio_asyncwr; u_int64_t n_change; /* old Change attribute */ struct nfsv4node *n_v4; /* extra V4 stuff */ + struct ucred *n_writecred; /* Cred. for putpages */ }; #define n_atim n_un1.nf_atim Modified: head/sys/nfsclient/nfs_bio.c ============================================================================== --- head/sys/nfsclient/nfs_bio.c Sat May 12 10:53:49 2012 (r235331) +++ head/sys/nfsclient/nfs_bio.c Sat May 12 12:02:51 2012 (r235332) @@ -275,7 +275,11 @@ nfs_putpages(struct vop_putpages_args *a vp = ap->a_vp; np = VTONFS(vp); td = curthread; /* XXX */ - cred = curthread->td_ucred; /* XXX */ + /* Set the cred to n_writecred for the write rpcs. */ + if (np->n_writecred != NULL) + cred = crhold(np->n_writecred); + else + cred = crhold(curthread->td_ucred); /* XXX */ nmp = VFSTONFS(vp->v_mount); pages = ap->a_m; count = ap->a_count; @@ -339,6 +343,7 @@ nfs_putpages(struct vop_putpages_args *a iomode = NFSV3WRITE_FILESYNC; error = (nmp->nm_rpcops->nr_writerpc)(vp, &uio, cred, &iomode, &must_commit); + crfree(cred); pmap_qremove(kva, npages); relpbuf(bp, &nfs_pbuf_freecnt); Modified: head/sys/nfsclient/nfs_node.c ============================================================================== --- head/sys/nfsclient/nfs_node.c Sat May 12 10:53:49 2012 (r235331) +++ head/sys/nfsclient/nfs_node.c Sat May 12 12:02:51 2012 (r235332) @@ -270,6 +270,8 @@ nfs_reclaim(struct vop_reclaim_args *ap) free((caddr_t)dp2, M_NFSDIROFF); } } + if (np->n_writecred != NULL) + crfree(np->n_writecred); if (np->n_fhsize > NFS_SMALLFH) { free((caddr_t)np->n_fhp, M_NFSBIGFH); } Modified: head/sys/nfsclient/nfs_vnops.c ============================================================================== --- head/sys/nfsclient/nfs_vnops.c Sat May 12 10:53:49 2012 (r235331) +++ head/sys/nfsclient/nfs_vnops.c Sat May 12 12:02:51 2012 (r235332) @@ -507,6 +507,7 @@ nfs_open(struct vop_open_args *ap) struct vattr vattr; int error; int fmode = ap->a_mode; + struct ucred *cred; if (vp->v_type != VREG && vp->v_type != VDIR && vp->v_type != VLNK) return (EOPNOTSUPP); @@ -563,7 +564,22 @@ nfs_open(struct vop_open_args *ap) } np->n_directio_opens++; } + + /* + * If this is an open for writing, capture a reference to the + * credentials, so they can be used by nfs_putpages(). Using + * these write credentials is preferable to the credentials of + * whatever thread happens to be doing the VOP_PUTPAGES() since + * the write RPCs are less likely to fail with EACCES. + */ + if ((fmode & FWRITE) != 0) { + cred = np->n_writecred; + np->n_writecred = crhold(ap->a_cred); + } else + cred = NULL; mtx_unlock(&np->n_mtx); + if (cred != NULL) + crfree(cred); vnode_create_vobject(vp, vattr.va_size, ap->a_td); return (0); } Modified: head/sys/nfsclient/nfsnode.h ============================================================================== --- head/sys/nfsclient/nfsnode.h Sat May 12 10:53:49 2012 (r235331) +++ head/sys/nfsclient/nfsnode.h Sat May 12 12:02:51 2012 (r235332) @@ -128,6 +128,7 @@ struct nfsnode { uint32_t n_namelen; int n_directio_opens; int n_directio_asyncwr; + struct ucred *n_writecred; /* Cred. for putpages */ }; #define n_atim n_un1.nf_atim _______________________________________________ svn-src-all@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscribe@freebsd.org"
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