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LU-17744 ldiskfs: mballoc stats fixes
[fs/lustre-release.git] / lustre / osc / osc_page.c
index d0fd5e2..b97d4f9 100644 (file)
@@ -27,7 +27,6 @@
  */
 /*
  * This file is part of Lustre, http://www.lustre.org/
- * Lustre is a trademark of Sun Microsystems, Inc.
  *
  * Implementation of cl_page for OSC layer.
  *
@@ -82,19 +81,20 @@ static void osc_page_transfer_put(const struct lu_env *env,
 static void osc_page_transfer_add(const struct lu_env *env,
                                   struct osc_page *opg, enum cl_req_type crt)
 {
-       struct osc_object *obj = cl2osc(opg->ops_cl.cpl_obj);
+       struct osc_object *obj = osc_page_object(opg);
 
        osc_lru_use(osc_cli(obj), opg);
 }
 
-int osc_page_cache_add(const struct lu_env *env, struct osc_page *opg,
-                      struct cl_io *io, cl_commit_cbt cb)
+int osc_page_cache_add(const struct lu_env *env, struct osc_object *osc,
+                      struct osc_page *opg, struct cl_io *io,
+                      cl_commit_cbt cb)
 {
        int result;
        ENTRY;
 
        osc_page_transfer_get(opg, "transfer\0cache");
-       result = osc_queue_async_io(env, io, opg, cb);
+       result = osc_queue_async_io(env, io, osc, opg, cb);
        if (result != 0)
                osc_page_transfer_put(env, opg);
        else
@@ -107,16 +107,8 @@ void osc_index2policy(union ldlm_policy_data *policy,
                      const struct cl_object *obj, pgoff_t start, pgoff_t end)
 {
        memset(policy, 0, sizeof *policy);
-       policy->l_extent.start = cl_offset(obj, start);
-       policy->l_extent.end   = cl_offset(obj, end + 1) - 1;
-}
-
-static inline s64 osc_submit_duration(struct osc_page *opg)
-{
-       if (ktime_to_ns(opg->ops_submit_time) == 0)
-               return 0;
-
-       return ktime_ms_delta(ktime_get(), opg->ops_submit_time);
+       policy->l_extent.start = start << PAGE_SHIFT;
+       policy->l_extent.end = ((end + 1) << PAGE_SHIFT) - 1;
 }
 
 static int osc_page_print(const struct lu_env *env,
@@ -125,32 +117,32 @@ static int osc_page_print(const struct lu_env *env,
 {
        struct osc_page *opg = cl2osc_page(slice);
        struct osc_async_page *oap = &opg->ops_oap;
-       struct osc_object *obj = cl2osc(slice->cpl_obj);
+       struct osc_object *obj = osc_page_object(opg);
        struct client_obd *cli = &osc_export(obj)->exp_obd->u.cli;
 
        return (*printer)(env, cookie, LUSTRE_OSC_NAME"-page@%p %lu: "
-                         "1< %#x %d %c %c > "
-                         "2< %lld %u %u %#x %#x | %p %p %p > "
-                         "3< %d %lld %d > "
+                         "1< %d %c %c > "
+                         "2< %lld %u %u %#x %#x | %p %p > "
+                         "3< %d %d > "
                          "4< %d %d %d %lu %c | %c %c %c %c > "
                          "5< %c %c %c %c | %d %c | %d %c %c>\n",
                          opg, osc_index(opg),
                          /* 1 */
-                         oap->oap_magic, oap->oap_cmd,
+                         oap->oap_cmd,
                          list_empty_marker(&oap->oap_pending_item),
                          list_empty_marker(&oap->oap_rpc_item),
                          /* 2 */
                          oap->oap_obj_off, oap->oap_page_off, oap->oap_count,
                          oap->oap_async_flags, oap->oap_brw_flags,
-                         oap->oap_request, oap->oap_cli, obj,
+                         cli, obj,
                          /* 3 */
                          opg->ops_transfer_pinned,
-                         osc_submit_duration(opg), opg->ops_srvlock,
+                         opg->ops_srvlock,
                          /* 4 */
                          cli->cl_r_in_flight, cli->cl_w_in_flight,
                          cli->cl_max_rpcs_in_flight,
                          cli->cl_avail_grant,
-                         list_empty_marker(&cli->cl_cache_waiters),
+                         waitqueue_active(&cli->cl_cache_waiters) ? '+' : '-',
                          list_empty_marker(&cli->cl_loi_ready_list),
                          list_empty_marker(&cli->cl_loi_hp_ready_list),
                          list_empty_marker(&cli->cl_loi_write_list),
@@ -171,7 +163,7 @@ static void osc_page_delete(const struct lu_env *env,
                            const struct cl_page_slice *slice)
 {
        struct osc_page   *opg = cl2osc_page(slice);
-       struct osc_object *obj = cl2osc(opg->ops_cl.cpl_obj);
+       struct osc_object *obj = osc_page_object(opg);
        int rc;
 
        ENTRY;
@@ -213,11 +205,12 @@ static void osc_page_clip(const struct lu_env *env,
        struct osc_page       *opg = cl2osc_page(slice);
        struct osc_async_page *oap = &opg->ops_oap;
 
+       CDEBUG(D_CACHE, "from %d, to %d\n", from, to);
+
        opg->ops_from = from;
-       opg->ops_to   = to;
-       spin_lock(&oap->oap_lock);
+       /* argument @to is exclusive, but @ops_to is inclusive */
+       opg->ops_to   = to - 1;
        oap->oap_async_flags |= ASYNC_COUNT_STABLE;
-       spin_unlock(&oap->oap_lock);
 }
 
 static int osc_page_flush(const struct lu_env *env,
@@ -235,11 +228,17 @@ static void osc_page_touch(const struct lu_env *env,
                          const struct cl_page_slice *slice, size_t to)
 {
        struct osc_page *opg = cl2osc_page(slice);
-       struct cl_object *obj = opg->ops_cl.cpl_obj;
+       struct cl_object *obj = osc2cl(osc_page_object(opg));
 
        osc_page_touch_at(env, obj, osc_index(opg), to);
 }
 
+static const struct cl_page_operations osc_transient_page_ops = {
+       .cpo_print         = osc_page_print,
+       .cpo_delete        = osc_page_delete,
+       .cpo_clip           = osc_page_clip,
+};
+
 static const struct cl_page_operations osc_page_ops = {
        .cpo_print         = osc_page_print,
        .cpo_delete        = osc_page_delete,
@@ -249,30 +248,30 @@ static const struct cl_page_operations osc_page_ops = {
 };
 
 int osc_page_init(const struct lu_env *env, struct cl_object *obj,
-                 struct cl_page *page, pgoff_t index)
+                 struct cl_page *cl_page, pgoff_t index)
 {
        struct osc_object *osc = cl2osc(obj);
-       struct osc_page   *opg = cl_object_page_slice(obj, page);
+       struct osc_page *opg = cl_object_page_slice(obj, cl_page);
        struct osc_io *oio = osc_env_io(env);
        int result;
 
        opg->ops_from = 0;
-       opg->ops_to   = PAGE_SIZE;
+       opg->ops_to = PAGE_SIZE - 1;
 
        INIT_LIST_HEAD(&opg->ops_lru);
 
-       result = osc_prep_async_page(osc, opg, page->cp_vmpage,
-                                    cl_offset(obj, index));
+       result = osc_prep_async_page(osc, opg, cl_page, index << PAGE_SHIFT);
        if (result != 0)
                return result;
 
        opg->ops_srvlock = osc_io_srvlock(oio);
-       cl_page_slice_add(page, &opg->ops_cl, obj, index,
-                         &osc_page_ops);
-
 
-       /* reserve an LRU space for this page */
-       if (page->cp_type == CPT_CACHEABLE) {
+       if (cl_page->cp_type == CPT_TRANSIENT) {
+               cl_page_slice_add(cl_page, &opg->ops_cl, obj,
+                                 &osc_transient_page_ops);
+       } else if (cl_page->cp_type == CPT_CACHEABLE) {
+               cl_page_slice_add(cl_page, &opg->ops_cl, obj, &osc_page_ops);
+               /* reserve an LRU space for this page */
                result = osc_lru_alloc(env, osc_cli(osc), opg);
                if (result == 0) {
                        result = radix_tree_preload(GFP_NOFS);
@@ -305,22 +304,17 @@ void osc_page_submit(const struct lu_env *env, struct osc_page *opg,
        struct osc_io *oio = osc_env_io(env);
        struct osc_async_page *oap = &opg->ops_oap;
 
-       LASSERTF(oap->oap_magic == OAP_MAGIC, "Bad oap magic: oap %p, "
-                "magic 0x%x\n", oap, oap->oap_magic);
        LASSERT(oap->oap_async_flags & ASYNC_READY);
        LASSERT(oap->oap_async_flags & ASYNC_COUNT_STABLE);
 
-       oap->oap_cmd       = crt == CRT_WRITE ? OBD_BRW_WRITE : OBD_BRW_READ;
-       oap->oap_page_off  = opg->ops_from;
-       oap->oap_count     = opg->ops_to - opg->ops_from;
+       oap->oap_cmd = crt == CRT_WRITE ? OBD_BRW_WRITE : OBD_BRW_READ;
+       oap->oap_page_off = opg->ops_from;
+       oap->oap_count = opg->ops_to - opg->ops_from + 1;
        oap->oap_brw_flags = OBD_BRW_SYNC | brw_flags;
 
-       if (oio->oi_cap_sys_resource) {
-               oap->oap_brw_flags |= OBD_BRW_NOQUOTA;
-               oap->oap_cmd |= OBD_BRW_NOQUOTA;
-       }
+       if (oio->oi_cap_sys_resource)
+               oap->oap_brw_flags |= OBD_BRW_SYS_RESOURCE;
 
-       opg->ops_submit_time = ktime_get();
        osc_page_transfer_get(opg, "transfer\0imm");
        osc_page_transfer_add(env, opg, crt);
 }
@@ -369,7 +363,7 @@ static int osc_cache_too_much(struct client_obd *cli)
        unsigned long budget;
 
        LASSERT(cache != NULL);
-       budget = cache->ccc_lru_max / (atomic_read(&cache->ccc_users) - 2);
+       budget = cache->ccc_lru_max / (refcount_read(&cache->ccc_users) - 2);
 
        /* if it's going to run out LRU slots, we should free some, but not
         * too much to maintain faireness among OSCs. */
@@ -503,25 +497,25 @@ static void osc_lru_use(struct client_obd *cli, struct osc_page *opg)
        }
 }
 
-static void discard_pagevec(const struct lu_env *env, struct cl_io *io,
-                               struct cl_page **pvec, int max_index)
+static void discard_cl_pages(const struct lu_env *env, struct cl_io *io,
+                            struct cl_page **pvec, int max_index)
 {
-       struct pagevec *pagevec = &osc_env_info(env)->oti_pagevec;
+       struct folio_batch *fbatch = &osc_env_info(env)->oti_fbatch;
        int i;
 
-       ll_pagevec_init(pagevec, 0);
+       ll_folio_batch_init(fbatch, 0);
        for (i = 0; i < max_index; i++) {
                struct cl_page *page = pvec[i];
 
+               LASSERT(page->cp_type != CPT_TRANSIENT);
                LASSERT(cl_page_is_owned(page, io));
-               cl_page_delete(env, page);
                cl_page_discard(env, io, page);
                cl_page_disown(env, io, page);
-               cl_pagevec_put(env, page, pagevec);
+               cl_batch_put(env, page, fbatch);
 
                pvec[i] = NULL;
        }
-       pagevec_release(pagevec);
+       folio_batch_release(fbatch);
 }
 
 /**
@@ -597,8 +591,8 @@ long osc_lru_shrink(const struct lu_env *env, struct client_obd *cli,
                if (--maxscan < 0)
                        break;
 
-               opg = list_entry(cli->cl_lru_list.next, struct osc_page,
-                                ops_lru);
+               opg = list_first_entry(&cli->cl_lru_list, struct osc_page,
+                                      ops_lru);
                page = opg->ops_cl.cpl_page;
                if (lru_page_busy(cli, page)) {
                        list_move_tail(&opg->ops_lru, &cli->cl_lru_list);
@@ -613,12 +607,13 @@ long osc_lru_shrink(const struct lu_env *env, struct client_obd *cli,
                        spin_unlock(&cli->cl_lru_list_lock);
 
                        if (clobj != NULL) {
-                               discard_pagevec(env, io, pvec, index);
+                               discard_cl_pages(env, io, pvec, index);
                                index = 0;
 
                                cl_io_fini(env, io);
                                cl_object_put(env, clobj);
                                clobj = NULL;
+                               cond_resched();
                        }
 
                        clobj = tmp;
@@ -658,7 +653,7 @@ long osc_lru_shrink(const struct lu_env *env, struct client_obd *cli,
                pvec[index++] = page;
                if (unlikely(index == OTI_PVEC_SIZE)) {
                        spin_unlock(&cli->cl_lru_list_lock);
-                       discard_pagevec(env, io, pvec, index);
+                       discard_cl_pages(env, io, pvec, index);
                        index = 0;
 
                        spin_lock(&cli->cl_lru_list_lock);
@@ -670,16 +665,17 @@ long osc_lru_shrink(const struct lu_env *env, struct client_obd *cli,
        spin_unlock(&cli->cl_lru_list_lock);
 
        if (clobj != NULL) {
-               discard_pagevec(env, io, pvec, index);
+               discard_cl_pages(env, io, pvec, index);
 
                cl_io_fini(env, io);
                cl_object_put(env, clobj);
+               cond_resched();
        }
 
        atomic_dec(&cli->cl_lru_shrinkers);
        if (count > 0) {
                atomic_long_add(count, cli->cl_lru_left);
-               wake_up_all(&osc_lru_waitq);
+               wake_up(&osc_lru_waitq);
        }
        RETURN(count > 0 ? count : rc);
 }
@@ -695,6 +691,7 @@ static long osc_lru_reclaim(struct client_obd *cli, unsigned long npages)
 {
        struct lu_env *env;
        struct cl_client_cache *cache = cli->cl_cache;
+       struct client_obd *scan;
        int max_scans;
        __u16 refcheck;
        long rc = 0;
@@ -732,21 +729,21 @@ static long osc_lru_reclaim(struct client_obd *cli, unsigned long npages)
        cache->ccc_lru_shrinkers++;
        list_move_tail(&cli->cl_lru_osc, &cache->ccc_lru);
 
-       max_scans = atomic_read(&cache->ccc_users) - 2;
-       while (--max_scans > 0 && !list_empty(&cache->ccc_lru)) {
-               cli = list_entry(cache->ccc_lru.next, struct client_obd,
-                                cl_lru_osc);
-
+       max_scans = refcount_read(&cache->ccc_users) - 2;
+       while (--max_scans > 0 &&
+              (scan = list_first_entry_or_null(&cache->ccc_lru,
+                                                 struct client_obd,
+                                                 cl_lru_osc)) != NULL) {
                CDEBUG(D_CACHE, "%s: cli %p LRU pages: %ld, busy: %ld.\n",
-                       cli_name(cli), cli,
-                       atomic_long_read(&cli->cl_lru_in_list),
-                       atomic_long_read(&cli->cl_lru_busy));
+                      cli_name(scan), scan,
+                      atomic_long_read(&scan->cl_lru_in_list),
+                      atomic_long_read(&scan->cl_lru_busy));
 
-               list_move_tail(&cli->cl_lru_osc, &cache->ccc_lru);
-               if (osc_cache_too_much(cli) > 0) {
+               list_move_tail(&scan->cl_lru_osc, &cache->ccc_lru);
+               if (osc_cache_too_much(scan) > 0) {
                        spin_unlock(&cache->ccc_lru_lock);
 
-                       rc = osc_lru_shrink(env, cli, npages, true);
+                       rc = osc_lru_shrink(env, scan, npages, true);
                        spin_lock(&cache->ccc_lru_lock);
                        if (rc >= npages)
                                break;
@@ -759,7 +756,7 @@ static long osc_lru_reclaim(struct client_obd *cli, unsigned long npages)
 out:
        cl_env_put(env, &refcheck);
        CDEBUG(D_CACHE, "%s: cli %p freed %ld pages.\n",
-               cli_name(cli), cli, rc);
+              cli_name(cli), cli, rc);
        return rc;
 }
 
@@ -794,6 +791,13 @@ static int osc_lru_alloc(const struct lu_env *env, struct client_obd *cli,
                        break;
                if (rc > 0)
                        continue;
+               /* IO issued by readahead, don't try hard */
+               if (oio->oi_is_readahead) {
+                       if (atomic_long_read(cli->cl_lru_left) > 0)
+                               continue;
+                       rc = -EBUSY;
+                       break;
+               }
 
                cond_resched();
                rc = l_wait_event_abortable(
@@ -826,16 +830,23 @@ unsigned long osc_lru_reserve(struct client_obd *cli, unsigned long npages)
        unsigned long reserved = 0;
        unsigned long max_pages;
        unsigned long c;
+       int rc;
 
-       /* reserve a full RPC window at most to avoid that a thread accidentally
-        * consumes too many LRU slots */
-       max_pages = cli->cl_max_pages_per_rpc * cli->cl_max_rpcs_in_flight;
-       if (npages > max_pages)
-               npages = max_pages;
-
+again:
        c = atomic_long_read(cli->cl_lru_left);
        if (c < npages && osc_lru_reclaim(cli, npages) > 0)
                c = atomic_long_read(cli->cl_lru_left);
+
+       if (c < npages) {
+               /*
+                * Trigger writeback in the hope some LRU slot could
+                * be freed.
+                */
+               rc = ptlrpcd_queue_work(cli->cl_writeback_work);
+               if (rc)
+                       return 0;
+       }
+
        while (c >= npages) {
                if (c == atomic_long_cmpxchg(cli->cl_lru_left, c, c - npages)) {
                        reserved = npages;
@@ -843,6 +854,16 @@ unsigned long osc_lru_reserve(struct client_obd *cli, unsigned long npages)
                }
                c = atomic_long_read(cli->cl_lru_left);
        }
+
+       if (reserved != npages) {
+               cond_resched();
+               rc = l_wait_event_abortable(
+                       osc_lru_waitq,
+                       atomic_long_read(cli->cl_lru_left) > 0);
+               goto again;
+       }
+
+       max_pages = cli->cl_max_pages_per_rpc * cli->cl_max_rpcs_in_flight;
        if (atomic_long_read(cli->cl_lru_left) < max_pages) {
                /* If there aren't enough pages in the per-OSC LRU then
                 * wake up the LRU thread to try and clear out space, so
@@ -866,7 +887,7 @@ unsigned long osc_lru_reserve(struct client_obd *cli, unsigned long npages)
 void osc_lru_unreserve(struct client_obd *cli, unsigned long npages)
 {
        atomic_long_add(npages, cli->cl_lru_left);
-       wake_up_all(&osc_lru_waitq);
+       wake_up(&osc_lru_waitq);
 }
 
 /**
@@ -875,8 +896,17 @@ void osc_lru_unreserve(struct client_obd *cli, unsigned long npages)
  * In practice this can work pretty good because the pages in the same RPC
  * are likely from the same page zone.
  */
+#ifdef HAVE_NR_UNSTABLE_NFS
+/* Old kernels use a separate counter for unstable pages,
+ * newer kernels treat them like any other writeback.
+ * (see Linux commit: v5.7-467-g8d92890bd6b8)
+ */
+#define NR_ZONE_WRITE_PENDING          ((enum zone_stat_item)NR_UNSTABLE_NFS)
+#elif !defined(HAVE_NR_ZONE_WRITE_PENDING)
+#define NR_ZONE_WRITE_PENDING          ((enum zone_stat_item)NR_WRITEBACK)
+#endif
+
 static inline void unstable_page_accounting(struct ptlrpc_bulk_desc *desc,
-                                           struct osc_brw_async_args *aa,
                                            int factor)
 {
        int page_count;
@@ -884,18 +914,15 @@ static inline void unstable_page_accounting(struct ptlrpc_bulk_desc *desc,
        int count = 0;
        int i;
 
-       if (desc != NULL) {
-               page_count = desc->bd_iov_count;
-       } else {
-               page_count = aa->aa_page_count;
-       }
+       ENTRY;
+
+       page_count = desc->bd_iov_count;
+
+       CDEBUG(D_PAGE, "%s %d unstable pages\n",
+              factor == 1 ? "adding" : "removing", page_count);
 
        for (i = 0; i < page_count; i++) {
-               void *pz;
-               if (desc)
-                       pz = page_zone(desc->bd_vec[i].kiov_page);
-               else
-                       pz = page_zone(aa->aa_ppga[i]->pg);
+               void *pz = page_zone(desc->bd_vec[i].bv_page);
 
                if (likely(pz == zone)) {
                        ++count;
@@ -903,7 +930,7 @@ static inline void unstable_page_accounting(struct ptlrpc_bulk_desc *desc,
                }
 
                if (count > 0) {
-                       mod_zone_page_state(zone, NR_UNSTABLE_NFS,
+                       mod_zone_page_state(zone, NR_ZONE_WRITE_PENDING,
                                            factor * count);
                        count = 0;
                }
@@ -911,19 +938,20 @@ static inline void unstable_page_accounting(struct ptlrpc_bulk_desc *desc,
                ++count;
        }
        if (count > 0)
-               mod_zone_page_state(zone, NR_UNSTABLE_NFS, factor * count);
+               mod_zone_page_state(zone, NR_ZONE_WRITE_PENDING,
+                                   factor * count);
+
+       EXIT;
 }
 
-static inline void add_unstable_page_accounting(struct ptlrpc_bulk_desc *desc,
-                                               struct osc_brw_async_args *aa)
+static inline void add_unstable_pages(struct ptlrpc_bulk_desc *desc)
 {
-       unstable_page_accounting(desc, aa, 1);
+       unstable_page_accounting(desc, 1);
 }
 
-static inline void dec_unstable_page_accounting(struct ptlrpc_bulk_desc *desc,
-                                               struct osc_brw_async_args *aa)
+static inline void dec_unstable_pages(struct ptlrpc_bulk_desc *desc)
 {
-       unstable_page_accounting(desc, aa, -1);
+       unstable_page_accounting(desc, -1);
 }
 
 /**
@@ -940,19 +968,21 @@ static inline void dec_unstable_page_accounting(struct ptlrpc_bulk_desc *desc,
 void osc_dec_unstable_pages(struct ptlrpc_request *req)
 {
        struct ptlrpc_bulk_desc *desc       = req->rq_bulk;
-       struct osc_brw_async_args *aa = (void *)&req->rq_async_args;
        struct client_obd       *cli        = &req->rq_import->imp_obd->u.cli;
        int                      page_count;
        long                     unstable_count;
 
-       if (desc)
-               page_count = desc->bd_iov_count;
-       else
-               page_count = aa->aa_page_count;
+       /* no desc means short io, which doesn't have separate unstable pages,
+        * it's just using space inside the RPC itself
+        */
+       if (!desc)
+               return;
+
+       page_count = desc->bd_iov_count;
 
        LASSERT(page_count >= 0);
 
-       dec_unstable_page_accounting(desc, aa);
+       dec_unstable_pages(desc);
 
        unstable_count = atomic_long_sub_return(page_count,
                                                &cli->cl_unstable_count);
@@ -961,8 +991,6 @@ void osc_dec_unstable_pages(struct ptlrpc_request *req)
        unstable_count = atomic_long_sub_return(page_count,
                                           &cli->cl_cache->ccc_unstable_nr);
        LASSERT(unstable_count >= 0);
-       if (unstable_count == 0)
-               wake_up_all(&cli->cl_cache->ccc_unstable_waitq);
 
        if (waitqueue_active(&osc_lru_waitq))
                (void)ptlrpcd_queue_work(cli->cl_lru_work);
@@ -974,7 +1002,6 @@ void osc_dec_unstable_pages(struct ptlrpc_request *req)
 void osc_inc_unstable_pages(struct ptlrpc_request *req)
 {
        struct ptlrpc_bulk_desc *desc = req->rq_bulk;
-       struct osc_brw_async_args *aa = (void *)&req->rq_async_args;
        struct client_obd       *cli  = &req->rq_import->imp_obd->u.cli;
        long                     page_count;
 
@@ -982,12 +1009,15 @@ void osc_inc_unstable_pages(struct ptlrpc_request *req)
        if (cli->cl_cache == NULL || !cli->cl_cache->ccc_unstable_check)
                return;
 
-       if (desc)
-               page_count = desc->bd_iov_count;
-       else
-               page_count = aa->aa_page_count;
+       /* no desc means short io, which doesn't have separate unstable pages,
+        * it's just using space inside the RPC itself
+        */
+       if (!desc)
+               return;
+
+       page_count = desc->bd_iov_count;
 
-       add_unstable_page_accounting(desc, aa);
+       add_unstable_pages(desc);
        atomic_long_add(page_count, &cli->cl_unstable_count);
        atomic_long_add(page_count, &cli->cl_cache->ccc_unstable_nr);
 
@@ -1049,6 +1079,9 @@ unsigned long osc_cache_shrink_count(struct shrinker *sk,
        struct client_obd *cli;
        unsigned long cached = 0;
 
+       if (!osc_page_cache_shrink_enabled)
+               return 0;
+
        spin_lock(&osc_shrink_lock);
        list_for_each_entry(cli, &osc_shrink_list, cl_shrink_list)
                cached += atomic_long_read(&cli->cl_lru_in_list);
@@ -1091,10 +1124,9 @@ unsigned long osc_cache_shrink_scan(struct shrinker *sk,
                return SHRINK_STOP;
 
        spin_lock(&osc_shrink_lock);
-       while (!list_empty(&osc_shrink_list)) {
-               cli = list_entry(osc_shrink_list.next, struct client_obd,
-                                cl_shrink_list);
-
+       while ((cli = list_first_entry_or_null(&osc_shrink_list,
+                                              struct client_obd,
+                                              cl_shrink_list)) != NULL) {
                if (stop_anchor == NULL)
                        stop_anchor = cli;
                else if (cli == stop_anchor)