>Number: 145999
>Category: kern
>Synopsis: optional offset for `mdconfig -t vnode'
>Confidential: no
>Severity: non-critical
>Priority: medium
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: change-request
>Submitter-Id: current-users
>Arrival-Date: Fri Apr 23 19:00:12 UTC 2010
>Closed-Date:
>Last-Modified:
>Originator: Mikhail T.
>Release: FreeBSD 7.3-STABLE amd64
>Organization:
Virtual Estates, Inc. http://sybpipe.com/
>Environment:
System: FreeBSD aldan.narawntapu 7.3-STABLE FreeBSD 7.3-STABLE #3: Fri Apr 9
17:20:45 EDT 2010 m...@aldan.narawntapu:/var/src/sys/amd64/compile/SILVER-SMP
amd64
>Description:
It is already possible to use only part of the file by
explicitly specifying the size (mdconfig -s) of the md.
For completeness, it should also be possible to request, that
certain number of bytes be skipped from the beginning...
If necessary, requiring that this offset be a multiple of
512 or some such is acceptable.
For example:
mdconfig -t vnode -f zhoo -b 8192
(-b would stand for "begin").
>How-To-Repeat:
This could be useful for people dealing with files, that have
file-system images embedded in them -- preceded by some other
data...
The only existing work-around for such situations is using
something like dd skip= to produce a separate file, which
can almost double the storage requirements and cause other
inconvenience.
I propose, that the md_base field of the md_ioctl struct
(currently in use only in the MD_PRELOAD cases) be used
for this purpose.
>Fix:
The userland changes (add an option for mdconfig.c) is easy.
The kernel changes required are beyond my knowledge...
>Release-Note:
>Audit-Trail:
>Unformatted:
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