Fix NFS client deadlock when read reports truncated node.

If node attribute returned in the reply for read rpc indicate
truncation, and it happens that the vnode is exclusively locked,
update of the node attributes would try to shrink vnode size.  Since
during the read some vnode pages were busied by the reading thread,
vnode_pager_setsize() deadlocks waiting for the busy state owned by
the caller.

Use a thread-local flag to indicate that NFS read owns some (s)busy
pages states and postpone the call to vnode_pager_setsize() until the
thread relinguishes the ownership.

Diagnosed by:	rlibby
Tested by:	pho, rlibby
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week

1 files changed, 35 insertions, 16 deletions

diff --git a/sys/fs/nfsclient/nfs_clbio.c b/sys/fs/nfsclient/nfs_clbio.c
index d8d4600c3ff9..a2cfcada2218 100644
--- a/sys/fs/nfsclient/nfs_clbio.c
+++ b/sys/fs/nfsclient/nfs_clbio.c
@@ -425,14 +425,11 @@ int
 ncl_bioread(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred)
 {
 	struct nfsnode *np = VTONFS(vp);
-	int biosize, i;
 	struct buf *bp, *rabp;
 	struct thread *td;
 	struct nfsmount *nmp = VFSTONFS(vp->v_mount);
 	daddr_t lbn, rabn;
-	int bcount;
-	int seqcount;
-	int nra, error = 0, n = 0, on = 0;
+	int biosize, bcount, error, i, n, nra, on, save2, seqcount;
 	off_t tmp_off;
 
 	KASSERT(uio->uio_rw == UIO_READ, ("ncl_read mode"));
@@ -464,6 +461,8 @@ ncl_bioread(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred)
 		/* No caching/ no readaheads. Just read data into the user buffer */
 		return ncl_readrpc(vp, uio, cred);
 
+	n = 0;
+	on = 0;
 	biosize = vp->v_bufobj.bo_bsize;
 	seqcount = (int)((off_t)(ioflag >> IO_SEQSHIFT) * biosize / BKVASIZE);
 
@@ -471,6 +470,7 @@ ncl_bioread(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred)
 	if (error)
 		return error;
 
+	save2 = curthread_pflags2_set(TDP2_SBPAGES);
 	do {
 	    u_quad_t nsize;
 
@@ -495,7 +495,9 @@ ncl_bioread(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred)
 			    rabp = nfs_getcacheblk(vp, rabn, biosize, td);
 			    if (!rabp) {
 				error = newnfs_sigintr(nmp, td);
-				return (error ? error : EINTR);
+				if (error == 0)
+					error = EINTR;
+				goto out;
 			    }
 			    if ((rabp->b_flags & (B_CACHE|B_DELWRI)) == 0) {
 				rabp->b_flags |= B_ASYNC;
@@ -526,7 +528,9 @@ ncl_bioread(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred)
 
 		if (!bp) {
 			error = newnfs_sigintr(nmp, td);
-			return (error ? error : EINTR);
+			if (error == 0)
+				error = EINTR;
+			goto out;
 		}
 
 		/*
@@ -540,7 +544,7 @@ ncl_bioread(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred)
 		    error = ncl_doio(vp, bp, cred, td, 0);
 		    if (error) {
 			brelse(bp);
-			return (error);
+			goto out;
 		    }
 		}
 
@@ -561,7 +565,9 @@ ncl_bioread(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred)
 		bp = nfs_getcacheblk(vp, (daddr_t)0, NFS_MAXPATHLEN, td);
 		if (!bp) {
 			error = newnfs_sigintr(nmp, td);
-			return (error ? error : EINTR);
+			if (error == 0)
+				error = EINTR;
+			goto out;
 		}
 		if ((bp->b_flags & B_CACHE) == 0) {
 		    bp->b_iocmd = BIO_READ;
@@ -570,7 +576,7 @@ ncl_bioread(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred)
 		    if (error) {
 			bp->b_ioflags |= BIO_ERROR;
 			brelse(bp);
-			return (error);
+			goto out;
 		    }
 		}
 		n = MIN(uio->uio_resid, NFS_MAXPATHLEN - bp->b_resid);
@@ -580,14 +586,17 @@ ncl_bioread(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred)
 		NFSINCRGLOBAL(nfsstatsv1.biocache_readdirs);
 		if (np->n_direofoffset
 		    && uio->uio_offset >= np->n_direofoffset) {
-		    return (0);
+			error = 0;
+			goto out;
 		}
 		lbn = (uoff_t)uio->uio_offset / NFS_DIRBLKSIZ;
 		on = uio->uio_offset & (NFS_DIRBLKSIZ - 1);
 		bp = nfs_getcacheblk(vp, lbn, NFS_DIRBLKSIZ, td);
 		if (!bp) {
-		    error = newnfs_sigintr(nmp, td);
-		    return (error ? error : EINTR);
+			error = newnfs_sigintr(nmp, td);
+			if (error == 0)
+				error = EINTR;
+			goto out;
 		}
 		if ((bp->b_flags & B_CACHE) == 0) {
 		    bp->b_iocmd = BIO_READ;
@@ -612,12 +621,16 @@ ncl_bioread(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred)
 			 */
 			for (i = 0; i <= lbn && !error; i++) {
 			    if (np->n_direofoffset
-				&& (i * NFS_DIRBLKSIZ) >= np->n_direofoffset)
-				    return (0);
+				&& (i * NFS_DIRBLKSIZ) >= np->n_direofoffset) {
+				    error = 0;
+				    goto out;
+			    }
 			    bp = nfs_getcacheblk(vp, i, NFS_DIRBLKSIZ, td);
 			    if (!bp) {
 				error = newnfs_sigintr(nmp, td);
-				return (error ? error : EINTR);
+				if (error == 0)
+					error = EINTR;
+				goto out;
 			    }
 			    if ((bp->b_flags & B_CACHE) == 0) {
 				    bp->b_iocmd = BIO_READ;
@@ -646,7 +659,7 @@ ncl_bioread(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred)
 		     * we give up.
 		     */
 		    if (error)
-			    return (error);
+			    goto out;
 		}
 
 		/*
@@ -706,6 +719,12 @@ ncl_bioread(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred)
 	    if (bp != NULL)
 		brelse(bp);
 	} while (error == 0 && uio->uio_resid > 0 && n > 0);
+out:
+	curthread_pflags2_restore(save2);
+	if ((curthread->td_pflags2 & TDP2_SBPAGES) == 0) {
+		NFSLOCKNODE(np);
+		ncl_pager_setsize(vp, NULL);
+	}
 	return (error);
 }