Zero filling

NTFSD
1

As a file system filter driver, I would like to know when shoud do fill zero or dirty cache.

Here are the scenario I encountered:

  1. While regular writing, it jumps to next valid sector boundary and leaving some residue which never called by CM to fill zero.
  2. Does SetEOF info should be taken care of to fill zero?

Requirment is to encrypt zero also on disk.

Thanks
Ramaraj

2

Zero filling> 2) Does SetEOF info should be taken care of to fill zero?

This seems to be real problem to me. You cannot just fill
the file with zeros in every case when the Iength of file is being changed;
this will double time of copy operations in almost every
file manager (explorer, total commander, …)

Maybe a good soluion is to do this only when the paging I/O
flag is set in the set end of file request, but I’m not sure by it.
Anywaym this will not solve situation like

CreateFile
SetFilePointer(4 GB from begin)
SetEndOfFile() // the IRP_MJ_SET_INFORMATION is called
CloseHandle() // The IRP_MJ_CLEANUP called

L.

3

Thanks for your reply.

But I take care filling zero during paging i/o write. That means I shouldnt do fill zero during paging i/o EOF and advance only EOF case. Thats what I learnt from forum also. If somebody can correct me it will be great.

Thanks
Ramaraj

-----Original Message-----
From: xxxxx@lists.osr.com [mailto:xxxxx@lists.osr.com]On Behalf Of Ladislav Zezula
Sent: Tuesday, May 31, 2005 11:47 PM
To: Windows File Systems Devs Interest List
Subject: Re: [ntfsd] Zero filling

  1. Does SetEOF info should be taken care of to fill zero?

This seems to be real problem to me. You cannot just fill
the file with zeros in every case when the Iength of file is being changed;
this will double time of copy operations in almost every
file manager (explorer, total commander, …)

Maybe a good soluion is to do this only when the paging I/O
flag is set in the set end of file request, but I’m not sure by it.
Anywaym this will not solve situation like

CreateFile
SetFilePointer(4 GB from begin)
SetEndOfFile() // the IRP_MJ_SET_INFORMATION is called
CloseHandle() // The IRP_MJ_CLEANUP called

L.

Questions? First check the IFS FAQ at https://www.osronline.com/article.cfm?id=17

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