[Cluster-devel] [PATCH 2/4] gfs2: low-memory forced flush fixes

[Andreas Gruenbacher <agruenba@redhat.com>]

Function gfs2_ail_flush_reqd checks the SDF_FORCE_AIL_FLUSH flag to
determine if an AIL flush should be forced in low-memory situations.
However, it also immediately clears the flag, and when called repeatedly
as in function gfs2_logd, the flag will be lost.  Fix that by pulling
the SDF_FORCE_AIL_FLUSH flag check out of gfs2_ail_flush_reqd.

In addition, in gfs2_writepages, logd needs to be woken up after setting
the SDF_FORCE_AIL_FLUSH flag.

Fixes: b066a4eebd4f ("gfs2: forcibly flush ail to relieve memory pressure")
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/aops.c | 4 +++-
 fs/gfs2/log.c  | 8 ++++----
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/fs/gfs2/aops.c b/fs/gfs2/aops.c
index 5f02542370c4..d15a10a18962 100644
--- a/fs/gfs2/aops.c
+++ b/fs/gfs2/aops.c
@@ -189,8 +189,10 @@ static int gfs2_writepages(struct address_space *mapping,
 	 * pages held in the ail that it can't find.
 	 */
 	ret = iomap_writepages(mapping, wbc, &wpc, &gfs2_writeback_ops);
-	if (ret == 0)
+	if (ret == 0) {
 		set_bit(SDF_FORCE_AIL_FLUSH, &sdp->sd_flags);
+		wake_up(&sdp->sd_logd_waitq);
+	}
 	return ret;
 }
 
diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index d3da259820e3..aaca22f2aa2d 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -1282,9 +1282,6 @@ static inline int gfs2_ail_flush_reqd(struct gfs2_sbd *sdp)
 {
 	unsigned int used_blocks = sdp->sd_jdesc->jd_blocks - atomic_read(&sdp->sd_log_blks_free);
 
-	if (test_and_clear_bit(SDF_FORCE_AIL_FLUSH, &sdp->sd_flags))
-		return 1;
-
 	return used_blocks + atomic_read(&sdp->sd_log_blks_needed) >=
 		atomic_read(&sdp->sd_log_thresh2);
 }
@@ -1325,7 +1322,9 @@ int gfs2_logd(void *data)
 						  GFS2_LFC_LOGD_JFLUSH_REQD);
 		}
 
-		if (gfs2_ail_flush_reqd(sdp)) {
+		if (test_bit(SDF_FORCE_AIL_FLUSH, &sdp->sd_flags) ||
+		    gfs2_ail_flush_reqd(sdp)) {
+			clear_bit(SDF_FORCE_AIL_FLUSH, &sdp->sd_flags);
 			gfs2_ail1_start(sdp);
 			gfs2_ail1_wait(sdp);
 			gfs2_ail1_empty(sdp, 0);
@@ -1338,6 +1337,7 @@ int gfs2_logd(void *data)
 		try_to_freeze();
 
 		t = wait_event_interruptible_timeout(sdp->sd_logd_waitq,
+				test_bit(SDF_FORCE_AIL_FLUSH, &sdp->sd_flags) ||
 				gfs2_ail_flush_reqd(sdp) ||
 				gfs2_jrnl_flush_reqd(sdp) ||
 				kthread_should_stop(),
-- 
2.40.1