/* $NetBSD: kern_physio.c,v 1.23 1995/07/27 02:37:12 mycroft Exp $ */ /*- * Copyright (c) 1994 Christopher G. Demetriou * Copyright (c) 1982, 1986, 1990, 1993 * The Regents of the University of California. All rights reserved. * (c) UNIX System Laboratories, Inc. * All or some portions of this file are derived from material licensed * to the University of California by American Telephone and Telegraph * Co. or Unix System Laboratories, Inc. and are reproduced herein with * the permission of UNIX System Laboratories, Inc. * * 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 the University of * California, Berkeley and its contributors. * 4. Neither the name of the University 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 BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS 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. * * @(#)kern_physio.c 8.1 (Berkeley) 6/10/93 */ #include #include #include #include #include /* * The routines implemented in this file are described in: * Leffler, et al.: The Design and Implementation of the 4.3BSD * UNIX Operating System (Addison Welley, 1989) * on pages 231-233. * * The routines "getphysbuf" and "putphysbuf" steal and return a swap * buffer. Leffler, et al., says that swap buffers are used to do the * I/O, so raw I/O requests don't have to be single-threaded. */ struct buf *getphysbuf __P((void)); void putphysbuf __P((struct buf *bp)); /* * Do "physical I/O" on behalf of a user. "Physical I/O" is I/O directly * from the raw device to user buffers, and bypasses the buffer cache. * * Comments in brackets are from Leffler, et al.'s pseudo-code implementation. */ int physio(strategy, bp, dev, flags, minphys, uio) void (*strategy) __P((struct buf *)); struct buf *bp; dev_t dev; int flags; u_int (*minphys) __P((struct buf *)); struct uio *uio; { struct iovec *iovp; struct proc *p = curproc; int error, done, i, nobuf, s, todo; error = 0; flags &= B_READ | B_WRITE; /* * [check user read/write access to the data buffer] * * Check each iov one by one. Note that we know if we're reading or * writing, so we ignore the uio's rw parameter. Also note that if * we're doing a read, that's a *write* to user-space. */ for (i = 0; i < uio->uio_iovcnt; i++) if (!useracc(uio->uio_iov[i].iov_base, uio->uio_iov[i].iov_len, (flags == B_READ) ? B_WRITE : B_READ)) return (EFAULT); /* Make sure we have a buffer, creating one if necessary. */ if (nobuf = (bp == NULL)) bp = getphysbuf(); /* [raise the processor priority level to splbio;] */ s = splbio(); /* [while the buffer is marked busy] */ while (bp->b_flags & B_BUSY) { /* [mark the buffer wanted] */ bp->b_flags |= B_WANTED; /* [wait until the buffer is available] */ tsleep((caddr_t)bp, PRIBIO+1, "physbuf", 0); } /* Mark it busy, so nobody else will use it. */ bp->b_flags |= B_BUSY; /* [lower the priority level] */ splx(s); /* [set up the fixed part of the buffer for a transfer] */ bp->b_dev = dev; bp->b_error = 0; bp->b_proc = p; /* * [while there are data to transfer and no I/O error] * Note that I/O errors are handled with a 'goto' at the bottom * of the 'while' loop. */ for (i = 0; i < uio->uio_iovcnt; i++) { iovp = &uio->uio_iov[i]; while (iovp->iov_len > 0) { /* * [mark the buffer busy for physical I/O] * (i.e. set B_PHYS (because it's an I/O to user * memory, and B_RAW, because B_RAW is to be * "Set by physio for raw transfers.", in addition * to the "busy" and read/write flag.) */ bp->b_flags = B_BUSY | B_PHYS | B_RAW | flags; /* [set up the buffer for a maximum-sized transfer] */ bp->b_blkno = btodb(uio->uio_offset); bp->b_bcount = iovp->iov_len; bp->b_data = iovp->iov_base; /* * [call minphys to bound the tranfer size] * and remember the amount of data to transfer, * for later comparison. */ todo = (*minphys)(bp); #ifdef DIAGNOSTIC if (todo > MAXPHYS) panic("todo > MAXPHYS; minphys broken"); #endif /* * [lock the part of the user address space involved * in the transfer] * Beware vmapbuf(); it clobbers b_data and * saves it in b_saveaddr. However, vunmapbuf() * restores it. */ p->p_holdcnt++; vslock(bp->b_data, todo); vmapbuf(bp, todo); /* [call strategy to start the transfer] */ (*strategy)(bp); /* * Note that the raise/wait/lower/get error * steps below would be done by biowait(), but * we want to unlock the address space before * we lower the priority. * * [raise the priority level to splbio] */ s = splbio(); /* [wait for the transfer to complete] */ while ((bp->b_flags & B_DONE) == 0) tsleep((caddr_t) bp, PRIBIO + 1, "physio", 0); /* Mark it busy again, so nobody else will use it. */ bp->b_flags |= B_BUSY; /* [lower the priority level] */ splx(s); /* * [unlock the part of the address space previously * locked] */ vunmapbuf(bp, todo); vsunlock(bp->b_data, todo); p->p_holdcnt--; /* remember error value (save a splbio/splx pair) */ if (bp->b_flags & B_ERROR) error = (bp->b_error ? bp->b_error : EIO); /* * [deduct the transfer size from the total number * of data to transfer] */ done = bp->b_bcount - bp->b_resid; iovp->iov_len -= done; iovp->iov_base += done; uio->uio_offset += done; uio->uio_resid -= done; /* * Now, check for an error. * Also, handle weird end-of-disk semantics. */ if (error || done < todo) goto done; } } done: /* * [clean up the state of the buffer] * Remember if somebody wants it, so we can wake them up below. * Also, if we had to steal it, give it back. */ s = splbio(); bp->b_flags &= ~(B_BUSY | B_PHYS | B_RAW); if (nobuf) putphysbuf(bp); else { /* * [if another process is waiting for the raw I/O buffer, * wake up processes waiting to do physical I/O; */ if (bp->b_flags & B_WANTED) { bp->b_flags &= ~B_WANTED; wakeup(bp); } } splx(s); return (error); } /* * Get a swap buffer structure, for use in physical I/O. * Mostly taken from /sys/vm/swap_pager.c, except that it no longer * records buffer list-empty conditions, and sleeps at PRIBIO + 1, * rather than PSWP + 1 (and on a different wchan). */ struct buf * getphysbuf() { struct buf *bp; int s; s = splbio(); while (bswlist.b_actf == NULL) { bswlist.b_flags |= B_WANTED; tsleep((caddr_t)&bswlist, PRIBIO + 1, "getphys", 0); } bp = bswlist.b_actf; bswlist.b_actf = bp->b_actf; splx(s); return (bp); } /* * Get rid of a swap buffer structure which has been used in physical I/O. * Mostly taken from /sys/vm/swap_pager.c, except that it now uses * wakeup() rather than the VM-internal thread_wakeup(), and that the caller * must mask disk interrupts, rather than putphysbuf() itself. */ void putphysbuf(bp) struct buf *bp; { bp->b_actf = bswlist.b_actf; bswlist.b_actf = bp; if (bp->b_vp) brelvp(bp); if (bswlist.b_flags & B_WANTED) { bswlist.b_flags &= ~B_WANTED; wakeup(&bswlist); } } /* * Leffler, et al., says on p. 231: * "The minphys() routine is called by physio() to adjust the * size of each I/O transfer before the latter is passed to * the strategy routine..." * * so, just adjust the buffer's count accounting to MAXPHYS here, * and return the new count; */ u_int minphys(bp) struct buf *bp; { bp->b_bcount = min(MAXPHYS, bp->b_bcount); return bp->b_bcount; }