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

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Message-ID: <20240830185921.2690798-1-gwendal@chromium.org>
Date: Fri, 30 Aug 2024 11:59:21 -0700
From: Gwendal Grignou <gwendal@...omium.org>
To: tytso@....edu,
	uekawa@...omium.org
Cc: linux-ext4@...r.kernel.org,
	Gwendal Grignou <gwendal@...omium.org>
Subject: [PATCH] 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 option always force a deep look.
| tune2fs -Qusrquota,grpquota -Q^prjquota -O quota unused | Y       |
                  See just above
| tune2fs -Qusrquota,grpquota -O quota unused             | N       |
                  No change from previous line.
| tune2fs -Qusrquota,^grpquota -O quota unused            | Y       |
                  Disabling a quota option always force a deep look.
| tune2fs -Qusrquota -O quota unused                      | N       |
                  No change from previous line.
| tune2fs -O ^quota unused                                | Y       |
                  Remove quota
| tune2fs -O quota unused                                 | X       |
                  function handle_quota_options() not called, default values
                  (-Qusrquota,grpquota) used.
| tune2fs -O quota -Qusrquota unused                      | N       |
                  Already set just above
---
 misc/tune2fs.c | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/misc/tune2fs.c b/misc/tune2fs.c
index 6de40e93..3cce8861 100644
--- a/misc/tune2fs.c
+++ b/misc/tune2fs.c
@@ -1804,6 +1804,41 @@ static int handle_quota_options(ext2_filsys fs)
 			qtype_bits |= 1 << qtype;
 	}
 
+	/*
+	 * Check if the filesystem already has quota enabled and more features
+	 * need to be enabled and are not, or some features need to be disabled.
+	 */
+	if (ext2fs_has_feature_quota(fs->super) && qtype_bits) {
+		for (qtype = 0 ; qtype < MAXQUOTAS; qtype++) {
+			if ((quota_enable[qtype] == QOPT_ENABLE &&
+			     *quota_sb_inump(fs->super, qtype) == 0) ||
+			    (quota_enable[qtype] == QOPT_DISABLE)) {
+				/* Some work needed to match the configuration. */
+				break;
+			}
+		}
+		if (qtype == MAXQUOTAS) {
+			/* Nothing to do. */
+			return 0;
+		}
+	}
+	/*
+	 * Check if the user wants all features disabled and it is already
+	 * the case.
+	 */
+	if (!ext2fs_has_feature_quota(fs->super) && !qtype_bits) {
+		for (qtype = 0 ; qtype < MAXQUOTAS; qtype++) {
+			if (*quota_sb_inump(fs->super, qtype)) {
+				/* Some work needed to match the configuration. */
+				break;
+			}
+		}
+		if (qtype == MAXQUOTAS) {
+			/* Nothing to do. */
+			return 0;
+		}
+	}
+
 	retval = quota_init_context(&qctx, fs, qtype_bits);
 	if (retval) {
 		com_err(program_name, retval,
-- 
2.46.0.469.g59c65b2a67-goog