[Cluster-devel] [PATCH 9/9] Revert "gfs2: Stop using glock holder auto-demotion for now"

[Andreas Gruenbacher]

With the glock holder auto-demotion in do_promote fixed, we can
re-enable this feature.

This reverts commit e1fa9ea85ce89207d2ac0316da35a4a7736801f9.

Signed-off-by: Andreas Gruenbacher <agruenba at redhat.com>
---
 fs/gfs2/file.c | 46 ++++++++++++++++++++++++++++++++--------------
 1 file changed, 32 insertions(+), 14 deletions(-)

diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index 2cceb193dcd8..fee69467f11e 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -832,6 +832,7 @@ static ssize_t gfs2_file_direct_read(struct kiocb *iocb, struct iov_iter *to,
 	ret = gfs2_glock_nq(gh);
 	if (ret)
 		goto out_uninit;
+retry_under_glock:
 	pagefault_disable();
 	to->nofault = true;
 	ret = iomap_dio_rw(iocb, to, &gfs2_iomap_ops, NULL,
@@ -845,10 +846,14 @@ static ssize_t gfs2_file_direct_read(struct kiocb *iocb, struct iov_iter *to,
 		read = ret;
 
 	if (should_fault_in_pages(to, iocb, &prev_count, &window_size)) {
-		gfs2_glock_dq(gh);
+		gfs2_holder_allow_demote(gh);
 		window_size -= fault_in_iov_iter_writeable(to, window_size);
-		if (window_size)
+		gfs2_holder_disallow_demote(gh);
+		if (window_size) {
+			if (gfs2_holder_queued(gh))
+				goto retry_under_glock;
 			goto retry;
+		}
 	}
 out_unlock:
 	if (gfs2_holder_queued(gh))
@@ -897,6 +902,7 @@ static ssize_t gfs2_file_direct_write(struct kiocb *iocb, struct iov_iter *from,
 	/* Silently fall back to buffered I/O when writing beyond EOF */
 	if (iocb->ki_pos + iov_iter_count(from) > i_size_read(&ip->i_inode))
 		goto out_unlock;
+retry_under_glock:
 
 	from->nofault = true;
 	ret = iomap_dio_rw(iocb, from, &gfs2_iomap_ops, NULL,
@@ -913,10 +919,14 @@ static ssize_t gfs2_file_direct_write(struct kiocb *iocb, struct iov_iter *from,
 		written = ret;
 
 	if (should_fault_in_pages(from, iocb, &prev_count, &window_size)) {
-		gfs2_glock_dq(gh);
+		gfs2_holder_allow_demote(gh);
 		window_size -= fault_in_iov_iter_readable(from, window_size);
-		if (window_size)
+		gfs2_holder_disallow_demote(gh);
+		if (window_size) {
+			if (gfs2_holder_queued(gh))
+				goto retry_under_glock;
 			goto retry;
+		}
 	}
 out_unlock:
 	if (gfs2_holder_queued(gh))
@@ -968,6 +978,7 @@ static ssize_t gfs2_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
 	ret = gfs2_glock_nq(&gh);
 	if (ret)
 		goto out_uninit;
+retry_under_glock:
 	pagefault_disable();
 	ret = generic_file_read_iter(iocb, to);
 	pagefault_enable();
@@ -977,10 +988,14 @@ static ssize_t gfs2_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
 		read += ret;
 
 	if (should_fault_in_pages(to, iocb, &prev_count, &window_size)) {
-		gfs2_glock_dq(&gh);
+		gfs2_holder_allow_demote(&gh);
 		window_size -= fault_in_iov_iter_writeable(to, window_size);
-		if (window_size)
+		gfs2_holder_disallow_demote(&gh);
+		if (window_size) {
+			if (gfs2_holder_queued(&gh))
+				goto retry_under_glock;
 			goto retry;
+		}
 	}
 out_unlock:
 	if (gfs2_holder_queued(&gh))
@@ -1019,17 +1034,22 @@ static ssize_t gfs2_file_buffered_write(struct kiocb *iocb,
 
 	gfs2_holder_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, gh);
 retry:
+	ret = gfs2_glock_nq(gh);
+	if (ret)
+		goto out_uninit;
 	if (should_fault_in_pages(from, iocb, &prev_count, &window_size)) {
+retry_under_glock:
+		gfs2_holder_allow_demote(gh);
 		window_size -= fault_in_iov_iter_readable(from, window_size);
+		gfs2_holder_disallow_demote(gh);
 		if (!window_size) {
 			ret = -EFAULT;
-			goto out_uninit;
+			goto out_unlock;
 		}
+		if (!gfs2_holder_queued(gh))
+			goto retry;
 		from->count = min(from->count, window_size);
 	}
-	ret = gfs2_glock_nq(gh);
-	if (ret)
-		goto out_uninit;
 
 	if (inode == sdp->sd_rindex) {
 		struct gfs2_inode *m_ip = GFS2_I(sdp->sd_statfs_inode);
@@ -1057,10 +1077,8 @@ static ssize_t gfs2_file_buffered_write(struct kiocb *iocb,
 		goto out_unlock;
 
 	from->count = orig_count - written;
-	if (should_fault_in_pages(from, iocb, &prev_count, &window_size)) {
-		gfs2_glock_dq(gh);
-		goto retry;
-	}
+	if (should_fault_in_pages(from, iocb, &prev_count, &window_size))
+		goto retry_under_glock;
 out_unlock:
 	if (gfs2_holder_queued(gh))
 		gfs2_glock_dq(gh);
-- 
2.35.1