linux-ext4 - [PATCH 09/10] fuse2fs: skip the gdt write in op

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <175798162503.391272.6658964627154863656.stgit@frogsfrogsfrogs>
Date: Mon, 15 Sep 2025 18:05:47 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: tytso@....edu
Cc: miklos@...redi.hu, neal@...pa.dev, linux-fsdevel@...r.kernel.org,
 linux-ext4@...r.kernel.org, John@...ves.net, bernd@...ernd.com,
 joannelkoong@...il.com
Subject: [PATCH 09/10] fuse2fs: skip the gdt write in op_destroy if syncfs is
 working

From: Darrick J. Wong <djwong@...nel.org>

As an umount-time performance enhancement, don't bother to write the
group descriptor tables in op_destroy if we know that op_syncfs will do
it for us.  That only happens if iomap is enabled.

Signed-off-by: "Darrick J. Wong" <djwong@...nel.org>
---
 fuse4fs/fuse4fs.c |   19 ++++++++++++++++---
 misc/fuse2fs.c    |   19 ++++++++++++++++---
 2 files changed, 32 insertions(+), 6 deletions(-)


diff --git a/fuse4fs/fuse4fs.c b/fuse4fs/fuse4fs.c
index 25c19c0f0deca0..4f5618e64a93c3 100644
--- a/fuse4fs/fuse4fs.c
+++ b/fuse4fs/fuse4fs.c
@@ -268,6 +268,7 @@ struct fuse4fs {
 	int noblkdev;
 	int translate_inums;
 	int iomap_passthrough_options;
+	int write_gdt_on_destroy;
 
 	enum fuse4fs_opstate opstate;
 	int logfd;
@@ -1475,9 +1476,11 @@ static void op_destroy(void *userdata)
 		if (fs->super->s_error_count)
 			fs->super->s_state |= EXT2_ERROR_FS;
 		ext2fs_mark_super_dirty(fs);
-		err = ext2fs_set_gdt_csum(fs);
-		if (err)
-			translate_error(fs, 0, err);
+		if (ff->write_gdt_on_destroy) {
+			err = ext2fs_set_gdt_csum(fs);
+			if (err)
+				translate_error(fs, 0, err);
+		}
 
 		err = ext2fs_flush2(fs, 0);
 		if (err)
@@ -5803,6 +5806,15 @@ static void op_syncfs(fuse_req_t req, fuse_ino_t ino)
 		}
 	}
 
+	/*
+	 * When iomap is enabled, the kernel will call syncfs right before
+	 * calling the destroy method.  If any syncfs succeeds, then we know
+	 * that there will be a last syncfs and that it will write the GDT, so
+	 * destroy doesn't need to waste time doing that.
+	 */
+	if (fuse4fs_iomap_enabled(ff))
+		ff->write_gdt_on_destroy = 0;
+
 out_unlock:
 	fuse4fs_finish(ff, ret);
 	fuse_reply_err(req, -ret);
@@ -7497,6 +7509,7 @@ int main(int argc, char *argv[])
 		.iomap_dev = FUSE_IOMAP_DEV_NULL,
 #endif
 		.translate_inums = 1,
+		.write_gdt_on_destroy = 1,
 	};
 	errcode_t err;
 	FILE *orig_stderr = stderr;
diff --git a/misc/fuse2fs.c b/misc/fuse2fs.c
index d4f1825dd695ad..b193e0b2c06b69 100644
--- a/misc/fuse2fs.c
+++ b/misc/fuse2fs.c
@@ -261,6 +261,7 @@ struct fuse2fs {
 	int unmount_in_destroy;
 	int noblkdev;
 	int iomap_passthrough_options;
+	int write_gdt_on_destroy;
 
 	enum fuse2fs_opstate opstate;
 	int logfd;
@@ -1301,9 +1302,11 @@ static void op_destroy(void *p EXT2FS_ATTR((unused)))
 		if (fs->super->s_error_count)
 			fs->super->s_state |= EXT2_ERROR_FS;
 		ext2fs_mark_super_dirty(fs);
-		err = ext2fs_set_gdt_csum(fs);
-		if (err)
-			translate_error(fs, 0, err);
+		if (ff->write_gdt_on_destroy) {
+			err = ext2fs_set_gdt_csum(fs);
+			if (err)
+				translate_error(fs, 0, err);
+		}
 
 		err = ext2fs_flush2(fs, 0);
 		if (err)
@@ -5360,6 +5363,15 @@ static int op_syncfs(const char *path)
 		}
 	}
 
+	/*
+	 * When iomap is enabled, the kernel will call syncfs right before
+	 * calling the destroy method.  If any syncfs succeeds, then we know
+	 * that there will be a last syncfs and that it will write the GDT, so
+	 * destroy doesn't need to waste time doing that.
+	 */
+	if (fuse2fs_iomap_enabled(ff))
+		ff->write_gdt_on_destroy = 0;
+
 out_unlock:
 	fuse2fs_finish(ff, ret);
 	return ret;
@@ -6944,6 +6956,7 @@ int main(int argc, char *argv[])
 		.iomap_state = IOMAP_UNKNOWN,
 		.iomap_dev = FUSE_IOMAP_DEV_NULL,
 #endif
+		.write_gdt_on_destroy = 1,
 	};
 	errcode_t err;
 	FILE *orig_stderr = stderr;