Skip site navigation (1)Skip section navigation (2) 
Date:      Sun, 14 Oct 2012 19:43:37 +0000 (UTC)
From:      Konstantin Belousov <kib@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r241556 - in head/sys: kern sys
Message-ID:  <201210141943.q9EJhclS029533@svn.freebsd.org>
next in thread | raw e-mail | index | archive | help 
Author: kib
Date: Sun Oct 14 19:43:37 2012
New Revision: 241556
URL: http://svn.freebsd.org/changeset/base/241556

Log:
  Add a KPI to allow to reserve some amount of space in the numvnodes
  counter, without actually allocating the vnodes. The supposed use of
  the getnewvnode_reserve(9) is to reclaim enough free vnodes while the
  code still does not hold any resources that might be needed during the
  reclamation, and to consume the slack later for getnewvnode() calls
  made from the innards. After the critical block is finished, the
  caller shall free any reserve left, by getnewvnode_drop_reserve(9).
  
  Reviewed by:	avg
  Tested by:	pho
  MFC after:	1 week

Modified:
  head/sys/kern/subr_trap.c
  head/sys/kern/vfs_subr.c
  head/sys/sys/proc.h
  head/sys/sys/vnode.h

Modified: head/sys/kern/subr_trap.c
==============================================================================
--- head/sys/kern/subr_trap.c	Sun Oct 14 19:15:54 2012	(r241555)
+++ head/sys/kern/subr_trap.c	Sun Oct 14 19:43:37 2012	(r241556)
@@ -154,6 +154,8 @@ userret(struct thread *td, struct trapfr
 	    ("userret: Returning with sleep disabled"));
 	KASSERT(td->td_pinned == 0,
 	    ("userret: Returning with with pinned thread"));
+	KASSERT(td->td_vp_reserv == 0,
+	    ("userret: Returning while holding vnode reservation"));
 #ifdef VIMAGE
 	/* Unfortunately td_vnet_lpush needs VNET_DEBUG. */
 	VNET_ASSERT(curvnet == NULL,

Modified: head/sys/kern/vfs_subr.c
==============================================================================
--- head/sys/kern/vfs_subr.c	Sun Oct 14 19:15:54 2012	(r241555)
+++ head/sys/kern/vfs_subr.c	Sun Oct 14 19:43:37 2012	(r241556)
@@ -935,34 +935,22 @@ vtryrecycle(struct vnode *vp)
 }
 
 /*
- * Return the next vnode from the free list.
+ * Wait for available vnodes.
  */
-int
-getnewvnode(const char *tag, struct mount *mp, struct vop_vector *vops,
-    struct vnode **vpp)
+static int
+getnewvnode_wait(int suspended)
 {
-	struct vnode *vp = NULL;
-	struct bufobj *bo;
 
-	CTR3(KTR_VFS, "%s: mp %p with tag %s", __func__, mp, tag);
-	mtx_lock(&vnode_free_list_mtx);
-	/*
-	 * Lend our context to reclaim vnodes if they've exceeded the max.
-	 */
-	if (freevnodes > wantfreevnodes)
-		vnlru_free(1);
-	/*
-	 * Wait for available vnodes.
-	 */
+	mtx_assert(&vnode_free_list_mtx, MA_OWNED);
 	if (numvnodes > desiredvnodes) {
-		if (mp != NULL && (mp->mnt_kern_flag & MNTK_SUSPEND)) {
+		if (suspended) {
 			/*
 			 * File system is beeing suspended, we cannot risk a
 			 * deadlock here, so allocate new vnode anyway.
 			 */
 			if (freevnodes > wantfreevnodes)
 				vnlru_free(freevnodes - wantfreevnodes);
-			goto alloc;
+			return (0);
 		}
 		if (vnlruproc_sig == 0) {
 			vnlruproc_sig = 1;	/* avoid unnecessary wakeups */
@@ -970,16 +958,76 @@ getnewvnode(const char *tag, struct moun
 		}
 		msleep(&vnlruproc_sig, &vnode_free_list_mtx, PVFS,
 		    "vlruwk", hz);
-#if 0	/* XXX Not all VFS_VGET/ffs_vget callers check returns. */
-		if (numvnodes > desiredvnodes) {
-			mtx_unlock(&vnode_free_list_mtx);
-			return (ENFILE);
+	}
+	return (numvnodes > desiredvnodes ? ENFILE : 0);
+}
+
+void
+getnewvnode_reserve(u_int count)
+{
+	struct thread *td;
+
+	td = curthread;
+	mtx_lock(&vnode_free_list_mtx);
+	while (count > 0) {
+		if (getnewvnode_wait(0) == 0) {
+			count--;
+			td->td_vp_reserv++;
+			numvnodes++;
 		}
-#endif
 	}
-alloc:
+	mtx_unlock(&vnode_free_list_mtx);
+}
+
+void
+getnewvnode_drop_reserve(void)
+{
+	struct thread *td;
+
+	td = curthread;
+	mtx_lock(&vnode_free_list_mtx);
+	KASSERT(numvnodes >= td->td_vp_reserv, ("reserve too large"));
+	numvnodes -= td->td_vp_reserv;
+	mtx_unlock(&vnode_free_list_mtx);
+	td->td_vp_reserv = 0;
+}
+
+/*
+ * Return the next vnode from the free list.
+ */
+int
+getnewvnode(const char *tag, struct mount *mp, struct vop_vector *vops,
+    struct vnode **vpp)
+{
+	struct vnode *vp;
+	struct bufobj *bo;
+	struct thread *td;
+	int error;
+
+	CTR3(KTR_VFS, "%s: mp %p with tag %s", __func__, mp, tag);
+	vp = NULL;
+	td = curthread;
+	if (td->td_vp_reserv > 0) {
+		td->td_vp_reserv -= 1;
+		goto alloc;
+	}
+	mtx_lock(&vnode_free_list_mtx);
+	/*
+	 * Lend our context to reclaim vnodes if they've exceeded the max.
+	 */
+	if (freevnodes > wantfreevnodes)
+		vnlru_free(1);
+	error = getnewvnode_wait(mp != NULL && (mp->mnt_kern_flag &
+	    MNTK_SUSPEND));
+#if 0	/* XXX Not all VFS_VGET/ffs_vget callers check returns. */
+	if (error != 0) {
+		mtx_unlock(&vnode_free_list_mtx);
+		return (error);
+	}
+#endif
 	numvnodes++;
 	mtx_unlock(&vnode_free_list_mtx);
+alloc:
 	vp = (struct vnode *) uma_zalloc(vnode_zone, M_WAITOK|M_ZERO);
 	/*
 	 * Setup locks.

Modified: head/sys/sys/proc.h
==============================================================================
--- head/sys/sys/proc.h	Sun Oct 14 19:15:54 2012	(r241555)
+++ head/sys/sys/proc.h	Sun Oct 14 19:43:37 2012	(r241556)
@@ -272,6 +272,7 @@ struct thread {
 	struct osd	td_osd;		/* (k) Object specific data. */
 	struct vm_map_entry *td_map_def_user; /* (k) Deferred entries. */
 	pid_t		td_dbg_forked;	/* (c) Child pid for debugger. */
+	u_int		td_vp_reserv;	/* (k) Count of reserved vnodes. */
 #define	td_endzero td_sigmask
 
 /* Copied during fork1() or create_thread(). */

Modified: head/sys/sys/vnode.h
==============================================================================
--- head/sys/sys/vnode.h	Sun Oct 14 19:15:54 2012	(r241555)
+++ head/sys/sys/vnode.h	Sun Oct 14 19:43:37 2012	(r241556)
@@ -600,6 +600,8 @@ void	cvtstat(struct stat *st, struct ost
 void	cvtnstat(struct stat *sb, struct nstat *nsb);
 int	getnewvnode(const char *tag, struct mount *mp, struct vop_vector *vops,
 	    struct vnode **vpp);
+void	getnewvnode_reserve(u_int count);
+void	getnewvnode_drop_reserve(void);
 int	insmntque1(struct vnode *vp, struct mount *mp,
 	    void (*dtr)(struct vnode *, void *), void *dtr_arg);
 int	insmntque(struct vnode *vp, struct mount *mp);

Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201210141943.q9EJhclS029533>