All of lore.kernel.org
 help / color / mirror / Atom feed
From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: Allison Henderson <achender@linux.vnet.ibm.com>
Cc: Andreas Dilger <adilger@dilger.ca>, linux-ext4@vger.kernel.org
Subject: Re: [PATCH 1/2 v3] EXT4: Secure Delete: Zero out file data
Date: Thu, 30 Jun 2011 21:18:59 -0400	[thread overview]
Message-ID: <yq17h82n6gs.fsf@sermon.lab.mkp.net> (raw)
In-Reply-To: <4E0D1AC4.6020003@linux.vnet.ibm.com> (Allison Henderson's message of "Thu, 30 Jun 2011 17:54:28 -0700")

>>>>> "Allison" == Allison Henderson <achender@linux.vnet.ibm.com> writes:

>> Does sb_issue_zeroout() use the SCSI "write same" feature in the
>> background?  That would avoid busying the CPU/controller/bus with
>> writing out zeroes, which might be expensive for a large file.
>> 
Allison> Hmm, that's a good question, I will dig into it and see if I
Allison> can find out.

This is a bit of an ongoing project.

Unfortunately WRITE SAME is quirk central as many drives only implement
block ranges corresponding to what RAID vendors told them they needed.
Many of the drives I tested have internal caps at 16 or 32MB and will
fail in interesting (i.e. not necessarily graceful) ways if given bigger
ranges.

I've been lobbying for a way for devices to report their WRITE SAME
limit for a while. That feature finally made it into the latest SBC3
draft. The changes required to support it went into the SCSI layer
during the last merge window. What remains is wiring this up to
blkdev_issue_zeroout(). I have some patches sitting in my queue that I
hope to get polished and submitted soon.

Anyway. From a filesystem perspective sb_issue_zeroout() interface is
definitely the way to go. WRITE SAME will eventually be called if the
device supports it.

-- 
Martin K. Petersen	Oracle Linux Engineering

  reply	other threads:[~2011-07-01  1:19 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-06-30 21:22 [PATCH 0/2 v3] EXT4: Secure Delete Allison Henderson
2011-06-30 21:22 ` [PATCH 1/2 v3] EXT4: Secure Delete: Zero out file data Allison Henderson
2011-06-30 22:15   ` Andreas Dilger
2011-07-01  0:54     ` Allison Henderson
2011-07-01  1:18       ` Martin K. Petersen [this message]
2011-07-01  1:41         ` Allison Henderson
2011-07-01 10:26   ` Lukas Czerner
2011-07-01 16:21     ` Allison Henderson
2011-07-02  9:33   ` Amir Goldstein
2011-07-03  7:00     ` Andreas Dilger
2011-07-03  7:37       ` Amir Goldstein
2011-07-04 17:19         ` Allison Henderson
2011-07-04 17:44           ` Amir Goldstein
2011-07-04 18:19             ` Andreas Dilger
2011-07-04 19:09               ` Allison Henderson
2011-07-06 21:05     ` Allison Henderson
2011-07-07  7:05       ` Amir Goldstein
2011-07-07 19:52         ` Andreas Dilger
2011-07-07 20:19           ` Allison Henderson
2011-07-08  0:09             ` Amir Goldstein
2011-07-08  1:55               ` Allison Henderson
2011-07-08  6:29                 ` Amir Goldstein
2011-07-08 20:43                   ` Allison Henderson
2011-07-10 23:13                   ` Ted Ts'o
2011-07-11 10:01                     ` Amir Goldstein
2011-07-08  2:46               ` Andreas Dilger
2011-07-08  5:46                 ` Ric Wheeler
2011-07-08  6:11                 ` Amir Goldstein
2011-07-08 18:20               ` Mingming Cao
2011-07-08 23:49                 ` Andreas Dilger
2011-07-10  8:19                   ` Ric Wheeler
2011-07-10 23:33                     ` Ted Ts'o
2011-07-11  6:42                       ` Ric Wheeler
2011-07-11  8:20                         ` Lukas Czerner
2011-07-11 14:24                           ` Allison Henderson
2011-06-30 21:22 ` [PATCH 2/2 v3] EXT4: Secure Delete: Zero out files directory entry Allison Henderson

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=yq17h82n6gs.fsf@sermon.lab.mkp.net \
    --to=martin.petersen@oracle.com \
    --cc=achender@linux.vnet.ibm.com \
    --cc=adilger@dilger.ca \
    --cc=linux-ext4@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.