From: Christoph Hellwig <hch@infradead.org>
To: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
Jens Axboe <axboe@kernel.dk>,
Christoph Hellwig <hch@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
Linux API <linux-api@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
shane.seymour@hpe.com, Bruce Fields <bfields@fieldses.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Jeff Layton <jlayton@poochiereds.net>
Subject: Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks
Date: Thu, 3 Mar 2016 10:09:24 -0800 [thread overview]
Message-ID: <20160303180924.GA4116@infradead.org> (raw)
In-Reply-To: <yq1bn6v8mqg.fsf@sermon.lab.mkp.net>
On Thu, Mar 03, 2016 at 01:01:11PM -0500, Martin K. Petersen wrote:
> That's not entirely true. Writing the blocks may cause them to be
> allocated on the storage device (depending on which flags we feed it in
> WRITE SAME).
>
> The filesystems people were wanted the following semantics:
>
> - deallocate, don't care about contents for future reads (discard)
> - deallocate, guarantee zeroes on future reads (zeroout)
> - (re)allocate, guarantee zeroes on future reads (zeroout)
>
> Maybe we just need a better naming scheme...
In filesystem terms we have two and three:
- FALLOC_FL_PUNCH_HOLE assures zeroes are returned, but space is
deallocated as much as possible
- FALLOC_FL_ZERO_RANGE assures zeroes are returned, AND blocks are
actually allocated
Returning stale blocks in a file system is a nasty security risk, so
we don't do that, and so shouldn't storage that offers any kind
of multi tenancy, and if it's just VMs using multiple partitions on it.
next prev parent reply other threads:[~2016-03-03 18:09 UTC|newest]
Thread overview: 82+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-02 4:09 [PATCH v5.1 0/2] create BLKZEROOUT ioctl that invalidates page cache Darrick J. Wong
2016-03-02 4:09 ` [PATCH 1/2] block: invalidate the page cache when issuing BLKZEROOUT Darrick J. Wong
2016-03-02 9:19 ` Christoph Hellwig
2016-03-02 4:09 ` [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Darrick J. Wong
2016-03-02 9:20 ` Christoph Hellwig
2016-03-02 18:52 ` Linus Torvalds
2016-03-02 22:56 ` Darrick J. Wong
2016-03-02 23:49 ` Linus Torvalds
2016-03-03 17:02 ` Theodore Ts'o
2016-03-03 17:55 ` Linus Torvalds
2016-03-03 18:00 ` Christoph Hellwig
2016-03-03 18:14 ` Martin K. Petersen
2016-03-03 18:21 ` Theodore Ts'o
2016-03-03 18:01 ` Martin K. Petersen
2016-03-03 18:09 ` Christoph Hellwig [this message]
2016-03-03 18:12 ` Darrick J. Wong
2016-03-03 18:54 ` Martin K. Petersen
2016-03-03 22:39 ` Theodore Ts'o
2016-03-03 23:10 ` Dave Chinner
2016-03-04 0:20 ` Theodore Ts'o
2016-03-09 22:20 ` Gregory Farnum
2016-03-09 23:08 ` Theodore Ts'o
2016-03-10 14:58 ` Ric Wheeler
2016-03-10 18:33 ` Linus Torvalds
2016-03-10 21:47 ` Theodore Ts'o
2016-03-11 4:42 ` Ric Wheeler
2016-03-11 13:59 ` One Thousand Gnomes
2016-03-11 15:27 ` Theodore Ts'o
2016-03-11 17:23 ` Linus Torvalds
2016-03-11 17:30 ` Andy Lutomirski
2016-03-11 18:25 ` Linus Torvalds
2016-03-11 22:30 ` Dave Chinner
2016-03-12 0:33 ` Linus Torvalds
2016-03-12 0:35 ` Theodore Ts'o
2016-03-12 0:44 ` Linus Torvalds
2016-03-12 7:19 ` Theodore Ts'o
2016-03-12 10:11 ` Thomas Schoebel-Theuer
2016-03-13 23:30 ` Dave Chinner
2016-03-14 10:34 ` Ric Wheeler
2016-03-14 14:46 ` Theodore Ts'o
2016-03-15 20:14 ` Dave Chinner
2016-03-15 20:43 ` Linus Torvalds
2016-03-15 21:29 ` Theodore Ts'o
2016-03-15 22:33 ` Dave Chinner
2016-03-15 22:52 ` Theodore Ts'o
2016-03-16 1:51 ` Darrick J. Wong
2016-03-16 21:45 ` Andreas Dilger
2016-03-17 0:15 ` Theodore Ts'o
2016-03-17 0:33 ` Eric Sandeen
2016-03-17 0:59 ` Theodore Ts'o
2016-03-17 5:18 ` Gregory Farnum
2016-03-17 12:36 ` Theodore Ts'o
2016-03-17 17:47 ` Linus Torvalds
2016-03-17 17:50 ` Ric Wheeler
2016-03-17 17:59 ` Linus Torvalds
2016-03-17 18:35 ` Chris Mason
2016-03-17 20:49 ` Andreas Dilger
2016-03-17 21:00 ` Chris Mason
2016-03-18 3:20 ` Theodore Ts'o
2016-03-18 15:15 ` Jeff Moyer
2016-03-18 20:05 ` Martin K. Petersen
2016-03-18 6:52 ` Gregory Farnum
2016-03-18 7:19 ` Linus Torvalds
2016-03-17 1:01 ` Dave Chinner
2016-03-17 2:38 ` Darrick J. Wong
2016-03-18 22:55 ` NeilBrown
2016-03-15 23:06 ` Linus Torvalds
2016-03-15 23:14 ` Linus Torvalds
2016-03-16 0:08 ` Dave Chinner
2016-03-15 23:52 ` Dave Chinner
2016-03-16 0:06 ` Linus Torvalds
2016-03-16 0:30 ` Eric Sandeen
2016-03-16 0:51 ` Chris Mason
2016-03-16 22:23 ` Chris Mason
2016-03-17 13:49 ` Ric Wheeler
2016-03-15 22:38 ` Eric Sandeen
2016-03-03 22:56 ` Dave Chinner
2016-03-04 2:30 ` Thomas Schoebel-Theuer
2016-03-03 18:14 ` Linus Torvalds
2016-03-02 9:15 ` [PATCH v5.1 0/2] create BLKZEROOUT ioctl that invalidates page cache Arnd Bergmann
2016-03-02 9:44 ` Christoph Hellwig
2016-03-02 10:55 ` Arnd Bergmann
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