Commit e1fa9ea8 authored by Andreas Gruenbacher's avatar Andreas Gruenbacher
Browse files

gfs2: Stop using glock holder auto-demotion for now 



We're having unresolved issues with the glock holder auto-demotion mechanism
introduced in commit dc732906.  This mechanism was assumed to be essential
for avoiding frequent short reads and writes until commit 296abc0d
("gfs2: No short reads or writes upon glock contention").  Since then,
when the inode glock is lost, it is simply re-acquired and the operation
is resumed.  This means that apart from the performance penalty, we
might as well drop the inode glock before faulting in pages, and
re-acquire it afterwards.

Signed-off-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
parent fa5dfa64

fs/gfs2/file.c

+14 −32
Original line number Diff line number Diff line
@@ -832,7 +832,6 @@ 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,
@@ -845,15 +844,11 @@ 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_holder_allow_demote(gh);

		gfs2_glock_dq(gh);

		window_size -= fault_in_iov_iter_writeable(to, window_size);

		gfs2_holder_disallow_demote(gh);

		if (window_size) {

			if (gfs2_holder_queued(gh))

				goto retry_under_glock;

		if (window_size)

			goto retry;

	}

	}

out_unlock:

	if (gfs2_holder_queued(gh))

		gfs2_glock_dq(gh);
@@ -900,7 +895,6 @@ 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,
@@ -916,15 +910,11 @@ 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_holder_allow_demote(gh);

		gfs2_glock_dq(gh);

		window_size -= fault_in_iov_iter_readable(from, window_size);

		gfs2_holder_disallow_demote(gh);

		if (window_size) {

			if (gfs2_holder_queued(gh))

				goto retry_under_glock;

		if (window_size)

			goto retry;

	}

	}

out_unlock:

	if (gfs2_holder_queued(gh))

		gfs2_glock_dq(gh);
@@ -974,7 +964,6 @@ 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();
@@ -984,15 +973,11 @@ 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_holder_allow_demote(&gh);

		gfs2_glock_dq(&gh);

		window_size -= fault_in_iov_iter_writeable(to, window_size);

		gfs2_holder_disallow_demote(&gh);

		if (window_size) {

			if (gfs2_holder_queued(&gh))

				goto retry_under_glock;

		if (window_size)

			goto retry;

	}

	}

out_unlock:

	if (gfs2_holder_queued(&gh))

		gfs2_glock_dq(&gh);
@@ -1030,22 +1015,17 @@ 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_unlock;

			goto out_uninit;

		}

		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);
@@ -1073,8 +1053,10 @@ 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))

		goto retry_under_glock;

	if (should_fault_in_pages(from, iocb, &prev_count, &window_size)) {

		gfs2_glock_dq(gh);

		goto retry;

	}

out_unlock:

	if (gfs2_holder_queued(gh))

		gfs2_glock_dq(gh);