Messages in this thread | | | Date | Thu, 11 Oct 2012 12:32:11 +0100 | From | James Hogan <> | Subject | Re: [RESEND PATCH] scsi: make struct scsi_varlen_cdb_hdr packed |
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On 11/10/12 11:24, James Bottomley wrote: > On Thu, 2012-10-11 at 10:15 +0100, James Hogan wrote: >> The struct scsi_varlen_cdb_hdr is expected to be exactly 10 bytes when >> used in struct osd_cdb_head, but it isn't marked as packed. Some >> architectures will round the struct size up which triggers BUILD_BUG_ON >> compile errors in osd_initiator.c when the outer structs are unexpected >> sizes. This is fixed by marking struct scsi_varlen_cdb_hdr as __packed. > > What actual problem have you encountered? The structure is {u8[8], u16} > which is naturally packed on every architecture I know about. I've even > built osd_initiator without problem on parisc, which has some of the > most rigid alignment rules I've seen.
Hi James,
The alignment is fine (the offset of the u16 is 8 bytes), but unfortunately with the metag port of gcc, sizeof(struct scsi_varlen_cdb_hdr) is rounded up to a 4 byte boundary (even though the largest data member alignment is only 2 bytes), which is 12 bytes instead of 10.
Cheers James
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