[Cluster-devel] [PATCH] gfs2: Take inode glock exclusively when mounted without noatime

[Andreas Gruenbacher <agruenba@redhat.com>]

Commit 20f829999c38 ("gfs2: Rework read and page fault locking") has lifted the
glock lock taking from the low-level ->readpage and ->readahead address space
operations to the higher-level ->read_iter file and ->fault vm operations.  The
glocks are still taken in LM_ST_SHARED mode only.  On filesystems mounted
without the noatime option, ->read_iter needs to update the atime as well
though, so we currently run into a failed locking mode assertion in
gfs2_dirty_inode.  Fix that by taking the glock in LM_ST_EXCLUSIVE mode on
filesystems mounted without the noatime mount option.

Faulting in pages doesn't update the atime, so in the ->fault vm operation,
taking the glock in LM_ST_SHARED mode is enough.

Reported-by: Alexander Aring <aahringo@redhat.com>
Fixes: 20f829999c38 ("gfs2: Rework read and page fault locking")
Cc: stable at vger.kernel.org # v5.8+
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index b39b339feddc..162a81873dcd 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -849,6 +849,7 @@ static ssize_t gfs2_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
 	struct gfs2_inode *ip;
 	struct gfs2_holder gh;
 	size_t written = 0;
+	unsigned int state;
 	ssize_t ret;
 
 	if (iocb->ki_flags & IOCB_DIRECT) {
@@ -871,7 +872,8 @@ static ssize_t gfs2_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
 			return ret;
 	}
 	ip = GFS2_I(iocb->ki_filp->f_mapping->host);
-	gfs2_holder_init(ip->i_gl, LM_ST_SHARED, 0, &gh);
+	state = IS_NOATIME(&ip->i_inode) ? LM_ST_SHARED : LM_ST_EXCLUSIVE;
+	gfs2_holder_init(ip->i_gl, state, 0, &gh);
 	ret = gfs2_glock_nq(&gh);
 	if (ret)
 		goto out_uninit;