linux-ext4 - [PATCH] common/rc: Fix _check_s

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Date:   Wed,  2 Dec 2020 13:41:45 -0800
From:   ira.weiny@...el.com
To:     fstests@...r.kernel.org, Christoph Hellwig <hch@....de>,
        Eric Sandeen <sandeen@...hat.com>
Cc:     Ira Weiny <ira.weiny@...el.com>, linux-kernel@...r.kernel.org,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Chinner <david@...morbit.com>,
        "Theodore Y. Ts'o" <tytso@....edu>, Jan Kara <jack@...e.cz>,
        Jeff Moyer <jmoyer@...hat.com>, linux-ext4@...r.kernel.org,
        linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        David Howells <dhowells@...hat.com>
Subject: [PATCH] common/rc: Fix _check_s_dax()

From: Ira Weiny <ira.weiny@...el.com>

There is a conflict with the user visible statx bits 'mount root' and
'dax'.  The kernel is changing the dax bit to correct this conflict.[1]

Adjust _check_s_dax() to use the new bit.  Because DAX tests do not run
on root mounts, STATX_ATTR_MOUNT_ROOT should always be 0, therefore we
can allow either bit to indicate DAX and cover any kernel which may be
running.

[1] https://lore.kernel.org/lkml/3e28d2c7-fbe5-298a-13ba-dcd8fd504666@redhat.com/

Signed-off-by: Ira Weiny <ira.weiny@...el.com>
---

I went ahead and used Christoph's suggestion regarding using both bits.

---
 common/rc | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/common/rc b/common/rc
index b5a504e0dcb4..322e682e5239 100644
--- a/common/rc
+++ b/common/rc
@@ -3221,11 +3221,24 @@ _check_s_dax()
 	local exp_s_dax=$2
 
 	local attributes=$($XFS_IO_PROG -c 'statx -r' $target | awk '/stat.attributes / { print $3 }')
-	if [ $exp_s_dax -eq 0 ]; then
-		(( attributes & 0x2000 )) && echo "$target has unexpected S_DAX flag"
-	else
-		(( attributes & 0x2000 )) || echo "$target doesn't have expected S_DAX flag"
-	fi
+
+	# The attribute bit value, STATX_ATTR_DAX (0x2000), conflicted with
+	# STATX_ATTR_MOUNT_ROOT.  Therefore, STATX_ATTR_DAX was changed to
+	# 0x00200000.
+	#
+	# Because DAX tests do not run on root mounts, STATX_ATTR_MOUNT_ROOT
+	# should always be 0, therefore we can allow either bit to indicate DAX
+	# and cover any kernel which may be running.
+
+        if [ $(( attributes & 0x00200000 )) -ne 0 ] || [ $(( attributes & 0x2000 )) -ne 0 ]; then
+                if [ $exp_s_dax -eq 0 ]; then
+                        echo "$target has unexpected S_DAX flag"
+                fi
+        else
+                if [ $exp_s_dax -ne 0 ]; then
+                        echo "$target doesn't have expected S_DAX flag"
+                fi
+        fi
 }
 
 _check_xflag()
-- 
2.28.0.rc0.12.gb6a658bd00c9