# /* */ #include "param.h" #include "user.h" #include "buf.h" #include "conf.h" #include "systm.h" #include "proc.h" #include "seg.h" /* * This is the set of buffers proper, whose heads * were declared in buf.h. There can exist buffer * headers not pointing here that are used purely * as arguments to the I/O routines to describe * I/O to be done-- e.g. swbuf, just below, for * swapping. */ char buffers[NBUF][516]; /***/ struct buf swbuf1; struct buf swbuf2; struct buf bfreelist; /*** queue of free buffers ***/ /* * Declarations of the tables for the magtape devices; * see bdwrite. */ extern int mtab; int httab; /* * The following several routines allocate and free * buffers with various side effects. In general the * arguments to an allocate routine are a device and * a block number, and the value is a pointer to * to the buffer header; the buffer is marked "busy" * so that no on else can touch it. If the block was * already in core, no I/O need be done; if it is * already busy, the process waits until it becomes free. * The following routines allocate a buffer: * getblk * bread * breada * Eventually the buffer must be released, possibly with the * side effect of writing it out, by using one of * bwrite * bdwrite * bawrite * brelse */ /* * Read in (if necessary) the block and return a buffer pointer. */ bread(dev, blkno) { register struct buf *rbp; rbp = getblk(dev, blkno); if (rbp->b_flags&B_DONE) return(rbp); rbp->b_flags =| B_READ; rbp->b_bcount = 512; /***/ (*bdevsw[dev.d_major].d_strategy)(rbp); iowait(rbp); return(rbp); } /* * Read in the block, like bread, but also start I/O on the * read-ahead block (which is not allocated to the caller) */ breada(adev, blkno, rablkno) { register struct buf *rbp, *rabp; register int dev; dev = adev; rbp = 0; if (!incore(dev, blkno)) { rbp = getblk(dev, blkno); if ((rbp->b_flags&B_DONE) == 0) { rbp->b_flags =| B_READ; rbp->b_bcount = 512; /***/ (*bdevsw[adev.d_major].d_strategy)(rbp); } } if (rablkno && !incore(dev, rablkno)) { rabp = getblk(dev, rablkno); if (rabp->b_flags & B_DONE) brelse(rabp); else { rabp->b_flags =| B_READ|B_ASYNC; rabp->b_bcount = 512; /***/ (*bdevsw[adev.d_major].d_strategy)(rabp); } } if (rbp==0) return(bread(dev, blkno)); iowait(rbp); return(rbp); } /* * Write the buffer, waiting for completion. * Then release the buffer. */ bwrite(bp) struct buf *bp; { register struct buf *rbp; register flag; rbp = bp; flag = rbp->b_flags; rbp->b_flags =& ~(B_READ | B_DONE | B_ERROR | B_DELWRI | B_AGE); rbp->b_bcount = 512; /***/ (*bdevsw[rbp->b_dev.d_major].d_strategy)(rbp); if ((flag&B_ASYNC) == 0) { iowait(rbp); brelse(rbp); } else if (flag & B_DELWRI) rbp->b_flags =| B_AGE; else geterror(rbp); } /* * Release the buffer, marking it so that if it is grabbed * for another purpose it will be written out before being * given up (e.g. when writing a partial block where it is * assumed that another write for the same block will soon follow). * This can't be done for magtape, since writes must be done * in the same order as requested. */ bdwrite(bp) struct buf *bp; { register struct buf *rbp; register struct devtab *dp; rbp = bp; dp = bdevsw[rbp->b_dev.d_major].d_tab; /***/ if (dp == &mtab || dp == &httab) bawrite(rbp); else { rbp->b_flags =| B_DELWRI | B_DONE; brelse(rbp); } } /* * Release the buffer, start I/O on it, but don't wait for completion. */ bawrite(bp) struct buf *bp; { register struct buf *rbp; rbp = bp; rbp->b_flags =| B_ASYNC; bwrite(rbp); } /* * release the buffer, with no I/O implied. */ brelse(bp) struct buf *bp; { register struct buf *rbp, **backp; register int sps; rbp = bp; if (rbp->b_flags&B_WANTED) wakeup(rbp); if (bfreelist.b_flags&B_WANTED) { bfreelist.b_flags =& ~B_WANTED; wakeup(&bfreelist); } if (rbp->b_flags&B_ERROR) rbp->b_dev.d_minor = -1; /* no assoc. on error */ sps = spl(6); if(rbp->b_flags & B_AGE) { backp = &bfreelist.av_forw; (*backp)->av_back = rbp; rbp->av_forw = *backp; *backp = rbp; rbp->av_back = &bfreelist; } else { backp = &bfreelist.av_back; (*backp)->av_forw = rbp; rbp->av_back = *backp; *backp = rbp; rbp->av_forw = &bfreelist; } rbp->b_flags =& ~(B_WANTED|B_BUSY|B_ASYNC|B_AGE); spl(sps); } /* * See if the block is associated with some buffer * (mainly to avoid getting hung up on a wait in breada) */ incore(adev, blkno) { register int dev; register struct buf *bp; register struct devtab *dp; dev = adev; dp = bdevsw[adev.d_major].d_tab; for (bp=dp->b_forw; bp != dp; bp = bp->b_forw) if (bp->b_blkno==blkno && bp->b_dev==dev) return(bp); return(0); } /* * Assign a buffer for the given block. If the appropriate * block is already associated, return it; otherwise search * for the oldest non-busy buffer and reassign it. * When a 512-byte area is wanted for some random reason * (e.g. during exec, for the user arglist) getblk can be called * with device NODEV to avoid unwanted associativity. */ getblk(dev, blkno) { register struct buf *bp; register struct devtab *dp; extern lbolt; trace(0x2000, "getblk", blkno); if (dev >= 0 && dev.d_major >= nblkdev) /***/ panic("blkdev"); loop: if (dev < 0) dp = &bfreelist; else { dp = bdevsw[dev.d_major].d_tab; if(dp == NULL) panic("devtab"); for (bp=dp->b_forw; bp != dp; bp = bp->b_forw) { if (bp->b_blkno!=blkno || bp->b_dev!=dev) continue; spl(6); if (bp->b_flags&B_BUSY) { bp->b_flags =| B_WANTED; sleep(bp, PRIBIO+1); spl(0); goto loop; } spl(0); notavail(bp); return(bp); } } spl(6); if (bfreelist.av_forw == &bfreelist) { bfreelist.b_flags =| B_WANTED; sleep(&bfreelist, PRIBIO+1); spl(0); goto loop; } spl(0); notavail(bp = bfreelist.av_forw); if (bp->b_flags & B_DELWRI) { bp->b_flags =| B_ASYNC; bwrite(bp); goto loop; } bp->b_flags = B_BUSY; bp->b_back->b_forw = bp->b_forw; bp->b_forw->b_back = bp->b_back; bp->b_forw = dp->b_forw; bp->b_back = dp; dp->b_forw->b_back = bp; dp->b_forw = bp; bp->b_dev = dev; bp->b_blkno = blkno; return(bp); } /* * Wait for I/O completion on the buffer; return errors * to the user. */ iowait(bp) struct buf *bp; { register struct buf *rbp; rbp = bp; spl(6); while ((rbp->b_flags&B_DONE)==0) sleep(rbp, PRIBIO); spl(0); geterror(rbp); } /* * Unlink a buffer from the available list and mark it busy. * (internal interface) */ notavail(bp) struct buf *bp; { register struct buf *rbp; register int sps; rbp = bp; sps = spl(6); rbp->av_back->av_forw = rbp->av_forw; rbp->av_forw->av_back = rbp->av_back; rbp->b_flags =| B_BUSY; spl(sps); } /* * Mark I/O complete on a buffer, release it if I/O is asynchronous, * and wake up anyone waiting for it. */ iodone(bp) struct buf *bp; { register struct buf *rbp; rbp = bp; trace(0x4000, "iodone", rbp); /*** if(rbp->b_flags&B_MAP) mapfree(rbp); ***/ rbp->b_flags =| B_DONE; if (rbp->b_flags&B_ASYNC) brelse(rbp); else { rbp->b_flags =& ~B_WANTED; wakeup(rbp); } } /* * Zero the core associated with a buffer. */ clrbuf(bp) int *bp; { register *p; register c; p = bp->b_addr; c = 128; /***/ do *p++ = 0; while (--c); } /* * Initialize the buffer I/O system by freeing * all buffers and setting all device buffer lists to empty. */ binit() { register struct buf *bp; register struct devtab *dp; register int i; struct bdevsw *bdp; bfreelist.b_forw = bfreelist.b_back = bfreelist.av_forw = bfreelist.av_back = &bfreelist; for (i=0; i<NBUF; i++) { bp = &buf[i]; bp->b_dev = -1; bp->b_addr = buffers[i]; bp->b_back = &bfreelist; bp->b_forw = bfreelist.b_forw; bfreelist.b_forw->b_back = bp; bfreelist.b_forw = bp; bp->b_flags = B_BUSY; brelse(bp); } i = 0; for (bdp = bdevsw; bdp->d_open; bdp++) { dp = bdp->d_tab; if(dp) { dp->b_forw = dp; dp->b_back = dp; } i++; } nblkdev = i; } /* * swap I/O */ swap(blkno, coreaddr, count, rdflg) { register struct buf *bp; bp = &swbuf1; if(bp->b_flags & B_BUSY) if((swbuf2.b_flags&B_WANTED) == 0) bp = &swbuf2; spl(6); while (bp->b_flags&B_BUSY) { bp->b_flags =| B_WANTED; sleep(bp, PSWP+1); } bp->b_flags = B_BUSY | B_PHYS | rdflg; bp->b_dev = swapdev; bp->b_bcount = count<<8; /*** 256 bytes/block ***/ bp->b_blkno = blkno; bp->b_addr = coreaddr<<8; /*** 256 b/block ***/ /*** bp->.b_xmem = (coreaddr>>10) & 077; ***/ (*bdevsw[swapdev.d_major].d_strategy)(bp); spl(6); while((bp->b_flags&B_DONE)==0) sleep(bp, PSWP); if (bp->b_flags&B_WANTED) wakeup(bp); spl(0); bp->b_flags =& ~(B_BUSY|B_WANTED); return(bp->b_flags&B_ERROR); } /* * make sure all write-behind blocks * on dev (or NODEV for all) * are flushed out. * (from umount and update) */ bflush(dev) { register struct buf *bp; loop: spl(6); for (bp = bfreelist.av_forw; bp != &bfreelist; bp = bp->av_forw) { if (bp->b_flags&B_DELWRI && (dev == NODEV||dev==bp->b_dev)) { bp->b_flags =| B_ASYNC; notavail(bp); bwrite(bp); goto loop; } } spl(0); } /* * Raw I/O. The arguments are * The strategy routine for the device * A buffer, which will always be a special buffer * header owned exclusively by the device for this purpose * The device number * Read/write flag * Essentially all the work is computing physical addresses and * validating them. */ physio(strat, abp, dev, rw) struct buf *abp; int (*strat)(); { register struct buf *bp; register char *base; register int nb; int ts; bp = abp; base = u.u_base; /* * Check odd base, odd count, and address wraparound */ if (base&01 || u.u_count&01 || base>=base+u.u_count) goto bad; ts = (u.u_tsize+255) & ~0377; /***/ if (u.u_sep) ts = 0; nb = base>>8; /***/ /* * Check overlap with text. (ts and nb now * in 256-byte clicks) *** */ if (nb < ts) goto bad; /* * Check that transfer is either entirely in the * data or in the stack: that is, either * the end is in the data or the start is in the stack * (remember wraparound was already checked). */ if (((base+u.u_count)>>8) >= ts+u.u_dsize /***/ && nb < (14<<8)) /***/ goto bad; /*** *** check for passing end of stack ***/ if ((base+u.u_count)>>8 >= (14<<8)+u.u_ssize) goto bad; spl(6); while (bp->b_flags&B_BUSY) { bp->b_flags =| B_WANTED; sleep(bp, PRIBIO+1); } bp->b_flags = B_BUSY | B_PHYS | rw; bp->b_dev = dev; /* * Compute physical address by simulating * the segmentation hardware. */ bp->b_addr = base; /***/ lraddr(&bp->b_addr, uisa); /***/ bp->b_blkno = lshift(u.u_offset, -9); bp->b_bcount = u.u_count; /***/ bp->b_error = 0; u.u_procp->p_flag =| SLOCK; (*strat)(bp); spl(6); while ((bp->b_flags&B_DONE) == 0) sleep(bp, PRIBIO); u.u_procp->p_flag =& ~SLOCK; if (bp->b_flags&B_WANTED) wakeup(bp); spl(0); bp->b_flags =& ~(B_BUSY|B_WANTED); u.u_count = bp->b_resid; /***/ geterror(bp); return; bad: u.u_error = EFAULT; } /* * Pick up the device's error number and pass it to the user; * if there is an error but the number is 0 set a generalized * code. Actually the latter is always true because devices * don't yet return specific errors. */ geterror(abp) struct buf *abp; { register struct buf *bp; bp = abp; if (bp->b_flags&B_ERROR) if ((u.u_error = bp->b_error)==0) u.u_error = EIO; }