[LU-10407] osc_cache.c:1141:osc_extent_make_ready()) ASSERTION( last_oap_count > 0 ) failed:

Related — Thu, 14 Jan 2021 22:35:31 +0000

while testing an own patch I hit a this panic.
As I see, it's result of not atomically counting of unstable pages.
osc_io_commit_async add to cache and unlock an osc object, and size will be update a short after. osc_io_unplug called from brw_queue_work and found a pages in cache, when tries to count an unstable pages number while panic a hit.

this panic can easy replicated if we have delay a size updates with patch

diff --git a/lustre/osc/osc_io.c b/lustre/osc/osc_io.c
index 3d353324f1..5471b96ec1 100644
--- a/lustre/osc/osc_io.c
+++ b/lustre/osc/osc_io.c
@@ -267,7 +267,7 @@ int osc_io_commit_async(const struct lu_env *env,
 	struct osc_object *osc = cl2osc(ios->cis_obj);
 	struct cl_page  *page;
 	struct cl_page  *last_page;
-	struct osc_page *opg;
+	struct osc_page *opg = NULL;
 	int result = 0;
 	ENTRY;
 
@@ -311,9 +311,6 @@ int osc_io_commit_async(const struct lu_env *env,
 				break;
 		}
 
-		osc_page_touch_at(env, osc2cl(osc), osc_index(opg),
-				  page == last_page ? to : PAGE_SIZE);
-
 		cl_page_list_del(env, qin, page);
 
 		(*cb)(env, io, page);
@@ -321,6 +318,9 @@ int osc_io_commit_async(const struct lu_env *env,
 		 * complete at any time. */
 	}
 
+	osc_page_touch_at(env, osc2cl(osc), osc_index(opg),
+			  page == last_page ? to : PAGE_SIZE);
+
 	/* for sync write, kernel will wait for this page to be flushed before
 	 * osc_io_end() is called, so release it earlier.
 	 * for mkwrite(), it's known there is no further pages. */

panic hit constantly with

ONLY=42 REFORMAT=yes sh sanity.sh

typically in 42e test,.

Whamcloud Community JIRA

[LU-10407] osc_cache.c:1141:osc_extent_make_ready()) ASSERTION( last_oap_count > 0 ) failed: