Skip site navigation (1)Skip section navigation (2)
Date:      Tue, 3 Apr 2012 19:34:00 +0000 (UTC)
From:      Gleb Kurtsou <gleb@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-9@freebsd.org
Subject:   svn commit: r233851 - stable/9/sys/fs/tmpfs
Message-ID:  <201204031934.q33JY0fO065372@svn.freebsd.org>

next in thread | raw e-mail | index | archive | help
Author: gleb
Date: Tue Apr  3 19:34:00 2012
New Revision: 233851
URL: http://svn.freebsd.org/changeset/base/233851

Log:
  MFC r232959 and r232960:
  
  Prevent tmpfs_rename() deadlock in a way similar to UFS. Unlock
  vnodes and try to lock them one by one. Relookup fvp and tvp.
  
  Don't enforce LK_RETRY to get existing vnode in tmpfs_alloc_vp().
  Doomed vnode is hardly of any use here, besides all callers handle
  error case. vfs_hash_get() does the same. Don't mess with vnode
  holdcount, vget() takes care of it already.
  
  Approved by:	mdf (mentor)

Modified:
  stable/9/sys/fs/tmpfs/tmpfs_subr.c
  stable/9/sys/fs/tmpfs/tmpfs_vnops.c
Directory Properties:
  stable/9/sys/   (props changed)
  stable/9/sys/fs/   (props changed)

Modified: stable/9/sys/fs/tmpfs/tmpfs_subr.c
==============================================================================
--- stable/9/sys/fs/tmpfs/tmpfs_subr.c	Tue Apr  3 18:38:00 2012	(r233850)
+++ stable/9/sys/fs/tmpfs/tmpfs_subr.c	Tue Apr  3 19:34:00 2012	(r233851)
@@ -42,6 +42,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/proc.h>
 #include <sys/stat.h>
 #include <sys/systm.h>
+#include <sys/sysctl.h>
 #include <sys/vnode.h>
 #include <sys/vmmeter.h>
 
@@ -55,6 +56,8 @@ __FBSDID("$FreeBSD$");
 #include <fs/tmpfs/tmpfs_fifoops.h>
 #include <fs/tmpfs/tmpfs_vnops.h>
 
+SYSCTL_NODE(_vfs, OID_AUTO, tmpfs, CTLFLAG_RW, 0, "tmpfs file system");
+
 /* --------------------------------------------------------------------- */
 
 /*
@@ -319,9 +322,11 @@ loop:
 		MPASS((node->tn_vpstate & TMPFS_VNODE_DOOMED) == 0);
 		VI_LOCK(vp);
 		TMPFS_NODE_UNLOCK(node);
-		vholdl(vp);
-		(void) vget(vp, lkflag | LK_INTERLOCK | LK_RETRY, curthread);
-		vdrop(vp);
+		error = vget(vp, lkflag | LK_INTERLOCK, curthread);
+		if (error != 0) {
+			vp = NULL;
+			goto out;
+		}
 
 		/*
 		 * Make sure the vnode is still there after
@@ -419,11 +424,13 @@ unlock:
 out:
 	*vpp = vp;
 
-	MPASS(IFF(error == 0, *vpp != NULL && VOP_ISLOCKED(*vpp)));
 #ifdef INVARIANTS
-	TMPFS_NODE_LOCK(node);
-	MPASS(*vpp == node->tn_vnode);
-	TMPFS_NODE_UNLOCK(node);
+	if (error == 0) {
+		MPASS(*vpp != NULL && VOP_ISLOCKED(*vpp));
+		TMPFS_NODE_LOCK(node);
+		MPASS(*vpp == node->tn_vnode);
+		TMPFS_NODE_UNLOCK(node);
+	}
 #endif
 
 	return error;

Modified: stable/9/sys/fs/tmpfs/tmpfs_vnops.c
==============================================================================
--- stable/9/sys/fs/tmpfs/tmpfs_vnops.c	Tue Apr  3 18:38:00 2012	(r233850)
+++ stable/9/sys/fs/tmpfs/tmpfs_vnops.c	Tue Apr  3 19:34:00 2012	(r233851)
@@ -46,6 +46,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/sf_buf.h>
 #include <sys/stat.h>
 #include <sys/systm.h>
+#include <sys/sysctl.h>
 #include <sys/unistd.h>
 #include <sys/vnode.h>
 
@@ -60,6 +61,13 @@ __FBSDID("$FreeBSD$");
 #include <fs/tmpfs/tmpfs_vnops.h>
 #include <fs/tmpfs/tmpfs.h>
 
+SYSCTL_DECL(_vfs_tmpfs);
+
+static volatile int tmpfs_rename_restarts;
+SYSCTL_INT(_vfs_tmpfs, OID_AUTO, rename_restarts, CTLFLAG_RD,
+    __DEVOLATILE(int *, &tmpfs_rename_restarts), 0,
+    "Times rename had to restart due to lock contention");
+
 /* --------------------------------------------------------------------- */
 
 static int
@@ -920,6 +928,139 @@ out:
 
 /* --------------------------------------------------------------------- */
 
+/*
+ * We acquire all but fdvp locks using non-blocking acquisitions.  If we
+ * fail to acquire any lock in the path we will drop all held locks,
+ * acquire the new lock in a blocking fashion, and then release it and
+ * restart the rename.  This acquire/release step ensures that we do not
+ * spin on a lock waiting for release.  On error release all vnode locks
+ * and decrement references the way tmpfs_rename() would do.
+ */
+static int
+tmpfs_rename_relock(struct vnode *fdvp, struct vnode **fvpp,
+    struct vnode *tdvp, struct vnode **tvpp,
+    struct componentname *fcnp, struct componentname *tcnp)
+{
+	struct vnode *nvp;
+	struct mount *mp;
+	struct tmpfs_dirent *de;
+	int error, restarts = 0;
+
+	VOP_UNLOCK(tdvp, 0);
+	if (*tvpp != NULL && *tvpp != tdvp)
+		VOP_UNLOCK(*tvpp, 0);
+	mp = fdvp->v_mount;
+
+relock:
+	restarts += 1;
+	error = vn_lock(fdvp, LK_EXCLUSIVE);
+	if (error)
+		goto releout;
+	if (vn_lock(tdvp, LK_EXCLUSIVE | LK_NOWAIT) != 0) {
+		VOP_UNLOCK(fdvp, 0);
+		error = vn_lock(tdvp, LK_EXCLUSIVE);
+		if (error)
+			goto releout;
+		VOP_UNLOCK(tdvp, 0);
+		goto relock;
+	}
+	/*
+	 * Re-resolve fvp to be certain it still exists and fetch the
+	 * correct vnode.
+	 */
+	de = tmpfs_dir_lookup(VP_TO_TMPFS_DIR(fdvp), NULL, fcnp);
+	if (de == NULL) {
+		VOP_UNLOCK(fdvp, 0);
+		VOP_UNLOCK(tdvp, 0);
+		if ((fcnp->cn_flags & ISDOTDOT) != 0 ||
+		    (fcnp->cn_namelen == 1 && fcnp->cn_nameptr[0] == '.'))
+			error = EINVAL;
+		else
+			error = ENOENT;
+		goto releout;
+	}
+	error = tmpfs_alloc_vp(mp, de->td_node, LK_EXCLUSIVE | LK_NOWAIT, &nvp);
+	if (error != 0) {
+		VOP_UNLOCK(fdvp, 0);
+		VOP_UNLOCK(tdvp, 0);
+		if (error != EBUSY)
+			goto releout;
+		error = tmpfs_alloc_vp(mp, de->td_node, LK_EXCLUSIVE, &nvp);
+		if (error != 0)
+			goto releout;
+		VOP_UNLOCK(nvp, 0);
+		/*
+		 * Concurrent rename race.
+		 */
+		if (nvp == tdvp) {
+			vrele(nvp);
+			error = EINVAL;
+			goto releout;
+		}
+		vrele(*fvpp);
+		*fvpp = nvp;
+		goto relock;
+	}
+	vrele(*fvpp);
+	*fvpp = nvp;
+	VOP_UNLOCK(*fvpp, 0);
+	/*
+	 * Re-resolve tvp and acquire the vnode lock if present.
+	 */
+	de = tmpfs_dir_lookup(VP_TO_TMPFS_DIR(tdvp), NULL, tcnp);
+	/*
+	 * If tvp disappeared we just carry on.
+	 */
+	if (de == NULL && *tvpp != NULL) {
+		vrele(*tvpp);
+		*tvpp = NULL;
+	}
+	/*
+	 * Get the tvp ino if the lookup succeeded.  We may have to restart
+	 * if the non-blocking acquire fails.
+	 */
+	if (de != NULL) {
+		nvp = NULL;
+		error = tmpfs_alloc_vp(mp, de->td_node,
+		    LK_EXCLUSIVE | LK_NOWAIT, &nvp);
+		if (*tvpp != NULL)
+			vrele(*tvpp);
+		*tvpp = nvp;
+		if (error != 0) {
+			VOP_UNLOCK(fdvp, 0);
+			VOP_UNLOCK(tdvp, 0);
+			if (error != EBUSY)
+				goto releout;
+			error = tmpfs_alloc_vp(mp, de->td_node, LK_EXCLUSIVE,
+			    &nvp);
+			if (error != 0)
+				goto releout;
+			VOP_UNLOCK(nvp, 0);
+			/*
+			 * fdvp contains fvp, thus tvp (=fdvp) is not empty.
+			 */
+			if (nvp == fdvp) {
+				error = ENOTEMPTY;
+				goto releout;
+			}
+			goto relock;
+		}
+	}
+	tmpfs_rename_restarts += restarts;
+
+	return (0);
+
+releout:
+	vrele(fdvp);
+	vrele(*fvpp);
+	vrele(tdvp);
+	if (*tvpp != NULL)
+		vrele(*tvpp);
+	tmpfs_rename_restarts += restarts;
+
+	return (error);
+}
+
 static int
 tmpfs_rename(struct vop_rename_args *v)
 {
@@ -929,6 +1070,7 @@ tmpfs_rename(struct vop_rename_args *v)
 	struct vnode *tdvp = v->a_tdvp;
 	struct vnode *tvp = v->a_tvp;
 	struct componentname *tcnp = v->a_tcnp;
+	struct mount *mp = NULL;
 
 	char *newname;
 	int error;
@@ -944,8 +1086,6 @@ tmpfs_rename(struct vop_rename_args *v)
 	MPASS(fcnp->cn_flags & HASBUF);
 	MPASS(tcnp->cn_flags & HASBUF);
 
-  	tnode = (tvp == NULL) ? NULL : VP_TO_TMPFS_NODE(tvp);
-
 	/* Disallow cross-device renames.
 	 * XXX Why isn't this done by the caller? */
 	if (fvp->v_mount != tdvp->v_mount ||
@@ -954,9 +1094,6 @@ tmpfs_rename(struct vop_rename_args *v)
 		goto out;
 	}
 
-	tmp = VFS_TO_TMPFS(tdvp->v_mount);
-	tdnode = VP_TO_TMPFS_DIR(tdvp);
-
 	/* If source and target are the same file, there is nothing to do. */
 	if (fvp == tvp) {
 		error = 0;
@@ -965,8 +1102,37 @@ tmpfs_rename(struct vop_rename_args *v)
 
 	/* If we need to move the directory between entries, lock the
 	 * source so that we can safely operate on it. */
-	if (fdvp != tdvp && fdvp != tvp)
-		vn_lock(fdvp, LK_EXCLUSIVE | LK_RETRY);
+	if (fdvp != tdvp && fdvp != tvp) {
+		if (vn_lock(fdvp, LK_EXCLUSIVE | LK_NOWAIT) != 0) {
+			mp = tdvp->v_mount;
+			error = vfs_busy(mp, 0);
+			if (error != 0) {
+				mp = NULL;
+				goto out;
+			}
+			error = tmpfs_rename_relock(fdvp, &fvp, tdvp, &tvp,
+			    fcnp, tcnp);
+			if (error != 0) {
+				vfs_unbusy(mp);
+				return (error);
+			}
+			ASSERT_VOP_ELOCKED(fdvp,
+			    "tmpfs_rename: fdvp not locked");
+			ASSERT_VOP_ELOCKED(tdvp,
+			    "tmpfs_rename: tdvp not locked");
+			if (tvp != NULL)
+				ASSERT_VOP_ELOCKED(tvp,
+				    "tmpfs_rename: tvp not locked");
+			if (fvp == tvp) {
+				error = 0;
+				goto out_locked;
+			}
+		}
+	}
+
+	tmp = VFS_TO_TMPFS(tdvp->v_mount);
+	tdnode = VP_TO_TMPFS_DIR(tdvp);
+	tnode = (tvp == NULL) ? NULL : VP_TO_TMPFS_NODE(tvp);
 	fdnode = VP_TO_TMPFS_DIR(fdvp);
 	fnode = VP_TO_TMPFS_NODE(fvp);
 	de = tmpfs_dir_lookup(fdnode, fnode, fcnp);
@@ -1160,6 +1326,9 @@ out:
 	vrele(fdvp);
 	vrele(fvp);
 
+	if (mp != NULL)
+		vfs_unbusy(mp);
+
 	return error;
 }
 



Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201204031934.q33JY0fO065372>