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From: Andreas Gruenbacher <agruenba@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Christoph Hellwig <hch@infradead.org>,
	"Darrick J. Wong" <djwong@kernel.org>
Cc: Jan Kara <jack@suse.cz>,
	Andreas Gruenbacher <agruenba@redhat.com>,
	linux-kernel@vger.kernel.org, cluster-devel@redhat.com,
	linux-fsdevel@vger.kernel.org, ocfs2-devel@oss.oracle.com
Subject: [Ocfs2-devel] [PATCH v6 11/19] gfs2: Move the inode glock locking to gfs2_file_buffered_write
Date: Thu, 19 Aug 2021 21:40:54 +0200	[thread overview]
Message-ID: <20210819194102.1491495-12-agruenba@redhat.com> (raw)
In-Reply-To: <20210819194102.1491495-1-agruenba@redhat.com>

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 user pages while holding a
glock in a subsequent patch.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/bmap.c | 60 +-------------------------------------------------
 fs/gfs2/file.c | 27 +++++++++++++++++++++++
 2 files changed, 28 insertions(+), 59 deletions(-)

diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index ed8b67b21718..0d90f1809efb 100644
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -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, struct iomap *iomap)
 {
@@ -1119,11 +1079,6 @@ 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)
@@ -1136,12 +1091,6 @@ 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;
@@ -1169,10 +1118,7 @@ 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;
 }
@@ -1220,15 +1166,11 @@ 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;
 }
 
diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index 55ec1cadc9e6..813154d60834 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -880,11 +880,38 @@ 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 (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;
 }
 
-- 
2.26.3


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  parent reply	other threads:[~2021-08-19 19:42 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-19 19:40 [Ocfs2-devel] [PATCH v6 00/19] gfs2: Fix mmap + page fault deadlocks Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 01/19] iov_iter: Fix iov_iter_get_pages{, _alloc} page fault return value Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 02/19] powerpc/kvm: Fix kvm_use_magic_page Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 03/19] Turn fault_in_pages_{readable, writeable} into fault_in_{readable, writeable} Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 04/19] Turn iov_iter_fault_in_readable into fault_in_iov_iter_readable Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 05/19] iov_iter: Introduce fault_in_iov_iter_writeable Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 06/19] gfs2: Add wrapper for iomap_file_buffered_write Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 07/19] gfs2: Clean up function may_grant Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 08/19] gfs2: Eliminate vestigial HIF_FIRST Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 09/19] gfs2: Remove redundant check from gfs2_glock_dq Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 10/19] gfs2: Introduce flag for glock holder auto-demotion Andreas Gruenbacher
2021-08-20  9:35   ` [Ocfs2-devel] [Cluster-devel] " Steven Whitehouse
2021-08-20 13:11     ` Bob Peterson
2021-08-20 13:41       ` Steven Whitehouse
2021-08-20 15:22       ` Andreas Gruenbacher
2021-08-23  8:14         ` Steven Whitehouse
2021-08-23 15:18           ` Andreas Gruenbacher
2021-08-23 16:05             ` Matthew Wilcox
2021-08-23 16:36               ` Bob Peterson
2021-08-23 19:12               ` Andreas Gruenbacher
2021-08-24  7:59             ` Steven Whitehouse
2021-08-20 13:17     ` Andreas Gruenbacher
2021-08-20 13:47       ` Steven Whitehouse
2021-08-20 14:43         ` Andreas Grünbacher
2021-08-19 19:40 ` Andreas Gruenbacher [this message]
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 12/19] gfs2: Fix mmap + page fault deadlocks for buffered I/O Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 13/19] iomap: Fix iomap_dio_rw return value for user copies Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 14/19] iomap: Support partial direct I/O on user copy failures Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 15/19] iomap: Add done_before argument to iomap_dio_rw Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 16/19] gup: Introduce FOLL_NOFAULT flag to disable page faults Andreas Gruenbacher
2021-08-19 19:41 ` [Ocfs2-devel] [PATCH v6 17/19] iov_iter: Introduce nofault " Andreas Gruenbacher
2021-08-19 19:41 ` [Ocfs2-devel] [PATCH v6 18/19] gfs2: Fix mmap + page fault deadlocks for direct I/O Andreas Gruenbacher
2021-08-19 19:41 ` [Ocfs2-devel] [PATCH v6 19/19] gfs2: Eliminate ip->i_gh Andreas Gruenbacher

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