+/**
+ * Returns a list of pages by a given [start, end] of \a obj.
+ *
+ * \param resched If not NULL, then we give up before hogging CPU for too
+ * long and set *resched = 1, in that case caller should implement a retry
+ * logic.
+ *
+ * Gang tree lookup (radix_tree_gang_lookup()) optimization is absolutely
+ * crucial in the face of [offset, EOF] locks.
+ *
+ * Return at least one page in @queue unless there is no covered page.
+ */
+int osc_page_gang_lookup(const struct lu_env *env, struct cl_io *io,
+ struct osc_object *osc, pgoff_t start, pgoff_t end,
+ osc_page_gang_cbt cb, void *cbdata)
+{
+ struct osc_page *ops;
+ void **pvec;
+ pgoff_t idx;
+ unsigned int nr;
+ unsigned int i;
+ unsigned int j;
+ int res = CLP_GANG_OKAY;
+ bool tree_lock = true;
+ ENTRY;
+
+ idx = start;
+ pvec = osc_env_info(env)->oti_pvec;
+ spin_lock(&osc->oo_tree_lock);
+ while ((nr = radix_tree_gang_lookup(&osc->oo_tree, pvec,
+ idx, OTI_PVEC_SIZE)) > 0) {
+ struct cl_page *page;
+ bool end_of_region = false;
+
+ for (i = 0, j = 0; i < nr; ++i) {
+ ops = pvec[i];
+ pvec[i] = NULL;
+
+ idx = osc_index(ops);
+ if (idx > end) {
+ end_of_region = true;
+ break;
+ }
+
+ page = cl_page_top(ops->ops_cl.cpl_page);
+ LASSERT(page->cp_type == CPT_CACHEABLE);
+ if (page->cp_state == CPS_FREEING)
+ continue;
+
+ cl_page_get(page);
+ lu_ref_add_atomic(&page->cp_reference,
+ "gang_lookup", current);
+ pvec[j++] = ops;
+ }
+ ++idx;
+
+ /*
+ * Here a delicate locking dance is performed. Current thread
+ * holds a reference to a page, but has to own it before it
+ * can be placed into queue. Owning implies waiting, so
+ * radix-tree lock is to be released. After a wait one has to
+ * check that pages weren't truncated (cl_page_own() returns
+ * error in the latter case).
+ */
+ spin_unlock(&osc->oo_tree_lock);
+ tree_lock = false;
+
+ for (i = 0; i < j; ++i) {
+ ops = pvec[i];
+ if (res == CLP_GANG_OKAY)
+ res = (*cb)(env, io, ops, cbdata);
+
+ page = cl_page_top(ops->ops_cl.cpl_page);
+ lu_ref_del(&page->cp_reference, "gang_lookup", current);
+ cl_page_put(env, page);
+ }
+ if (nr < OTI_PVEC_SIZE || end_of_region)
+ break;
+
+ if (res == CLP_GANG_OKAY && need_resched())
+ res = CLP_GANG_RESCHED;
+ if (res != CLP_GANG_OKAY)
+ break;
+
+ spin_lock(&osc->oo_tree_lock);
+ tree_lock = true;
+ }
+ if (tree_lock)
+ spin_unlock(&osc->oo_tree_lock);
+ RETURN(res);
+}
+
+/**
+ * Check if page @page is covered by an extra lock or discard it.
+ */
+static int check_and_discard_cb(const struct lu_env *env, struct cl_io *io,
+ struct osc_page *ops, void *cbdata)
+{
+ struct osc_thread_info *info = osc_env_info(env);
+ struct cl_lock *lock = cbdata;
+ pgoff_t index;
+
+ index = osc_index(ops);
+ if (index >= info->oti_fn_index) {
+ struct cl_lock *tmp;
+ struct cl_page *page = cl_page_top(ops->ops_cl.cpl_page);
+
+ /* refresh non-overlapped index */
+ tmp = cl_lock_at_pgoff(env, lock->cll_descr.cld_obj, index,
+ lock, 1, 0);
+ if (tmp != NULL) {
+ /* Cache the first-non-overlapped index so as to skip
+ * all pages within [index, oti_fn_index). This
+ * is safe because if tmp lock is canceled, it will
+ * discard these pages. */
+ info->oti_fn_index = tmp->cll_descr.cld_end + 1;
+ if (tmp->cll_descr.cld_end == CL_PAGE_EOF)
+ info->oti_fn_index = CL_PAGE_EOF;
+ cl_lock_put(env, tmp);
+ } else if (cl_page_own(env, io, page) == 0) {
+ /* discard the page */
+ cl_page_discard(env, io, page);
+ cl_page_disown(env, io, page);
+ } else {
+ LASSERT(page->cp_state == CPS_FREEING);
+ }
+ }
+
+ info->oti_next_index = index + 1;
+ return CLP_GANG_OKAY;
+}
+
+static int discard_cb(const struct lu_env *env, struct cl_io *io,
+ struct osc_page *ops, void *cbdata)
+{
+ struct osc_thread_info *info = osc_env_info(env);
+ struct cl_lock *lock = cbdata;
+ struct cl_page *page = cl_page_top(ops->ops_cl.cpl_page);
+
+ LASSERT(lock->cll_descr.cld_mode >= CLM_WRITE);
+ KLASSERT(ergo(page->cp_type == CPT_CACHEABLE,
+ !PageWriteback(cl_page_vmpage(env, page))));
+ KLASSERT(ergo(page->cp_type == CPT_CACHEABLE,
+ !PageDirty(cl_page_vmpage(env, page))));
+
+ /* page is top page. */
+ info->oti_next_index = osc_index(ops) + 1;
+ if (cl_page_own(env, io, page) == 0) {
+ /* discard the page */
+ cl_page_discard(env, io, page);
+ cl_page_disown(env, io, page);
+ } else {
+ LASSERT(page->cp_state == CPS_FREEING);
+ }
+
+ return CLP_GANG_OKAY;
+}
+
+/**
+ * Discard pages protected by the given lock. This function traverses radix
+ * tree to find all covering pages and discard them. If a page is being covered
+ * by other locks, it should remain in cache.
+ *
+ * If error happens on any step, the process continues anyway (the reasoning
+ * behind this being that lock cancellation cannot be delayed indefinitely).
+ */
+int osc_lock_discard_pages(const struct lu_env *env, struct osc_lock *ols)
+{
+ struct osc_thread_info *info = osc_env_info(env);
+ struct cl_io *io = &info->oti_io;
+ struct cl_object *osc = ols->ols_cl.cls_obj;
+ struct cl_lock *lock = ols->ols_cl.cls_lock;
+ struct cl_lock_descr *descr = &lock->cll_descr;
+ osc_page_gang_cbt cb;
+ int res;
+ int result;
+
+ ENTRY;
+
+ io->ci_obj = cl_object_top(osc);
+ io->ci_ignore_layout = 1;
+ result = cl_io_init(env, io, CIT_MISC, io->ci_obj);
+ if (result != 0)
+ GOTO(out, result);
+
+ cb = descr->cld_mode == CLM_READ ? check_and_discard_cb : discard_cb;
+ info->oti_fn_index = info->oti_next_index = descr->cld_start;
+ do {
+ res = osc_page_gang_lookup(env, io, cl2osc(osc),
+ info->oti_next_index, descr->cld_end,
+ cb, (void *)lock);
+ if (info->oti_next_index > descr->cld_end)
+ break;
+
+ if (res == CLP_GANG_RESCHED)
+ cond_resched();
+ } while (res != CLP_GANG_OKAY);
+out:
+ cl_io_fini(env, io);
+ RETURN(result);
+}
+
+
git://git.whamcloud.com / fs / lustre-release.git / commitdiff