amd64/89202: Kernel crash when accessing filesystem
bde at zeta.org.au
Thu Nov 17 12:31:02 PST 2005
On Thu, 17 Nov 2005, Ivo Janssen wrote:
> I recreated the filesystem without the huge -f (avg filesize) option,
> which we had initially set to 1Gb:
> # newfs -U -O2 -b 8192 -f 1024
> # tunefs -e 20480 (10x the default)
> With the defaults of avg filesize of 16384, we don't see a crash. I
> then started playing with tunefs.
> Increasing the avg filesize to -f 16777216 (16Mb), we don't see a crash.
> Increasing the avg filesize to -f 33554432 (32Mb), we repro the crash.
I have had the following comment about this bug (but haven't fixed it) for
% Index: ffs_alloc.c
% RCS file: /home/ncvs/src/sys/ufs/ffs/ffs_alloc.c,v
% retrieving revision 1.121
% diff -u -2 -r1.121 ffs_alloc.c
% --- ffs_alloc.c 16 Jun 2004 09:47:25 -0000 1.121
% +++ ffs_alloc.c 28 Oct 2004 15:12:47 -0000
% @@ -964,4 +991,11 @@
% minbfree = 1;
% cgsize = fs->fs_fsize * fs->fs_fpg;
% + /*
% + * XXX the following multiplication can overflow, since newfs can
% + * be abused to set fs_avgfilesize and fs_avgfpdir to preposterous
% + * values. For the particular preposterous values of (64M, 16),
% + * the multiplication overflows to 0 and then dirsize = 0 sometimes
% + * causes division by 0.
% + */
% dirsize = fs->fs_avgfilesize * fs->fs_avgfpdir;
% curdirsize = avgndir ? (cgsize - avgbfree * fs->fs_bsize) / avgndir : 0;
This bug is easy to work around by not changing fs->fs_avgfilesize or
fs->fs_avgfpdir. Tuning them has limited useful effects.
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