diff options
| -rw-r--r-- | sys/fs/pseudofs/pseudofs_vncache.c | 65 |
1 files changed, 39 insertions, 26 deletions
diff --git a/sys/fs/pseudofs/pseudofs_vncache.c b/sys/fs/pseudofs/pseudofs_vncache.c index 49258ab..d237cd2 100644 --- a/sys/fs/pseudofs/pseudofs_vncache.c +++ b/sys/fs/pseudofs/pseudofs_vncache.c @@ -80,8 +80,7 @@ extern vop_t **pfs_vnodeop_p; void pfs_vncache_load(void) { - mtx_init(&pfs_vncache_mutex, "pseudofs_vncache", NULL, - MTX_DEF | MTX_RECURSE); + mtx_init(&pfs_vncache_mutex, "pseudofs_vncache", NULL, MTX_DEF); pfs_exit_tag = EVENTHANDLER_REGISTER(process_exit, pfs_exit, NULL, EVENTHANDLER_PRI_ANY); } @@ -220,24 +219,35 @@ pfs_vncache_free(struct vnode *vp) static void pfs_exit(void *arg, struct proc *p) { - struct pfs_vdata *pvd, *prev; + struct pfs_vdata *pvd; + struct vnode *vnp; mtx_lock(&Giant); - mtx_lock(&pfs_vncache_mutex); /* - * The double loop is necessary because vgone() indirectly - * calls pfs_vncache_free() which frees pvd, so we have to - * backtrace one step every time we free a vnode. + * This is extremely inefficient due to the fact that vgone() not + * only indirectly modifies the vnode cache, but may also sleep. + * We can neither hold pfs_vncache_mutex across a vgone() call, + * nor make any assumptions about the state of the cache after + * vgone() returns. In consequence, we must start over after + * every vgone() call, and keep trying until we manage to traverse + * the entire cache. + * + * The only way to improve this situation is to change the data + * structure used to implement the cache. An obvious choice in + * this particular case would be a BST sorted by PID. */ - /* XXX linear search... not very efficient */ - for (pvd = pfs_vncache; pvd != NULL; pvd = pvd->pvd_next) { - while (pvd != NULL && pvd->pvd_pid == p->p_pid) { - prev = pvd->pvd_prev; - vgone(pvd->pvd_vnode); - pvd = prev ? prev->pvd_next : pfs_vncache; + mtx_lock(&pfs_vncache_mutex); + pvd = pfs_vncache; + while (pvd != NULL) { + if (pvd->pvd_pid == p->p_pid) { + vnp = pvd->pvd_vnode; + mtx_unlock(&pfs_vncache_mutex); + vgone(vnp); + mtx_lock(&pfs_vncache_mutex); + pvd = pfs_vncache; + } else { + pvd = pvd->pvd_next; } - if (pvd == NULL) - break; } mtx_unlock(&pfs_vncache_mutex); mtx_unlock(&Giant); @@ -249,22 +259,25 @@ pfs_exit(void *arg, struct proc *p) int pfs_disable(struct pfs_node *pn) { - struct pfs_vdata *pvd, *prev; + struct pfs_vdata *pvd; + struct vnode *vnp; if (pn->pn_flags & PFS_DISABLED) return (0); - mtx_lock(&pfs_vncache_mutex); pn->pn_flags |= PFS_DISABLED; - /* see the comment about the double loop in pfs_exit() */ - /* XXX linear search... not very efficient */ - for (pvd = pfs_vncache; pvd != NULL; pvd = pvd->pvd_next) { - while (pvd != NULL && pvd->pvd_pn == pn) { - prev = pvd->pvd_prev; - vgone(pvd->pvd_vnode); - pvd = prev ? prev->pvd_next : pfs_vncache; + /* XXX see comment above nearly identical code in pfs_exit() */ + mtx_lock(&pfs_vncache_mutex); + pvd = pfs_vncache; + while (pvd != NULL) { + if (pvd->pvd_pn == pn) { + vnp = pvd->pvd_vnode; + mtx_unlock(&pfs_vncache_mutex); + vgone(vnp); + mtx_lock(&pfs_vncache_mutex); + pvd = pfs_vncache; + } else { + pvd = pvd->pvd_next; } - if (pvd == NULL) - break; } mtx_unlock(&pfs_vncache_mutex); return (0); |
