On 11/21/2009 09:43 PM, Mark Lord wrote:
Matthew Wilcox wrote:
On Sat, Nov 21, 2009 at 05:13:56AM -0500, Christoph Hellwig wrote:
On Fri, Nov 20, 2009 at 09:45:21PM -0500, Martin K. Petersen wrote:
The discard ioctl is used by mkfs utilities to clear a block device
prior to putting metadata down. However, not all devices return
zeroed
blocks after a discard. Some drives return stale data, potentially
containing old superblocks. It is therefore important to know whether
discarded blocks are properly zeroed.
At least for mkfs.xfs we make sure to still zero the important areas
after the TRIM ioctl anyway.
Could you change that to zero _before_ the TRIM?
..
Hopefully not for the drives that *don't* guarantee zeros after TRIM.
Eg. most existing ones, including all of the Indilinx chipset drives.
Cheers
Note that writing to a block after a discard (write or trim) changes the
state of that block back to allocated (mapped) in the target. Basically,
that would seem to make the trim redundant and irrelevant.
You can zero before the discard but that can still fail is the device
returns garbage for a trim'ed block I think,
Ric
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