[PATCH 5.5 20/80] ext4: improve explanation of a mount failure caused by a misconfigured kernel

[Greg Kroah-Hartman]

From: Theodore Ts'o <tytso@xxxxxxx>

commit d65d87a07476aa17df2dcb3ad18c22c154315bec upstream.

If CONFIG_QFMT_V2 is not enabled, but CONFIG_QUOTA is enabled, when a
user tries to mount a file system with the quota or project quota
enabled, the kernel will emit a very confusing messsage:

    EXT4-fs warning (device vdc): ext4_enable_quotas:5914: Failed to enable quota tracking (type=0, err=-3). Please run e2fsck to fix.
    EXT4-fs (vdc): mount failed

We will now report an explanatory message indicating which kernel
configuration options have to be enabled, to avoid customer/sysadmin
confusion.

Link: https://lore.kernel.org/r/20200215012738.565735-1-tytso@xxxxxxx
Google-Bug-Id: 149093531
Fixes: 7c319d328505b778 ("ext4: make quota as first class supported feature")
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Cc: stable@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/ext4/super.c |   14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2964,17 +2964,11 @@ static int ext4_feature_set_ok(struct su
 		return 0;
 	}
 
-#ifndef CONFIG_QUOTA
-	if (ext4_has_feature_quota(sb) && !readonly) {
+#if !defined(CONFIG_QUOTA) || !defined(CONFIG_QFMT_V2)
+	if (!readonly && (ext4_has_feature_quota(sb) ||
+			  ext4_has_feature_project(sb))) {
 		ext4_msg(sb, KERN_ERR,
-			 "Filesystem with quota feature cannot be mounted RDWR "
-			 "without CONFIG_QUOTA");
-		return 0;
-	}
-	if (ext4_has_feature_project(sb) && !readonly) {
-		ext4_msg(sb, KERN_ERR,
-			 "Filesystem with project quota feature cannot be mounted RDWR "
-			 "without CONFIG_QUOTA");
+			 "The kernel was not built with CONFIG_QUOTA and CONFIG_QFMT_V2");
 		return 0;
 	}
 #endif  /* CONFIG_QUOTA */