/*- * Copyright (c) 1997, 1998 * Cybernet Corporation and Nan Yang Computer Services Limited. * All rights reserved. * * This software was developed as part of the NetMAX project. * * Written by Greg Lehey * * This software is distributed under the so-called ``Berkeley * License'': * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by Cybernet Corporation * and Nan Yang Computer Services Limited * 4. Neither the name of the Companies nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * This software is provided ``as is'', and any express or implied * warranties, including, but not limited to, the implied warranties of * merchantability and fitness for a particular purpose are disclaimed. * In no event shall the company or contributors be liable for any * direct, indirect, incidental, special, exemplary, or consequential * damages (including, but not limited to, procurement of substitute * goods or services; loss of use, data, or profits; or business * interruption) however caused and on any theory of liability, whether * in contract, strict liability, or tort (including negligence or * otherwise) arising in any way out of the use of this software, even if * advised of the possibility of such damage. * * $Id: vinumraid5.c,v 1.21 2001/01/09 04:21:27 grog Exp grog $ * $FreeBSD: src/sys/dev/vinum/vinumraid5.c,v 1.6.2.2 2001/03/13 02:59:43 grog Exp $ */ #include "vinumhdr.h" #include "request.h" #include <sys/resourcevar.h> /* * Parameters which describe the current transfer. * These are only used for calculation, but they * need to be passed to other functions, so it's * tidier to put them in a struct */ struct metrics { vinum_off_t stripebase; /* base address of stripe (1st subdisk) */ int stripeoffset; /* offset in stripe */ int stripesectors; /* total sectors to transfer in this stripe */ vinum_off_t sdbase; /* offset in subdisk of stripe base */ int sdcount; /* number of disks involved in this transfer */ vinum_off_t diskstart; /* remember where this transfer starts */ int psdno; /* number of parity subdisk */ int badsdno; /* number of down subdisk, if there is one */ int firstsdno; /* first data subdisk number */ /* These correspond to the fields in rqelement, sort of */ int useroffset; /* * Initial offset and length values for the first * data block */ int initoffset; /* start address of block to transfer */ short initlen; /* length in sectors of data transfer */ /* Define a normal operation */ int dataoffset; /* start address of block to transfer */ int datalen; /* length in sectors of data transfer */ /* Define a group operation */ int groupoffset; /* subdisk offset of group operation */ int grouplen; /* length in sectors of group operation */ /* Define a normal write operation */ int writeoffset; /* subdisk offset of normal write */ int writelen; /* length in sectors of write operation */ enum xferinfo flags; /* to check what we're doing */ int rqcount; /* number of elements in request */ }; enum requeststatus bre5(struct request *rq, int plexno, vinum_off_t * diskstart, vinum_off_t diskend); void complete_raid5_write(struct rqelement *); enum requeststatus build_rq_buffer(struct rqelement *rqe, struct plex *plex); void setrqebounds(struct rqelement *rqe, struct metrics *mp); /* * define the low-level requests needed to perform * a high-level I/O operation for a specific plex * 'plexno'. * * Return 0 if all subdisks involved in the * request are up, 1 if some subdisks are not up, * and -1 if the request is at least partially * outside the bounds of the subdisks. * * Modify the pointer *diskstart to point to the * end address. On read, return on the first bad * subdisk, so that the caller * (build_read_request) can try alternatives. * * On entry to this routine, the prq structures * are not assigned. The assignment is performed * by expandrq(). Strictly speaking, the elements * rqe->sdno of all entries should be set to -1, * since 0 (from bzero) is a valid subdisk number. * We avoid this problem by initializing the ones * we use, and not looking at the others (index >= * prq->requests). */ enum requeststatus bre5(struct request *rq, int plexno, vinum_off_t * diskaddr, vinum_off_t diskend) { struct metrics m; /* most of the information */ struct sd *sd; struct plex *plex; struct bio *bio; /* user's bp */ struct buf *bp; struct rqgroup *rqg; /* the request group that we will create */ struct rqelement *rqe; /* point to this request information */ int rsectors; /* sectors remaining in this stripe */ int mysdno; /* another sd index in loops */ int rqno; /* request number */ rqg = NULL; /* shut up, damn compiler */ m.diskstart = *diskaddr; /* start of transfer */ bio = rq->bio; /* buffer pointer */ bp = bio->bio_buf; plex = &PLEX[plexno]; /* point to the plex */ while (*diskaddr < diskend) { /* until we get it all sorted out */ if (*diskaddr >= plex->length) /* beyond the end of the plex */ return REQUEST_EOF; /* can't continue */ m.badsdno = -1; /* no bad subdisk yet */ /* Part A: Define the request */ /* * First, calculate some sizes: * The offset of the start address from * the start of the stripe. */ m.stripeoffset = *diskaddr % (plex->stripesize * (plex->subdisks - 1)); /* * The plex-relative address of the * start of the stripe. */ m.stripebase = *diskaddr - m.stripeoffset; /* subdisk containing the parity stripe */ if (plex->organization == plex_raid5) m.psdno = plex->subdisks - 1 - (*diskaddr / (plex->stripesize * (plex->subdisks - 1))) % plex->subdisks; else /* RAID-4 */ m.psdno = plex->subdisks - 1; /* * The number of the subdisk in which * the start is located. */ m.firstsdno = m.stripeoffset / plex->stripesize; if (m.firstsdno >= m.psdno) /* at or past parity sd */ m.firstsdno++; /* increment it */ /* * The offset from the beginning of * the stripe on this subdisk. */ m.initoffset = m.stripeoffset % plex->stripesize; /* The offset of the stripe start relative to this subdisk */ m.sdbase = m.stripebase / (plex->subdisks - 1); m.useroffset = *diskaddr - m.diskstart; /* The offset of the start in the user buffer */ /* * The number of sectors to transfer in the * current (first) subdisk. */ m.initlen = umin(diskend - *diskaddr, /* the amount remaining to transfer */ plex->stripesize - m.initoffset); /* and the amount left in this block */ /* * The number of sectors to transfer in this stripe * is the minumum of the amount remaining to transfer * and the amount left in this stripe. */ m.stripesectors = umin(diskend - *diskaddr, plex->stripesize * (plex->subdisks - 1) - m.stripeoffset); /* The number of data subdisks involved in this request */ m.sdcount = (m.stripesectors + m.initoffset + plex->stripesize - 1) / plex->stripesize; /* Part B: decide what kind of transfer this will be. * start and end addresses of the transfer in * the current block. * * There are a number of different kinds of * transfer, each of which relates to a * specific subdisk: * * 1. Normal read. All participating subdisks * are up, and the transfer can be made * directly to the user buffer. The bounds * of the transfer are described by * m.dataoffset and m.datalen. We have * already calculated m.initoffset and * m.initlen, which define the parameters * for the first data block. * * 2. Recovery read. One participating * subdisk is down. To recover data, all * the other subdisks, including the parity * subdisk, must be read. The data is * recovered by exclusive-oring all the * other blocks. The bounds of the * transfer are described by m.groupoffset * and m.grouplen. * * 3. A read request may request reading both * available data (normal read) and * non-available data (recovery read). * This can be a problem if the address * ranges of the two reads do not coincide: * in this case, the normal read needs to * be extended to cover the address range * of the recovery read, and must thus be * performed out of malloced memory. * * 4. Normal write. All the participating * subdisks are up. The bounds of the * transfer are described by m.dataoffset * and m.datalen. Since these values * differ for each block, we calculate the * bounds for the parity block * independently as the maximum of the * individual blocks and store these values * in m.writeoffset and m.writelen. This * write proceeds in four phases: * * i. Read the old contents of each block * and the parity block. * ii. ``Remove'' the old contents from * the parity block with exclusive or. * iii. ``Insert'' the new contents of the * block in the parity block, again * with exclusive or. * * iv. Write the new contents of the data * blocks and the parity block. The data * block transfers can be made directly from * the user buffer. * * 5. Degraded write where the data block is * not available. The bounds of the * transfer are described by m.groupoffset * and m.grouplen. This requires the * following steps: * * i. Read in all the other data blocks, * excluding the parity block. * * ii. Recreate the parity block from the * other data blocks and the data to be * written. * * iii. Write the parity block. * * 6. Parityless write, a write where the * parity block is not available. This is * in fact the simplest: just write the * data blocks. This can proceed directly * from the user buffer. The bounds of the * transfer are described by m.dataoffset * and m.datalen. * * 7. Combination of degraded data block write * and normal write. In this case the * address ranges of the reads may also * need to be extended to cover all * participating blocks. * * All requests in a group transfer transfer * the same address range relative to their * subdisk. The individual transfers may * vary, but since our group of requests is * all in a single slice, we can define a * range in which they all fall. * * In the following code section, we determine * which kind of transfer we will perform. If * there is a group transfer, we also decide * its bounds relative to the subdisks. At * the end, we have the following values: * * m.flags indicates the kinds of transfers * we will perform. * m.initoffset indicates the offset of the * beginning of any data operation relative * to the beginning of the stripe base. * m.initlen specifies the length of any data * operation. * m.dataoffset contains the same value as * m.initoffset. * m.datalen contains the same value as * m.initlen. Initially dataoffset and * datalen describe the parameters for the * first data block; while building the data * block requests, they are updated for each * block. * m.groupoffset indicates the offset of any * group operation relative to the beginning * of the stripe base. * m.grouplen specifies the length of any * group operation. * m.writeoffset indicates the offset of a * normal write relative to the beginning of * the stripe base. This value differs from * m.dataoffset in that it applies to the * entire operation, and not just the first * block. * m.writelen specifies the total span of a * normal write operation. writeoffset and * writelen are used to define the parity * block. */ m.groupoffset = 0; /* assume no group... */ m.grouplen = 0; /* until we know we have one */ m.writeoffset = m.initoffset; /* start offset of transfer */ m.writelen = 0; /* nothing to write yet */ m.flags = 0; /* no flags yet */ rsectors = m.stripesectors; /* remaining sectors to examine */ m.dataoffset = m.initoffset; /* start at the beginning of the transfer */ m.datalen = m.initlen; if (m.sdcount > 1) { plex->multiblock++; /* more than one block for the request */ /* * If we have two transfers that don't overlap, * (one at the end of the first block, the other * at the beginning of the second block), * it's cheaper to split them. */ if (rsectors < plex->stripesize) { m.sdcount = 1; /* just one subdisk */ m.stripesectors = m.initlen; /* and just this many sectors */ rsectors = m.initlen; /* and in the loop counter */ } } if (SD[plex->sdnos[m.psdno]].state < sd_reborn) /* is our parity subdisk down? */ m.badsdno = m.psdno; /* note that it's down */ if (bp->b_cmd == BUF_CMD_READ) { /* read operation */ for (mysdno = m.firstsdno; rsectors > 0; mysdno++) { if (mysdno == m.psdno) /* ignore parity on read */ mysdno++; if (mysdno == plex->subdisks) /* wraparound */ mysdno = 0; if (mysdno == m.psdno) /* parity, */ mysdno++; /* we've given already */ if (SD[plex->sdnos[mysdno]].state < sd_reborn) { /* got a bad subdisk, */ if (m.badsdno >= 0) /* we had one already, */ return REQUEST_DOWN; /* we can't take a second */ m.badsdno = mysdno; /* got the first */ m.groupoffset = m.dataoffset; /* define the bounds */ m.grouplen = m.datalen; m.flags |= XFR_RECOVERY_READ; /* we need recovery */ plex->recovered_reads++; /* count another one */ } else m.flags |= XFR_NORMAL_READ; /* normal read */ /* Update the pointers for the next block */ m.dataoffset = 0; /* back to the start of the stripe */ rsectors -= m.datalen; /* remaining sectors to examine */ m.datalen = umin(rsectors, plex->stripesize); /* amount that will fit in this block */ } } else { /* write operation */ for (mysdno = m.firstsdno; rsectors > 0; mysdno++) { if (mysdno == m.psdno) /* parity stripe, we've dealt with that */ mysdno++; if (mysdno == plex->subdisks) /* wraparound */ mysdno = 0; if (mysdno == m.psdno) /* parity, */ mysdno++; /* we've given already */ sd = &SD[plex->sdnos[mysdno]]; if (sd->state != sd_up) { enum requeststatus s; s = checksdstate(sd, rq, *diskaddr, diskend); /* do we need to change state? */ if (s && (m.badsdno >= 0)) { /* second bad disk, */ int sdno; /* * If the parity disk is down, there's * no recovery. We make all involved * subdisks stale. Otherwise, we * should be able to recover, but it's * like pulling teeth. Fix it later. */ for (sdno = 0; sdno < m.sdcount; sdno++) { struct sd *sd = &SD[plex->sdnos[sdno]]; if (sd->state >= sd_reborn) /* sort of up, */ set_sd_state(sd->sdno, sd_stale, setstate_force); /* make it stale */ } return s; /* and crap out */ } m.badsdno = mysdno; /* note which one is bad */ m.flags |= XFR_DEGRADED_WRITE; /* we need recovery */ plex->degraded_writes++; /* count another one */ m.groupoffset = m.dataoffset; /* define the bounds */ m.grouplen = m.datalen; } else { m.flags |= XFR_NORMAL_WRITE; /* normal write operation */ if (m.writeoffset > m.dataoffset) { /* move write operation lower */ m.writelen = umax(m.writeoffset + m.writelen, m.dataoffset + m.datalen) - m.dataoffset; m.writeoffset = m.dataoffset; } else m.writelen = umax(m.writeoffset + m.writelen, m.dataoffset + m.datalen) - m.writeoffset; } /* Update the pointers for the next block */ m.dataoffset = 0; /* back to the start of the stripe */ rsectors -= m.datalen; /* remaining sectors to examine */ m.datalen = umin(rsectors, plex->stripesize); /* amount that will fit in this block */ } if (m.badsdno == m.psdno) { /* got a bad parity block, */ struct sd *psd = &SD[plex->sdnos[m.psdno]]; if (psd->state == sd_down) set_sd_state(psd->sdno, sd_obsolete, setstate_force); /* it's obsolete now */ else if (psd->state == sd_crashed) set_sd_state(psd->sdno, sd_stale, setstate_force); /* it's stale now */ m.flags &= ~XFR_NORMAL_WRITE; /* this write isn't normal, */ m.flags |= XFR_PARITYLESS_WRITE; /* it's parityless */ plex->parityless_writes++; /* count another one */ } } /* reset the initial transfer values */ m.dataoffset = m.initoffset; /* start at the beginning of the transfer */ m.datalen = m.initlen; /* decide how many requests we need */ if (m.flags & (XFR_RECOVERY_READ | XFR_DEGRADED_WRITE)) /* doing a recovery read or degraded write, */ m.rqcount = plex->subdisks; /* all subdisks */ else if (m.flags & XFR_NORMAL_WRITE) /* normal write, */ m.rqcount = m.sdcount + 1; /* all data blocks and the parity block */ else /* parityless write or normal read */ m.rqcount = m.sdcount; /* just the data blocks */ /* Part C: build the requests */ rqg = allocrqg(rq, m.rqcount); /* get a request group */ if (rqg == NULL) { /* malloc failed */ bp->b_error = ENOMEM; bp->b_flags |= B_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_cmd = BUF_CMD_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_cmd = BUF_CMD_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 = umin(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_cmd = BUF_CMD_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 * role. Select this case by setting the * parameter for parity != 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 = umax(rqe->dataoffset + rqe->datalen, /* total buffer length */ rqe->groupoffset + rqe->grouplen); }
