/*      $NetBSD: nfs_clbio.c,v 1.7 2021/03/29 02:13:37 simonb Exp $     */
/*-
 * Copyright (c) 1989, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Rick Macklem at The University of Guelph.
 *
 * 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.
 * 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.
 *
 *      @(#)nfs_bio.c   8.9 (Berkeley) 3/30/95
 */

#include <sys/cdefs.h>
/* __FBSDID("FreeBSD: head/sys/fs/nfsclient/nfs_clbio.c 304026 2016-08-12 22:44:59Z rmacklem "); */
__RCSID("$NetBSD: nfs_clbio.c,v 1.7 2021/03/29 02:13:37 simonb Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/buf.h>
#include <sys/kernel.h>
#include <sys/mount.h>
#include <sys/rwlock.h>
#include <sys/vmmeter.h>
#include <sys/vnode.h>

#include <fs/nfs/common/nfsport.h>
#include <fs/nfs/client/nfsmount.h>
#include <fs/nfs/client/nfs.h>
#include <fs/nfs/client/nfsnode.h>
#include <fs/nfs/client/nfs_kdtrace.h>

extern int newnfs_directio_allow_mmap;
extern struct nfsstatsv1 nfsstatsv1;
extern struct mtx ncl_iod_mutex;
extern int ncl_numasync;
extern enum nfsiod_state ncl_iodwant[NFS_MAXASYNCDAEMON];
extern struct nfsmount *ncl_iodmount[NFS_MAXASYNCDAEMON];
extern int newnfs_directio_enable;
extern int nfs_keep_dirty_on_error;

int ncl_pbuf_freecnt = -1;      /* start out unlimited */

static struct buf *nfs_getcacheblk(struct vnode *vp, daddr_t bn, int size,
    struct thread *td);
static int nfs_directio_write(struct vnode *vp, struct uio *uiop,
    struct ucred *cred, int ioflag);

/*
 * Vnode op for VM getpages.
 */
int
ncl_getpages(struct vop_getpages_args *ap)
{
        int i, error, nextoff, size, toff, count, npages;
        struct uio uio;
        struct iovec iov;
        vaddr_t kva;
        struct buf *bp;
        struct vnode *vp;
        struct thread *td;
        struct ucred *cred;
        struct nfsmount *nmp;
        vm_object_t object;
        vm_page_t *pages;
        struct nfsnode *np;

        vp = ap->a_vp;
        np = VTONFS(vp);
        td = curthread;                         /* XXX */
        cred = curthread->td_ucred;             /* XXX */
        nmp = VFSTONFS(vp->v_mount);
        pages = ap->a_m;
        npages = ap->a_count;

        if ((object = vp->v_object) == NULL) {
                printf("ncl_getpages: called with non-merged cache vnode\n");
                return (VM_PAGER_ERROR);
        }

        if (newnfs_directio_enable && !newnfs_directio_allow_mmap) {
                mtx_lock(&np->n_mtx);
                if ((np->n_flag & NNONCACHE) && (vp->v_type == VREG)) {
                        mtx_unlock(&np->n_mtx);
                        printf("ncl_getpages: called on non-cacheable vnode\n");
                        return (VM_PAGER_ERROR);
                } else
                        mtx_unlock(&np->n_mtx);
        }

        mtx_lock(&nmp->nm_mtx);
        if ((nmp->nm_flag & NFSMNT_NFSV3) != 0 &&
            (nmp->nm_state & NFSSTA_GOTFSINFO) == 0) {
                mtx_unlock(&nmp->nm_mtx);
                /* We'll never get here for v4, because we always have fsinfo */
                (void)ncl_fsinfo(nmp, vp, cred, td);
        } else
                mtx_unlock(&nmp->nm_mtx);

        /*
         * If the requested page is partially valid, just return it and
         * allow the pager to zero-out the blanks.  Partially valid pages
         * can only occur at the file EOF.
         *
         * XXXGL: is that true for NFS, where short read can occur???
         */
        VM_OBJECT_WLOCK(object);
        if (pages[npages - 1]->valid != 0 && --npages == 0)
                goto out;
        VM_OBJECT_WUNLOCK(object);

        /*
         * We use only the kva address for the buffer, but this is extremely
         * convenient and fast.
         */
        bp = getpbuf(&ncl_pbuf_freecnt);

        kva = (vaddr_t) bp->b_data;
        pmap_qenter(kva, pages, npages);
        PCPU_INC(cnt.v_vnodein);
        PCPU_ADD(cnt.v_vnodepgsin, npages);

        count = npages << PAGE_SHIFT;
        iov.iov_base = (caddr_t) kva;
        iov.iov_len = count;
        uio.uio_iov = &iov;
        uio.uio_iovcnt = 1;
        uio.uio_offset = IDX_TO_OFF(pages[0]->pindex);
        uio.uio_resid = count;
        uio.uio_segflg = UIO_SYSSPACE;
        uio.uio_rw = UIO_READ;
        uio.uio_td = td;

        error = ncl_readrpc(vp, &uio, cred);
        pmap_qremove(kva, npages);

        relpbuf(bp, &ncl_pbuf_freecnt);

        if (error && (uio.uio_resid == count)) {
                printf("ncl_getpages: error %d\n", error);
                return (VM_PAGER_ERROR);
        }

        /*
         * Calculate the number of bytes read and validate only that number
         * of bytes.  Note that due to pending writes, size may be 0.  This
         * does not mean that the remaining data is invalid!
         */

        size = count - uio.uio_resid;
        VM_OBJECT_WLOCK(object);
        for (i = 0, toff = 0; i < npages; i++, toff = nextoff) {
                vm_page_t m;
                nextoff = toff + PAGE_SIZE;
                m = pages[i];

                if (nextoff <= size) {
                        /*
                         * Read operation filled an entire page
                         */
                        m->valid = VM_PAGE_BITS_ALL;
                        KASSERT(m->dirty == 0,
                            ("nfs_getpages: page %p is dirty", m));
                } else if (size > toff) {
                        /*
                         * Read operation filled a partial page.
                         */
                        m->valid = 0;
                        vm_page_set_valid_range(m, 0, size - toff);
                        KASSERT(m->dirty == 0,
                            ("nfs_getpages: page %p is dirty", m));
                } else {
                        /*
                         * Read operation was short.  If no error
                         * occurred we may have hit a zero-fill
                         * section.  We leave valid set to 0, and page
                         * is freed by vm_page_readahead_finish() if
                         * its index is not equal to requested, or
                         * page is zeroed and set valid by
                         * vm_pager_get_pages() for requested page.
                         */
                        ;
                }
        }
out:
        VM_OBJECT_WUNLOCK(object);
        if (ap->a_rbehind)
                *ap->a_rbehind = 0;
        if (ap->a_rahead)
                *ap->a_rahead = 0;
        return (VM_PAGER_OK);
}

/*
 * Vnode op for VM putpages.
 */
int
ncl_putpages(struct vop_putpages_args *ap)
{
        struct uio uio;
        struct iovec iov;
        vaddr_t kva;
        struct buf *bp;
        int iomode, must_commit, i, error, npages, count;
        off_t offset;
        int *rtvals;
        struct vnode *vp;
        struct thread *td;
        struct ucred *cred;
        struct nfsmount *nmp;
        struct nfsnode *np;
        vm_page_t *pages;

        vp = ap->a_vp;
        np = VTONFS(vp);
        td = curthread;                         /* XXX */
        /* Set the cred to n_writecred for the write rpcs. */
        if (np->n_writecred != NULL)
                cred = crhold(np->n_writecred);
        else
                cred = crhold(curthread->td_ucred);     /* XXX */
        nmp = VFSTONFS(vp->v_mount);
        pages = ap->a_m;
        count = ap->a_count;
        rtvals = ap->a_rtvals;
        npages = btoc(count);
        offset = IDX_TO_OFF(pages[0]->pindex);

        mtx_lock(&nmp->nm_mtx);
        if ((nmp->nm_flag & NFSMNT_NFSV3) != 0 &&
            (nmp->nm_state & NFSSTA_GOTFSINFO) == 0) {
                mtx_unlock(&nmp->nm_mtx);
                (void)ncl_fsinfo(nmp, vp, cred, td);
        } else
                mtx_unlock(&nmp->nm_mtx);

        mtx_lock(&np->n_mtx);
        if (newnfs_directio_enable && !newnfs_directio_allow_mmap &&
            (np->n_flag & NNONCACHE) && (vp->v_type == VREG)) {
                mtx_unlock(&np->n_mtx);
                printf("ncl_putpages: called on noncache-able vnode\n");
                mtx_lock(&np->n_mtx);
        }

        for (i = 0; i < npages; i++)
                rtvals[i] = VM_PAGER_ERROR;

        /*
         * When putting pages, do not extend file past EOF.
         */
        if (offset + count > np->n_size) {
                count = np->n_size - offset;
                if (count < 0)
                        count = 0;
        }
        mtx_unlock(&np->n_mtx);

        /*
         * We use only the kva address for the buffer, but this is extremely
         * convenient and fast.
         */
        bp = getpbuf(&ncl_pbuf_freecnt);

        kva = (vaddr_t) bp->b_data;
        pmap_qenter(kva, pages, npages);
        PCPU_INC(cnt.v_vnodeout);
        PCPU_ADD(cnt.v_vnodepgsout, count);

        iov.iov_base = (caddr_t) kva;
        iov.iov_len = count;
        uio.uio_iov = &iov;
        uio.uio_iovcnt = 1;
        uio.uio_offset = offset;
        uio.uio_resid = count;
        uio.uio_segflg = UIO_SYSSPACE;
        uio.uio_rw = UIO_WRITE;
        uio.uio_td = td;

        if ((ap->a_sync & VM_PAGER_PUT_SYNC) == 0)
            iomode = NFSWRITE_UNSTABLE;
        else
            iomode = NFSWRITE_FILESYNC;

        error = ncl_writerpc(vp, &uio, cred, &iomode, &must_commit, 0);
        crfree(cred);

        pmap_qremove(kva, npages);
        relpbuf(bp, &ncl_pbuf_freecnt);

        if (error == 0 || !nfs_keep_dirty_on_error) {
                vnode_pager_undirty_pages(pages, rtvals, count - uio.uio_resid);
                if (must_commit)
                        ncl_clearcommit(vp->v_mount);
        }
        return rtvals[0];
}

/*
 * For nfs, cache consistency can only be maintained approximately.
 * Although RFC1094 does not specify the criteria, the following is
 * believed to be compatible with the reference port.
 * For nfs:
 * If the file's modify time on the server has changed since the
 * last read rpc or you have written to the file,
 * you may have lost data cache consistency with the
 * server, so flush all of the file's data out of the cache.
 * Then force a getattr rpc to ensure that you have up to date
 * attributes.
 * NB: This implies that cache data can be read when up to
 * NFS_ATTRTIMEO seconds out of date. If you find that you need current
 * attributes this could be forced by setting n_attrstamp to 0 before
 * the VOP_GETATTR() call.
 */
static inline int
nfs_bioread_check_cons(struct vnode *vp, struct thread *td, struct ucred *cred)
{
        int error = 0;
        struct vattr vattr;
        struct nfsnode *np = VTONFS(vp);
        int old_lock;

        /*
         * Grab the exclusive lock before checking whether the cache is
         * consistent.
         * XXX - We can make this cheaper later (by acquiring cheaper locks).
         * But for now, this suffices.
         */
        old_lock = ncl_upgrade_vnlock(vp);
        if (vp->v_iflag & VI_DOOMED) {
                ncl_downgrade_vnlock(vp, old_lock);
                return (EBADF);
        }

        mtx_lock(&np->n_mtx);
        if (np->n_flag & NMODIFIED) {
                mtx_unlock(&np->n_mtx);
                if (vp->v_type != VREG) {
                        if (vp->v_type != VDIR)
                                panic("nfs: bioread, not dir");
                        ncl_invaldir(vp);
                        error = ncl_vinvalbuf(vp, V_SAVE, td, 1);
                        if (error)
                                goto out;
                }
                np->n_attrstamp = 0;
                KDTRACE_NFS_ATTRCACHE_FLUSH_DONE(vp);
                error = VOP_GETATTR(vp, &vattr, cred);
                if (error)
                        goto out;
                mtx_lock(&np->n_mtx);
                np->n_mtime = vattr.va_mtime;
                mtx_unlock(&np->n_mtx);
        } else {
                mtx_unlock(&np->n_mtx);
                error = VOP_GETATTR(vp, &vattr, cred);
                if (error)
                        return (error);
                mtx_lock(&np->n_mtx);
                if ((np->n_flag & NSIZECHANGED)
                    || (NFS_TIMESPEC_COMPARE(&np->n_mtime, &vattr.va_mtime))) {
                        mtx_unlock(&np->n_mtx);
                        if (vp->v_type == VDIR)
                                ncl_invaldir(vp);
                        error = ncl_vinvalbuf(vp, V_SAVE, td, 1);
                        if (error)
                                goto out;
                        mtx_lock(&np->n_mtx);
                        np->n_mtime = vattr.va_mtime;
                        np->n_flag &= ~NSIZECHANGED;
                }
                mtx_unlock(&np->n_mtx);
        }
out:
        ncl_downgrade_vnlock(vp, old_lock);
        return error;
}

/*
 * Vnode op for read using bio
 */
int
ncl_bioread(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred)
{
        struct nfsnode *np = VTONFS(vp);
        int biosize, i;
        struct buf *bp, *rabp;
        struct thread *td;
        struct nfsmount *nmp = VFSTONFS(vp->v_mount);
        daddr_t lbn, rabn;
        int bcount;
        int seqcount;
        int nra, error = 0, n = 0, on = 0;
        off_t tmp_off;

        KASSERT(uio->uio_rw == UIO_READ, ("ncl_read mode"));
        if (uio->uio_resid == 0)
                return (0);
        if (uio->uio_offset < 0)        /* XXX VDIR cookies can be negative */
                return (EINVAL);
        td = uio->uio_td;

        mtx_lock(&nmp->nm_mtx);
        if ((nmp->nm_flag & NFSMNT_NFSV3) != 0 &&
            (nmp->nm_state & NFSSTA_GOTFSINFO) == 0) {
                mtx_unlock(&nmp->nm_mtx);
                (void)ncl_fsinfo(nmp, vp, cred, td);
                mtx_lock(&nmp->nm_mtx);
        }
        if (nmp->nm_rsize == 0 || nmp->nm_readdirsize == 0)
                (void) newnfs_iosize(nmp);

        tmp_off = uio->uio_offset + uio->uio_resid;
        if (vp->v_type != VDIR &&
            (tmp_off > nmp->nm_maxfilesize || tmp_off < uio->uio_offset)) {
                mtx_unlock(&nmp->nm_mtx);
                return (EFBIG);
        }
        mtx_unlock(&nmp->nm_mtx);

        if (newnfs_directio_enable && (ioflag & IO_DIRECT) && (vp->v_type == VREG))
                /* No caching/ no readaheads. Just read data into the user buffer */
                return ncl_readrpc(vp, uio, cred);

        biosize = vp->v_bufobj.bo_bsize;
        seqcount = (int)((off_t)(ioflag >> IO_SEQSHIFT) * biosize / BKVASIZE);

        error = nfs_bioread_check_cons(vp, td, cred);
        if (error)
                return error;

        do {
            u_quad_t nsize;

            mtx_lock(&np->n_mtx);
            nsize = np->n_size;
            mtx_unlock(&np->n_mtx);

            switch (vp->v_type) {
            case VREG:
                NFSINCRGLOBAL(nfsstatsv1.biocache_reads);
                lbn = uio->uio_offset / biosize;
                on = uio->uio_offset - (lbn * biosize);

                /*
                 * Start the read ahead(s), as required.
                 */
                if (nmp->nm_readahead > 0) {
                    for (nra = 0; nra < nmp->nm_readahead && nra < seqcount &&
                        (off_t)(lbn + 1 + nra) * biosize < nsize; nra++) {
                        rabn = lbn + 1 + nra;
                        if (incore(&vp->v_bufobj, rabn) == NULL) {
                            rabp = nfs_getcacheblk(vp, rabn, biosize, td);
                            if (!rabp) {
                                error = newnfs_sigintr(nmp, td);
                                return (error ? error : EINTR);
                            }
                            if ((rabp->b_flags & (B_CACHE|B_DELWRI)) == 0) {
                                rabp->b_flags |= B_ASYNC;
                                rabp->b_iocmd = BIO_READ;
                                vfs_busy_pages(rabp, 0);
                                if (ncl_asyncio(nmp, rabp, cred, td)) {
                                    rabp->b_flags |= B_INVAL;
                                    rabp->b_ioflags |= BIO_ERROR;
                                    vfs_unbusy_pages(rabp);
                                    brelse(rabp);
                                    break;
                                }
                            } else {
                                brelse(rabp);
                            }
                        }
                    }
                }

                /* Note that bcount is *not* DEV_BSIZE aligned. */
                bcount = biosize;
                if ((off_t)lbn * biosize >= nsize) {
                        bcount = 0;
                } else if ((off_t)(lbn + 1) * biosize > nsize) {
                        bcount = nsize - (off_t)lbn * biosize;
                }
                bp = nfs_getcacheblk(vp, lbn, bcount, td);

                if (!bp) {
                        error = newnfs_sigintr(nmp, td);
                        return (error ? error : EINTR);
                }

                /*
                 * If B_CACHE is not set, we must issue the read.  If this
                 * fails, we return an error.
                 */

                if ((bp->b_flags & B_CACHE) == 0) {
                    bp->b_iocmd = BIO_READ;
                    vfs_busy_pages(bp, 0);
                    error = ncl_doio(vp, bp, cred, td, 0);
                    if (error) {
                        brelse(bp);
                        return (error);
                    }
                }

                /*
                 * on is the offset into the current bp.  Figure out how many
                 * bytes we can copy out of the bp.  Note that bcount is
                 * NOT DEV_BSIZE aligned.
                 *
                 * Then figure out how many bytes we can copy into the uio.
                 */

                n = 0;
                if (on < bcount)
                        n = MIN((unsigned)(bcount - on), uio->uio_resid);
                break;
            case VLNK:
                NFSINCRGLOBAL(nfsstatsv1.biocache_readlinks);
                bp = nfs_getcacheblk(vp, (daddr_t)0, NFS_MAXPATHLEN, td);
                if (!bp) {
                        error = newnfs_sigintr(nmp, td);
                        return (error ? error : EINTR);
                }
                if ((bp->b_flags & B_CACHE) == 0) {
                    bp->b_iocmd = BIO_READ;
                    vfs_busy_pages(bp, 0);
                    error = ncl_doio(vp, bp, cred, td, 0);
                    if (error) {
                        bp->b_ioflags |= BIO_ERROR;
                        brelse(bp);
                        return (error);
                    }
                }
                n = MIN(uio->uio_resid, NFS_MAXPATHLEN - bp->b_resid);
                on = 0;
                break;
            case VDIR:
                NFSINCRGLOBAL(nfsstatsv1.biocache_readdirs);
                if (np->n_direofoffset
                    && uio->uio_offset >= np->n_direofoffset) {
                    return (0);
                }
                lbn = (uoff_t)uio->uio_offset / NFS_DIRBLKSIZ;
                on = uio->uio_offset & (NFS_DIRBLKSIZ - 1);
                bp = nfs_getcacheblk(vp, lbn, NFS_DIRBLKSIZ, td);
                if (!bp) {
                    error = newnfs_sigintr(nmp, td);
                    return (error ? error : EINTR);
                }
                if ((bp->b_flags & B_CACHE) == 0) {
                    bp->b_iocmd = BIO_READ;
                    vfs_busy_pages(bp, 0);
                    error = ncl_doio(vp, bp, cred, td, 0);
                    if (error) {
                            brelse(bp);
                    }
                    while (error == NFSERR_BAD_COOKIE) {
                        ncl_invaldir(vp);
                        error = ncl_vinvalbuf(vp, 0, td, 1);
                        /*
                         * Yuck! The directory has been modified on the
                         * server. The only way to get the block is by
                         * reading from the beginning to get all the
                         * offset cookies.
                         *
                         * Leave the last bp intact unless there is an error.
                         * Loop back up to the while if the error is another
                         * NFSERR_BAD_COOKIE (double yuch!).
                         */
                        for (i = 0; i <= lbn && !error; i++) {
                            if (np->n_direofoffset
                                && (i * NFS_DIRBLKSIZ) >= np->n_direofoffset)
                                    return (0);
                            bp = nfs_getcacheblk(vp, i, NFS_DIRBLKSIZ, td);
                            if (!bp) {
                                error = newnfs_sigintr(nmp, td);
                                return (error ? error : EINTR);
                            }
                            if ((bp->b_flags & B_CACHE) == 0) {
                                    bp->b_iocmd = BIO_READ;
                                    vfs_busy_pages(bp, 0);
                                    error = ncl_doio(vp, bp, cred, td, 0);
                                    /*
                                     * no error + B_INVAL == directory EOF,
                                     * use the block.
                                     */
                                    if (error == 0 && (bp->b_flags & B_INVAL))
                                            break;
                            }
                            /*
                             * An error will throw away the block and the
                             * for loop will break out.  If no error and this
                             * is not the block we want, we throw away the
                             * block and go for the next one via the for loop.
                             */
                            if (error || i < lbn)
                                    brelse(bp);
                        }
                    }
                    /*
                     * The above while is repeated if we hit another cookie
                     * error.  If we hit an error and it wasn't a cookie error,
                     * we give up.
                     */
                    if (error)
                            return (error);
                }

                /*
                 * If not eof and read aheads are enabled, start one.
                 * (You need the current block first, so that you have the
                 *  directory offset cookie of the next block.)
                 */
                if (nmp->nm_readahead > 0 &&
                    (bp->b_flags & B_INVAL) == 0 &&
                    (np->n_direofoffset == 0 ||
                    (lbn + 1) * NFS_DIRBLKSIZ < np->n_direofoffset) &&
                    incore(&vp->v_bufobj, lbn + 1) == NULL) {
                        rabp = nfs_getcacheblk(vp, lbn + 1, NFS_DIRBLKSIZ, td);
                        if (rabp) {
                            if ((rabp->b_flags & (B_CACHE|B_DELWRI)) == 0) {
                                rabp->b_flags |= B_ASYNC;
                                rabp->b_iocmd = BIO_READ;
                                vfs_busy_pages(rabp, 0);
                                if (ncl_asyncio(nmp, rabp, cred, td)) {
                                    rabp->b_flags |= B_INVAL;
                                    rabp->b_ioflags |= BIO_ERROR;
                                    vfs_unbusy_pages(rabp);
                                    brelse(rabp);
                                }
                            } else {
                                brelse(rabp);
                            }
                        }
                }
                /*
                 * Unlike VREG files, whos buffer size ( bp->b_bcount ) is
                 * chopped for the EOF condition, we cannot tell how large
                 * NFS directories are going to be until we hit EOF.  So
                 * an NFS directory buffer is *not* chopped to its EOF.  Now,
                 * it just so happens that b_resid will effectively chop it
                 * to EOF.  *BUT* this information is lost if the buffer goes
                 * away and is reconstituted into a B_CACHE state ( due to
                 * being VMIO ) later.  So we keep track of the directory eof
                 * in np->n_direofoffset and chop it off as an extra step
                 * right here.
                 */
                n = lmin(uio->uio_resid, NFS_DIRBLKSIZ - bp->b_resid - on);
                if (np->n_direofoffset && n > np->n_direofoffset - uio->uio_offset)
                        n = np->n_direofoffset - uio->uio_offset;
                break;
            default:
                printf(" ncl_bioread: type %x unexpected\n", vp->v_type);
                bp = NULL;
                break;
            }

            if (n > 0) {
                    error = vn_io_fault_uiomove(bp->b_data + on, (int)n, uio);
            }
            if (vp->v_type == VLNK)
                n = 0;
            if (bp != NULL)
                brelse(bp);
        } while (error == 0 && uio->uio_resid > 0 && n > 0);
        return (error);
}

/*
 * The NFS write path cannot handle iovecs with len > 1. So we need to
 * break up iovecs accordingly (restricting them to wsize).
 * For the SYNC case, we can do this with 1 copy (user buffer -> mbuf).
 * For the ASYNC case, 2 copies are needed. The first a copy from the
 * user buffer to a staging buffer and then a second copy from the staging
 * buffer to mbufs. This can be optimized by copying from the user buffer
 * directly into mbufs and passing the chain down, but that requires a
 * fair amount of re-working of the relevant codepaths (and can be done
 * later).
 */
static int
nfs_directio_write(vp, uiop, cred, ioflag)
        struct vnode *vp;
        struct uio *uiop;
        struct ucred *cred;
        int ioflag;
{
        int error;
        struct nfsmount *nmp = VFSTONFS(vp->v_mount);
        struct thread *td = uiop->uio_td;
        int size;
        int wsize;

        mtx_lock(&nmp->nm_mtx);
        wsize = nmp->nm_wsize;
        mtx_unlock(&nmp->nm_mtx);
        if (ioflag & IO_SYNC) {
                int iomode, must_commit;
                struct uio uio;
                struct iovec iov;
do_sync:
                while (uiop->uio_resid > 0) {
                        size = MIN(uiop->uio_resid, wsize);
                        size = MIN(uiop->uio_iov->iov_len, size);
                        iov.iov_base = uiop->uio_iov->iov_base;
                        iov.iov_len = size;
                        uio.uio_iov = &iov;
                        uio.uio_iovcnt = 1;
                        uio.uio_offset = uiop->uio_offset;
                        uio.uio_resid = size;
                        uio.uio_segflg = UIO_USERSPACE;
                        uio.uio_rw = UIO_WRITE;
                        uio.uio_td = td;
                        iomode = NFSWRITE_FILESYNC;
                        error = ncl_writerpc(vp, &uio, cred, &iomode,
                            &must_commit, 0);
                        KASSERT((must_commit == 0),
                                ("ncl_directio_write: Did not commit write"));
                        if (error)
                                return (error);
                        uiop->uio_offset += size;
                        uiop->uio_resid -= size;
                        if (uiop->uio_iov->iov_len <= size) {
                                uiop->uio_iovcnt--;
                                uiop->uio_iov++;
                        } else {
                                uiop->uio_iov->iov_base =
                                        (char *)uiop->uio_iov->iov_base + size;
                                uiop->uio_iov->iov_len -= size;
                        }
                }
        } else {
                struct uio *t_uio;
                struct iovec *t_iov;
                struct buf *bp;

                /*
                 * Break up the write into blocksize chunks and hand these
                 * over to nfsiod's for write back.
                 * Unfortunately, this incurs a copy of the data. Since
                 * the user could modify the buffer before the write is
                 * initiated.
                 *
                 * The obvious optimization here is that one of the 2 copies
                 * in the async write path can be eliminated by copying the
                 * data here directly into mbufs and passing the mbuf chain
                 * down. But that will require a fair amount of re-working
                 * of the code and can be done if there's enough interest
                 * in NFS directio access.
                 */
                while (uiop->uio_resid > 0) {
                        size = MIN(uiop->uio_resid, wsize);
                        size = MIN(uiop->uio_iov->iov_len, size);
                        bp = getpbuf(&ncl_pbuf_freecnt);
                        t_uio = malloc(sizeof(struct uio), M_NFSDIRECTIO, M_WAITOK);
                        t_iov = malloc(sizeof(struct iovec), M_NFSDIRECTIO, M_WAITOK);
                        t_iov->iov_base = malloc(size, M_NFSDIRECTIO, M_WAITOK);
                        t_iov->iov_len = size;
                        t_uio->uio_iov = t_iov;
                        t_uio->uio_iovcnt = 1;
                        t_uio->uio_offset = uiop->uio_offset;
                        t_uio->uio_resid = size;
                        t_uio->uio_segflg = UIO_SYSSPACE;
                        t_uio->uio_rw = UIO_WRITE;
                        t_uio->uio_td = td;
                        KASSERT(uiop->uio_segflg == UIO_USERSPACE ||
                            uiop->uio_segflg == UIO_SYSSPACE,
                            ("nfs_directio_write: Bad uio_segflg"));
                        if (uiop->uio_segflg == UIO_USERSPACE) {
                                error = copyin(uiop->uio_iov->iov_base,
                                    t_iov->iov_base, size);
                                if (error != 0)
                                        goto err_free;
                        } else
                                /*
                                 * UIO_SYSSPACE may never happen, but handle
                                 * it just in case it does.
                                 */
                                bcopy(uiop->uio_iov->iov_base, t_iov->iov_base,
                                    size);
                        bp->b_flags |= B_DIRECT;
                        bp->b_iocmd = BIO_WRITE;
                        if (cred != NOCRED) {
                                crhold(cred);
                                bp->b_wcred = cred;
                        } else
                                bp->b_wcred = NOCRED;
                        bp->b_caller1 = (void *)t_uio;
                        bp->b_vp = vp;
                        error = ncl_asyncio(nmp, bp, NOCRED, td);
err_free:
                        if (error) {
                                free(t_iov->iov_base, M_NFSDIRECTIO);
                                free(t_iov, M_NFSDIRECTIO);
                                free(t_uio, M_NFSDIRECTIO);
                                bp->b_vp = NULL;
                                relpbuf(bp, &ncl_pbuf_freecnt);
                                if (error == EINTR)
                                        return (error);
                                goto do_sync;
                        }
                        uiop->uio_offset += size;
                        uiop->uio_resid -= size;
                        if (uiop->uio_iov->iov_len <= size) {
                                uiop->uio_iovcnt--;
                                uiop->uio_iov++;
                        } else {
                                uiop->uio_iov->iov_base =
                                        (char *)uiop->uio_iov->iov_base + size;
                                uiop->uio_iov->iov_len -= size;
                        }
                }
        }
        return (0);
}

/*
 * Vnode op for write using bio
 */
int
ncl_write(struct vop_write_args *ap)
{
        int biosize;
        struct uio *uio = ap->a_uio;
        struct thread *td = uio->uio_td;
        struct vnode *vp = ap->a_vp;
        struct nfsnode *np = VTONFS(vp);
        struct ucred *cred = ap->a_cred;
        int ioflag = ap->a_ioflag;
        struct buf *bp;
        struct vattr vattr;
        struct nfsmount *nmp = VFSTONFS(vp->v_mount);
        daddr_t lbn;
        int bcount, noncontig_write, obcount;
        int bp_cached, n, on, error = 0, error1, wouldcommit;
        size_t orig_resid, local_resid;
        off_t orig_size, tmp_off;

        KASSERT(uio->uio_rw == UIO_WRITE, ("ncl_write mode"));
        KASSERT(uio->uio_segflg != UIO_USERSPACE || uio->uio_td == curthread,
            ("ncl_write proc"));
        if (vp->v_type != VREG)
                return (EIO);
        mtx_lock(&np->n_mtx);
        if (np->n_flag & NWRITEERR) {
                np->n_flag &= ~NWRITEERR;
                mtx_unlock(&np->n_mtx);
                return (np->n_error);
        } else
                mtx_unlock(&np->n_mtx);
        mtx_lock(&nmp->nm_mtx);
        if ((nmp->nm_flag & NFSMNT_NFSV3) != 0 &&
            (nmp->nm_state & NFSSTA_GOTFSINFO) == 0) {
                mtx_unlock(&nmp->nm_mtx);
                (void)ncl_fsinfo(nmp, vp, cred, td);
                mtx_lock(&nmp->nm_mtx);
        }
        if (nmp->nm_wsize == 0)
                (void) newnfs_iosize(nmp);
        mtx_unlock(&nmp->nm_mtx);

        /*
         * Synchronously flush pending buffers if we are in synchronous
         * mode or if we are appending.
         */
        if (ioflag & (IO_APPEND | IO_SYNC)) {
                mtx_lock(&np->n_mtx);
                if (np->n_flag & NMODIFIED) {
                        mtx_unlock(&np->n_mtx);
#ifdef notyet /* Needs matching nonblock semantics elsewhere, too. */
                        /*
                         * Require non-blocking, synchronous writes to
                         * dirty files to inform the program it needs
                         * to fsync(2) explicitly.
                         */
                        if (ioflag & IO_NDELAY)
                                return (EAGAIN);
#endif
                        np->n_attrstamp = 0;
                        KDTRACE_NFS_ATTRCACHE_FLUSH_DONE(vp);
                        error = ncl_vinvalbuf(vp, V_SAVE, td, 1);
                        if (error)
                                return (error);
                } else
                        mtx_unlock(&np->n_mtx);
        }

        orig_resid = uio->uio_resid;
        mtx_lock(&np->n_mtx);
        orig_size = np->n_size;
        mtx_unlock(&np->n_mtx);

        /*
         * If IO_APPEND then load uio_offset.  We restart here if we cannot
         * get the append lock.
         */
        if (ioflag & IO_APPEND) {
                np->n_attrstamp = 0;
                KDTRACE_NFS_ATTRCACHE_FLUSH_DONE(vp);
                error = VOP_GETATTR(vp, &vattr, cred);
                if (error)
                        return (error);
                mtx_lock(&np->n_mtx);
                uio->uio_offset = np->n_size;
                mtx_unlock(&np->n_mtx);
        }

        if (uio->uio_offset < 0)
                return (EINVAL);
        tmp_off = uio->uio_offset + uio->uio_resid;
        if (tmp_off > nmp->nm_maxfilesize || tmp_off < uio->uio_offset)
                return (EFBIG);
        if (uio->uio_resid == 0)
                return (0);

        if (newnfs_directio_enable && (ioflag & IO_DIRECT) && vp->v_type == VREG)
                return nfs_directio_write(vp, uio, cred, ioflag);

        /*
         * Maybe this should be above the vnode op call, but so long as
         * file servers have no limits, i don't think it matters
         */
        if (vn_rlimit_fsize(vp, uio, td))
                return (EFBIG);

        biosize = vp->v_bufobj.bo_bsize;
        /*
         * Find all of this file's B_NEEDCOMMIT buffers.  If our writes
         * would exceed the local maximum per-file write commit size when
         * combined with those, we must decide whether to flush,
         * go synchronous, or return error.  We don't bother checking
         * IO_UNIT -- we just make all writes atomic anyway, as there's
         * no point optimizing for something that really won't ever happen.
         */
        wouldcommit = 0;
        if (!(ioflag & IO_SYNC)) {
                int nflag;

                mtx_lock(&np->n_mtx);
                nflag = np->n_flag;
                mtx_unlock(&np->n_mtx);
                if (nflag & NMODIFIED) {
                        BO_LOCK(&vp->v_bufobj);
                        if (vp->v_bufobj.bo_dirty.bv_cnt != 0) {
                                TAILQ_FOREACH(bp, &vp->v_bufobj.bo_dirty.bv_hd,
                                    b_bobufs) {
                                        if (bp->b_flags & B_NEEDCOMMIT)
                                                wouldcommit += bp->b_bcount;
                                }
                        }
                        BO_UNLOCK(&vp->v_bufobj);
                }
        }

        do {
                if (!(ioflag & IO_SYNC)) {
                        wouldcommit += biosize;
                        if (wouldcommit > nmp->nm_wcommitsize) {
                                np->n_attrstamp = 0;
                                KDTRACE_NFS_ATTRCACHE_FLUSH_DONE(vp);
                                error = ncl_vinvalbuf(vp, V_SAVE, td, 1);
                                if (error)
                                        return (error);
                                wouldcommit = biosize;
                        }
                }

                NFSINCRGLOBAL(nfsstatsv1.biocache_writes);
                lbn = uio->uio_offset / biosize;
                on = uio->uio_offset - (lbn * biosize);
                n = MIN((unsigned)(biosize - on), uio->uio_resid);
again:
                /*
                 * Handle direct append and file extension cases, calculate
                 * unaligned buffer size.
                 */
                mtx_lock(&np->n_mtx);
                if ((np->n_flag & NHASBEENLOCKED) == 0 &&
                    (nmp->nm_flag & NFSMNT_NONCONTIGWR) != 0)
                        noncontig_write = 1;
                else
                        noncontig_write = 0;
                if ((uio->uio_offset == np->n_size ||
                    (noncontig_write != 0 &&
                    lbn == (np->n_size / biosize) &&
                    uio->uio_offset + n > np->n_size)) && n) {
                        mtx_unlock(&np->n_mtx);
                        /*
                         * Get the buffer (in its pre-append state to maintain
                         * B_CACHE if it was previously set).  Resize the
                         * nfsnode after we have locked the buffer to prevent
                         * readers from reading garbage.
                         */
                        obcount = np->n_size - (lbn * biosize);
                        bp = nfs_getcacheblk(vp, lbn, obcount, td);

                        if (bp != NULL) {
                                long save;

                                mtx_lock(&np->n_mtx);
                                np->n_size = uio->uio_offset + n;
                                np->n_flag |= NMODIFIED;
                                vnode_pager_setsize(vp, np->n_size);
                                mtx_unlock(&np->n_mtx);

                                save = bp->b_flags & B_CACHE;
                                bcount = on + n;
                                allocbuf(bp, bcount);
                                bp->b_flags |= save;
                                if (noncontig_write != 0 && on > obcount)
                                        vfs_bio_bzero_buf(bp, obcount, on -
                                            obcount);
                        }
                } else {
                        /*
                         * Obtain the locked cache block first, and then
                         * adjust the file's size as appropriate.
                         */
                        bcount = on + n;
                        if ((off_t)lbn * biosize + bcount < np->n_size) {
                                if ((off_t)(lbn + 1) * biosize < np->n_size)
                                        bcount = biosize;
                                else
                                        bcount = np->n_size - (off_t)lbn * biosize;
                        }
                        mtx_unlock(&np->n_mtx);
                        bp = nfs_getcacheblk(vp, lbn, bcount, td);
                        mtx_lock(&np->n_mtx);
                        if (uio->uio_offset + n > np->n_size) {
                                np->n_size = uio->uio_offset + n;
                                np->n_flag |= NMODIFIED;
                                vnode_pager_setsize(vp, np->n_size);
                        }
                        mtx_unlock(&np->n_mtx);
                }

                if (!bp) {
                        error = newnfs_sigintr(nmp, td);
                        if (!error)
                                error = EINTR;
                        break;
                }

                /*
                 * Issue a READ if B_CACHE is not set.  In special-append
                 * mode, B_CACHE is based on the buffer prior to the write
                 * op and is typically set, avoiding the read.  If a read
                 * is required in special append mode, the server will
                 * probably send us a short-read since we extended the file
                 * on our end, resulting in b_resid == 0 and, thusly,
                 * B_CACHE getting set.
                 *
                 * We can also avoid issuing the read if the write covers
                 * the entire buffer.  We have to make sure the buffer state
                 * is reasonable in this case since we will not be initiating
                 * I/O.  See the comments in kern/vfs_bio.c's getblk() for
                 * more information.
                 *
                 * B_CACHE may also be set due to the buffer being cached
                 * normally.
                 */

                bp_cached = 1;
                if (on == 0 && n == bcount) {
                        if ((bp->b_flags & B_CACHE) == 0)
                                bp_cached = 0;
                        bp->b_flags |= B_CACHE;
                        bp->b_flags &= ~B_INVAL;
                        bp->b_ioflags &= ~BIO_ERROR;
                }

                if ((bp->b_flags & B_CACHE) == 0) {
                        bp->b_iocmd = BIO_READ;
                        vfs_busy_pages(bp, 0);
                        error = ncl_doio(vp, bp, cred, td, 0);
                        if (error) {
                                brelse(bp);
                                break;
                        }
                }
                if (bp->b_wcred == NOCRED)
                        bp->b_wcred = crhold(cred);
                mtx_lock(&np->n_mtx);
                np->n_flag |= NMODIFIED;
                mtx_unlock(&np->n_mtx);

                /*
                 * If dirtyend exceeds file size, chop it down.  This should
                 * not normally occur but there is an append race where it
                 * might occur XXX, so we log it.
                 *
                 * If the chopping creates a reverse-indexed or degenerate
                 * situation with dirtyoff/end, we 0 both of them.
                 */

                if (bp->b_dirtyend > bcount) {
                        printf("NFS append race @%lx:%d\n",
                            (long)bp->b_blkno * DEV_BSIZE,
                            bp->b_dirtyend - bcount);
                        bp->b_dirtyend = bcount;
                }

                if (bp->b_dirtyoff >= bp->b_dirtyend)
                        bp->b_dirtyoff = bp->b_dirtyend = 0;

                /*
                 * If the new write will leave a contiguous dirty
                 * area, just update the b_dirtyoff and b_dirtyend,
                 * otherwise force a write rpc of the old dirty area.
                 *
                 * If there has been a file lock applied to this file
                 * or vfs.nfs.old_noncontig_writing is set, do the following:
                 * While it is possible to merge discontiguous writes due to
                 * our having a B_CACHE buffer ( and thus valid read data
                 * for the hole), we don't because it could lead to
                 * significant cache coherency problems with multiple clients,
                 * especially if locking is implemented later on.
                 *
                 * If vfs.nfs.old_noncontig_writing is not set and there has
                 * not been file locking done on this file:
                 * Relax coherency a bit for the sake of performance and
                 * expand the current dirty region to contain the new
                 * write even if it means we mark some non-dirty data as
                 * dirty.
                 */

                if (noncontig_write == 0 && bp->b_dirtyend > 0 &&
                    (on > bp->b_dirtyend || (on + n) < bp->b_dirtyoff)) {
                        if (bwrite(bp) == EINTR) {
                                error = EINTR;
                                break;
                        }
                        goto again;
                }

                local_resid = uio->uio_resid;
                error = vn_io_fault_uiomove((char *)bp->b_data + on, n, uio);

                if (error != 0 && !bp_cached) {
                        /*
                         * This block has no other content than what
                         * possibly was written by the faulty uiomove.
                         * Release it, forgetting the data pages, to
                         * prevent the leak of uninitialized data to
                         * usermode.
                         */
                        bp->b_ioflags |= BIO_ERROR;
                        brelse(bp);
                        uio->uio_offset -= local_resid - uio->uio_resid;
                        uio->uio_resid = local_resid;
                        break;
                }

                /*
                 * Since this block is being modified, it must be written
                 * again and not just committed.  Since write clustering does
                 * not work for the stage 1 data write, only the stage 2
                 * commit rpc, we have to clear B_CLUSTEROK as well.
                 */
                bp->b_flags &= ~(B_NEEDCOMMIT | B_CLUSTEROK);

                /*
                 * Get the partial update on the progress made from
                 * uiomove, if an error occurred.
                 */
                if (error != 0)
                        n = local_resid - uio->uio_resid;

                /*
                 * Only update dirtyoff/dirtyend if not a degenerate
                 * condition.
                 */
                if (n > 0) {
                        if (bp->b_dirtyend > 0) {
                                bp->b_dirtyoff = uimin(on, bp->b_dirtyoff);
                                bp->b_dirtyend = uimax((on + n), bp->b_dirtyend);
                        } else {
                                bp->b_dirtyoff = on;
                                bp->b_dirtyend = on + n;
                        }
                        vfs_bio_set_valid(bp, on, n);
                }

                /*
                 * If IO_SYNC do bwrite().
                 *
                 * IO_INVAL appears to be unused.  The idea appears to be
                 * to turn off caching in this case.  Very odd.  XXX
                 */
                if ((ioflag & IO_SYNC)) {
                        if (ioflag & IO_INVAL)
                                bp->b_flags |= B_NOCACHE;
                        error1 = bwrite(bp);
                        if (error1 != 0) {
                                if (error == 0)
                                        error = error1;
                                break;
                        }
                } else if ((n + on) == biosize) {
                        bp->b_flags |= B_ASYNC;
                        (void) ncl_writebp(bp, 0, NULL);
                } else {
                        bdwrite(bp);
                }

                if (error != 0)
                        break;
        } while (uio->uio_resid > 0 && n > 0);

        if (error != 0) {
                if (ioflag & IO_UNIT) {
                        VATTR_NULL(&vattr);
                        vattr.va_size = orig_size;
                        /* IO_SYNC is handled implicitly */
                        (void)VOP_SETATTR(vp, &vattr, cred);
                        uio->uio_offset -= orig_resid - uio->uio_resid;
                        uio->uio_resid = orig_resid;
                }
        }

        return (error);
}

/*
 * Get an nfs cache block.
 *
 * Allocate a new one if the block isn't currently in the cache
 * and return the block marked busy. If the calling process is
 * interrupted by a signal for an interruptible mount point, return
 * NULL.
 *
 * The caller must carefully deal with the possible B_INVAL state of
 * the buffer.  ncl_doio() clears B_INVAL (and ncl_asyncio() clears it
 * indirectly), so synchronous reads can be issued without worrying about
 * the B_INVAL state.  We have to be a little more careful when dealing
 * with writes (see comments in nfs_write()) when extending a file past
 * its EOF.
 */
static struct buf *
nfs_getcacheblk(struct vnode *vp, daddr_t bn, int size, struct thread *td)
{
        struct buf *bp;
        struct mount *mp;
        struct nfsmount *nmp;

        mp = vp->v_mount;
        nmp = VFSTONFS(mp);

        if (nmp->nm_flag & NFSMNT_INT) {
                sigset_t oldset;

                newnfs_set_sigmask(td, &oldset);
                bp = getblk(vp, bn, size, PCATCH, 0, 0);
                newnfs_restore_sigmask(td, &oldset);
                while (bp == NULL) {
                        if (newnfs_sigintr(nmp, td))
                                return (NULL);
                        bp = getblk(vp, bn, size, 0, 2 * hz, 0);
                }
        } else {
                bp = getblk(vp, bn, size, 0, 0, 0);
        }

        if (vp->v_type == VREG)
                bp->b_blkno = bn * (vp->v_bufobj.bo_bsize / DEV_BSIZE);
        return (bp);
}

/*
 * Flush and invalidate all dirty buffers. If another process is already
 * doing the flush, just wait for completion.
 */
int
ncl_vinvalbuf(struct vnode *vp, int flags, struct thread *td, int intrflg)
{
        struct nfsnode *np = VTONFS(vp);
        struct nfsmount *nmp = VFSTONFS(vp->v_mount);
        int error = 0, slpflag, slptimeo;
        int old_lock = 0;

        ASSERT_VOP_LOCKED(vp, "ncl_vinvalbuf");

        if ((nmp->nm_flag & NFSMNT_INT) == 0)
                intrflg = 0;
        if ((nmp->nm_mountp->mnt_kern_flag & MNTK_UNMOUNTF))
                intrflg = 1;
        if (intrflg) {
                slpflag = PCATCH;
                slptimeo = 2 * hz;
        } else {
                slpflag = 0;
                slptimeo = 0;
        }

        old_lock = ncl_upgrade_vnlock(vp);
        if (vp->v_iflag & VI_DOOMED) {
                /*
                 * Since vgonel() uses the generic vinvalbuf() to flush
                 * dirty buffers and it does not call this function, it
                 * is safe to just return OK when VI_DOOMED is set.
                 */
                ncl_downgrade_vnlock(vp, old_lock);
                return (0);
        }

        /*
         * Now, flush as required.
         */
        if ((flags & V_SAVE) && (vp->v_bufobj.bo_object != NULL)) {
                VM_OBJECT_WLOCK(vp->v_bufobj.bo_object);
                vm_object_page_clean(vp->v_bufobj.bo_object, 0, 0, OBJPC_SYNC);
                VM_OBJECT_WUNLOCK(vp->v_bufobj.bo_object);
                /*
                 * If the page clean was interrupted, fail the invalidation.
                 * Not doing so, we run the risk of losing dirty pages in the
                 * vinvalbuf() call below.
                 */
                if (intrflg && (error = newnfs_sigintr(nmp, td)))
                        goto out;
        }

        error = vinvalbuf(vp, flags, slpflag, 0);
        while (error) {
                if (intrflg && (error = newnfs_sigintr(nmp, td)))
                        goto out;
                error = vinvalbuf(vp, flags, 0, slptimeo);
        }
        if (NFSHASPNFS(nmp)) {
                nfscl_layoutcommit(vp, td);
                /*
                 * Invalidate the attribute cache, since writes to a DS
                 * won't update the size attribute.
                 */
                mtx_lock(&np->n_mtx);
                np->n_attrstamp = 0;
        } else
                mtx_lock(&np->n_mtx);
        if (np->n_directio_asyncwr == 0)
                np->n_flag &= ~NMODIFIED;
        mtx_unlock(&np->n_mtx);
out:
        ncl_downgrade_vnlock(vp, old_lock);
        return error;
}

/*
 * Initiate asynchronous I/O. Return an error if no nfsiods are available.
 * This is mainly to avoid queueing async I/O requests when the nfsiods
 * are all hung on a dead server.
 *
 * Note: ncl_asyncio() does not clear (BIO_ERROR|B_INVAL) but when the bp
 * is eventually dequeued by the async daemon, ncl_doio() *will*.
 */
int
ncl_asyncio(struct nfsmount *nmp, struct buf *bp, struct ucred *cred, struct thread *td)
{
        int iod;
        int gotiod;
        int slpflag = 0;
        int slptimeo = 0;
        int error, error2;

        /*
         * Commits are usually short and sweet so lets save some cpu and
         * leave the async daemons for more important rpc's (such as reads
         * and writes).
         *
         * Readdirplus RPCs do vget()s to acquire the vnodes for entries
         * in the directory in order to update attributes. This can deadlock
         * with another thread that is waiting for async I/O to be done by
         * an nfsiod thread while holding a lock on one of these vnodes.
         * To avoid this deadlock, don't allow the async nfsiod threads to
         * perform Readdirplus RPCs.
         */
        mtx_lock(&ncl_iod_mutex);
        if ((bp->b_iocmd == BIO_WRITE && (bp->b_flags & B_NEEDCOMMIT) &&
             (nmp->nm_bufqiods > ncl_numasync / 2)) ||
            (bp->b_vp->v_type == VDIR && (nmp->nm_flag & NFSMNT_RDIRPLUS))) {
                mtx_unlock(&ncl_iod_mutex);
                return(EIO);
        }
again:
        if (nmp->nm_flag & NFSMNT_INT)
                slpflag = PCATCH;
        gotiod = FALSE;

        /*
         * Find a free iod to process this request.
         */
        for (iod = 0; iod < ncl_numasync; iod++)
                if (ncl_iodwant[iod] == NFSIOD_AVAILABLE) {
                        gotiod = TRUE;
                        break;
                }

        /*
         * Try to create one if none are free.
         */
        if (!gotiod)
                ncl_nfsiodnew();
        else {
                /*
                 * Found one, so wake it up and tell it which
                 * mount to process.
                 */
                NFS_DPF(ASYNCIO, ("ncl_asyncio: waking iod %d for mount %p\n",
                    iod, nmp));
                ncl_iodwant[iod] = NFSIOD_NOT_AVAILABLE;
                ncl_iodmount[iod] = nmp;
                nmp->nm_bufqiods++;
                wakeup(&ncl_iodwant[iod]);
        }

        /*
         * If none are free, we may already have an iod working on this mount
         * point.  If so, it will process our request.
         */
        if (!gotiod) {
                if (nmp->nm_bufqiods > 0) {
                        NFS_DPF(ASYNCIO,
                                ("ncl_asyncio: %d iods are already processing mount %p\n",
                                 nmp->nm_bufqiods, nmp));
                        gotiod = TRUE;
                }
        }

        /*
         * If we have an iod which can process the request, then queue
         * the buffer.
         */
        if (gotiod) {
                /*
                 * Ensure that the queue never grows too large.  We still want
                 * to asynchronize so we block rather than return EIO.
                 */
                while (nmp->nm_bufqlen >= 2*ncl_numasync) {
                        NFS_DPF(ASYNCIO,
                                ("ncl_asyncio: waiting for mount %p queue to drain\n", nmp));
                        nmp->nm_bufqwant = TRUE;
                        error = newnfs_msleep(td, &nmp->nm_bufq,
                            &ncl_iod_mutex, slpflag | PRIBIO, "nfsaio",
                           slptimeo);
                        if (error) {
                                error2 = newnfs_sigintr(nmp, td);
                                if (error2) {
                                        mtx_unlock(&ncl_iod_mutex);
                                        return (error2);
                                }
                                if (slpflag == PCATCH) {
                                        slpflag = 0;
                                        slptimeo = 2 * hz;
                                }
                        }
                        /*
                         * We might have lost our iod while sleeping,
                         * so check and loop if necessary.
                         */
                        goto again;
                }

                /* We might have lost our nfsiod */
                if (nmp->nm_bufqiods == 0) {
                        NFS_DPF(ASYNCIO,
                                ("ncl_asyncio: no iods after mount %p queue was drained, looping\n", nmp));
                        goto again;
                }

                if (bp->b_iocmd == BIO_READ) {
                        if (bp->b_rcred == NOCRED && cred != NOCRED)
                                bp->b_rcred = crhold(cred);
                } else {
                        if (bp->b_wcred == NOCRED && cred != NOCRED)
                                bp->b_wcred = crhold(cred);
                }

                if (bp->b_flags & B_REMFREE)
                        bremfreef(bp);
                BUF_KERNPROC(bp);
                TAILQ_INSERT_TAIL(&nmp->nm_bufq, bp, b_freelist);
                nmp->nm_bufqlen++;
                if ((bp->b_flags & B_DIRECT) && bp->b_iocmd == BIO_WRITE) {
                        mtx_lock(&(VTONFS(bp->b_vp))->n_mtx);
                        VTONFS(bp->b_vp)->n_flag |= NMODIFIED;
                        VTONFS(bp->b_vp)->n_directio_asyncwr++;
                        mtx_unlock(&(VTONFS(bp->b_vp))->n_mtx);
                }
                mtx_unlock(&ncl_iod_mutex);
                return (0);
        }

        mtx_unlock(&ncl_iod_mutex);

        /*
         * All the iods are busy on other mounts, so return EIO to
         * force the caller to process the i/o synchronously.
         */
        NFS_DPF(ASYNCIO, ("ncl_asyncio: no iods available, i/o is synchronous\n"));
        return (EIO);
}

void
ncl_doio_directwrite(struct buf *bp)
{
        int iomode, must_commit;
        struct uio *uiop = (struct uio *)bp->b_caller1;
        char *iov_base = uiop->uio_iov->iov_base;

        iomode = NFSWRITE_FILESYNC;
        uiop->uio_td = NULL; /* NULL since we're in nfsiod */
        ncl_writerpc(bp->b_vp, uiop, bp->b_wcred, &iomode, &must_commit, 0);
        KASSERT((must_commit == 0), ("ncl_doio_directwrite: Did not commit write"));
        free(iov_base, M_NFSDIRECTIO);
        free(uiop->uio_iov, M_NFSDIRECTIO);
        free(uiop, M_NFSDIRECTIO);
        if ((bp->b_flags & B_DIRECT) && bp->b_iocmd == BIO_WRITE) {
                struct nfsnode *np = VTONFS(bp->b_vp);
                mtx_lock(&np->n_mtx);
                if (NFSHASPNFS(VFSTONFS(vnode_mount(bp->b_vp)))) {
                        /*
                         * Invalidate the attribute cache, since writes to a DS
                         * won't update the size attribute.
                         */
                        np->n_attrstamp = 0;
                }
                np->n_directio_asyncwr--;
                if (np->n_directio_asyncwr == 0) {
                        np->n_flag &= ~NMODIFIED;
                        if ((np->n_flag & NFSYNCWAIT)) {
                                np->n_flag &= ~NFSYNCWAIT;
                                wakeup((caddr_t)&np->n_directio_asyncwr);
                        }
                }
                mtx_unlock(&np->n_mtx);
        }
        bp->b_vp = NULL;
        relpbuf(bp, &ncl_pbuf_freecnt);
}

/*
 * Do an I/O operation to/from a cache block. This may be called
 * synchronously or from an nfsiod.
 */
int
ncl_doio(struct vnode *vp, struct buf *bp, struct ucred *cr, struct thread *td,
    int called_from_strategy)
{
        struct uio *uiop;
        struct nfsnode *np;
        struct nfsmount *nmp;
        int error = 0, iomode, must_commit = 0;
        struct uio uio;
        struct iovec io;
        struct proc *p = td ? td->td_proc : NULL;
        uint8_t iocmd;

        np = VTONFS(vp);
        nmp = VFSTONFS(vp->v_mount);
        uiop = &uio;
        uiop->uio_iov = &io;
        uiop->uio_iovcnt = 1;
        uiop->uio_segflg = UIO_SYSSPACE;
        uiop->uio_td = td;

        /*
         * clear BIO_ERROR and B_INVAL state prior to initiating the I/O.  We
         * do this here so we do not have to do it in all the code that
         * calls us.
         */
        bp->b_flags &= ~B_INVAL;
        bp->b_ioflags &= ~BIO_ERROR;

        KASSERT(!(bp->b_flags & B_DONE), ("ncl_doio: bp %p already marked done", bp));
        iocmd = bp->b_iocmd;
        if (iocmd == BIO_READ) {
            io.iov_len = uiop->uio_resid = bp->b_bcount;
            io.iov_base = bp->b_data;
            uiop->uio_rw = UIO_READ;

            switch (vp->v_type) {
            case VREG:
                uiop->uio_offset = ((off_t)bp->b_blkno) * DEV_BSIZE;
                NFSINCRGLOBAL(nfsstatsv1.read_bios);
                error = ncl_readrpc(vp, uiop, cr);

                if (!error) {
                    if (uiop->uio_resid) {
                        /*
                         * If we had a short read with no error, we must have
                         * hit a file hole.  We should zero-fill the remainder.
                         * This can also occur if the server hits the file EOF.
                         *
                         * Holes used to be able to occur due to pending
                         * writes, but that is not possible any longer.
                         */
                        int nread = bp->b_bcount - uiop->uio_resid;
                        ssize_t left = uiop->uio_resid;

                        if (left > 0)
                                bzero((char *)bp->b_data + nread, left);
                        uiop->uio_resid = 0;
                    }
                }
                /* ASSERT_VOP_LOCKED(vp, "ncl_doio"); */
                if (p && (vp->v_vflag & VV_TEXT)) {
                        mtx_lock(&np->n_mtx);
                        if (NFS_TIMESPEC_COMPARE(&np->n_mtime, &np->n_vattr.na_mtime)) {
                                mtx_unlock(&np->n_mtx);
                                PROC_LOCK(p);
                                killproc(p, "text file modification");
                                PROC_UNLOCK(p);
                        } else
                                mtx_unlock(&np->n_mtx);
                }
                break;
            case VLNK:
                uiop->uio_offset = (off_t)0;
                NFSINCRGLOBAL(nfsstatsv1.readlink_bios);
                error = ncl_readlinkrpc(vp, uiop, cr);
                break;
            case VDIR:
                NFSINCRGLOBAL(nfsstatsv1.readdir_bios);
                uiop->uio_offset = ((u_quad_t)bp->b_lblkno) * NFS_DIRBLKSIZ;
                if ((nmp->nm_flag & NFSMNT_RDIRPLUS) != 0) {
                        error = ncl_readdirplusrpc(vp, uiop, cr, td);
                        if (error == NFSERR_NOTSUPP)
                                nmp->nm_flag &= ~NFSMNT_RDIRPLUS;
                }
                if ((nmp->nm_flag & NFSMNT_RDIRPLUS) == 0)
                        error = ncl_readdirrpc(vp, uiop, cr, td);
                /*
                 * end-of-directory sets B_INVAL but does not generate an
                 * error.
                 */
                if (error == 0 && uiop->uio_resid == bp->b_bcount)
                        bp->b_flags |= B_INVAL;
                break;
            default:
                printf("ncl_doio:  type %x unexpected\n", vp->v_type);
                break;
            }
            if (error) {
                bp->b_ioflags |= BIO_ERROR;
                bp->b_error = error;
            }
        } else {
            /*
             * If we only need to commit, try to commit
             */
            if (bp->b_flags & B_NEEDCOMMIT) {
                    int retv;
                    off_t off;

                    off = ((u_quad_t)bp->b_blkno) * DEV_BSIZE + bp->b_dirtyoff;
                    retv = ncl_commit(vp, off, bp->b_dirtyend-bp->b_dirtyoff,
                        bp->b_wcred, td);
                    if (retv == 0) {
                            bp->b_dirtyoff = bp->b_dirtyend = 0;
                            bp->b_flags &= ~(B_NEEDCOMMIT | B_CLUSTEROK);
                            bp->b_resid = 0;
                            bufdone(bp);
                            return (0);
                    }
                    if (retv == NFSERR_STALEWRITEVERF) {
                            ncl_clearcommit(vp->v_mount);
                    }
            }

            /*
             * Setup for actual write
             */
            mtx_lock(&np->n_mtx);
            if ((off_t)bp->b_blkno * DEV_BSIZE + bp->b_dirtyend > np->n_size)
                bp->b_dirtyend = np->n_size - (off_t)bp->b_blkno * DEV_BSIZE;
            mtx_unlock(&np->n_mtx);

            if (bp->b_dirtyend > bp->b_dirtyoff) {
                io.iov_len = uiop->uio_resid = bp->b_dirtyend
                    - bp->b_dirtyoff;
                uiop->uio_offset = (off_t)bp->b_blkno * DEV_BSIZE
                    + bp->b_dirtyoff;
                io.iov_base = (char *)bp->b_data + bp->b_dirtyoff;
                uiop->uio_rw = UIO_WRITE;
                NFSINCRGLOBAL(nfsstatsv1.write_bios);

                if ((bp->b_flags & (B_ASYNC | B_NEEDCOMMIT | B_NOCACHE | B_CLUSTER)) == B_ASYNC)
                    iomode = NFSWRITE_UNSTABLE;
                else
                    iomode = NFSWRITE_FILESYNC;

                error = ncl_writerpc(vp, uiop, cr, &iomode, &must_commit,
                    called_from_strategy);

                /*
                 * When setting B_NEEDCOMMIT also set B_CLUSTEROK to try
                 * to cluster the buffers needing commit.  This will allow
                 * the system to submit a single commit rpc for the whole
                 * cluster.  We can do this even if the buffer is not 100%
                 * dirty (relative to the NFS blocksize), so we optimize the
                 * append-to-file-case.
                 *
                 * (when clearing B_NEEDCOMMIT, B_CLUSTEROK must also be
                 * cleared because write clustering only works for commit
                 * rpc's, not for the data portion of the write).
                 */

                if (!error && iomode == NFSWRITE_UNSTABLE) {
                    bp->b_flags |= B_NEEDCOMMIT;
                    if (bp->b_dirtyoff == 0
                        && bp->b_dirtyend == bp->b_bcount)
                        bp->b_flags |= B_CLUSTEROK;
                } else {
                    bp->b_flags &= ~(B_NEEDCOMMIT | B_CLUSTEROK);
                }

                /*
                 * For an interrupted write, the buffer is still valid
                 * and the write hasn't been pushed to the server yet,
                 * so we can't set BIO_ERROR and report the interruption
                 * by setting B_EINTR. For the B_ASYNC case, B_EINTR
                 * is not relevant, so the rpc attempt is essentially
                 * a noop.  For the case of a V3 write rpc not being
                 * committed to stable storage, the block is still
                 * dirty and requires either a commit rpc or another
                 * write rpc with iomode == NFSV3WRITE_FILESYNC before
                 * the block is reused. This is indicated by setting
                 * the B_DELWRI and B_NEEDCOMMIT flags.
                 *
                 * EIO is returned by ncl_writerpc() to indicate a recoverable
                 * write error and is handled as above, except that
                 * B_EINTR isn't set. One cause of this is a stale stateid
                 * error for the RPC that indicates recovery is required,
                 * when called with called_from_strategy != 0.
                 *
                 * If the buffer is marked B_PAGING, it does not reside on
                 * the vp's paging queues so we cannot call bdirty().  The
                 * bp in this case is not an NFS cache block so we should
                 * be safe. XXX
                 *
                 * The logic below breaks up errors into recoverable and
                 * unrecoverable. For the former, we clear B_INVAL|B_NOCACHE
                 * and keep the buffer around for potential write retries.
                 * For the latter (eg ESTALE), we toss the buffer away (B_INVAL)
                 * and save the error in the nfsnode. This is less than ideal
                 * but necessary. Keeping such buffers around could potentially
                 * cause buffer exhaustion eventually (they can never be written
                 * out, so will get constantly be re-dirtied). It also causes
                 * all sorts of vfs panics. For non-recoverable write errors,
                 * also invalidate the attrcache, so we'll be forced to go over
                 * the wire for this object, returning an error to user on next
                 * call (most of the time).
                 */
                if (error == EINTR || error == EIO || error == ETIMEDOUT
                    || (!error && (bp->b_flags & B_NEEDCOMMIT))) {
                        int s;

                        s = splbio();
                        bp->b_flags &= ~(B_INVAL|B_NOCACHE);
                        if ((bp->b_flags & B_PAGING) == 0) {
                            bdirty(bp);
                            bp->b_flags &= ~B_DONE;
                        }
                        if ((error == EINTR || error == ETIMEDOUT) &&
                            (bp->b_flags & B_ASYNC) == 0)
                            bp->b_flags |= B_EINTR;
                        splx(s);
                } else {
                    if (error) {
                        bp->b_ioflags |= BIO_ERROR;
                        bp->b_flags |= B_INVAL;
                        bp->b_error = np->n_error = error;
                        mtx_lock(&np->n_mtx);
                        np->n_flag |= NWRITEERR;
                        np->n_attrstamp = 0;
                        KDTRACE_NFS_ATTRCACHE_FLUSH_DONE(vp);
                        mtx_unlock(&np->n_mtx);
                    }
                    bp->b_dirtyoff = bp->b_dirtyend = 0;
                }
            } else {
                bp->b_resid = 0;
                bufdone(bp);
                return (0);
            }
        }
        bp->b_resid = uiop->uio_resid;
        if (must_commit)
            ncl_clearcommit(vp->v_mount);
        bufdone(bp);
        return (error);
}

/*
 * Used to aid in handling ftruncate() operations on the NFS client side.
 * Truncation creates a number of special problems for NFS.  We have to
 * throw away VM pages and buffer cache buffers that are beyond EOF, and
 * we have to properly handle VM pages or (potentially dirty) buffers
 * that straddle the truncation point.
 */

int
ncl_meta_setsize(struct vnode *vp, struct ucred *cred, struct thread *td, u_quad_t nsize)
{
        struct nfsnode *np = VTONFS(vp);
        u_quad_t tsize;
        int biosize = vp->v_bufobj.bo_bsize;
        int error = 0;

        mtx_lock(&np->n_mtx);
        tsize = np->n_size;
        np->n_size = nsize;
        mtx_unlock(&np->n_mtx);

        if (nsize < tsize) {
                struct buf *bp;
                daddr_t lbn;
                int bufsize;

                /*
                 * vtruncbuf() doesn't get the buffer overlapping the
                 * truncation point.  We may have a B_DELWRI and/or B_CACHE
                 * buffer that now needs to be truncated.
                 */
                error = vtruncbuf(vp, cred, nsize, biosize);
                lbn = nsize / biosize;
                bufsize = nsize - (lbn * biosize);
                bp = nfs_getcacheblk(vp, lbn, bufsize, td);
                if (!bp)
                        return EINTR;
                if (bp->b_dirtyoff > bp->b_bcount)
                        bp->b_dirtyoff = bp->b_bcount;
                if (bp->b_dirtyend > bp->b_bcount)
                        bp->b_dirtyend = bp->b_bcount;
                bp->b_flags |= B_RELBUF;  /* don't leave garbage around */
                brelse(bp);
        } else {
                vnode_pager_setsize(vp, nsize);
        }
        return(error);
}