Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks

From	Dave Chinner <david@fromorbit.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks
Date	2016-03-04 00:20 +0100
Message-ID	<r8KHf-66N-1@gated-at.bofh.it> (permalink)
References	(4 earlier) <r8oQq-6Vq-13@gated-at.bofh.it> <r8FRh-2vI-7@gated-at.bofh.it> <r8FRh-2vI-11@gated-at.bofh.it> <r8GDD-2P0-3@gated-at.bofh.it> <r8Kee-5DY-17@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Thu, Mar 03, 2016 at 05:39:52PM -0500, Theodore Ts'o wrote:
> On Thu, Mar 03, 2016 at 01:54:54PM -0500, Martin K. Petersen wrote:
> > >>>>> "Christoph" == Christoph Hellwig <hch@infradead.org> writes:
> > 
> > Christoph>  - FALLOC_FL_PUNCH_HOLE assures zeroes are returned, but
> > Christoph> space is deallocated as much as possible -
> > Christoph> FALLOC_FL_ZERO_RANGE assures zeroes are returned, AND blocks
> > Christoph> are actually allocated
> > 
> > That works for me. I think it would be great if we could have consistent
> > interfaces for fs and block. The more commonality the merrier.
> 
> So a question I have is do we want to add a "discard-as-a-hint" analog
> for fallocate?

Well defined, reliable behaviour only, please. If the device can't
provide the required hardware offload, then it needs to use the
generic, slow implementation of the functionality or report
EOPNOTSUPP.

> P.S.  Speaking of things that are powerful and too dangerous for
> application programmers, after the Linux FAST workshop, I was having
> dinner with the Ceph developers and Ric Wheeler, and we were talking
> about things they really needed.  Turns out they also could use an
> FALLOC_FL_NO_HIDE_STALE functionality. 

For better or for worse, Ceph is moving away from using filesystems
for its back end object store, so the use of such a hack in Ceph
has a very limited life.

> I told them I had an
> out-of-tree patch that had that functionality, and even Ric Wheeler
> started getting tempted....  :-)

You can tempt all you want, but it does not change the basic fact
that it is dangerous and compromises system security. As such, it
does not belong in upstream kernels. Especially in this day and age
where ensuring the fundamental integrity of our systems is more
important than ever.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

Thread

[PATCH v5.1 0/2] create BLKZEROOUT ioctl that invalidates page cache "Darrick J. Wong" <darrick.wong@oracle.com> - 2016-03-02 05:20 +0100
  [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks "Darrick J. Wong" <darrick.wong@oracle.com> - 2016-03-02 05:20 +0100
    Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Christoph Hellwig <hch@infradead.org> - 2016-03-02 10:30 +0100
    Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-02 20:00 +0100
      Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks "Darrick J. Wong" <darrick.wong@oracle.com> - 2016-03-03 00:00 +0100
        Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-03 01:00 +0100
          Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-03 18:10 +0100
            Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-03 19:00 +0100
              Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Christoph Hellwig <hch@infradead.org> - 2016-03-03 19:10 +0100
              Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks "Martin K. Petersen" <martin.petersen@oracle.com> - 2016-03-03 19:20 +0100
              Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-03 19:30 +0100
          Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks "Martin K. Petersen" <martin.petersen@oracle.com> - 2016-03-03 19:10 +0100
            Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Christoph Hellwig <hch@infradead.org> - 2016-03-03 19:10 +0100
              Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks "Darrick J. Wong" <darrick.wong@oracle.com> - 2016-03-03 19:20 +0100
              Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks "Martin K. Petersen" <martin.petersen@oracle.com> - 2016-03-03 20:00 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-03 23:50 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Dave Chinner <david@fromorbit.com> - 2016-03-04 00:20 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-04 01:30 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Gregory Farnum <greg@gregs42.com> - 2016-03-09 23:30 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-10 00:10 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Ric Wheeler <ricwheeler@gmail.com> - 2016-03-10 16:00 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-10 19:40 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-10 22:50 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Ric Wheeler <rwheeler@redhat.com> - 2016-03-11 05:50 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range  of blocks One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-03-11 15:10 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-11 16:30 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-11 18:30 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Andy Lutomirski <luto@amacapital.net> - 2016-03-11 18:40 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-11 19:30 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Dave Chinner <david@fromorbit.com> - 2016-03-11 23:40 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-12 01:40 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-12 01:50 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-12 08:30 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Thomas Schoebel-Theuer <tst@schoebel-theuer.de> - 2016-03-12 11:20 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Dave Chinner <david@fromorbit.com> - 2016-03-14 00:40 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Ric Wheeler <rwheeler@redhat.com> - 2016-03-14 11:40 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-14 15:50 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Dave Chinner <david@fromorbit.com> - 2016-03-15 21:20 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-15 21:50 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-15 22:30 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Dave Chinner <david@fromorbit.com> - 2016-03-15 23:40 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-16 00:00 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks "Darrick J. Wong" <darrick.wong@oracle.com> - 2016-03-16 03:00 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Andreas Dilger <adilger@dilger.ca> - 2016-03-16 22:50 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-17 01:20 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Eric Sandeen <esandeen@redhat.com> - 2016-03-17 01:40 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-17 02:00 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Gregory Farnum <greg@gregs42.com> - 2016-03-17 06:20 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-17 13:40 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Dave Chinner <david@fromorbit.com> - 2016-03-17 02:10 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks "Darrick J. Wong" <darrick.wong@oracle.com> - 2016-03-17 03:50 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-16 00:10 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-16 00:20 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Dave Chinner <david@fromorbit.com> - 2016-03-16 01:10 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Dave Chinner <david@fromorbit.com> - 2016-03-16 01:00 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-16 01:10 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Eric Sandeen <esandeen@redhat.com> - 2016-03-16 01:40 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Chris Mason <clm@fb.com> - 2016-03-16 02:00 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Chris Mason <clm@fb.com> - 2016-03-16 23:30 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Ric Wheeler <rwheeler@redhat.com> - 2016-03-17 14:50 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Eric Sandeen <esandeen@redhat.com> - 2016-03-15 23:40 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-12 01:40 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Dave Chinner <david@fromorbit.com> - 2016-03-04 00:00 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Thomas Schoebel-Theuer <tst@schoebel-theuer.de> - 2016-03-04 03:40 +0100
            Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-03 19:20 +0100
  Re: [PATCH v5.1 0/2] create BLKZEROOUT ioctl that invalidates page cache Arnd Bergmann <arnd@arndb.de> - 2016-03-02 10:20 +0100
    Re: [PATCH v5.1 0/2] create BLKZEROOUT ioctl that invalidates page  cache Christoph Hellwig <hch@infradead.org> - 2016-03-02 10:50 +0100
      Re: [PATCH v5.1 0/2] create BLKZEROOUT ioctl that invalidates page cache Arnd Bergmann <arnd@arndb.de> - 2016-03-02 12:00 +0100

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