linux-ext4 - [PATCH] ext4: prevent delalloc to nodelalloc on remount

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Message-Id: <20241014034143.59779-1-bretznic@gmail.com>
Date: Sun, 13 Oct 2024 20:41:43 -0700
From: Nicolas Bretz <bretznic@...il.com>
To: tytso@....edu
Cc: linux-ext4@...r.kernel.org,
	Nicolas Bretz <bretznic@...il.com>
Subject: [PATCH] ext4: prevent delalloc to nodelalloc on remount

Implemented the suggested solution mentioned in the bug
https://bugzilla.kernel.org/show_bug.cgi?id=218820

Preventing the disabling of delayed allocation mode on remount.
delalloc to nodelalloc not permitted anymore
nodelalloc to delalloc permitted, not affected

Signed-off-by: Nicolas Bretz <bretznic@...il.com>
---
 fs/ext4/super.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 03373471131c..ef22d227802d 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5875,6 +5875,12 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
 	if (sbi->s_mount_flags & EXT4_MF_FS_ABORTED)
 		ext4_abort(sb, EXT4_ERR_ESHUTDOWN, "Abort forced by user");
 
+	if ((old_opts.s_mount_opt & EXT4_MOUNT_DELALLOC) & ~test_opt(sb, DELALLOC)) {
+		ext4_msg(sb, KERN_ERR, "can't disable delalloc during remount");
+		err = -EINVAL;
+		goto restore_opts;
+	}
+
 	sb->s_flags = (sb->s_flags & ~SB_POSIXACL) |
 		(test_opt(sb, POSIX_ACL) ? SB_POSIXACL : 0);
 
-- 
2.39.5