minix/servers/vfs/vnode.c
Thomas Veerman 8f55767619 VFS: make m_in job local
By making m_in job local (i.e., each job has its own copy of m_in instead
of refering to the global m_in) we don't have to store and restore m_in
on every thread yield. This reduces overhead. Moreover, remove the
assumption that m_in is preserved. Do_XXX functions have to copy the
system call parameters as soon as possible and only pass those copies to
other functions.

Furthermore, this patch cleans up some code and uses better types in a lot
of places.
2012-04-13 12:50:38 +00:00

309 lines
8.5 KiB
C

/* This file contains the routines related to vnodes.
* The entry points are:
*
* get_vnode - increase counter and get details of an inode
* get_free_vnode - get a pointer to a free vnode obj
* find_vnode - find a vnode according to the FS endpoint and the inode num.
* dup_vnode - duplicate vnode (i.e. increase counter)
* put_vnode - drop vnode (i.e. decrease counter)
*/
#include "fs.h"
#include "threads.h"
#include "vnode.h"
#include "vmnt.h"
#include "fproc.h"
#include "file.h"
#include <minix/vfsif.h>
#include <assert.h>
/* Is vnode pointer reasonable? */
#if NDEBUG
#define SANEVP(v)
#define CHECKVN(v)
#define ASSERTVP(v)
#else
#define SANEVP(v) ((((v) >= &vnode[0] && (v) < &vnode[NR_VNODES])))
#define BADVP(v, f, l) printf("%s:%d: bad vp %p\n", f, l, v)
/* vp check that returns 0 for use in check_vrefs() */
#define CHECKVN(v) if(!SANEVP(v)) { \
BADVP(v, __FILE__, __LINE__); \
return 0; \
}
/* vp check that panics */
#define ASSERTVP(v) if(!SANEVP(v)) { \
BADVP(v, __FILE__, __LINE__); panic("bad vp"); }
#endif
#if LOCK_DEBUG
/*===========================================================================*
* check_vnode_locks_by_me *
*===========================================================================*/
void check_vnode_locks_by_me(struct fproc *rfp)
{
/* Check whether this thread still has locks held on vnodes */
struct vnode *vp;
for (vp = &vnode[0]; vp < &vnode[NR_VNODES]; vp++) {
if (tll_locked_by_me(&vp->v_lock)) {
panic("Thread %d still holds vnode lock on vp %x call_nr=%d\n",
mthread_self(), vp, job_call_nr);
}
}
if (rfp->fp_vp_rdlocks != 0)
panic("Thread %d still holds read locks on a vnode (%d) call_nr=%d\n",
mthread_self(), rfp->fp_vp_rdlocks, job_call_nr);
}
#endif
/*===========================================================================*
* check_vnode_locks *
*===========================================================================*/
void check_vnode_locks()
{
struct vnode *vp;
int count = 0;
for (vp = &vnode[0]; vp < &vnode[NR_VNODES]; vp++)
if (is_vnode_locked(vp)) {
count++;
}
if (count) panic("%d locked vnodes\n", count);
#if 0
printf("check_vnode_locks OK\n");
#endif
}
/*===========================================================================*
* get_free_vnode *
*===========================================================================*/
struct vnode *get_free_vnode()
{
/* Find a free vnode slot in the vnode table (it's not actually allocated) */
struct vnode *vp;
for (vp = &vnode[0]; vp < &vnode[NR_VNODES]; ++vp) {
if (vp->v_ref_count == 0 && !is_vnode_locked(vp)) {
vp->v_pipe = NO_PIPE;
vp->v_uid = -1;
vp->v_gid = -1;
vp->v_sdev = NO_DEV;
vp->v_mapfs_e = NONE;
vp->v_mapfs_count = 0;
vp->v_mapinode_nr = 0;
return(vp);
}
}
err_code = ENFILE;
return(NULL);
}
/*===========================================================================*
* find_vnode *
*===========================================================================*/
struct vnode *find_vnode(int fs_e, int ino)
{
/* Find a specified (FS endpoint and inode number) vnode in the
* vnode table */
struct vnode *vp;
for (vp = &vnode[0]; vp < &vnode[NR_VNODES]; ++vp)
if (vp->v_ref_count > 0 && vp->v_inode_nr == ino && vp->v_fs_e == fs_e)
return(vp);
return(NULL);
}
/*===========================================================================*
* is_vnode_locked *
*===========================================================================*/
int is_vnode_locked(struct vnode *vp)
{
/* Find out whether a thread holds a lock on this vnode or is trying to obtain
* a lock. */
ASSERTVP(vp);
return(tll_islocked(&vp->v_lock) || tll_haspendinglock(&vp->v_lock));
}
/*===========================================================================*
* init_vnodes *
*===========================================================================*/
void init_vnodes(void)
{
struct vnode *vp;
for (vp = &vnode[0]; vp < &vnode[NR_VNODES]; ++vp) {
vp->v_fs_e = NONE;
vp->v_mapfs_e = NONE;
vp->v_inode_nr = 0;
vp->v_ref_count = 0;
vp->v_fs_count = 0;
vp->v_mapfs_count = 0;
tll_init(&vp->v_lock);
}
}
/*===========================================================================*
* lock_vnode *
*===========================================================================*/
int lock_vnode(struct vnode *vp, tll_access_t locktype)
{
int r;
ASSERTVP(vp);
r = tll_lock(&vp->v_lock, locktype);
#if LOCK_DEBUG
if (locktype == VNODE_READ) {
fp->fp_vp_rdlocks++;
}
#endif
if (r == EBUSY) return(r);
return(OK);
}
/*===========================================================================*
* unlock_vnode *
*===========================================================================*/
void unlock_vnode(struct vnode *vp)
{
#if LOCK_DEBUG
int i;
register struct vnode *rvp;
struct worker_thread *w;
#endif
ASSERTVP(vp);
#if LOCK_DEBUG
/* Decrease read-only lock counter when not locked as VNODE_OPCL or
* VNODE_WRITE */
if (!tll_locked_by_me(&vp->v_lock)) {
fp->fp_vp_rdlocks--;
}
for (i = 0; i < NR_VNODES; i++) {
rvp = &vnode[i];
w = rvp->v_lock.t_write;
assert(w != self);
while (w && w->w_next != NULL) {
w = w->w_next;
assert(w != self);
}
w = rvp->v_lock.t_serial;
assert(w != self);
while (w && w->w_next != NULL) {
w = w->w_next;
assert(w != self);
}
}
#endif
tll_unlock(&vp->v_lock);
}
/*===========================================================================*
* dup_vnode *
*===========================================================================*/
void dup_vnode(struct vnode *vp)
{
/* dup_vnode() is called to increment the vnode and therefore the
* referred inode's counter.
*/
ASSERTVP(vp);
vp->v_ref_count++;
}
/*===========================================================================*
* put_vnode *
*===========================================================================*/
void put_vnode(struct vnode *vp)
{
/* Decrease vnode's usage counter and decrease inode's usage counter in the
* corresponding FS process. Decreasing the fs_count each time we decrease the
* ref count would lead to poor performance. Instead, only decrease fs_count
* when the ref count hits zero. However, this could lead to fs_count to wrap.
* To prevent this, we drop the counter to 1 when the counter hits 256.
* We maintain fs_count as a sanity check to make sure VFS and the FS are in
* sync.
*/
int r, lock_vp;
ASSERTVP(vp);
/* Lock vnode. It's quite possible this thread already has a lock on this
* vnode. That's no problem, because the reference counter will not decrease
* to zero in that case. However, if the counter does decrease to zero *and*
* is already locked, we have a consistency problem somewhere. */
lock_vp = lock_vnode(vp, VNODE_OPCL);
if (vp->v_ref_count > 1) {
/* Decrease counter */
vp->v_ref_count--;
if (vp->v_fs_count > 256)
vnode_clean_refs(vp);
if (lock_vp != EBUSY) unlock_vnode(vp);
return;
}
/* If we already had a lock, there is a consistency problem */
assert(lock_vp != EBUSY);
tll_upgrade(&vp->v_lock); /* Make sure nobody else accesses this vnode */
/* A vnode that's not in use can't be put back. */
if (vp->v_ref_count <= 0)
panic("put_vnode failed: bad v_ref_count %d\n", vp->v_ref_count);
/* fs_count should indicate that the file is in use. */
if (vp->v_fs_count <= 0)
panic("put_vnode failed: bad v_fs_count %d\n", vp->v_fs_count);
/* Tell FS we don't need this inode to be open anymore. */
r = req_putnode(vp->v_fs_e, vp->v_inode_nr, vp->v_fs_count);
if (r != OK) {
printf("VFS: putnode failed: %d\n", r);
util_stacktrace();
}
/* This inode could've been mapped. If so, tell mapped FS to close it as
* well. If mapped onto same FS, this putnode is not needed. */
if (vp->v_mapfs_e != NONE && vp->v_mapfs_e != vp->v_fs_e)
req_putnode(vp->v_mapfs_e, vp->v_mapinode_nr, vp->v_mapfs_count);
vp->v_fs_count = 0;
vp->v_ref_count = 0;
vp->v_mapfs_count = 0;
unlock_vnode(vp);
}
/*===========================================================================*
* vnode_clean_refs *
*===========================================================================*/
void vnode_clean_refs(struct vnode *vp)
{
/* Tell the underlying FS to drop all reference but one. */
if (vp == NULL) return;
if (vp->v_fs_count <= 1) return; /* Nothing to do */
/* Drop all references except one */
req_putnode(vp->v_fs_e, vp->v_inode_nr, vp->v_fs_count - 1);
vp->v_fs_count = 1;
}