svn commit: r348737 - head/sys/kern

[Alan Somers]

Author: asomers
Date: Thu Jun  6 15:04:50 2019
New Revision: 348737
URL: https://svnweb.freebsd.org/changeset/base/348737

Log:
  Add a testing facility to manually reclaim a vnode
  
  Add the debug.try_reclaim_vnode sysctl. When a pathname is written to it, it
  will be reclaimed, as long as it isn't already or doomed. The purpose is to
  gain test coverage for vnode reclamation, which is otherwise hard to
  achieve.
  
  Add the debug.ftry_reclaim_vnode sysctl.  It does the same thing, except
  that its argument is a file descriptor instead of a pathname.
  
  Reviewed by:	kib
  MFC after:	2 weeks
  Sponsored by:	The FreeBSD Foundation
  Differential Revision:	https://reviews.freebsd.org/D20519

Modified:
  head/sys/kern/vfs_subr.c

Modified: head/sys/kern/vfs_subr.c
==============================================================================
--- head/sys/kern/vfs_subr.c	Thu Jun  6 12:44:43 2019	(r348736)
+++ head/sys/kern/vfs_subr.c	Thu Jun  6 15:04:50 2019	(r348737)
@@ -50,6 +50,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/systm.h>
 #include <sys/bio.h>
 #include <sys/buf.h>
+#include <sys/capsicum.h>
 #include <sys/condvar.h>
 #include <sys/conf.h>
 #include <sys/counter.h>
@@ -338,6 +339,93 @@ SYSCTL_ULONG(_kern, OID_AUTO, minvnodes, CTLFLAG_RW,
 static int vnlru_nowhere;
 SYSCTL_INT(_debug, OID_AUTO, vnlru_nowhere, CTLFLAG_RW,
     &vnlru_nowhere, 0, "Number of times the vnlru process ran without success");
+
+static int
+sysctl_try_reclaim_vnode(SYSCTL_HANDLER_ARGS)
+{
+	struct vnode *vp;
+	struct nameidata nd;
+	char *buf;
+	unsigned long ndflags;
+	int error;
+
+	if (req->newptr == NULL)
+		return (EINVAL);
+	if (req->newlen > PATH_MAX)
+		return (E2BIG);
+
+	buf = malloc(PATH_MAX + 1, M_TEMP, M_WAITOK);
+	error = SYSCTL_IN(req, buf, req->newlen);
+	if (error != 0)
+		goto out;
+
+	buf[req->newlen] = '\0';
+
+	ndflags = LOCKLEAF | NOFOLLOW | AUDITVNODE1 | NOCACHE | SAVENAME;
+	NDINIT(&nd, LOOKUP, ndflags, UIO_SYSSPACE, buf, curthread);
+	if ((error = namei(&nd)) != 0)
+		goto out;
+	vp = nd.ni_vp;
+
+	if ((vp->v_iflag & VI_DOOMED) != 0) {
+		/*
+		 * This vnode is being recycled.  Return != 0 to let the caller
+		 * know that the sysctl had no effect.  Return EAGAIN because a
+		 * subsequent call will likely succeed (since namei will create
+		 * a new vnode if necessary)
+		 */
+		error = EAGAIN;
+		goto putvnode;
+	}
+
+	counter_u64_add(recycles_count, 1);
+	vgone(vp);
+putvnode:
+	NDFREE(&nd, 0);
+out:
+	free(buf, M_TEMP);
+	return (error);
+}
+
+static int
+sysctl_ftry_reclaim_vnode(SYSCTL_HANDLER_ARGS)
+{
+	struct thread *td = curthread;
+	struct vnode *vp;
+	struct file *fp;
+	int error;
+	int fd;
+
+	if (req->newptr == NULL)
+		return (EBADF);
+
+        error = sysctl_handle_int(oidp, &fd, 0, req);
+        if (error != 0)
+                return (error);
+	error = getvnode(curthread, fd, &cap_fcntl_rights, &fp);
+	if (error != 0)
+		return (error);
+	vp = fp->f_vnode;
+
+	error = vn_lock(vp, LK_EXCLUSIVE);
+	if (error != 0)
+		goto drop;
+
+	counter_u64_add(recycles_count, 1);
+	vgone(vp);
+	VOP_UNLOCK(vp, 0);
+drop:
+	fdrop(fp, td);
+	return (error);
+}
+
+SYSCTL_PROC(_debug, OID_AUTO, try_reclaim_vnode,
+    CTLTYPE_STRING | CTLFLAG_MPSAFE | CTLFLAG_WR, NULL, 0,
+    sysctl_try_reclaim_vnode, "A", "Try to reclaim a vnode by its pathname");
+SYSCTL_PROC(_debug, OID_AUTO, ftry_reclaim_vnode,
+    CTLTYPE_INT | CTLFLAG_MPSAFE | CTLFLAG_WR, NULL, 0,
+    sysctl_ftry_reclaim_vnode, "I",
+    "Try to reclaim a vnode by its file descriptor");
 
 /* Shift count for (uintptr_t)vp to initialize vp->v_hash. */
 static int vnsz2log;