block_dev.c: fsync() on close() considered harmful

Hi Alan,

I don't see any standard specifying that fsync should be done on every blockdevice close.

Any chance you could add the below patch to the next -ac release?

Christoph

Date: Thu, 22 Nov 2001 14:34:50 +0100
From: Miquel van Smoorenburg <[email protected]>
To: Andrea Arcangeli <[email protected]>
Cc: [email protected]
Subject: [PATCH] block_dev.c: fsync() on close() considered harmful
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I'm running an INN usenet news server that uses raw partitions for storage. I.e. it opens /dev/sda7 etc. and mmap()s [which finally works in 2.4, hurray]

Even though the server is keeping those devices open, when a utility program (sm) opens that file/device and closes() it the close() causes a fsync() on the device, something that is not wanted.

I applied the following patch which fixes it for me, it prevents the sync-after-close if it was close() calling blkdev_put() and we're not the last one to call blkdev_put().

That means fsync() will still be done on unmounts or when the last user of the device closes it, but not otherwise.

Is this correct or am I overlooking something?

@@ -603,7 +603,7 @@
 

	down(&bdev->bd_sem);
	lock_kernel();
-	if (kind == BDEV_FILE)
+	if (kind == BDEV_FILE && bdev->bd_openers == 1)
		__block_fsync(bd_inode);
	else if (kind == BDEV_FS)
		fsync_no_super(rdev);

Mike.

"Only two things are infinite, the universe and human stupidity,
 and I'm not sure about the former" -- Albert Einstein.