Date: Tue, 11 Dec 2007 00:18:28 -0300 From: Alejandro Pulver <alepulver@FreeBSD.org> To: freebsd-hackers@FreeBSD.org Subject: Disk sync at shutdown and fusefs filesystems Message-ID: <20071211001828.54e1da6b@deimos.mars.bsd>
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--Sig_/K03ZYGnj2m=1mJj1y458J5r Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Hello. The port fusefs-ntfs (NTFS-3G is the official name) is a NTFS read/write driver using FUSE (a user-space kernel independent API for writing filesystem drivers). The latter uses a (user-space) cache for improving performance as there isn't a block device cache in the kernel, and it was originally made in Linux with that assumption. The problem with NTFS-3G (and all other FUSE based drivers maybe) is that it doesn't flush the cache data to the disk at shutdown, but it does when unmounted (and I guess this doesn't happen automatically). I noticed this when files I write before manually unmounting persist, and otherwise sometimes they don't. So I guess with native (here I mean written directly for the system kernel, using the kernel cache) FreeBSD filesystems the kernel flushes the cache at shutdown, but they aren't unmounted. Generally this isn't a problem since most FUSE filesystems are "virtual" (for example: over SSH, FTP, HTTP, etc.) and don't use cache nor need flushing. But this isn't the case with NTFS-3G. Are my assumptions right? Then I have to look for some way to manually unmount FUSE filesystems at shutdown, because they are already mounted at startup. I thought about instructing the fusefs-kmod rc.d script to unmount FUSE filesystems before attempting to unload the kernel module (currently it only loads/unloads fuse.ko). Thanks and Best Regards, Ale --Sig_/K03ZYGnj2m=1mJj1y458J5r Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (FreeBSD) iD8DBQFHXgGEiV05EpRcP2ERAhskAJ0Yny548w/aZocDSDs7hbp3zxkMnACginqC p+HxdhxpRCoeoGtzV+ScZb8= =31sz -----END PGP SIGNATURE----- --Sig_/K03ZYGnj2m=1mJj1y458J5r--
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