Commit b924bdab authored by Andreas Gruenbacher's avatar Andreas Gruenbacher
Browse files

gfs2: Move the inode glock locking to gfs2_file_buffered_write 



So far, for buffered writes, we were taking the inode glock in
gfs2_iomap_begin and dropping it in gfs2_iomap_end with the intention of
not holding the inode glock while iomap_write_actor faults in user
pages.  It turns out that iomap_write_actor is called inside iomap_begin
... iomap_end, so the user pages were still faulted in while holding the
inode glock and the locking code in iomap_begin / iomap_end was
completely pointless.

Move the locking into gfs2_file_buffered_write instead.  We'll take care
of the potential deadlocks due to faulting in user pages while holding a
glock in a subsequent patch.

Signed-off-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
parent dc732906

fs/gfs2/bmap.c

+1 −59
Original line number Diff line number Diff line
@@ -961,46 +961,6 @@ static int __gfs2_iomap_get(struct inode *inode, loff_t pos, loff_t length, 
	goto out;

}



static int gfs2_write_lock(struct inode *inode)

{

	struct gfs2_inode *ip = GFS2_I(inode);

	struct gfs2_sbd *sdp = GFS2_SB(inode);

	int error;



	gfs2_holder_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &ip->i_gh);

	error = gfs2_glock_nq(&ip->i_gh);

	if (error)

		goto out_uninit;

	if (&ip->i_inode == sdp->sd_rindex) {

		struct gfs2_inode *m_ip = GFS2_I(sdp->sd_statfs_inode);



		error = gfs2_glock_nq_init(m_ip->i_gl, LM_ST_EXCLUSIVE,

					   GL_NOCACHE, &m_ip->i_gh);

		if (error)

			goto out_unlock;

	}

	return 0;



out_unlock:

	gfs2_glock_dq(&ip->i_gh);

out_uninit:

	gfs2_holder_uninit(&ip->i_gh);

	return error;

}



static void gfs2_write_unlock(struct inode *inode)

{

	struct gfs2_inode *ip = GFS2_I(inode);

	struct gfs2_sbd *sdp = GFS2_SB(inode);



	if (&ip->i_inode == sdp->sd_rindex) {

		struct gfs2_inode *m_ip = GFS2_I(sdp->sd_statfs_inode);



		gfs2_glock_dq_uninit(&m_ip->i_gh);

	}

	gfs2_glock_dq_uninit(&ip->i_gh);

}



static int gfs2_iomap_page_prepare(struct inode *inode, loff_t pos,

				   unsigned len)

{
@@ -1118,11 +1078,6 @@ static int gfs2_iomap_begin_write(struct inode *inode, loff_t pos, 
	return ret;

}



static inline bool gfs2_iomap_need_write_lock(unsigned flags)

{

	return (flags & IOMAP_WRITE) && !(flags & IOMAP_DIRECT);

}



static int gfs2_iomap_begin(struct inode *inode, loff_t pos, loff_t length,

			    unsigned flags, struct iomap *iomap,

			    struct iomap *srcmap)
@@ -1135,12 +1090,6 @@ static int gfs2_iomap_begin(struct inode *inode, loff_t pos, loff_t length, 
		iomap->flags |= IOMAP_F_BUFFER_HEAD;



	trace_gfs2_iomap_start(ip, pos, length, flags);

	if (gfs2_iomap_need_write_lock(flags)) {

		ret = gfs2_write_lock(inode);

		if (ret)

			goto out;

	}



	ret = __gfs2_iomap_get(inode, pos, length, flags, iomap, &mp);

	if (ret)

		goto out_unlock;
@@ -1168,10 +1117,7 @@ static int gfs2_iomap_begin(struct inode *inode, loff_t pos, loff_t length, 
	ret = gfs2_iomap_begin_write(inode, pos, length, flags, iomap, &mp);



out_unlock:

	if (ret && gfs2_iomap_need_write_lock(flags))

		gfs2_write_unlock(inode);

	release_metapath(&mp);

out:

	trace_gfs2_iomap_end(ip, iomap, ret);

	return ret;

}
@@ -1219,15 +1165,11 @@ static int gfs2_iomap_end(struct inode *inode, loff_t pos, loff_t length, 
	}



	if (unlikely(!written))

		goto out_unlock;

		return 0;



	if (iomap->flags & IOMAP_F_SIZE_CHANGED)

		mark_inode_dirty(inode);

	set_bit(GLF_DIRTY, &ip->i_gl->gl_flags);



out_unlock:

	if (gfs2_iomap_need_write_lock(flags))

		gfs2_write_unlock(inode);

	return 0;

}

fs/gfs2/file.c

+27 −0
Original line number Diff line number Diff line
@@ -880,13 +880,40 @@ static ssize_t gfs2_file_buffered_write(struct kiocb *iocb, struct iov_iter *fro 
{

	struct file *file = iocb->ki_filp;

	struct inode *inode = file_inode(file);

	struct gfs2_inode *ip = GFS2_I(inode);

	struct gfs2_sbd *sdp = GFS2_SB(inode);

	ssize_t ret;



	gfs2_holder_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &ip->i_gh);

	ret = gfs2_glock_nq(&ip->i_gh);

	if (ret)

		goto out_uninit;



	if (inode == sdp->sd_rindex) {

		struct gfs2_inode *m_ip = GFS2_I(sdp->sd_statfs_inode);



		ret = gfs2_glock_nq_init(m_ip->i_gl, LM_ST_EXCLUSIVE,

					 GL_NOCACHE, &m_ip->i_gh);

		if (ret)

			goto out_unlock;

	}



	current->backing_dev_info = inode_to_bdi(inode);

	ret = iomap_file_buffered_write(iocb, from, &gfs2_iomap_ops);

	current->backing_dev_info = NULL;

	if (ret > 0)

		iocb->ki_pos += ret;



	if (inode == sdp->sd_rindex) {

		struct gfs2_inode *m_ip = GFS2_I(sdp->sd_statfs_inode);



		gfs2_glock_dq_uninit(&m_ip->i_gh);

	}



out_unlock:

	gfs2_glock_dq(&ip->i_gh);

out_uninit:

	gfs2_holder_uninit(&ip->i_gh);

	return ret;

}