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Date:   Fri, 22 Mar 2019 17:38:13 -0700
From:   "Darrick J. Wong" <darrick.wong@...cle.com>
To:     "Theodore Ts'o" <tytso@....edu>
Cc:     Eryu Guan <guaneryu@...il.com>, fstests <fstests@...r.kernel.org>,
        xfs <linux-xfs@...r.kernel.org>,
        linux-ext4 <linux-ext4@...r.kernel.org>
Subject: [PATCH] ext4: prohibit fstrim in norecovery mode

From: Darrick J. Wong <darrick.wong@...cle.com>

The ext4 fstrim implementation uses the block bitmaps to find free space
that can be discarded.  If we haven't replayed the journal, the bitmaps
will be stale and we absolutely *cannot* use stale metadata to zap the
underlying storage.

Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
---
 fs/ext4/ioctl.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index 3c4f8bb59f8a..bab3da4f1e0d 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -1000,6 +1000,13 @@ long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		if (!blk_queue_discard(q))
 			return -EOPNOTSUPP;
 
+		/*
+		 * We haven't replayed the journal, so we cannot use our
+		 * block-bitmap-guided storage zapping commands.
+		 */
+		if (test_opt(sb, NOLOAD) && ext4_has_feature_journal(sb))
+			return -EROFS;
+
 		if (copy_from_user(&range, (struct fstrim_range __user *)arg,
 		    sizeof(range)))
 			return -EFAULT;

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