cvs commit: src/sys/fs/msdosfs msdosfs_denode.c

[Dmitry Pryanishnikov]

Hello!

> Date:      Wed, 7 Sep 2005 12:24:30 -0500 (CDT)
> From:      Mike Silbersack <silby at silby.com>
>
> Heh, I was going to request a regression test, but I guess a 24 gig swap 
> backed partition would be a bit difficult to create. :)
>>  PR:             85503
>>  Submitted by:   Dmitry Pryanishnikov <dmitry at atlantis.dp.ua>

  I've thought about it too ;)

  Actually, to trigger this error one should have little more than 4Gb device,
but carefully placed directory on it ;) If we have 2 files, which directory
entries begin at byte offsets from the start of the media with identical 
low-order 32 bits; e.g., 64-bit offsets

0x0000000000001000 and
0x0000000100001000

and we've enough memory to hold first directory entry in the vfs cache while 
looking up the second, then this bug will manifest itself. So if somebody
knows the tools with which this situation could be created (or enough time
and inspiration to create it manually with some kind of binary data editor),
it would be possible to keep this disk image as a regression test for
this particular bug (it could be compressed just fine ;). It's just very 
probable that on large filesystems (as my 24Gb) with many files and reach
directory tree (yes, yes, WinXP lives there ;) + a lot of free memory for vfs 
cache (my machine has 512Mb) that this situation will happen
"automagically"...


Sincerely, Dmitry
-- 
Atlantis ISP, System Administrator
e-mail:  dmitry at atlantis.dp.ua
nic-hdl: LYNX-RIPE