ext4: improve explanation of a mount failure caused by a misconfigured kernel

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@mit.edu
Google-Bug-Id: 149093531
Fixes: 7c319d328505b778 ("ext4: make quota as first class supported feature")
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index b0b9150..f131eaa 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3009,17 +3009,11 @@ static int ext4_feature_set_ok(struct super_block *sb, int readonly)
                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 */