From: Theodore Ts'o <tytso@mit.edu>
To: Andreas Dilger <adilger@dilger.ca>
Cc: linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [RFC] Draft Linux kernel interfaces for SMR/ZBC drives
Date: Wed, 12 Feb 2014 22:09:47 -0500 [thread overview]
Message-ID: <20140213030947.GA22382@thunk.org> (raw)
In-Reply-To: <932C36A9-55F9-4221-ACA8-385EE14D124D@dilger.ca>
On Wed, Feb 12, 2014 at 07:08:20PM -0700, Andreas Dilger wrote:
>
> What about FITRIM? I'm not sure of the exact semantics of ZBCRESETZONE,
> but at first glance it seems similar to resetting an erase block on an
> SSD. That might also be beneficial if the SMR drives have directly
> addressible on-board flash that is mapped to a Z_FLAG_TYPE_RANDOM zone
> type (I wish...) and it would pass the FITRIM straight through., it
But that's not what the FITRIM ioctl does. The FITRIM ioctl is a
request for the file system to send trim/discard for all blocks which
are not in use by the file system. It doesn't map well to how
ZBCRESETZONE.
It is possible to map ZBCRESETZONE to BLKDISCARD, except that
non-SMR/ZBC drives don't have a concept of a write pointer, so while
it is true that the all of the data blocks are "reset" ala an erase
block, with a MTD flash device, once an erase block is reset, you can
write to any page within the rease block, in any order, whereas this
is not true for an SMR/ZBC device.
> For non-SSD "trim" it would just reset the SMR zone but not return zeroes.
I think you are thinking of BLKDISCARD, not FITRIM.
- Ted
next prev parent reply other threads:[~2014-02-13 3:09 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-31 5:38 [RFC] Draft Linux kernel interfaces for ZBC drives Theodore Ts'o
2014-01-31 13:07 ` Matthew Wilcox
2014-01-31 15:44 ` Theodore Ts'o
2014-02-03 21:01 ` Jeff Moyer
2014-02-03 21:07 ` Martin K. Petersen
2014-02-03 21:38 ` Theodore Ts'o
2014-02-03 22:26 ` Jeff Moyer
2014-02-03 21:03 ` Eric Sandeen
2014-02-03 22:17 ` Theodore Ts'o
2014-02-04 2:00 ` HanBin Yoon
2014-02-04 16:27 ` Theodore Ts'o
2014-02-11 18:43 ` [RFC] Draft Linux kernel interfaces for SMR/ZBC drives Theodore Ts'o
2014-02-11 19:04 ` Andreas Dilger
2014-02-11 19:53 ` Theodore Ts'o
2014-02-13 2:08 ` Andreas Dilger
2014-02-13 3:09 ` Theodore Ts'o [this message]
2014-02-21 10:02 ` [RFC] Draft Linux kernel interfaces for ZBC drives Rohan Puri
2014-02-21 15:49 ` Theodore Ts'o
2014-02-25 9:36 ` Rohan Puri
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