linux-ext4 - [PATCH v2] tune2fs: do not update quota when not needed

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Message-ID: <20250103235042.4029197-1-gwendal@chromium.org>
Date: Fri,  3 Jan 2025 15:50:42 -0800
From: Gwendal Grignou <gwendal@...omium.org>
To: jack@...e.cz
Cc: gwendal@...omium.org,
	linux-ext4@...r.kernel.org,
	tytso@....edu,
	uekawa@...omium.org
Subject: [PATCH v2] 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@...omium.org>

---
Changes in v2:
Logic has been simplified, based on jack@...e.cz feedback.

 misc/tune2fs.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/misc/tune2fs.c b/misc/tune2fs.c
index 2548a766..3db57632 100644
--- 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,
-- 
2.47.1.613.gc27f4b7a9f-goog