Correct an error of omission in the reimplementation of the page
cache: vm_object_page_remove() should convert any cached pages that fall with the specified range to free pages. Otherwise, there could be a problem if a file is first truncated and then regrown. Specifically, some old data from prior to the truncation might reappear. Generalize vm_page_cache_free() to support the conversion of either a subset or the entirety of an object's cached pages. Reported by: tegge Reviewed by: tegge Approved by: re (kensmith)
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parent
fed3ad6334
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c944491426
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=172341
@ -653,7 +653,7 @@ vm_object_terminate(vm_object_t object)
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vm_page_unlock_queues();
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if (__predict_false(object->cache != NULL))
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vm_page_cache_free(object);
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vm_page_cache_free(object, 0, 0);
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/*
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* Let the pager know object is dead.
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@ -1680,7 +1680,7 @@ vm_object_collapse(vm_object_t object)
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* Free any cached pages from backing_object.
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*/
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if (__predict_false(backing_object->cache != NULL))
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vm_page_cache_free(backing_object);
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vm_page_cache_free(backing_object, 0, 0);
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}
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/*
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* Object now shadows whatever backing_object did.
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@ -1849,6 +1849,8 @@ vm_object_page_remove(vm_object_t object, vm_pindex_t start, vm_pindex_t end,
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}
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vm_page_unlock_queues();
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vm_object_pip_wakeup(object);
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if (__predict_false(object->cache != NULL))
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vm_page_cache_free(object, start, end);
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}
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/*
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@ -794,28 +794,55 @@ vm_page_rename(vm_page_t m, vm_object_t new_object, vm_pindex_t new_pindex)
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}
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/*
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* Convert all of the cached pages belonging to the given object
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* into free pages. If the given object has cached pages and is
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* backed by a vnode, reduce the vnode's hold count.
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* Convert all of the given object's cached pages that have a
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* pindex within the given range into free pages. If the value
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* zero is given for "end", then the range's upper bound is
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* infinity. If the given object is backed by a vnode and it
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* transitions from having one or more cached pages to none, the
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* vnode's hold count is reduced.
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*/
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void
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vm_page_cache_free(vm_object_t object)
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vm_page_cache_free(vm_object_t object, vm_pindex_t start, vm_pindex_t end)
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{
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vm_page_t m, root;
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vm_page_t m, m_next;
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boolean_t empty;
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mtx_lock(&vm_page_queue_free_mtx);
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empty = object->cache == NULL;
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while ((m = object->cache) != NULL) {
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if (m->left == NULL)
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root = m->right;
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else if (m->right == NULL)
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root = m->left;
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if (__predict_false(object->cache == NULL)) {
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mtx_unlock(&vm_page_queue_free_mtx);
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return;
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}
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m = object->cache = vm_page_splay(start, object->cache);
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if (m->pindex < start) {
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if (m->right == NULL)
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m = NULL;
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else {
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root = vm_page_splay(m->pindex, m->left);
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root->right = m->right;
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m_next = vm_page_splay(start, m->right);
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m_next->left = m;
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m->right = NULL;
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m = object->cache = m_next;
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}
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m->object->cache = root;
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}
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/*
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* At this point, "m" is either (1) a reference to the page
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* with the least pindex that is greater than or equal to
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* "start" or (2) NULL.
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*/
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for (; m != NULL && (m->pindex < end || end == 0); m = m_next) {
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/*
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* Find "m"'s successor and remove "m" from the
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* object's cache.
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*/
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if (m->right == NULL) {
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object->cache = m->left;
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m_next = NULL;
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} else {
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m_next = vm_page_splay(start, m->right);
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m_next->left = m->left;
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object->cache = m_next;
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}
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/* Convert "m" to a free page. */
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m->object = NULL;
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m->valid = 0;
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/* Clear PG_CACHED and set PG_FREE. */
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@ -825,8 +852,9 @@ vm_page_cache_free(vm_object_t object)
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cnt.v_cache_count--;
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cnt.v_free_count++;
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}
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empty = object->cache == NULL;
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mtx_unlock(&vm_page_queue_free_mtx);
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if (object->type == OBJT_VNODE && !empty)
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if (object->type == OBJT_VNODE && empty)
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vdrop(object->handle);
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}
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@ -320,7 +320,7 @@ void vm_page_activate (vm_page_t);
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vm_page_t vm_page_alloc (vm_object_t, vm_pindex_t, int);
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vm_page_t vm_page_grab (vm_object_t, vm_pindex_t, int);
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void vm_page_cache (register vm_page_t);
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void vm_page_cache_free(vm_object_t);
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void vm_page_cache_free(vm_object_t, vm_pindex_t, vm_pindex_t);
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void vm_page_cache_remove(vm_page_t);
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void vm_page_cache_transfer(vm_object_t, vm_pindex_t, vm_object_t);
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int vm_page_try_to_cache (vm_page_t);
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