Messages in this thread | | | Date | Sat, 29 Aug 2009 22:43:44 -0400 | From | Douglas Gilbert <> | Subject | Re: [PATCH 4/7] sd: add support for WRITE SAME (16) with unmap bit |
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Christoph Hellwig wrote: > On Sat, Aug 29, 2009 at 08:43:27PM -0400, Douglas Gilbert wrote: >>> + if (buffer[14] & 0x80) >>> + sdkp->thin_provisioning = 1; >>> + >> So you are checking the TPE bit (Thin Provisioning Enabled) but >> not the TPRZ bit (Thin Provisioning Read Zeros). Shouldn't >> there also be a sdkp->thin_provisioning_read_zeros bit defined >> in struct scsi_disk? >> >> Is your application well defined when TPRZ==0 ? > > Filesystems do not care if these blocks are in a defined state, as > they must never return the content of uninitilized blocks to userspace. > Now if we do want to support discard through raid arrays we might start > to care, and will have check the TPRZ bit.
Another reason to note the TPRZ bit is that if it is 1 then the data given to WRITE SAME (16 and 32) must be a logical block of zeros for the UNMAP bit to be honoured (sbc3r19.pdf section 4.6.3.2 last paragraph).
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