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Add mnt_hashseed to struct mount and initialize it witn PRNG bits, use

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it to get better hashing in vfs_hash.

In case of an insert collision in vfs_hash_insert(), put the loosing vnode
on a special list so that vfs_hash_remove() can just assume that it is on
a list.

Drop the VI_HASHED flag.
This commit is contained in:
Poul-Henning Kamp 2005-03-16 07:35:06 +00:00
parent beddd41467
commit 78bb3c21ed
4 changed files with 19 additions and 16 deletions
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32
sys/kern/vfs_hash.c
View File

@ -32,11 +32,13 @@ __FBSDID("$FreeBSD$");
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/vnode.h>
static MALLOC_DEFINE(M_VFS_HASH, "VFS hash", "VFS hash table");
static LIST_HEAD(vfs_hashhead, vnode) *vfs_hash_tbl;
static LIST_HEAD(vfs_hash_head, vnode) *vfs_hash_tbl;
static LIST_HEAD(,vnode) vfs_hash_side;
static u_long vfs_hash_mask;
static struct mtx vfs_hash_mtx;
@ -46,11 +48,19 @@ vfs_hashinit(void *dummy __unused)
vfs_hash_tbl = hashinit(desiredvnodes, M_VFS_HASH, &vfs_hash_mask);
mtx_init(&vfs_hash_mtx, "vfs hash", NULL, MTX_DEF);
LIST_INIT(&vfs_hash_side);
}
/* Must be SI_ORDER_SECOND so desiredvnodes is available */
SYSINIT(vfs_hash, SI_SUB_VFS, SI_ORDER_SECOND, vfs_hashinit, NULL)
static struct vfs_hash_head *
vfs_hash_index(struct mount *mp, u_int hash)
{
return(&vfs_hash_tbl[(hash + mp->mnt_hashseed) & vfs_hash_mask]);
}
int
vfs_hash_get(struct mount *mp, u_int hash, int flags, struct thread *td, struct vnode **vpp)
{
@ -59,8 +69,7 @@ vfs_hash_get(struct mount *mp, u_int hash, int flags, struct thread *td, struct
while (1) {
mtx_lock(&vfs_hash_mtx);
LIST_FOREACH(vp,
&vfs_hash_tbl[hash & vfs_hash_mask], v_hashlist) {
LIST_FOREACH(vp, vfs_hash_index(mp, hash), v_hashlist) {
if (vp->v_hash != hash)
continue;
if (vp->v_mount != mp)
@ -88,11 +97,7 @@ vfs_hash_remove(struct vnode *vp)
{
mtx_lock(&vfs_hash_mtx);
VI_LOCK(vp);
VNASSERT(vp->v_iflag & VI_HASHED, vp, ("vfs_hash_remove: not hashed"));
LIST_REMOVE(vp, v_hashlist);
vp->v_iflag &= ~VI_HASHED;
VI_UNLOCK(vp);
mtx_unlock(&vfs_hash_mtx);
}
@ -107,7 +112,7 @@ vfs_hash_insert(struct vnode *vp, u_int hash, int flags, struct thread *td, stru
while (1) {
mtx_lock(&vfs_hash_mtx);
LIST_FOREACH(vp2,
&vfs_hash_tbl[hash & vfs_hash_mask], v_hashlist) {
vfs_hash_index(vp->v_mount, hash), v_hashlist) {
if (vp2->v_hash != hash)
continue;
if (vp2->v_mount != vp->v_mount)
@ -117,6 +122,9 @@ vfs_hash_insert(struct vnode *vp, u_int hash, int flags, struct thread *td, stru
error = vget(vp2, flags | LK_INTERLOCK, td);
if (error == ENOENT)
break;
mtx_lock(&vfs_hash_mtx);
LIST_INSERT_HEAD(&vfs_hash_side, vp, v_hashlist);
mtx_unlock(&vfs_hash_mtx);
vput(vp);
if (!error)
*vpp = vp2;
@ -126,13 +134,8 @@ vfs_hash_insert(struct vnode *vp, u_int hash, int flags, struct thread *td, stru
break;
}
VI_LOCK(vp);
VNASSERT(!(vp->v_iflag & VI_HASHED), vp,
("vfs_hash_insert: already hashed"));
vp->v_hash = hash;
LIST_INSERT_HEAD(&vfs_hash_tbl[hash & vfs_hash_mask], vp, v_hashlist);
vp->v_iflag |= VI_HASHED;
VI_UNLOCK(vp);
LIST_INSERT_HEAD(vfs_hash_index(vp->v_mount, hash), vp, v_hashlist);
mtx_unlock(&vfs_hash_mtx);
return (0);
}
@ -142,7 +145,6 @@ vfs_hash_rehash(struct vnode *vp, u_int hash)
{
mtx_lock(&vfs_hash_mtx);
VNASSERT(vp->v_iflag & VI_HASHED, vp, ("vfs_hash_rehash: not hashed"));
LIST_REMOVE(vp, v_hashlist);
LIST_INSERT_HEAD(&vfs_hash_tbl[hash & vfs_hash_mask], vp, v_hashlist);
vp->v_hash = hash;

1
sys/kern/vfs_mount.c
View File

@ -428,6 +428,7 @@ vfs_mount_alloc(struct vnode *vp, struct vfsconf *vfsp,
mac_init_mount(mp);
mac_create_mount(td->td_ucred, mp);
#endif
arc4rand(&mp->mnt_hashseed, sizeof mp->mnt_hashseed, 0);
*mpp = mp;
return (0);
}

1
sys/sys/mount.h
View File

@ -159,6 +159,7 @@ struct mount {
struct label *mnt_mntlabel; /* MAC label for the mount */
struct label *mnt_fslabel; /* MAC label for the fs */
int mnt_nvnodelistsize; /* # of vnodes on this mount */
u_int mnt_hashseed; /* Random seed for vfs_hash */
};
struct vnode *__mnt_vnode_next(struct vnode **nvp, struct mount *mp);

1
sys/sys/vnode.h
View File

@ -238,7 +238,6 @@ struct xvnode {
* VI flags are protected by interlock and live in v_iflag
* VV flags are protected by the vnode lock and live in v_vflag
*/
#define VI_HASHED 0x0004 /* vnode is hashed in vfs_hash */
#define VI_MOUNT 0x0020 /* Mount in progress */
#define VI_AGE 0x0040 /* Insert vnode at head of free list */
#define VI_DOOMED 0x0080 /* This vnode is being recycled */