NFS - Fix BIO size panics

* NFS calculates the BIO block size and stores it in mnt_stat.f_iosize.
  This field was getting overwritten with default values by STATFS
  being passing &mp->mnt_stat from the kernel.

  Conditionalize the field so it no longer gets overwritten, and also
  correct nm_rsize/nm_wsize tests to use the smaller of the two
  specifications for the BIO block size.

* Fixes diskless NFS root mounts, and NFS mounts which use smaller
  blocksizes.

Reported-by: Rumko <rumcic@gmail.com>, and others

diff --git a/sys/vfs/nfs/nfs_vfsops.c b/sys/vfs/nfs/nfs_vfsops.c
index fd3988f..e1152ba 100644 (file)
--- a/sys/vfs/nfs/nfs_vfsops.c
+++ b/sys/vfs/nfs/nfs_vfsops.c
@@ -334,7 +334,6 @@ nfs_statfs(struct mount *mp, struct statfs *sbp, struct ucred *cred)
        }
        NULLOUT(sfp = nfsm_dissect(&info, NFSX_STATFS(info.v3)));
        sbp->f_flags = nmp->nm_flag;
-       sbp->f_iosize = nfs_iosize(info.v3, nmp->nm_sotype);
 
        if (info.v3) {
                sbp->f_bsize = NFS_FABLKSIZE;
@@ -356,9 +355,16 @@ nfs_statfs(struct mount *mp, struct statfs *sbp, struct ucred *cred)
                sbp->f_files = 0;
                sbp->f_ffree = 0;
        }
+
+       /*
+        * Some values are pre-set in mnt_stat.  Note in particular f_iosize
+        * cannot be changed once the filesystem is mounted as it is used
+        * as the basis for BIOs.
+        */
        if (sbp != &mp->mnt_stat) {
                sbp->f_type = mp->mnt_vfc->vfc_typenum;
                bcopy(mp->mnt_stat.f_mntfromname, sbp->f_mntfromname, MNAMELEN);
+               sbp->f_iosize = mp->mnt_stat.f_iosize;
        }
        m_freem(info.mrep);
        info.mrep = NULL;
@@ -500,6 +506,14 @@ nfs_fsinfo(struct nfsmount *nmp, struct vnode *vp, struct thread *td)
                if (maxfsize > 0 && maxfsize < nmp->nm_maxfilesize)
                        nmp->nm_maxfilesize = maxfsize;
                nmp->nm_state |= NFSSTA_GOTFSINFO;
+
+               /*
+                * Use the smaller of rsize/wsize for the biosize.
+                */
+               if (nmp->nm_rsize < nmp->nm_wsize)
+                       nmp->nm_mountp->mnt_stat.f_iosize = nmp->nm_rsize;
+               else
+                       nmp->nm_mountp->mnt_stat.f_iosize = nmp->nm_wsize;
        }
        m_freem(info.mrep);
        info.mrep = NULL;
@@ -1218,11 +1232,14 @@ nfs_root(struct mount *mp, struct vnode **vpp)
 
        /*
         * Get transfer parameters and root vnode attributes
+        *
+        * NOTE: nfs_fsinfo() is expected to override the default
+        *       f_iosize we set.
         */
        if ((nmp->nm_state & NFSSTA_GOTFSINFO) == 0) {
            if (nmp->nm_flag & NFSMNT_NFSV3) {
-               error = nfs_fsinfo(nmp, vp, curthread);
                mp->mnt_stat.f_iosize = nfs_iosize(1, nmp->nm_sotype);
+               error = nfs_fsinfo(nmp, vp, curthread);
            } else {
                if ((error = VOP_GETATTR(vp, &attrs)) == 0)
                        nmp->nm_state |= NFSSTA_GOTFSINFO;