linux-ext4 - [PATCH 8/8] fuse2fs: skip the gdt write in op

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Message-ID: <175573714537.22854.4387913032128676357.stgit@frogsfrogsfrogs>
Date: Wed, 20 Aug 2025 18:23:15 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: tytso@....edu
Cc: John@...ves.net, bernd@...ernd.com, linux-fsdevel@...r.kernel.org,
 linux-ext4@...r.kernel.org, miklos@...redi.hu, joannelkoong@...il.com,
 neal@...pa.dev
Subject: [PATCH 8/8] 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>
---
 misc/fuse2fs.c |   19 ++++++++++++++++---
 misc/fuse4fs.c |   19 ++++++++++++++++---
 2 files changed, 32 insertions(+), 6 deletions(-)


diff --git a/misc/fuse2fs.c b/misc/fuse2fs.c
index 62aca0ab56ec07..f5d68cc549ad69 100644
--- a/misc/fuse2fs.c
+++ b/misc/fuse2fs.c
@@ -269,6 +269,7 @@ struct fuse2fs {
 	uint8_t unmount_in_destroy;
 	uint8_t noblkdev;
 	uint8_t iomap_passthrough_options;
+	uint8_t write_gdt_on_destroy;
 
 	enum fuse2fs_opstate opstate;
 	int logfd;
@@ -1309,9 +1310,11 @@ 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)
@@ -5443,6 +5446,15 @@ 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;
@@ -7088,6 +7100,7 @@ int main(int argc, char *argv[])
 		.iomap_dev = FUSE_IOMAP_DEV_NULL,
 		.iomap_cache = 1,
 #endif
+		.write_gdt_on_destroy = 1,
 	};
 	errcode_t err;
 	FILE *orig_stderr = stderr;
diff --git a/misc/fuse4fs.c b/misc/fuse4fs.c
index e01b83e271415c..6f03c6a0933a3d 100644
--- a/misc/fuse4fs.c
+++ b/misc/fuse4fs.c
@@ -265,6 +265,7 @@ struct fuse4fs {
 	uint8_t noblkdev;
 	uint8_t iomap_passthrough_options;
 	uint8_t translate_inums;
+	uint8_t write_gdt_on_destroy;
 
 	enum fuse4fs_opstate opstate;
 	int logfd;
@@ -1472,9 +1473,11 @@ 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)
@@ -5736,6 +5739,15 @@ 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);
@@ -7472,6 +7484,7 @@ int main(int argc, char *argv[])
 		.iomap_cache = 1,
 #endif
 		.translate_inums = 1,
+		.write_gdt_on_destroy = 1,
 	};
 	errcode_t err;
 	FILE *orig_stderr = stderr;