Re: [Xen-devel] [PATCH 1 of 2] blkfront: sector size > 512

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

Samuel Thibault wrote:

> Stefano Stabellini, le Fri 22 May 2009 15:31:28 +0100, a Ãcrit :
>> Keir Fraser wrote:
>>> Yeah, I'd take a patch to add a nice clear comment about this to blkif.h.
>>> ;-)
>> Is this comment clear enough?
> 
> Could you also document whether the 'sectors' node in the xenstore is
> expressed in sector size or in 512 sectors?



OK.

---

diff -r 61404d971c92 xen/include/public/io/blkif.h
--- a/xen/include/public/io/blkif.h     Thu May 21 04:31:47 2009 +0100
+++ b/xen/include/public/io/blkif.h     Fri May 22 15:54:29 2009 +0100
@@ -84,6 +84,14 @@
  */
 #define BLKIF_MAX_SEGMENTS_PER_REQUEST 11
 
+/* 
+ * first_sect and last_sect in blkif_request_segment, as well as
+ * sector_number in blkif_request are all expressed in 512 bytes units,
+ * however they must be properly aligned to the real sector size of
+ * the physical disk, that is reported in the "sector-size" node in
+ * backend xenbus info.
+ * Also the "sectors" node on xenbus is expressed in 512 bytes units.
+ */
 struct blkif_request_segment {
     grant_ref_t gref;        /* reference to I/O buffer frame        */
     /* @first_sect: first sector in frame to transfer (inclusive).   */

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