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Kernel: * Add runtime quantity lfs_ravail, the number of disk-blocks reserved for writing. Writes to the filesystem first reserve a maximum amount of blocks before their write is allowed to proceed; after the blocks are allocated the reserved total is reduced by a corresponding amount. If the lfs_reserve function cannot immediately reserve the requested number of blocks, the inode is unlocked, and the thread sleeps until the cleaner has made enough space available for the blocks to be reserved. In this way large files can be written to the filesystem (or, smaller files can be written to a nearly-full but thoroughly clean filesystem) and the cleaner can still function properly. * Remove explicit switching on dlfs_minfreeseg from the kernel code; it is now merely a fs-creation parameter used to compute dlfs_avail and dlfs_bfree (and used by fsck_lfs(8) to check their accuracy). Its former role is better assumed by a properly computed dlfs_avail. * Bounds-check inode numbers submitted through lfs_bmapv and lfs_markv. This prevents a panic, but, if the cleaner is feeding the filesystem the wrong data, you are still in a world of hurt. * Cleanup: remove explicit references of DEV_BSIZE in favor of btodb()/dbtob(). lfs_cleanerd: * Make -n mean "send N segments' blocks through a single call to lfs_markv". Previously it had meant "clean N segments though N calls to lfs_markv, before looking again to see if more need to be cleaned". The new behavior gives better packing of direct data on disk with as little metadata as possible, largely alleviating the problem that the cleaner can consume more disk through inefficient use of metadata than it frees by moving dirty data away from clean "holes" to produce entirely clean segments. * Make -b mean "read as many segments as necessary to write N segments of dirty data back to disk", rather than its former meaning of "read as many segments as necessary to free N segments worth of space". The new meaning, combined with the new -n behavior described above, further aids in cleaning storage efficiency as entire segments can be written at once, using as few blocks as possible for segment summaries and inode blocks. * Make the cleaner take note of segments which could not be cleaned due to error, and not attempt to clean them until they are entirely free of dirty blocks. This prevents the case in which a cleanerd running with -n 1 and without -b (formerly the default) would spin trying repeatedly to clean a corrupt segment, while the remaining space filled and deadlocked the filesystem. * Update the lfs_cleanerd manual page to describe all the options, including the changes mentioned here (in particular, the -b and -n flags were previously undocumented). fsck_lfs: * Check, and optionally fix, lfs_avail (to an exact figure) and lfs_bfree (within a margin of error) in pass 5. newfs_lfs: * Reduce the default dlfs_minfreeseg to 1/20 of the total segments. * Add a warning if the sgs disklabel field is 16 (the default for FFS' cpg, but not usually desirable for LFS' sgs: 5--8 is a better range). * Change the calculation of lfs_avail and lfs_bfree, corresponding to the kernel changes mentioned above. mount_lfs: * Add -N and -b options to pass corresponding -n and -b options to lfs_cleanerd. * Default to calling lfs_cleanerd with "-b -n 4". [All of these changes were largely tested in the 1.5 branch, with the idea that they (along with previous un-pulled-up work) could be applied to the branch while it was still in ALPHA2; however my test system has experienced corruption on another filesystem (/dev/console has gone missing :^), and, while I believe this unrelated to the LFS changes, I cannot with good conscience request that the changes be pulled up.]
139 lines
4.0 KiB
Groff
139 lines
4.0 KiB
Groff
.\" $NetBSD: mount_lfs.8,v 1.7 2000/09/09 04:49:56 perseant Exp $
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.\"
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.\" Copyright (c) 1993, 1994
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)mount_lfs.8 8.5 (Berkeley) 3/30/94
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.\"
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.Dd March 30, 1994
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.Dt MOUNT_LFS 8
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.Os BSD 4.4
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.Sh NAME
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.Nm mount_lfs
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.Nd mount a log-structured file system
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.Sh SYNOPSIS
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.Nm ""
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.Op Fl bdns
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.Op Fl N Ar nsegs
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.Op Fl o Ar options
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.Ar special
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.Ar node
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.Sh DESCRIPTION
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The
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.Nm
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command attaches a log-structured file system
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.Ar special
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device on to the file system tree at the point
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.Ar node .
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In addition, the
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.Xr lfs_cleanerd 8
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utility is invoked to clean the file system periodically.
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.Pp
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This command is normally executed by
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.Xr mount 8
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at boot time.
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.Pp
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The options are as follows:
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.Bl -tag -width Ds
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.It Fl b
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Instruct the cleaner to count bytes written, rather than segments read,
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to determine how many segments to clean at once.
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.It Fl d
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Run
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.Xr lfs_cleanerd 8
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in debug mode.
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.It Fl o
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Options are specified with a
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.Fl o
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flag followed by a comma separated string of options.
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See the
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.Xr mount 8
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man page for possible options and their meanings.
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.It Fl N Ar nsegs
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Clean
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.Ar nsegs
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segments (or bytes' worth of segments if
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.Fl b
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is also specified) at a time.
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.It Fl n
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Don't start
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.Xr lfs_cleanerd 8
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on the file system.
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.It Fl s
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Cause
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.Xr lfs_cleanerd 8
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to read data in small chunks when cleaning the file system.
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.El
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.Sh SEE ALSO
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.Xr mount 2 ,
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.Xr unmount 2 ,
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.Xr fstab 5 ,
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.Xr lfs_cleanerd 8 ,
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.Xr mount 8
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.sp
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.Rs
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.%A Ousterhout and Douglis
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.%D 1989
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.%T "Beating the I/O Bottleneck: A Case for Log-structured File Systems"
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.%J "Operating Systems Review"
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.%V Vol. 23
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.%N No. 1
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.%P pp. 11-27
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.%O "also available as Technical Report UCB/CSD 88/467"
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.Re
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.Rs
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.%A Rosenblum and Ousterhout
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.%D 1991
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.%T "The Design and Implementation of a Log-Structured File System"
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.%J "ACM SIGOPS Operating Systems Review"
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.%V Vol. 25
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.%N No. 5
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.Re
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.Rs
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.%A Seltzer
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.%D 1992
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.%T "File System Performance and Transaction Support"
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.%B "PhD Thesis, University of California, Berkeley"
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.%O "also available as Technical Report UCB/ERL M92"
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.Re
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.Rs
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.%A Seltzer, Bostic, McKusick and Staelin
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.%D 1993
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.%T "An Implementation of a Log-Structured File System for UNIX"
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.%J "Proc. of the Winter 1993 USENIX Conf."
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.%P pp. 315-331
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.Re
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.Sh HISTORY
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The
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.Nm
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function first appeared in
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.Bx 4.4 .
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