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Add a testing facility to manually reclaim a vnode

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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
This commit is contained in:
Alan Somers 2019-06-06 15:04:50 +00:00
parent bc04586c21
commit 46f8169aea
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=348737
1 changed files with 88 additions and 0 deletions
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88
sys/kern/vfs_subr.c
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@ -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>
@ -339,6 +340,93 @@ 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;