Date: Thu, 13 Dec 2001 16:15:06 -0800 (PST) From: Kirk McKusick <mckusick@FreeBSD.org> To: cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: cvs commit: src/sys/ufs/ffs ffs_alloc.c ffs_snapshot.c ffs_vfsops.c fs.h Message-ID: <200112140015.fBE0F6Q99440@freefall.freebsd.org>
next in thread | raw e-mail | index | archive | help
mckusick 2001/12/13 16:15:06 PST
Modified files:
sys/ufs/ffs ffs_alloc.c ffs_snapshot.c ffs_vfsops.c
fs.h
Log:
Minimize the time necessary to suspend operations on a filesystem
when taking a snapshot. The two time consuming operations are
scanning all the filesystem bitmaps to determine which blocks
are in use and scanning all the other snapshots so as to be able
to expunge their blocks from the view of the current snapshot.
The bitmap scanning is broken into two passes. Before suspending
the filesystem all bitmaps are scanned. After the suspension,
those bitmaps that changed after being scanned the first time
are rescanned. Typically there are few bitmaps that need to be
rescanned. The expunging of other snapshots is now done after
the suspension is released by observing that we can easily
identify any blocks that were allocated to them after the
suspension (they will be maked as `not needing to be copied'
in the just created snapshot). For all the gory details, see
the ``Running fsck in the Background'' paper in the Usenix
BSDCon 2002 Conference Proceedings, pages 55-64.
Revision Changes Path
1.82 +15 -1 src/sys/ufs/ffs/ffs_alloc.c
1.24 +193 -96 src/sys/ufs/ffs/ffs_snapshot.c
1.164 +1 -0 src/sys/ufs/ffs/ffs_vfsops.c
1.24 +3 -2 src/sys/ufs/ffs/fs.h
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe cvs-all" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200112140015.fBE0F6Q99440>