699 lines
28 KiB
C
699 lines
28 KiB
C
/*-
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* Copyright (c) 1997, 1998
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* Cybernet Corporation and Nan Yang Computer Services Limited.
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* All rights reserved.
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*
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* This software was developed as part of the NetMAX project.
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*
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* Written by Greg Lehey
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*
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* This software is distributed under the so-called ``Berkeley
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* License'':
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by Cybernet Corporation
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* and Nan Yang Computer Services Limited
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* 4. Neither the name of the Companies nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* This software is provided ``as is'', and any express or implied
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* warranties, including, but not limited to, the implied warranties of
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* merchantability and fitness for a particular purpose are disclaimed.
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* In no event shall the company or contributors be liable for any
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* direct, indirect, incidental, special, exemplary, or consequential
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* damages (including, but not limited to, procurement of substitute
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* goods or services; loss of use, data, or profits; or business
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* interruption) however caused and on any theory of liability, whether
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* in contract, strict liability, or tort (including negligence or
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* otherwise) arising in any way out of the use of this software, even if
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* advised of the possibility of such damage.
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*
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* $Id: vinumraid5.c,v 1.21 2001/01/09 04:21:27 grog Exp grog $
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* $FreeBSD$
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*/
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#include <dev/vinum/vinumhdr.h>
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#include <dev/vinum/request.h>
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#include <sys/resourcevar.h>
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/*
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* Parameters which describe the current transfer.
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* These are only used for calculation, but they
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* need to be passed to other functions, so it's
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* tidier to put them in a struct
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*/
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struct metrics {
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daddr_t stripebase; /* base address of stripe (1st subdisk) */
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int stripeoffset; /* offset in stripe */
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int stripesectors; /* total sectors to transfer in this stripe */
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daddr_t sdbase; /* offset in subdisk of stripe base */
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int sdcount; /* number of disks involved in this transfer */
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daddr_t diskstart; /* remember where this transfer starts */
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int psdno; /* number of parity subdisk */
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int badsdno; /* number of down subdisk, if there is one */
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int firstsdno; /* first data subdisk number */
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/* These correspond to the fields in rqelement, sort of */
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int useroffset;
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/*
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* Initial offset and length values for the first
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* data block
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*/
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int initoffset; /* start address of block to transfer */
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short initlen; /* length in sectors of data transfer */
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/* Define a normal operation */
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int dataoffset; /* start address of block to transfer */
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int datalen; /* length in sectors of data transfer */
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/* Define a group operation */
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int groupoffset; /* subdisk offset of group operation */
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int grouplen; /* length in sectors of group operation */
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/* Define a normal write operation */
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int writeoffset; /* subdisk offset of normal write */
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int writelen; /* length in sectors of write operation */
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enum xferinfo flags; /* to check what we're doing */
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int rqcount; /* number of elements in request */
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};
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enum requeststatus bre5(struct request *rq,
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int plexno,
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daddr_t * diskstart,
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daddr_t diskend);
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void complete_raid5_write(struct rqelement *);
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enum requeststatus build_rq_buffer(struct rqelement *rqe, struct plex *plex);
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void setrqebounds(struct rqelement *rqe, struct metrics *mp);
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/*
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* define the low-level requests needed to perform
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* a high-level I/O operation for a specific plex
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* 'plexno'.
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*
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* Return 0 if all subdisks involved in the
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* request are up, 1 if some subdisks are not up,
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* and -1 if the request is at least partially
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* outside the bounds of the subdisks.
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*
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* Modify the pointer *diskstart to point to the
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* end address. On read, return on the first bad
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* subdisk, so that the caller
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* (build_read_request) can try alternatives.
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*
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* On entry to this routine, the prq structures
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* are not assigned. The assignment is performed
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* by expandrq(). Strictly speaking, the elements
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* rqe->sdno of all entries should be set to -1,
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* since 0 (from bzero) is a valid subdisk number.
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* We avoid this problem by initializing the ones
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* we use, and not looking at the others (index >=
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* prq->requests).
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*/
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enum requeststatus
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bre5(struct request *rq,
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int plexno,
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daddr_t * diskaddr,
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daddr_t diskend)
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{
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struct metrics m; /* most of the information */
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struct sd *sd;
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struct plex *plex;
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struct buf *bp; /* user's bp */
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struct rqgroup *rqg; /* the request group that we will create */
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struct rqelement *rqe; /* point to this request information */
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int rsectors; /* sectors remaining in this stripe */
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int mysdno; /* another sd index in loops */
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int rqno; /* request number */
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rqg = NULL; /* shut up, damn compiler */
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m.diskstart = *diskaddr; /* start of transfer */
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bp = rq->bp; /* buffer pointer */
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plex = &PLEX[plexno]; /* point to the plex */
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while (*diskaddr < diskend) { /* until we get it all sorted out */
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if (*diskaddr >= plex->length) /* beyond the end of the plex */
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return REQUEST_EOF; /* can't continue */
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m.badsdno = -1; /* no bad subdisk yet */
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/* Part A: Define the request */
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/*
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* First, calculate some sizes:
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* The offset of the start address from
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* the start of the stripe.
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*/
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m.stripeoffset = *diskaddr % (plex->stripesize * (plex->subdisks - 1));
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/*
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* The plex-relative address of the
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* start of the stripe.
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*/
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m.stripebase = *diskaddr - m.stripeoffset;
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/* subdisk containing the parity stripe */
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if (plex->organization == plex_raid5)
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m.psdno = plex->subdisks - 1
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- (*diskaddr / (plex->stripesize * (plex->subdisks - 1)))
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% plex->subdisks;
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else /* RAID-4 */
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m.psdno = plex->subdisks - 1;
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/*
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* The number of the subdisk in which
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* the start is located.
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*/
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m.firstsdno = m.stripeoffset / plex->stripesize;
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if (m.firstsdno >= m.psdno) /* at or past parity sd */
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m.firstsdno++; /* increment it */
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/*
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* The offset from the beginning of
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* the stripe on this subdisk.
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*/
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m.initoffset = m.stripeoffset % plex->stripesize;
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/* The offset of the stripe start relative to this subdisk */
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m.sdbase = m.stripebase / (plex->subdisks - 1);
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m.useroffset = *diskaddr - m.diskstart; /* The offset of the start in the user buffer */
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/*
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* The number of sectors to transfer in the
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* current (first) subdisk.
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*/
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m.initlen = min(diskend - *diskaddr, /* the amount remaining to transfer */
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plex->stripesize - m.initoffset); /* and the amount left in this block */
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/*
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* The number of sectors to transfer in this stripe
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* is the minumum of the amount remaining to transfer
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* and the amount left in this stripe.
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*/
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m.stripesectors = min(diskend - *diskaddr,
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plex->stripesize * (plex->subdisks - 1) - m.stripeoffset);
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/* The number of data subdisks involved in this request */
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m.sdcount = (m.stripesectors + m.initoffset + plex->stripesize - 1) / plex->stripesize;
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/* Part B: decide what kind of transfer this will be.
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* start and end addresses of the transfer in
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* the current block.
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*
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* There are a number of different kinds of
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* transfer, each of which relates to a
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* specific subdisk:
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*
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* 1. Normal read. All participating subdisks
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* are up, and the transfer can be made
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* directly to the user buffer. The bounds
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* of the transfer are described by
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* m.dataoffset and m.datalen. We have
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* already calculated m.initoffset and
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* m.initlen, which define the parameters
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* for the first data block.
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*
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* 2. Recovery read. One participating
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* subdisk is down. To recover data, all
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* the other subdisks, including the parity
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* subdisk, must be read. The data is
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* recovered by exclusive-oring all the
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* other blocks. The bounds of the
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* transfer are described by m.groupoffset
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* and m.grouplen.
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*
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* 3. A read request may request reading both
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* available data (normal read) and
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* non-available data (recovery read).
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* This can be a problem if the address
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* ranges of the two reads do not coincide:
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* in this case, the normal read needs to
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* be extended to cover the address range
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* of the recovery read, and must thus be
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* performed out of malloced memory.
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*
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* 4. Normal write. All the participating
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* subdisks are up. The bounds of the
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* transfer are described by m.dataoffset
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* and m.datalen. Since these values
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* differ for each block, we calculate the
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* bounds for the parity block
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* independently as the maximum of the
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* individual blocks and store these values
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* in m.writeoffset and m.writelen. This
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* write proceeds in four phases:
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*
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* i. Read the old contents of each block
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* and the parity block.
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* ii. ``Remove'' the old contents from
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* the parity block with exclusive or.
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* iii. ``Insert'' the new contents of the
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* block in the parity block, again
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* with exclusive or.
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*
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* iv. Write the new contents of the data
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* blocks and the parity block. The data
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* block transfers can be made directly from
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* the user buffer.
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*
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* 5. Degraded write where the data block is
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* not available. The bounds of the
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* transfer are described by m.groupoffset
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* and m.grouplen. This requires the
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* following steps:
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*
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* i. Read in all the other data blocks,
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* excluding the parity block.
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*
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* ii. Recreate the parity block from the
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* other data blocks and the data to be
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* written.
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*
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* iii. Write the parity block.
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*
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* 6. Parityless write, a write where the
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* parity block is not available. This is
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* in fact the simplest: just write the
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* data blocks. This can proceed directly
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* from the user buffer. The bounds of the
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* transfer are described by m.dataoffset
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* and m.datalen.
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*
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* 7. Combination of degraded data block write
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* and normal write. In this case the
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* address ranges of the reads may also
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* need to be extended to cover all
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* participating blocks.
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*
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* All requests in a group transfer transfer
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* the same address range relative to their
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* subdisk. The individual transfers may
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* vary, but since our group of requests is
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* all in a single slice, we can define a
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* range in which they all fall.
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*
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* In the following code section, we determine
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* which kind of transfer we will perform. If
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* there is a group transfer, we also decide
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* its bounds relative to the subdisks. At
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* the end, we have the following values:
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*
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* m.flags indicates the kinds of transfers
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* we will perform.
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* m.initoffset indicates the offset of the
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* beginning of any data operation relative
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* to the beginning of the stripe base.
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* m.initlen specifies the length of any data
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* operation.
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* m.dataoffset contains the same value as
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* m.initoffset.
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* m.datalen contains the same value as
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* m.initlen. Initially dataoffset and
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* datalen describe the parameters for the
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* first data block; while building the data
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* block requests, they are updated for each
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* block.
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* m.groupoffset indicates the offset of any
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* group operation relative to the beginning
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* of the stripe base.
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* m.grouplen specifies the length of any
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* group operation.
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* m.writeoffset indicates the offset of a
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* normal write relative to the beginning of
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* the stripe base. This value differs from
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* m.dataoffset in that it applies to the
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* entire operation, and not just the first
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* block.
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* m.writelen specifies the total span of a
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* normal write operation. writeoffset and
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* writelen are used to define the parity
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* block.
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*/
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m.groupoffset = 0; /* assume no group... */
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m.grouplen = 0; /* until we know we have one */
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m.writeoffset = m.initoffset; /* start offset of transfer */
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m.writelen = 0; /* nothing to write yet */
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m.flags = 0; /* no flags yet */
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rsectors = m.stripesectors; /* remaining sectors to examine */
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m.dataoffset = m.initoffset; /* start at the beginning of the transfer */
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m.datalen = m.initlen;
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if (m.sdcount > 1) {
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plex->multiblock++; /* more than one block for the request */
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/*
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* If we have two transfers that don't overlap,
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* (one at the end of the first block, the other
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* at the beginning of the second block),
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* it's cheaper to split them.
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*/
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if (rsectors < plex->stripesize) {
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m.sdcount = 1; /* just one subdisk */
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m.stripesectors = m.initlen; /* and just this many sectors */
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rsectors = m.initlen; /* and in the loop counter */
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}
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}
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if (SD[plex->sdnos[m.psdno]].state < sd_reborn) /* is our parity subdisk down? */
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m.badsdno = m.psdno; /* note that it's down */
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if (bp->b_iocmd == BIO_READ) { /* read operation */
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for (mysdno = m.firstsdno; rsectors > 0; mysdno++) {
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if (mysdno == m.psdno) /* ignore parity on read */
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mysdno++;
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if (mysdno == plex->subdisks) /* wraparound */
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mysdno = 0;
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if (mysdno == m.psdno) /* parity, */
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mysdno++; /* we've given already */
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if (SD[plex->sdnos[mysdno]].state < sd_reborn) { /* got a bad subdisk, */
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if (m.badsdno >= 0) /* we had one already, */
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return REQUEST_DOWN; /* we can't take a second */
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m.badsdno = mysdno; /* got the first */
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m.groupoffset = m.dataoffset; /* define the bounds */
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m.grouplen = m.datalen;
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m.flags |= XFR_RECOVERY_READ; /* we need recovery */
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plex->recovered_reads++; /* count another one */
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} else
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m.flags |= XFR_NORMAL_READ; /* normal read */
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/* Update the pointers for the next block */
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m.dataoffset = 0; /* back to the start of the stripe */
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rsectors -= m.datalen; /* remaining sectors to examine */
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m.datalen = min(rsectors, plex->stripesize); /* amount that will fit in this block */
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}
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} else { /* write operation */
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for (mysdno = m.firstsdno; rsectors > 0; mysdno++) {
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if (mysdno == m.psdno) /* parity stripe, we've dealt with that */
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mysdno++;
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if (mysdno == plex->subdisks) /* wraparound */
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mysdno = 0;
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if (mysdno == m.psdno) /* parity, */
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mysdno++; /* we've given already */
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sd = &SD[plex->sdnos[mysdno]];
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if (sd->state != sd_up) {
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enum requeststatus s;
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s = checksdstate(sd, rq, *diskaddr, diskend); /* do we need to change state? */
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if (s && (m.badsdno >= 0)) { /* second bad disk, */
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int sdno;
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/*
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* If the parity disk is down, there's
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* no recovery. We make all involved
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* subdisks stale. Otherwise, we
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* should be able to recover, but it's
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* like pulling teeth. Fix it later.
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*/
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for (sdno = 0; sdno < m.sdcount; sdno++) {
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struct sd *sd = &SD[plex->sdnos[sdno]];
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if (sd->state >= sd_reborn) /* sort of up, */
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set_sd_state(sd->sdno, sd_stale, setstate_force); /* make it stale */
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}
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return s; /* and crap out */
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}
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m.badsdno = mysdno; /* note which one is bad */
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m.flags |= XFR_DEGRADED_WRITE; /* we need recovery */
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plex->degraded_writes++; /* count another one */
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m.groupoffset = m.dataoffset; /* define the bounds */
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m.grouplen = m.datalen;
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} else {
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m.flags |= XFR_NORMAL_WRITE; /* normal write operation */
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if (m.writeoffset > m.dataoffset) { /* move write operation lower */
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m.writelen = max(m.writeoffset + m.writelen,
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m.dataoffset + m.datalen)
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- m.dataoffset;
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m.writeoffset = m.dataoffset;
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} else
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m.writelen = max(m.writeoffset + m.writelen,
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m.dataoffset + m.datalen)
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- m.writeoffset;
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}
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/* Update the pointers for the next block */
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m.dataoffset = 0; /* back to the start of the stripe */
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rsectors -= m.datalen; /* remaining sectors to examine */
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m.datalen = min(rsectors, plex->stripesize); /* amount that will fit in this block */
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}
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if (m.badsdno == m.psdno) { /* got a bad parity block, */
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struct sd *psd = &SD[plex->sdnos[m.psdno]];
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if (psd->state == sd_down)
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set_sd_state(psd->sdno, sd_obsolete, setstate_force); /* it's obsolete now */
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else if (psd->state == sd_crashed)
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set_sd_state(psd->sdno, sd_stale, setstate_force); /* it's stale now */
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m.flags &= ~XFR_NORMAL_WRITE; /* this write isn't normal, */
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m.flags |= XFR_PARITYLESS_WRITE; /* it's parityless */
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plex->parityless_writes++; /* count another one */
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}
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}
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/* reset the initial transfer values */
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m.dataoffset = m.initoffset; /* start at the beginning of the transfer */
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m.datalen = m.initlen;
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/* decide how many requests we need */
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if (m.flags & (XFR_RECOVERY_READ | XFR_DEGRADED_WRITE))
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/* doing a recovery read or degraded write, */
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m.rqcount = plex->subdisks; /* all subdisks */
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else if (m.flags & XFR_NORMAL_WRITE) /* normal write, */
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m.rqcount = m.sdcount + 1; /* all data blocks and the parity block */
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else /* parityless write or normal read */
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m.rqcount = m.sdcount; /* just the data blocks */
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/* Part C: build the requests */
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rqg = allocrqg(rq, m.rqcount); /* get a request group */
|
||
if (rqg == NULL) { /* malloc failed */
|
||
bp->b_error = ENOMEM;
|
||
bp->b_ioflags |= BIO_ERROR;
|
||
return REQUEST_ENOMEM;
|
||
}
|
||
rqg->plexno = plexno;
|
||
rqg->flags = m.flags;
|
||
rqno = 0; /* index in the request group */
|
||
|
||
/* 1: PARITY BLOCK */
|
||
/*
|
||
* Are we performing an operation which requires parity? In that case,
|
||
* work out the parameters and define the parity block.
|
||
* XFR_PARITYOP is XFR_NORMAL_WRITE | XFR_RECOVERY_READ | XFR_DEGRADED_WRITE
|
||
*/
|
||
if (m.flags & XFR_PARITYOP) { /* need parity */
|
||
rqe = &rqg->rqe[rqno]; /* point to element */
|
||
sd = &SD[plex->sdnos[m.psdno]]; /* the subdisk in question */
|
||
rqe->rqg = rqg; /* point back to group */
|
||
rqe->flags = (m.flags | XFR_PARITY_BLOCK | XFR_MALLOCED) /* always malloc parity block */
|
||
&~(XFR_NORMAL_READ | XFR_PARITYLESS_WRITE); /* transfer flags without data op stuf */
|
||
setrqebounds(rqe, &m); /* set up the bounds of the transfer */
|
||
rqe->sdno = sd->sdno; /* subdisk number */
|
||
rqe->driveno = sd->driveno;
|
||
if (build_rq_buffer(rqe, plex)) /* build the buffer */
|
||
return REQUEST_ENOMEM; /* can't do it */
|
||
rqe->b.b_iocmd = BIO_READ; /* we must read first */
|
||
m.sdcount++; /* adjust the subdisk count */
|
||
rqno++; /* and point to the next request */
|
||
}
|
||
/*
|
||
* 2: DATA BLOCKS
|
||
* Now build up requests for the blocks required
|
||
* for individual transfers
|
||
*/
|
||
for (mysdno = m.firstsdno; rqno < m.sdcount; mysdno++, rqno++) {
|
||
if (mysdno == m.psdno) /* parity, */
|
||
mysdno++; /* we've given already */
|
||
if (mysdno == plex->subdisks) /* got to the end, */
|
||
mysdno = 0; /* wrap around */
|
||
if (mysdno == m.psdno) /* parity, */
|
||
mysdno++; /* we've given already */
|
||
|
||
rqe = &rqg->rqe[rqno]; /* point to element */
|
||
sd = &SD[plex->sdnos[mysdno]]; /* the subdisk in question */
|
||
rqe->rqg = rqg; /* point to group */
|
||
if (m.flags & XFR_NEEDS_MALLOC) /* we need a malloced buffer first */
|
||
rqe->flags = m.flags | XFR_DATA_BLOCK | XFR_MALLOCED; /* transfer flags */
|
||
else
|
||
rqe->flags = m.flags | XFR_DATA_BLOCK; /* transfer flags */
|
||
if (mysdno == m.badsdno) { /* this is the bad subdisk */
|
||
rqg->badsdno = rqno; /* note which one */
|
||
rqe->flags |= XFR_BAD_SUBDISK; /* note that it's dead */
|
||
/*
|
||
* we can't read or write from/to it,
|
||
* but we don't need to malloc
|
||
*/
|
||
rqe->flags &= ~(XFR_MALLOCED | XFR_NORMAL_READ | XFR_NORMAL_WRITE);
|
||
}
|
||
setrqebounds(rqe, &m); /* set up the bounds of the transfer */
|
||
rqe->useroffset = m.useroffset; /* offset in user buffer */
|
||
rqe->sdno = sd->sdno; /* subdisk number */
|
||
rqe->driveno = sd->driveno;
|
||
if (build_rq_buffer(rqe, plex)) /* build the buffer */
|
||
return REQUEST_ENOMEM; /* can't do it */
|
||
if ((m.flags & XFR_PARITYOP) /* parity operation, */
|
||
&&((m.flags & XFR_BAD_SUBDISK) == 0)) /* and not the bad subdisk, */
|
||
rqe->b.b_iocmd = BIO_READ; /* we must read first */
|
||
|
||
/* Now update pointers for the next block */
|
||
*diskaddr += m.datalen; /* skip past what we've done */
|
||
m.stripesectors -= m.datalen; /* deduct from what's left */
|
||
m.useroffset += m.datalen; /* and move on in the user buffer */
|
||
m.datalen = min(m.stripesectors, plex->stripesize); /* and recalculate */
|
||
m.dataoffset = 0; /* start at the beginning of next block */
|
||
}
|
||
|
||
/*
|
||
* 3: REMAINING BLOCKS FOR RECOVERY
|
||
* Finally, if we have a recovery operation, build
|
||
* up transfers for the other subdisks. Follow the
|
||
* subdisks around until we get to where we started.
|
||
* These requests use only the group parameters.
|
||
*/
|
||
if ((rqno < m.rqcount) /* haven't done them all already */
|
||
&&(m.flags & (XFR_RECOVERY_READ | XFR_DEGRADED_WRITE))) {
|
||
for (; rqno < m.rqcount; rqno++, mysdno++) {
|
||
if (mysdno == m.psdno) /* parity, */
|
||
mysdno++; /* we've given already */
|
||
if (mysdno == plex->subdisks) /* got to the end, */
|
||
mysdno = 0; /* wrap around */
|
||
if (mysdno == m.psdno) /* parity, */
|
||
mysdno++; /* we've given already */
|
||
|
||
rqe = &rqg->rqe[rqno]; /* point to element */
|
||
sd = &SD[plex->sdnos[mysdno]]; /* the subdisk in question */
|
||
rqe->rqg = rqg; /* point to group */
|
||
|
||
rqe->sdoffset = m.sdbase + m.groupoffset; /* start of transfer */
|
||
rqe->dataoffset = 0; /* for tidiness' sake */
|
||
rqe->groupoffset = 0; /* group starts at the beginining */
|
||
rqe->datalen = 0;
|
||
rqe->grouplen = m.grouplen;
|
||
rqe->buflen = m.grouplen;
|
||
rqe->flags = (m.flags | XFR_MALLOCED) /* transfer flags without data op stuf */
|
||
&~XFR_DATAOP;
|
||
rqe->sdno = sd->sdno; /* subdisk number */
|
||
rqe->driveno = sd->driveno;
|
||
if (build_rq_buffer(rqe, plex)) /* build the buffer */
|
||
return REQUEST_ENOMEM; /* can't do it */
|
||
rqe->b.b_iocmd = BIO_READ; /* we must read first */
|
||
}
|
||
}
|
||
/*
|
||
* We need to lock the address range before
|
||
* doing anything. We don't have to be
|
||
* performing a recovery operation: somebody
|
||
* else could be doing so, and the results could
|
||
* influence us. Note the fact here, we'll perform
|
||
* the lock in launch_requests.
|
||
*/
|
||
rqg->lockbase = m.stripebase;
|
||
if (*diskaddr < diskend) /* didn't finish the request on this stripe */
|
||
plex->multistripe++; /* count another one */
|
||
}
|
||
return REQUEST_OK;
|
||
}
|
||
|
||
/*
|
||
* Helper function for rqe5: adjust the bounds of
|
||
* the transfers to minimize the buffer
|
||
* allocation.
|
||
*
|
||
* Each request can handle two of three different
|
||
* data ranges:
|
||
*
|
||
* 1. The range described by the parameters
|
||
* dataoffset and datalen, for normal read or
|
||
* parityless write.
|
||
* 2. The range described by the parameters
|
||
* groupoffset and grouplen, for recovery read
|
||
* and degraded write.
|
||
* 3. For normal write, the range depends on the
|
||
* kind of block. For data blocks, the range
|
||
* is defined by dataoffset and datalen. For
|
||
* parity blocks, it is defined by writeoffset
|
||
* and writelen.
|
||
*
|
||
* In order not to allocate more memory than
|
||
* necessary, this function adjusts the bounds
|
||
* parameter for each request to cover just the
|
||
* minimum necessary for the function it performs.
|
||
* This will normally vary from one request to the
|
||
* next.
|
||
*
|
||
* Things are slightly different for the parity
|
||
* block. In this case, the bounds defined by
|
||
* mp->writeoffset and mp->writelen also play a
|
||
* r<>le. Select this case by setting the
|
||
* parameter forparity != 0
|
||
*/
|
||
void
|
||
setrqebounds(struct rqelement *rqe, struct metrics *mp)
|
||
{
|
||
/* parity block of a normal write */
|
||
if ((rqe->flags & (XFR_NORMAL_WRITE | XFR_PARITY_BLOCK))
|
||
== (XFR_NORMAL_WRITE | XFR_PARITY_BLOCK)) { /* case 3 */
|
||
if (rqe->flags & XFR_DEGRADED_WRITE) { /* also degraded write */
|
||
/*
|
||
* With a combined normal and degraded write, we
|
||
* will zero out the area of the degraded write
|
||
* in the second phase, so we don't need to read
|
||
* it in. Unfortunately, we need a way to tell
|
||
* build_request_buffer the size of the buffer,
|
||
* and currently that's the length of the read.
|
||
* As a result, we read everything, even the stuff
|
||
* that we're going to nuke.
|
||
* FIXME XXX
|
||
*/
|
||
if (mp->groupoffset < mp->writeoffset) { /* group operation starts lower */
|
||
rqe->sdoffset = mp->sdbase + mp->groupoffset; /* start of transfer */
|
||
rqe->dataoffset = mp->writeoffset - mp->groupoffset; /* data starts here */
|
||
rqe->groupoffset = 0; /* and the group at the beginning */
|
||
} else { /* individual data starts first */
|
||
rqe->sdoffset = mp->sdbase + mp->writeoffset; /* start of transfer */
|
||
rqe->dataoffset = 0; /* individual data starts at the beginning */
|
||
rqe->groupoffset = mp->groupoffset - mp->writeoffset; /* group starts here */
|
||
}
|
||
rqe->datalen = mp->writelen;
|
||
rqe->grouplen = mp->grouplen;
|
||
} else { /* just normal write (case 3) */
|
||
rqe->sdoffset = mp->sdbase + mp->writeoffset; /* start of transfer */
|
||
rqe->dataoffset = 0; /* degradation starts at the beginning */
|
||
rqe->groupoffset = 0; /* for tidiness' sake */
|
||
rqe->datalen = mp->writelen;
|
||
rqe->grouplen = 0;
|
||
}
|
||
} else if (rqe->flags & XFR_DATAOP) { /* data operation (case 1 or 3) */
|
||
if (rqe->flags & XFR_GROUPOP) { /* also a group operation (case 2) */
|
||
if (mp->groupoffset < mp->dataoffset) { /* group operation starts lower */
|
||
rqe->sdoffset = mp->sdbase + mp->groupoffset; /* start of transfer */
|
||
rqe->dataoffset = mp->dataoffset - mp->groupoffset; /* data starts here */
|
||
rqe->groupoffset = 0; /* and the group at the beginning */
|
||
} else { /* individual data starts first */
|
||
rqe->sdoffset = mp->sdbase + mp->dataoffset; /* start of transfer */
|
||
rqe->dataoffset = 0; /* individual data starts at the beginning */
|
||
rqe->groupoffset = mp->groupoffset - mp->dataoffset; /* group starts here */
|
||
}
|
||
rqe->datalen = mp->datalen;
|
||
rqe->grouplen = mp->grouplen;
|
||
} else { /* just data operation (case 1) */
|
||
rqe->sdoffset = mp->sdbase + mp->dataoffset; /* start of transfer */
|
||
rqe->dataoffset = 0; /* degradation starts at the beginning */
|
||
rqe->groupoffset = 0; /* for tidiness' sake */
|
||
rqe->datalen = mp->datalen;
|
||
rqe->grouplen = 0;
|
||
}
|
||
} else { /* just group operations (case 2) */
|
||
rqe->sdoffset = mp->sdbase + mp->groupoffset; /* start of transfer */
|
||
rqe->dataoffset = 0; /* for tidiness' sake */
|
||
rqe->groupoffset = 0; /* group starts at the beginining */
|
||
rqe->datalen = 0;
|
||
rqe->grouplen = mp->grouplen;
|
||
}
|
||
rqe->buflen = max(rqe->dataoffset + rqe->datalen, /* total buffer length */
|
||
rqe->groupoffset + rqe->grouplen);
|
||
}
|
||
/* Local Variables: */
|
||
/* fill-column: 50 */
|
||
/* End: */
|