tune2fs: do not update quota when not needed

Enabling quota is expensive: All inodes in the filesystem are scanned.
Only do it when the requested quota configuration does not match the
existing configuration.

Test:
Add a tiny patch to print out when core of function
handle_quota_options() is triggered.
Issue commands:
truncate -s 1G unused ; mkfs.ext4 unused

| commands                                                | trigger |
comments
+---------------------------------------------------------+---------+---------
| tune2fs -Qusrquota,grpquota -Qprjquota -O quota unused  | Y       |
                  Quota not set at formatting.
| tune2fs -Qusrquota,grpquota -Qprjquota -O quota unused  | N       |
                  Already set just above
| tune2fs -Qusrquota,grpquota -Q^prjquota -O quota unused | Y       |
                  Disabling a quota
| tune2fs -Qusrquota,grpquota -Q^prjquota -O quota unused | N       |
                  No change from previous line.
| tune2fs -Qusrquota,grpquota -O quota unused             | N       |
                  No change from previous line.
| tune2fs -Qusrquota,^grpquota -O quota unused            | Y       |
                  Disabling a quota
| tune2fs -Qusrquota -O quota unused                      | N       |
                  No change from previous line.
| tune2fs -O ^quota unused                                | Y       |
                  Remove quota
| tune2fs -O quota unused                                 | Y       |
                  Re-enable quota, default values
                  (-Qusrquota,grpquota) used.
| tune2fs -O quota -Qusrquota unused                      | N       |
                  Already set just above

Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20250103235042.4029197-1-gwendal@chromium.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/misc/tune2fs.c b/misc/tune2fs.c
index 2548a7669ae3c33443106f81fc3217e8c96149f5..3db57632c88d42dadb092bf88ea6592683e77227 100644 (file)
--- a/misc/tune2fs.c
+++ b/misc/tune2fs.c
@@ -1799,11 +1799,27 @@ static int handle_quota_options(ext2_filsys fs)
                return 1;
        }
 
+       for (qtype = 0; qtype < MAXQUOTAS; qtype++) {
+               if (quota_enable[qtype] == QOPT_ENABLE &&
+                   *quota_sb_inump(fs->super, qtype) == 0) {
+                       /* Some work needed to match the configuration. */
+                       break;
+               }
+               if (quota_enable[qtype] == QOPT_DISABLE &&
+                   *quota_sb_inump(fs->super, qtype)) {
+                       /* Some work needed to match the configuration. */
+                       break;
+               }
+       }
+       if (qtype == MAXQUOTAS) {
+               /* Nothing to do. */
+               return 0;
+       }
+
        for (qtype = 0; qtype < MAXQUOTAS; qtype++) {
                if (quota_enable[qtype] == QOPT_ENABLE)
                        qtype_bits |= 1 << qtype;
        }
-
        retval = quota_init_context(&qctx, fs, qtype_bits);
        if (retval) {
                com_err(program_name, retval,