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IABSD.fr/src/sys/kern/kern_physio.c
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- sys/kern/kern_physio.c
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/* $OpenBSD: kern_physio.c,v 1.49 2024/02/03 18:51:58 beck Exp $ */ /* $NetBSD: kern_physio.c,v 1.28 1997/05/19 10:43:28 pk 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. 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 <sys/param.h> #include <sys/systm.h> #include <sys/buf.h> #include <sys/pool.h> #include <uvm/uvm_extern.h> /* * 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. */ /* * 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(void (*strategy)(struct buf *), dev_t dev, int flags, void (*minphys)(struct buf *), struct uio *uio) { struct iovec *iovp; struct proc *p = curproc; long done, todo; int error, i, s; struct buf *bp; if ((uio->uio_offset % DEV_BSIZE) != 0) return (EINVAL); error = 0; flags &= B_READ | B_WRITE; /* Create a buffer. */ s = splbio(); bp = pool_get(&bufpool, PR_WAITOK | PR_ZERO); /* [set up the fixed part of the buffer for a transfer] */ bp->b_vnbufs.le_next = NOLIST; bp->b_dev = dev; bp->b_error = 0; bp->b_proc = p; bp->b_flags = B_BUSY; splx(s); /* * [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) { void *map = NULL; /* * [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.) */ CLR(bp->b_flags, B_DONE | B_ERROR); 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); /* * Because iov_len is size_t (unsigned) but b_bcount is * long (signed), an overflow is possible. Therefore * limit b_bcount to LONG_MAX before calling the * provided minphys. */ if (iovp->iov_len > LONG_MAX) bp->b_bcount = LONG_MAX; else bp->b_bcount = iovp->iov_len; /* * [call minphys to bound the transfer size] * and remember the amount of data to transfer, * for later comparison. */ (*minphys)(bp); todo = bp->b_bcount; KASSERTMSG(todo >= 0, "minphys broken"); /* * [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. */ error = uvm_vslock_device(p, iovp->iov_base, todo, (flags & B_READ) ? PROT_READ | PROT_WRITE : PROT_READ, &map); if (error) goto done; if (map) { bp->b_data = map; } else { bp->b_data = iovp->iov_base; 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_nsec(bp, PRIBIO + 1, "physio", INFSLP); /* 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] */ if (!map) vunmapbuf(bp, todo); uvm_vsunlock_device(p, iovp->iov_base, todo, map); /* 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] */ KASSERTMSG(bp->b_resid <= LONG_MAX, "strategy broken"); done = bp->b_bcount - bp->b_resid; KASSERTMSG(done >= 0, "strategy broken"); KASSERTMSG(done <= todo, "strategy broken"); iovp->iov_len -= done; iovp->iov_base = (caddr_t)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] */ s = splbio(); /* XXXCDC: is this necessary? */ if (bp->b_vp) brelvp(bp); splx(s); pool_put(&bufpool, bp); return (error); } /* * 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; */ void minphys(struct buf *bp) { if (bp->b_bcount > MAXPHYS) bp->b_bcount = MAXPHYS; }