// SPDX-License-Identifier: GPL-2.0-only
/*
 * 9P Client
 *
 *  Copyright (C) 2008 by Eric Van Hensbergen <ericvh@gmail.com>
 *  Copyright (C) 2007 by Latchesar Ionkov <lucho@ionkov.net>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/poll.h>
#include <linux/idr.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/sched/signal.h>
#include <linux/uaccess.h>
#include <linux/uio.h>
#include <net/9p/9p.h>
#include <linux/parser.h>
#include <linux/seq_file.h>
#include <net/9p/client.h>
#include <net/9p/transport.h>
#include "protocol.h"

#define CREATE_TRACE_POINTS
#include <trace/events/9p.h>

#define DEFAULT_MSIZE (128 * 1024)

/* Client Option Parsing (code inspired by NFS code)
 *  - a little lazy - parse all client options
 */

enum {
        Opt_msize,
        Opt_trans,
        Opt_legacy,
        Opt_version,
        Opt_err,
};

static const match_table_t tokens = {
        {Opt_msize, "msize=%u"},
        {Opt_legacy, "noextend"},
        {Opt_trans, "trans=%s"},
        {Opt_version, "version=%s"},
        {Opt_err, NULL},
};

inline int p9_is_proto_dotl(struct p9_client *clnt)
{
        return clnt->proto_version == p9_proto_2000L;
}
EXPORT_SYMBOL(p9_is_proto_dotl);

inline int p9_is_proto_dotu(struct p9_client *clnt)
{
        return clnt->proto_version == p9_proto_2000u;
}
EXPORT_SYMBOL(p9_is_proto_dotu);

int p9_show_client_options(struct seq_file *m, struct p9_client *clnt)
{
        if (clnt->msize != DEFAULT_MSIZE)
                seq_printf(m, ",msize=%u", clnt->msize);
        seq_printf(m, ",trans=%s", clnt->trans_mod->name);

        switch (clnt->proto_version) {
        case p9_proto_legacy:
                seq_puts(m, ",noextend");
                break;
        case p9_proto_2000u:
                seq_puts(m, ",version=9p2000.u");
                break;
        case p9_proto_2000L:
                /* Default */
                break;
        }

        if (clnt->trans_mod->show_options)
                return clnt->trans_mod->show_options(m, clnt);
        return 0;
}
EXPORT_SYMBOL(p9_show_client_options);

/* Some error codes are taken directly from the server replies,
 * make sure they are valid.
 */
static int safe_errno(int err)
{
        if (err > 0 || err < -MAX_ERRNO) {
                p9_debug(P9_DEBUG_ERROR, "Invalid error code %d\n", err);
                return -EPROTO;
        }
        return err;
}

/* Interpret mount option for protocol version */
static int get_protocol_version(char *s)
{
        int version = -EINVAL;

        if (!strcmp(s, "9p2000")) {
                version = p9_proto_legacy;
                p9_debug(P9_DEBUG_9P, "Protocol version: Legacy\n");
        } else if (!strcmp(s, "9p2000.u")) {
                version = p9_proto_2000u;
                p9_debug(P9_DEBUG_9P, "Protocol version: 9P2000.u\n");
        } else if (!strcmp(s, "9p2000.L")) {
                version = p9_proto_2000L;
                p9_debug(P9_DEBUG_9P, "Protocol version: 9P2000.L\n");
        } else {
                pr_info("Unknown protocol version %s\n", s);
        }

        return version;
}

/**
 * parse_opts - parse mount options into client structure
 * @opts: options string passed from mount
 * @clnt: existing v9fs client information
 *
 * Return 0 upon success, -ERRNO upon failure
 */

static int parse_opts(char *opts, struct p9_client *clnt)
{
        char *options, *tmp_options;
        char *p;
        substring_t args[MAX_OPT_ARGS];
        int option;
        char *s;
        int ret = 0;

        clnt->proto_version = p9_proto_2000L;
        clnt->msize = DEFAULT_MSIZE;

        if (!opts)
                return 0;

        tmp_options = kstrdup(opts, GFP_KERNEL);
        if (!tmp_options)
                return -ENOMEM;
        options = tmp_options;

        while ((p = strsep(&options, ",")) != NULL) {
                int token, r;

                if (!*p)
                        continue;
                token = match_token(p, tokens, args);
                switch (token) {
                case Opt_msize:
                        r = match_int(&args[0], &option);
                        if (r < 0) {
                                p9_debug(P9_DEBUG_ERROR,
                                         "integer field, but no integer?\n");
                                ret = r;
                                continue;
                        }
                        if (option < 4096) {
                                p9_debug(P9_DEBUG_ERROR,
                                         "msize should be at least 4k\n");
                                ret = -EINVAL;
                                continue;
                        }
                        clnt->msize = option;
                        break;
                case Opt_trans:
                        s = match_strdup(&args[0]);
                        if (!s) {
                                ret = -ENOMEM;
                                p9_debug(P9_DEBUG_ERROR,
                                         "problem allocating copy of trans arg\n");
                                goto free_and_return;
                        }

                        v9fs_put_trans(clnt->trans_mod);
                        clnt->trans_mod = v9fs_get_trans_by_name(s);
                        if (!clnt->trans_mod) {
                                pr_info("Could not find request transport: %s\n",
                                        s);
                                ret = -EINVAL;
                        }
                        kfree(s);
                        break;
                case Opt_legacy:
                        clnt->proto_version = p9_proto_legacy;
                        break;
                case Opt_version:
                        s = match_strdup(&args[0]);
                        if (!s) {
                                ret = -ENOMEM;
                                p9_debug(P9_DEBUG_ERROR,
                                         "problem allocating copy of version arg\n");
                                goto free_and_return;
                        }
                        r = get_protocol_version(s);
                        if (r < 0)
                                ret = r;
                        else
                                clnt->proto_version = r;
                        kfree(s);
                        break;
                default:
                        continue;
                }
        }

free_and_return:
        if (ret)
                v9fs_put_trans(clnt->trans_mod);
        kfree(tmp_options);
        return ret;
}

static int p9_fcall_init(struct p9_client *c, struct p9_fcall *fc,
                         int alloc_msize)
{
        if (likely(c->fcall_cache) && alloc_msize == c->msize) {
                fc->sdata = kmem_cache_alloc(c->fcall_cache, GFP_NOFS);
                fc->cache = c->fcall_cache;
        } else {
                fc->sdata = kmalloc(alloc_msize, GFP_NOFS);
                fc->cache = NULL;
        }
        if (!fc->sdata)
                return -ENOMEM;
        fc->capacity = alloc_msize;
        return 0;
}

void p9_fcall_fini(struct p9_fcall *fc)
{
        /* sdata can be NULL for interrupted requests in trans_rdma,
         * and kmem_cache_free does not do NULL-check for us
         */
        if (unlikely(!fc->sdata))
                return;

        if (fc->cache)
                kmem_cache_free(fc->cache, fc->sdata);
        else
                kfree(fc->sdata);
}
EXPORT_SYMBOL(p9_fcall_fini);

static struct kmem_cache *p9_req_cache;

/**
 * p9_tag_alloc - Allocate a new request.
 * @c: Client session.
 * @type: Transaction type.
 * @max_size: Maximum packet size for this request.
 *
 * Context: Process context.
 * Return: Pointer to new request.
 */
static struct p9_req_t *
p9_tag_alloc(struct p9_client *c, int8_t type, unsigned int max_size)
{
        struct p9_req_t *req = kmem_cache_alloc(p9_req_cache, GFP_NOFS);
        int alloc_msize = min(c->msize, max_size);
        int tag;

        if (!req)
                return ERR_PTR(-ENOMEM);

        if (p9_fcall_init(c, &req->tc, alloc_msize))
                goto free_req;
        if (p9_fcall_init(c, &req->rc, alloc_msize))
                goto free;

        p9pdu_reset(&req->tc);
        p9pdu_reset(&req->rc);
        req->t_err = 0;
        req->status = REQ_STATUS_ALLOC;
        init_waitqueue_head(&req->wq);
        INIT_LIST_HEAD(&req->req_list);

        idr_preload(GFP_NOFS);
        spin_lock_irq(&c->lock);
        if (type == P9_TVERSION)
                tag = idr_alloc(&c->reqs, req, P9_NOTAG, P9_NOTAG + 1,
                                GFP_NOWAIT);
        else
                tag = idr_alloc(&c->reqs, req, 0, P9_NOTAG, GFP_NOWAIT);
        req->tc.tag = tag;
        spin_unlock_irq(&c->lock);
        idr_preload_end();
        if (tag < 0)
                goto free;

        /* Init ref to two because in the general case there is one ref
         * that is put asynchronously by a writer thread, one ref
         * temporarily given by p9_tag_lookup and put by p9_client_cb
         * in the recv thread, and one ref put by p9_tag_remove in the
         * main thread. The only exception is virtio that does not use
         * p9_tag_lookup but does not have a writer thread either
         * (the write happens synchronously in the request/zc_request
         * callback), so p9_client_cb eats the second ref there
         * as the pointer is duplicated directly by virtqueue_add_sgs()
         */
        refcount_set(&req->refcount.refcount, 2);

        return req;

free:
        p9_fcall_fini(&req->tc);
        p9_fcall_fini(&req->rc);
free_req:
        kmem_cache_free(p9_req_cache, req);
        return ERR_PTR(-ENOMEM);
}

/**
 * p9_tag_lookup - Look up a request by tag.
 * @c: Client session.
 * @tag: Transaction ID.
 *
 * Context: Any context.
 * Return: A request, or %NULL if there is no request with that tag.
 */
struct p9_req_t *p9_tag_lookup(struct p9_client *c, u16 tag)
{
        struct p9_req_t *req;

        rcu_read_lock();
again:
        req = idr_find(&c->reqs, tag);
        if (req) {
                /* We have to be careful with the req found under rcu_read_lock
                 * Thanks to SLAB_TYPESAFE_BY_RCU we can safely try to get the
                 * ref again without corrupting other data, then check again
                 * that the tag matches once we have the ref
                 */
                if (!p9_req_try_get(req))
                        goto again;
                if (req->tc.tag != tag) {
                        p9_req_put(req);
                        goto again;
                }
        }
        rcu_read_unlock();

        return req;
}
EXPORT_SYMBOL(p9_tag_lookup);

/**
 * p9_tag_remove - Remove a tag.
 * @c: Client session.
 * @r: Request of reference.
 *
 * Context: Any context.
 */
static int p9_tag_remove(struct p9_client *c, struct p9_req_t *r)
{
        unsigned long flags;
        u16 tag = r->tc.tag;

        p9_debug(P9_DEBUG_MUX, "clnt %p req %p tag: %d\n", c, r, tag);
        spin_lock_irqsave(&c->lock, flags);
        idr_remove(&c->reqs, tag);
        spin_unlock_irqrestore(&c->lock, flags);
        return p9_req_put(r);
}

static void p9_req_free(struct kref *ref)
{
        struct p9_req_t *r = container_of(ref, struct p9_req_t, refcount);

        p9_fcall_fini(&r->tc);
        p9_fcall_fini(&r->rc);
        kmem_cache_free(p9_req_cache, r);
}

int p9_req_put(struct p9_req_t *r)
{
        return kref_put(&r->refcount, p9_req_free);
}
EXPORT_SYMBOL(p9_req_put);

/**
 * p9_tag_cleanup - cleans up tags structure and reclaims resources
 * @c:  v9fs client struct
 *
 * This frees resources associated with the tags structure
 *
 */
static void p9_tag_cleanup(struct p9_client *c)
{
        struct p9_req_t *req;
        int id;

        rcu_read_lock();
        idr_for_each_entry(&c->reqs, req, id) {
                pr_info("Tag %d still in use\n", id);
                if (p9_tag_remove(c, req) == 0)
                        pr_warn("Packet with tag %d has still references",
                                req->tc.tag);
        }
        rcu_read_unlock();
}

/**
 * p9_client_cb - call back from transport to client
 * @c: client state
 * @req: request received
 * @status: request status, one of REQ_STATUS_*
 *
 */
void p9_client_cb(struct p9_client *c, struct p9_req_t *req, int status)
{
        p9_debug(P9_DEBUG_MUX, " tag %d\n", req->tc.tag);

        /* This barrier is needed to make sure any change made to req before
         * the status change is visible to another thread
         */
        smp_wmb();
        req->status = status;

        wake_up(&req->wq);
        p9_debug(P9_DEBUG_MUX, "wakeup: %d\n", req->tc.tag);
        p9_req_put(req);
}
EXPORT_SYMBOL(p9_client_cb);

/**
 * p9_parse_header - parse header arguments out of a packet
 * @pdu: packet to parse
 * @size: size of packet
 * @type: type of request
 * @tag: tag of packet
 * @rewind: set if we need to rewind offset afterwards
 */

int
p9_parse_header(struct p9_fcall *pdu, int32_t *size, int8_t *type,
                int16_t *tag, int rewind)
{
        s8 r_type;
        s16 r_tag;
        s32 r_size;
        int offset = pdu->offset;
        int err;

        pdu->offset = 0;

        err = p9pdu_readf(pdu, 0, "dbw", &r_size, &r_type, &r_tag);
        if (err)
                goto rewind_and_exit;

        if (type)
                *type = r_type;
        if (tag)
                *tag = r_tag;
        if (size)
                *size = r_size;

        if (pdu->size != r_size || r_size < 7) {
                err = -EINVAL;
                goto rewind_and_exit;
        }

        pdu->id = r_type;
        pdu->tag = r_tag;

        p9_debug(P9_DEBUG_9P, "<<< size=%d type: %d tag: %d\n",
                 pdu->size, pdu->id, pdu->tag);

rewind_and_exit:
        if (rewind)
                pdu->offset = offset;
        return err;
}
EXPORT_SYMBOL(p9_parse_header);

/**
 * p9_check_errors - check 9p packet for error return and process it
 * @c: current client instance
 * @req: request to parse and check for error conditions
 *
 * returns error code if one is discovered, otherwise returns 0
 *
 * this will have to be more complicated if we have multiple
 * error packet types
 */

static int p9_check_errors(struct p9_client *c, struct p9_req_t *req)
{
        s8 type;
        int err;
        int ecode;

        err = p9_parse_header(&req->rc, NULL, &type, NULL, 0);
        if (req->rc.size >= c->msize) {
                p9_debug(P9_DEBUG_ERROR,
                         "requested packet size too big: %d\n",
                         req->rc.size);
                return -EIO;
        }
        /* dump the response from server
         * This should be after check errors which poplulate pdu_fcall.
         */
        trace_9p_protocol_dump(c, &req->rc);
        if (err) {
                p9_debug(P9_DEBUG_ERROR, "couldn't parse header %d\n", err);
                return err;
        }
        if (type != P9_RERROR && type != P9_RLERROR)
                return 0;

        if (!p9_is_proto_dotl(c)) {
                char *ename;

                err = p9pdu_readf(&req->rc, c->proto_version, "s?d",
                                  &ename, &ecode);
                if (err)
                        goto out_err;

                if (p9_is_proto_dotu(c) && ecode < 512)
                        err = -ecode;

                if (!err) {
                        err = p9_errstr2errno(ename, strlen(ename));

                        p9_debug(P9_DEBUG_9P, "<<< RERROR (%d) %s\n",
                                 -ecode, ename);
                }
                kfree(ename);
        } else {
                err = p9pdu_readf(&req->rc, c->proto_version, "d", &ecode);
                if (err)
                        goto out_err;
                err = -ecode;

                p9_debug(P9_DEBUG_9P, "<<< RLERROR (%d)\n", -ecode);
        }

        return err;

out_err:
        p9_debug(P9_DEBUG_ERROR, "couldn't parse error%d\n", err);

        return err;
}

/**
 * p9_check_zc_errors - check 9p packet for error return and process it
 * @c: current client instance
 * @req: request to parse and check for error conditions
 * @uidata: external buffer containing error
 * @in_hdrlen: Size of response protocol buffer.
 *
 * returns error code if one is discovered, otherwise returns 0
 *
 * this will have to be more complicated if we have multiple
 * error packet types
 */

static int p9_check_zc_errors(struct p9_client *c, struct p9_req_t *req,
                              struct iov_iter *uidata, int in_hdrlen)
{
        int err;
        int ecode;
        s8 type;
        char *ename = NULL;

        err = p9_parse_header(&req->rc, NULL, &type, NULL, 0);
        /* dump the response from server
         * This should be after parse_header which poplulate pdu_fcall.
         */
        trace_9p_protocol_dump(c, &req->rc);
        if (err) {
                p9_debug(P9_DEBUG_ERROR, "couldn't parse header %d\n", err);
                return err;
        }

        if (type != P9_RERROR && type != P9_RLERROR)
                return 0;

        if (!p9_is_proto_dotl(c)) {
                /* Error is reported in string format */
                int len;
                /* 7 = header size for RERROR; */
                int inline_len = in_hdrlen - 7;

                len = req->rc.size - req->rc.offset;
                if (len > (P9_ZC_HDR_SZ - 7)) {
                        err = -EFAULT;
                        goto out_err;
                }

                ename = &req->rc.sdata[req->rc.offset];
                if (len > inline_len) {
                        /* We have error in external buffer */
                        if (!copy_from_iter_full(ename + inline_len,
                                                 len - inline_len, uidata)) {
                                err = -EFAULT;
                                goto out_err;
                        }
                }
                ename = NULL;
                err = p9pdu_readf(&req->rc, c->proto_version, "s?d",
                                  &ename, &ecode);
                if (err)
                        goto out_err;

                if (p9_is_proto_dotu(c) && ecode < 512)
                        err = -ecode;

                if (!err) {
                        err = p9_errstr2errno(ename, strlen(ename));

                        p9_debug(P9_DEBUG_9P, "<<< RERROR (%d) %s\n",
                                 -ecode, ename);
                }
                kfree(ename);
        } else {
                err = p9pdu_readf(&req->rc, c->proto_version, "d", &ecode);
                err = -ecode;

                p9_debug(P9_DEBUG_9P, "<<< RLERROR (%d)\n", -ecode);
        }
        return err;

out_err:
        p9_debug(P9_DEBUG_ERROR, "couldn't parse error%d\n", err);
        return err;
}

static struct p9_req_t *
p9_client_rpc(struct p9_client *c, int8_t type, const char *fmt, ...);

/**
 * p9_client_flush - flush (cancel) a request
 * @c: client state
 * @oldreq: request to cancel
 *
 * This sents a flush for a particular request and links
 * the flush request to the original request.  The current
 * code only supports a single flush request although the protocol
 * allows for multiple flush requests to be sent for a single request.
 *
 */

static int p9_client_flush(struct p9_client *c, struct p9_req_t *oldreq)
{
        struct p9_req_t *req;
        s16 oldtag;
        int err;

        err = p9_parse_header(&oldreq->tc, NULL, NULL, &oldtag, 1);
        if (err)
                return err;

        p9_debug(P9_DEBUG_9P, ">>> TFLUSH tag %d\n", oldtag);

        req = p9_client_rpc(c, P9_TFLUSH, "w", oldtag);
        if (IS_ERR(req))
                return PTR_ERR(req);

        /* if we haven't received a response for oldreq,
         * remove it from the list
         */
        if (oldreq->status == REQ_STATUS_SENT) {
                if (c->trans_mod->cancelled)
                        c->trans_mod->cancelled(c, oldreq);
        }

        p9_tag_remove(c, req);
        return 0;
}

static struct p9_req_t *p9_client_prepare_req(struct p9_client *c,
                                              int8_t type, int req_size,
                                              const char *fmt, va_list ap)
{
        int err;
        struct p9_req_t *req;

        p9_debug(P9_DEBUG_MUX, "client %p op %d\n", c, type);

        /* we allow for any status other than disconnected */
        if (c->status == Disconnected)
                return ERR_PTR(-EIO);

        /* if status is begin_disconnected we allow only clunk request */
        if (c->status == BeginDisconnect && type != P9_TCLUNK)
                return ERR_PTR(-EIO);

        req = p9_tag_alloc(c, type, req_size);
        if (IS_ERR(req))
                return req;

        /* marshall the data */
        p9pdu_prepare(&req->tc, req->tc.tag, type);
        err = p9pdu_vwritef(&req->tc, c->proto_version, fmt, ap);
        if (err)
                goto reterr;
        p9pdu_finalize(c, &req->tc);
        trace_9p_client_req(c, type, req->tc.tag);
        return req;
reterr:
        p9_tag_remove(c, req);
        /* We have to put also the 2nd reference as it won't be used */
        p9_req_put(req);
        return ERR_PTR(err);
}

/**
 * p9_client_rpc - issue a request and wait for a response
 * @c: client session
 * @type: type of request
 * @fmt: protocol format string (see protocol.c)
 *
 * Returns request structure (which client must free using p9_tag_remove)
 */

static struct p9_req_t *
p9_client_rpc(struct p9_client *c, int8_t type, const char *fmt, ...)
{
        va_list ap;
        int sigpending, err;
        unsigned long flags;
        struct p9_req_t *req;

        va_start(ap, fmt);
        req = p9_client_prepare_req(c, type, c->msize, fmt, ap);
        va_end(ap);
        if (IS_ERR(req))
                return req;

        if (signal_pending(current)) {
                sigpending = 1;
                clear_thread_flag(TIF_SIGPENDING);
        } else {
                sigpending = 0;
        }

        err = c->trans_mod->request(c, req);
        if (err < 0) {
                /* write won't happen */
                p9_req_put(req);
                if (err != -ERESTARTSYS && err != -EFAULT)
                        c->status = Disconnected;
                goto recalc_sigpending;
        }
again:
        /* Wait for the response */
        err = wait_event_killable(req->wq, req->status >= REQ_STATUS_RCVD);

        /* Make sure our req is coherent with regard to updates in other
         * threads - echoes to wmb() in the callback
         */
        smp_rmb();

        if (err == -ERESTARTSYS && c->status == Connected &&
            type == P9_TFLUSH) {
                sigpending = 1;
                clear_thread_flag(TIF_SIGPENDING);
                goto again;
        }

        if (req->status == REQ_STATUS_ERROR) {
                p9_debug(P9_DEBUG_ERROR, "req_status error %d\n", req->t_err);
                err = req->t_err;
        }
        if (err == -ERESTARTSYS && c->status == Connected) {
                p9_debug(P9_DEBUG_MUX, "flushing\n");
                sigpending = 1;
                clear_thread_flag(TIF_SIGPENDING);

                if (c->trans_mod->cancel(c, req))
                        p9_client_flush(c, req);

                /* if we received the response anyway, don't signal error */
                if (req->status == REQ_STATUS_RCVD)
                        err = 0;
        }
recalc_sigpending:
        if (sigpending) {
                spin_lock_irqsave(&current->sighand->siglock, flags);
                recalc_sigpending();
                spin_unlock_irqrestore(&current->sighand->siglock, flags);
        }
        if (err < 0)
                goto reterr;

        err = p9_check_errors(c, req);
        trace_9p_client_res(c, type, req->rc.tag, err);
        if (!err)
                return req;
reterr:
        p9_tag_remove(c, req);
        return ERR_PTR(safe_errno(err));
}

/**
 * p9_client_zc_rpc - issue a request and wait for a response
 * @c: client session
 * @type: type of request
 * @uidata: destination for zero copy read
 * @uodata: source for zero copy write
 * @inlen: read buffer size
 * @olen: write buffer size
 * @in_hdrlen: reader header size, This is the size of response protocol data
 * @fmt: protocol format string (see protocol.c)
 *
 * Returns request structure (which client must free using p9_tag_remove)
 */
static struct p9_req_t *p9_client_zc_rpc(struct p9_client *c, int8_t type,
                                         struct iov_iter *uidata,
                                         struct iov_iter *uodata,
                                         int inlen, int olen, int in_hdrlen,
                                         const char *fmt, ...)
{
        va_list ap;
        int sigpending, err;
        unsigned long flags;
        struct p9_req_t *req;

        va_start(ap, fmt);
        /* We allocate a inline protocol data of only 4k bytes.
         * The actual content is passed in zero-copy fashion.
         */
        req = p9_client_prepare_req(c, type, P9_ZC_HDR_SZ, fmt, ap);
        va_end(ap);
        if (IS_ERR(req))
                return req;

        if (signal_pending(current)) {
                sigpending = 1;
                clear_thread_flag(TIF_SIGPENDING);
        } else {
                sigpending = 0;
        }

        err = c->trans_mod->zc_request(c, req, uidata, uodata,
                                       inlen, olen, in_hdrlen);
        if (err < 0) {
                if (err == -EIO)
                        c->status = Disconnected;
                if (err != -ERESTARTSYS)
                        goto recalc_sigpending;
        }
        if (req->status == REQ_STATUS_ERROR) {
                p9_debug(P9_DEBUG_ERROR, "req_status error %d\n", req->t_err);
                err = req->t_err;
        }
        if (err == -ERESTARTSYS && c->status == Connected) {
                p9_debug(P9_DEBUG_MUX, "flushing\n");
                sigpending = 1;
                clear_thread_flag(TIF_SIGPENDING);

                if (c->trans_mod->cancel(c, req))
                        p9_client_flush(c, req);

                /* if we received the response anyway, don't signal error */
                if (req->status == REQ_STATUS_RCVD)
                        err = 0;
        }
recalc_sigpending:
        if (sigpending) {
                spin_lock_irqsave(&current->sighand->siglock, flags);
                recalc_sigpending();
                spin_unlock_irqrestore(&current->sighand->siglock, flags);
        }
        if (err < 0)
                goto reterr;

        err = p9_check_zc_errors(c, req, uidata, in_hdrlen);
        trace_9p_client_res(c, type, req->rc.tag, err);
        if (!err)
                return req;
reterr:
        p9_tag_remove(c, req);
        return ERR_PTR(safe_errno(err));
}

static struct p9_fid *p9_fid_create(struct p9_client *clnt)
{
        int ret;
        struct p9_fid *fid;

        p9_debug(P9_DEBUG_FID, "clnt %p\n", clnt);
        fid = kmalloc(sizeof(*fid), GFP_KERNEL);
        if (!fid)
                return NULL;

        memset(&fid->qid, 0, sizeof(fid->qid));
        fid->mode = -1;
        fid->uid = current_fsuid();
        fid->clnt = clnt;
        fid->rdir = NULL;
        fid->fid = 0;
        refcount_set(&fid->count, 1);

        idr_preload(GFP_KERNEL);
        spin_lock_irq(&clnt->lock);
        ret = idr_alloc_u32(&clnt->fids, fid, &fid->fid, P9_NOFID - 1,
                            GFP_NOWAIT);
        spin_unlock_irq(&clnt->lock);
        idr_preload_end();
        if (!ret)
                return fid;

        kfree(fid);
        return NULL;
}

static void p9_fid_destroy(struct p9_fid *fid)
{
        struct p9_client *clnt;
        unsigned long flags;

        p9_debug(P9_DEBUG_FID, "fid %d\n", fid->fid);
        clnt = fid->clnt;
        spin_lock_irqsave(&clnt->lock, flags);
        idr_remove(&clnt->fids, fid->fid);
        spin_unlock_irqrestore(&clnt->lock, flags);
        kfree(fid->rdir);
        kfree(fid);
}

static int p9_client_version(struct p9_client *c)
{
        int err = 0;
        struct p9_req_t *req;
        char *version = NULL;
        int msize;

        p9_debug(P9_DEBUG_9P, ">>> TVERSION msize %d protocol %d\n",
                 c->msize, c->proto_version);

        switch (c->proto_version) {
        case p9_proto_2000L:
                req = p9_client_rpc(c, P9_TVERSION, "ds",
                                    c->msize, "9P2000.L");
                break;
        case p9_proto_2000u:
                req = p9_client_rpc(c, P9_TVERSION, "ds",
                                    c->msize, "9P2000.u");
                break;
        case p9_proto_legacy:
                req = p9_client_rpc(c, P9_TVERSION, "ds",
                                    c->msize, "9P2000");
                break;
        default:
                return -EINVAL;
        }

        if (IS_ERR(req))
                return PTR_ERR(req);

        err = p9pdu_readf(&req->rc, c->proto_version, "ds", &msize, &version);
        if (err) {
                p9_debug(P9_DEBUG_9P, "version error %d\n", err);
                trace_9p_protocol_dump(c, &req->rc);
                goto error;
        }

        p9_debug(P9_DEBUG_9P, "<<< RVERSION msize %d %s\n", msize, version);
        if (!strncmp(version, "9P2000.L", 8)) {
                c->proto_version = p9_proto_2000L;
        } else if (!strncmp(version, "9P2000.u", 8)) {
                c->proto_version = p9_proto_2000u;
        } else if (!strncmp(version, "9P2000", 6)) {
                c->proto_version = p9_proto_legacy;
        } else {
                p9_debug(P9_DEBUG_ERROR,
                         "server returned an unknown version: %s\n", version);
                err = -EREMOTEIO;
                goto error;
        }

        if (msize < 4096) {
                p9_debug(P9_DEBUG_ERROR,
                         "server returned a msize < 4096: %d\n", msize);
                err = -EREMOTEIO;
                goto error;
        }
        if (msize < c->msize)
                c->msize = msize;

error:
        kfree(version);
        p9_tag_remove(c, req);

        return err;
}

struct p9_client *p9_client_create(const char *dev_name, char *options)
{
        int err;

        struct p9_client *clnt;
        char *client_id;

        err = 0;
        clnt = kmalloc(sizeof(*clnt), GFP_KERNEL);
        if (!clnt)
                return ERR_PTR(-ENOMEM);

        clnt->trans_mod = NULL;
        clnt->trans = NULL;
        clnt->fcall_cache = NULL;

        client_id = utsname()->nodename;
        memcpy(clnt->name, client_id, strlen(client_id) + 1);

        spin_lock_init(&clnt->lock);
        idr_init(&clnt->fids);
        idr_init(&clnt->reqs);

        err = parse_opts(options, clnt);
        if (err < 0)
                goto free_client;

        if (!clnt->trans_mod)
                clnt->trans_mod = v9fs_get_default_trans();

        if (!clnt->trans_mod) {
                err = -EPROTONOSUPPORT;
                p9_debug(P9_DEBUG_ERROR,
                         "No transport defined or default transport\n");
                goto free_client;
        }

        p9_debug(P9_DEBUG_MUX, "clnt %p trans %p msize %d protocol %d\n",
                 clnt, clnt->trans_mod, clnt->msize, clnt->proto_version);

        err = clnt->trans_mod->create(clnt, dev_name, options);
        if (err)
                goto put_trans;

        if (clnt->msize > clnt->trans_mod->maxsize) {
                clnt->msize = clnt->trans_mod->maxsize;
                pr_info("Limiting 'msize' to %d as this is the maximum "
                        "supported by transport %s\n",
                        clnt->msize, clnt->trans_mod->name
                );
        }

        if (clnt->msize < 4096) {
                p9_debug(P9_DEBUG_ERROR,
                         "Please specify a msize of at least 4k\n");
                err = -EINVAL;
                goto close_trans;
        }

        err = p9_client_version(clnt);
        if (err)
                goto close_trans;

        /* P9_HDRSZ + 4 is the smallest packet header we can have that is
         * followed by data accessed from userspace by read
         */
        clnt->fcall_cache =
                kmem_cache_create_usercopy("9p-fcall-cache", clnt->msize,
                                           0, 0, P9_HDRSZ + 4,
                                           clnt->msize - (P9_HDRSZ + 4),
                                           NULL);

        return clnt;

close_trans:
        clnt->trans_mod->close(clnt);
put_trans:
        v9fs_put_trans(clnt->trans_mod);
free_client:
        kfree(clnt);
        return ERR_PTR(err);
}
EXPORT_SYMBOL(p9_client_create);

void p9_client_destroy(struct p9_client *clnt)
{
        struct p9_fid *fid;
        int id;

        p9_debug(P9_DEBUG_MUX, "clnt %p\n", clnt);

        if (clnt->trans_mod)
                clnt->trans_mod->close(clnt);

        v9fs_put_trans(clnt->trans_mod);

        idr_for_each_entry(&clnt->fids, fid, id) {
                pr_info("Found fid %d not clunked\n", fid->fid);
                p9_fid_destroy(fid);
        }

        p9_tag_cleanup(clnt);

        kmem_cache_destroy(clnt->fcall_cache);
        kfree(clnt);
}
EXPORT_SYMBOL(p9_client_destroy);

void p9_client_disconnect(struct p9_client *clnt)
{
        p9_debug(P9_DEBUG_9P, "clnt %p\n", clnt);
        clnt->status = Disconnected;
}
EXPORT_SYMBOL(p9_client_disconnect);

void p9_client_begin_disconnect(struct p9_client *clnt)
{
        p9_debug(P9_DEBUG_9P, "clnt %p\n", clnt);
        clnt->status = BeginDisconnect;
}
EXPORT_SYMBOL(p9_client_begin_disconnect);

struct p9_fid *p9_client_attach(struct p9_client *clnt, struct p9_fid *afid,
                                const char *uname, kuid_t n_uname,
                                const char *aname)
{
        int err = 0;
        struct p9_req_t *req;
        struct p9_fid *fid;
        struct p9_qid qid;

        p9_debug(P9_DEBUG_9P, ">>> TATTACH afid %d uname %s aname %s\n",
                 afid ? afid->fid : -1, uname, aname);
        fid = p9_fid_create(clnt);
        if (!fid) {
                err = -ENOMEM;
                goto error;
        }
        fid->uid = n_uname;

        req = p9_client_rpc(clnt, P9_TATTACH, "ddss?u", fid->fid,
                            afid ? afid->fid : P9_NOFID, uname, aname, n_uname);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto error;
        }

        err = p9pdu_readf(&req->rc, clnt->proto_version, "Q", &qid);
        if (err) {
                trace_9p_protocol_dump(clnt, &req->rc);
                p9_tag_remove(clnt, req);
                goto error;
        }

        p9_debug(P9_DEBUG_9P, "<<< RATTACH qid %x.%llx.%x\n",
                 qid.type, qid.path, qid.version);

        memmove(&fid->qid, &qid, sizeof(struct p9_qid));

        p9_tag_remove(clnt, req);
        return fid;

error:
        if (fid)
                p9_fid_destroy(fid);
        return ERR_PTR(err);
}
EXPORT_SYMBOL(p9_client_attach);

struct p9_fid *p9_client_walk(struct p9_fid *oldfid, uint16_t nwname,
                              const unsigned char * const *wnames, int clone)
{
        int err;
        struct p9_client *clnt;
        struct p9_fid *fid;
        struct p9_qid *wqids;
        struct p9_req_t *req;
        u16 nwqids, count;

        err = 0;
        wqids = NULL;
        clnt = oldfid->clnt;
        if (clone) {
                fid = p9_fid_create(clnt);
                if (!fid) {
                        err = -ENOMEM;
                        goto error;
                }

                fid->uid = oldfid->uid;
        } else {
                fid = oldfid;
        }

        p9_debug(P9_DEBUG_9P, ">>> TWALK fids %d,%d nwname %ud wname[0] %s\n",
                 oldfid->fid, fid->fid, nwname, wnames ? wnames[0] : NULL);
        req = p9_client_rpc(clnt, P9_TWALK, "ddT", oldfid->fid, fid->fid,
                            nwname, wnames);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto error;
        }

        err = p9pdu_readf(&req->rc, clnt->proto_version, "R", &nwqids, &wqids);
        if (err) {
                trace_9p_protocol_dump(clnt, &req->rc);
                p9_tag_remove(clnt, req);
                goto clunk_fid;
        }
        p9_tag_remove(clnt, req);

        p9_debug(P9_DEBUG_9P, "<<< RWALK nwqid %d:\n", nwqids);

        if (nwqids != nwname) {
                err = -ENOENT;
                goto clunk_fid;
        }

        for (count = 0; count < nwqids; count++)
                p9_debug(P9_DEBUG_9P, "<<<     [%d] %x.%llx.%x\n",
                         count, wqids[count].type,
                         wqids[count].path,
                         wqids[count].version);

        if (nwname)
                memmove(&fid->qid, &wqids[nwqids - 1], sizeof(struct p9_qid));
        else
                memmove(&fid->qid, &oldfid->qid, sizeof(struct p9_qid));

        kfree(wqids);
        return fid;

clunk_fid:
        kfree(wqids);
        p9_client_clunk(fid);
        fid = NULL;

error:
        if (fid && fid != oldfid)
                p9_fid_destroy(fid);

        return ERR_PTR(err);
}
EXPORT_SYMBOL(p9_client_walk);

int p9_client_open(struct p9_fid *fid, int mode)
{
        int err;
        struct p9_client *clnt;
        struct p9_req_t *req;
        struct p9_qid qid;
        int iounit;

        clnt = fid->clnt;
        p9_debug(P9_DEBUG_9P, ">>> %s fid %d mode %d\n",
                 p9_is_proto_dotl(clnt) ? "TLOPEN" : "TOPEN", fid->fid, mode);
        err = 0;

        if (fid->mode != -1)
                return -EINVAL;

        if (p9_is_proto_dotl(clnt))
                req = p9_client_rpc(clnt, P9_TLOPEN, "dd", fid->fid, mode);
        else
                req = p9_client_rpc(clnt, P9_TOPEN, "db", fid->fid, mode);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto error;
        }

        err = p9pdu_readf(&req->rc, clnt->proto_version, "Qd", &qid, &iounit);
        if (err) {
                trace_9p_protocol_dump(clnt, &req->rc);
                goto free_and_error;
        }

        p9_debug(P9_DEBUG_9P, "<<< %s qid %x.%llx.%x iounit %x\n",
                 p9_is_proto_dotl(clnt) ? "RLOPEN" : "ROPEN",  qid.type,
                 qid.path, qid.version, iounit);

        memmove(&fid->qid, &qid, sizeof(struct p9_qid));
        fid->mode = mode;
        fid->iounit = iounit;

free_and_error:
        p9_tag_remove(clnt, req);
error:
        return err;
}
EXPORT_SYMBOL(p9_client_open);

int p9_client_create_dotl(struct p9_fid *ofid, const char *name, u32 flags,
                          u32 mode, kgid_t gid, struct p9_qid *qid)
{
        int err = 0;
        struct p9_client *clnt;
        struct p9_req_t *req;
        int iounit;

        p9_debug(P9_DEBUG_9P,
                 ">>> TLCREATE fid %d name %s flags %d mode %d gid %d\n",
                 ofid->fid, name, flags, mode,
                 from_kgid(&init_user_ns, gid));
        clnt = ofid->clnt;

        if (ofid->mode != -1)
                return -EINVAL;

        req = p9_client_rpc(clnt, P9_TLCREATE, "dsddg", ofid->fid, name, flags,
                            mode, gid);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto error;
        }

        err = p9pdu_readf(&req->rc, clnt->proto_version, "Qd", qid, &iounit);
        if (err) {
                trace_9p_protocol_dump(clnt, &req->rc);
                goto free_and_error;
        }

        p9_debug(P9_DEBUG_9P, "<<< RLCREATE qid %x.%llx.%x iounit %x\n",
                 qid->type, qid->path, qid->version, iounit);

        memmove(&ofid->qid, qid, sizeof(struct p9_qid));
        ofid->mode = mode;
        ofid->iounit = iounit;

free_and_error:
        p9_tag_remove(clnt, req);
error:
        return err;
}
EXPORT_SYMBOL(p9_client_create_dotl);

int p9_client_fcreate(struct p9_fid *fid, const char *name, u32 perm, int mode,
                     char *extension)
{
        int err;
        struct p9_client *clnt;
        struct p9_req_t *req;
        struct p9_qid qid;
        int iounit;

        p9_debug(P9_DEBUG_9P, ">>> TCREATE fid %d name %s perm %d mode %d\n",
                 fid->fid, name, perm, mode);
        err = 0;
        clnt = fid->clnt;

        if (fid->mode != -1)
                return -EINVAL;

        req = p9_client_rpc(clnt, P9_TCREATE, "dsdb?s", fid->fid, name, perm,
                            mode, extension);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto error;
        }

        err = p9pdu_readf(&req->rc, clnt->proto_version, "Qd", &qid, &iounit);
        if (err) {
                trace_9p_protocol_dump(clnt, &req->rc);
                goto free_and_error;
        }

        p9_debug(P9_DEBUG_9P, "<<< RCREATE qid %x.%llx.%x iounit %x\n",
                 qid.type, qid.path, qid.version, iounit);

        memmove(&fid->qid, &qid, sizeof(struct p9_qid));
        fid->mode = mode;
        fid->iounit = iounit;

free_and_error:
        p9_tag_remove(clnt, req);
error:
        return err;
}
EXPORT_SYMBOL(p9_client_fcreate);

int p9_client_symlink(struct p9_fid *dfid, const char *name,
                      const char *symtgt, kgid_t gid, struct p9_qid *qid)
{
        int err = 0;
        struct p9_client *clnt;
        struct p9_req_t *req;

        p9_debug(P9_DEBUG_9P, ">>> TSYMLINK dfid %d name %s  symtgt %s\n",
                 dfid->fid, name, symtgt);
        clnt = dfid->clnt;

        req = p9_client_rpc(clnt, P9_TSYMLINK, "dssg", dfid->fid, name, symtgt,
                            gid);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto error;
        }

        err = p9pdu_readf(&req->rc, clnt->proto_version, "Q", qid);
        if (err) {
                trace_9p_protocol_dump(clnt, &req->rc);
                goto free_and_error;
        }

        p9_debug(P9_DEBUG_9P, "<<< RSYMLINK qid %x.%llx.%x\n",
                 qid->type, qid->path, qid->version);

free_and_error:
        p9_tag_remove(clnt, req);
error:
        return err;
}
EXPORT_SYMBOL(p9_client_symlink);

int p9_client_link(struct p9_fid *dfid, struct p9_fid *oldfid, const char *newname)
{
        struct p9_client *clnt;
        struct p9_req_t *req;

        p9_debug(P9_DEBUG_9P, ">>> TLINK dfid %d oldfid %d newname %s\n",
                 dfid->fid, oldfid->fid, newname);
        clnt = dfid->clnt;
        req = p9_client_rpc(clnt, P9_TLINK, "dds", dfid->fid, oldfid->fid,
                            newname);
        if (IS_ERR(req))
                return PTR_ERR(req);

        p9_debug(P9_DEBUG_9P, "<<< RLINK\n");
        p9_tag_remove(clnt, req);
        return 0;
}
EXPORT_SYMBOL(p9_client_link);

int p9_client_fsync(struct p9_fid *fid, int datasync)
{
        int err;
        struct p9_client *clnt;
        struct p9_req_t *req;

        p9_debug(P9_DEBUG_9P, ">>> TFSYNC fid %d datasync:%d\n",
                 fid->fid, datasync);
        err = 0;
        clnt = fid->clnt;

        req = p9_client_rpc(clnt, P9_TFSYNC, "dd", fid->fid, datasync);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto error;
        }

        p9_debug(P9_DEBUG_9P, "<<< RFSYNC fid %d\n", fid->fid);

        p9_tag_remove(clnt, req);

error:
        return err;
}
EXPORT_SYMBOL(p9_client_fsync);

int p9_client_clunk(struct p9_fid *fid)
{
        int err;
        struct p9_client *clnt;
        struct p9_req_t *req;
        int retries = 0;

        if (!fid || IS_ERR(fid)) {
                pr_warn("%s (%d): Trying to clunk with invalid fid\n",
                        __func__, task_pid_nr(current));
                dump_stack();
                return 0;
        }
        if (!refcount_dec_and_test(&fid->count))
                return 0;

again:
        p9_debug(P9_DEBUG_9P, ">>> TCLUNK fid %d (try %d)\n",
                 fid->fid, retries);
        err = 0;
        clnt = fid->clnt;

        req = p9_client_rpc(clnt, P9_TCLUNK, "d", fid->fid);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto error;
        }

        p9_debug(P9_DEBUG_9P, "<<< RCLUNK fid %d\n", fid->fid);

        p9_tag_remove(clnt, req);
error:
        /* Fid is not valid even after a failed clunk
         * If interrupted, retry once then give up and
         * leak fid until umount.
         */
        if (err == -ERESTARTSYS) {
                if (retries++ == 0)
                        goto again;
        } else {
                p9_fid_destroy(fid);
        }
        return err;
}
EXPORT_SYMBOL(p9_client_clunk);

int p9_client_remove(struct p9_fid *fid)
{
        int err;
        struct p9_client *clnt;
        struct p9_req_t *req;

        p9_debug(P9_DEBUG_9P, ">>> TREMOVE fid %d\n", fid->fid);
        err = 0;
        clnt = fid->clnt;

        req = p9_client_rpc(clnt, P9_TREMOVE, "d", fid->fid);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto error;
        }

        p9_debug(P9_DEBUG_9P, "<<< RREMOVE fid %d\n", fid->fid);

        p9_tag_remove(clnt, req);
error:
        if (err == -ERESTARTSYS)
                p9_client_clunk(fid);
        else
                p9_fid_destroy(fid);
        return err;
}
EXPORT_SYMBOL(p9_client_remove);

int p9_client_unlinkat(struct p9_fid *dfid, const char *name, int flags)
{
        int err = 0;
        struct p9_req_t *req;
        struct p9_client *clnt;

        p9_debug(P9_DEBUG_9P, ">>> TUNLINKAT fid %d %s %d\n",
                 dfid->fid, name, flags);

        clnt = dfid->clnt;
        req = p9_client_rpc(clnt, P9_TUNLINKAT, "dsd", dfid->fid, name, flags);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto error;
        }
        p9_debug(P9_DEBUG_9P, "<<< RUNLINKAT fid %d %s\n", dfid->fid, name);

        p9_tag_remove(clnt, req);
error:
        return err;
}
EXPORT_SYMBOL(p9_client_unlinkat);

int
p9_client_read(struct p9_fid *fid, u64 offset, struct iov_iter *to, int *err)
{
        int total = 0;
        *err = 0;

        while (iov_iter_count(to)) {
                int count;

                count = p9_client_read_once(fid, offset, to, err);
                if (!count || *err)
                        break;
                offset += count;
                total += count;
        }
        return total;
}
EXPORT_SYMBOL(p9_client_read);

int
p9_client_read_once(struct p9_fid *fid, u64 offset, struct iov_iter *to,
                    int *err)
{
        struct p9_client *clnt = fid->clnt;
        struct p9_req_t *req;
        int count = iov_iter_count(to);
        int rsize, non_zc = 0;
        char *dataptr;

        *err = 0;
        p9_debug(P9_DEBUG_9P, ">>> TREAD fid %d offset %llu %zu\n",
                 fid->fid, offset, iov_iter_count(to));

        rsize = fid->iounit;
        if (!rsize || rsize > clnt->msize - P9_IOHDRSZ)
                rsize = clnt->msize - P9_IOHDRSZ;

        if (count < rsize)
                rsize = count;

        /* Don't bother zerocopy for small IO (< 1024) */
        if (clnt->trans_mod->zc_request && rsize > 1024) {
                /* response header len is 11
                 * PDU Header(7) + IO Size (4)
                 */
                req = p9_client_zc_rpc(clnt, P9_TREAD, to, NULL, rsize,
                                       0, 11, "dqd", fid->fid,
                                       offset, rsize);
        } else {
                non_zc = 1;
                req = p9_client_rpc(clnt, P9_TREAD, "dqd", fid->fid, offset,
                                    rsize);
        }
        if (IS_ERR(req)) {
                *err = PTR_ERR(req);
                return 0;
        }

        *err = p9pdu_readf(&req->rc, clnt->proto_version,
                           "D", &count, &dataptr);
        if (*err) {
                trace_9p_protocol_dump(clnt, &req->rc);
                p9_tag_remove(clnt, req);
                return 0;
        }
        if (rsize < count) {
                pr_err("bogus RREAD count (%d > %d)\n", count, rsize);
                count = rsize;
        }

        p9_debug(P9_DEBUG_9P, "<<< RREAD count %d\n", count);

        if (non_zc) {
                int n = copy_to_iter(dataptr, count, to);

                if (n != count) {
                        *err = -EFAULT;
                        p9_tag_remove(clnt, req);
                        return n;
                }
        } else {
                iov_iter_advance(to, count);
        }
        p9_tag_remove(clnt, req);
        return count;
}
EXPORT_SYMBOL(p9_client_read_once);

int
p9_client_write(struct p9_fid *fid, u64 offset, struct iov_iter *from, int *err)
{
        struct p9_client *clnt = fid->clnt;
        struct p9_req_t *req;
        int total = 0;
        *err = 0;

        p9_debug(P9_DEBUG_9P, ">>> TWRITE fid %d offset %llu count %zd\n",
                 fid->fid, offset, iov_iter_count(from));

        while (iov_iter_count(from)) {
                int count = iov_iter_count(from);
                int rsize = fid->iounit;

                if (!rsize || rsize > clnt->msize - P9_IOHDRSZ)
                        rsize = clnt->msize - P9_IOHDRSZ;

                if (count < rsize)
                        rsize = count;

                /* Don't bother zerocopy for small IO (< 1024) */
                if (clnt->trans_mod->zc_request && rsize > 1024) {
                        req = p9_client_zc_rpc(clnt, P9_TWRITE, NULL, from, 0,
                                               rsize, P9_ZC_HDR_SZ, "dqd",
                                               fid->fid, offset, rsize);
                } else {
                        req = p9_client_rpc(clnt, P9_TWRITE, "dqV", fid->fid,
                                            offset, rsize, from);
                }
                if (IS_ERR(req)) {
                        *err = PTR_ERR(req);
                        break;
                }

                *err = p9pdu_readf(&req->rc, clnt->proto_version, "d", &count);
                if (*err) {
                        trace_9p_protocol_dump(clnt, &req->rc);
                        p9_tag_remove(clnt, req);
                        break;
                }
                if (rsize < count) {
                        pr_err("bogus RWRITE count (%d > %d)\n", count, rsize);
                        count = rsize;
                }

                p9_debug(P9_DEBUG_9P, "<<< RWRITE count %d\n", count);

                p9_tag_remove(clnt, req);
                iov_iter_advance(from, count);
                total += count;
                offset += count;
        }
        return total;
}
EXPORT_SYMBOL(p9_client_write);

struct p9_wstat *p9_client_stat(struct p9_fid *fid)
{
        int err;
        struct p9_client *clnt;
        struct p9_wstat *ret;
        struct p9_req_t *req;
        u16 ignored;

        p9_debug(P9_DEBUG_9P, ">>> TSTAT fid %d\n", fid->fid);

        ret = kmalloc(sizeof(*ret), GFP_KERNEL);
        if (!ret)
                return ERR_PTR(-ENOMEM);

        err = 0;
        clnt = fid->clnt;

        req = p9_client_rpc(clnt, P9_TSTAT, "d", fid->fid);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto error;
        }

        err = p9pdu_readf(&req->rc, clnt->proto_version, "wS", &ignored, ret);
        if (err) {
                trace_9p_protocol_dump(clnt, &req->rc);
                p9_tag_remove(clnt, req);
                goto error;
        }

        p9_debug(P9_DEBUG_9P,
                 "<<< RSTAT sz=%x type=%x dev=%x qid=%x.%llx.%x\n"
                 "<<<    mode=%8.8x atime=%8.8x mtime=%8.8x length=%llx\n"
                 "<<<    name=%s uid=%s gid=%s muid=%s extension=(%s)\n"
                 "<<<    uid=%d gid=%d n_muid=%d\n",
                 ret->size, ret->type, ret->dev, ret->qid.type, ret->qid.path,
                 ret->qid.version, ret->mode,
                 ret->atime, ret->mtime, ret->length,
                 ret->name, ret->uid, ret->gid, ret->muid, ret->extension,
                 from_kuid(&init_user_ns, ret->n_uid),
                 from_kgid(&init_user_ns, ret->n_gid),
                 from_kuid(&init_user_ns, ret->n_muid));

        p9_tag_remove(clnt, req);
        return ret;

error:
        kfree(ret);
        return ERR_PTR(err);
}
EXPORT_SYMBOL(p9_client_stat);

struct p9_stat_dotl *p9_client_getattr_dotl(struct p9_fid *fid,
                                            u64 request_mask)
{
        int err;
        struct p9_client *clnt;
        struct p9_stat_dotl *ret;
        struct p9_req_t *req;

        p9_debug(P9_DEBUG_9P, ">>> TGETATTR fid %d, request_mask %lld\n",
                 fid->fid, request_mask);

        ret = kmalloc(sizeof(*ret), GFP_KERNEL);
        if (!ret)
                return ERR_PTR(-ENOMEM);

        err = 0;
        clnt = fid->clnt;

        req = p9_client_rpc(clnt, P9_TGETATTR, "dq", fid->fid, request_mask);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto error;
        }

        err = p9pdu_readf(&req->rc, clnt->proto_version, "A", ret);
        if (err) {
                trace_9p_protocol_dump(clnt, &req->rc);
                p9_tag_remove(clnt, req);
                goto error;
        }

        p9_debug(P9_DEBUG_9P, "<<< RGETATTR st_result_mask=%lld\n"
                 "<<< qid=%x.%llx.%x\n"
                 "<<< st_mode=%8.8x st_nlink=%llu\n"
                 "<<< st_uid=%d st_gid=%d\n"
                 "<<< st_rdev=%llx st_size=%llx st_blksize=%llu st_blocks=%llu\n"
                 "<<< st_atime_sec=%lld st_atime_nsec=%lld\n"
                 "<<< st_mtime_sec=%lld st_mtime_nsec=%lld\n"
                 "<<< st_ctime_sec=%lld st_ctime_nsec=%lld\n"
                 "<<< st_btime_sec=%lld st_btime_nsec=%lld\n"
                 "<<< st_gen=%lld st_data_version=%lld\n",
                 ret->st_result_mask,
                 ret->qid.type, ret->qid.path, ret->qid.version,
                 ret->st_mode, ret->st_nlink,
                 from_kuid(&init_user_ns, ret->st_uid),
                 from_kgid(&init_user_ns, ret->st_gid),
                 ret->st_rdev, ret->st_size, ret->st_blksize, ret->st_blocks,
                 ret->st_atime_sec, ret->st_atime_nsec,
                 ret->st_mtime_sec, ret->st_mtime_nsec,
                 ret->st_ctime_sec, ret->st_ctime_nsec,
                 ret->st_btime_sec, ret->st_btime_nsec,
                 ret->st_gen, ret->st_data_version);

        p9_tag_remove(clnt, req);
        return ret;

error:
        kfree(ret);
        return ERR_PTR(err);
}
EXPORT_SYMBOL(p9_client_getattr_dotl);

static int p9_client_statsize(struct p9_wstat *wst, int proto_version)
{
        int ret;

        /* NOTE: size shouldn't include its own length */
        /* size[2] type[2] dev[4] qid[13] */
        /* mode[4] atime[4] mtime[4] length[8]*/
        /* name[s] uid[s] gid[s] muid[s] */
        ret = 2 + 4 + 13 + 4 + 4 + 4 + 8 + 2 + 2 + 2 + 2;

        if (wst->name)
                ret += strlen(wst->name);
        if (wst->uid)
                ret += strlen(wst->uid);
        if (wst->gid)
                ret += strlen(wst->gid);
        if (wst->muid)
                ret += strlen(wst->muid);

        if (proto_version == p9_proto_2000u ||
            proto_version == p9_proto_2000L) {
                /* extension[s] n_uid[4] n_gid[4] n_muid[4] */
                ret += 2 + 4 + 4 + 4;
                if (wst->extension)
                        ret += strlen(wst->extension);
        }

        return ret;
}

int p9_client_wstat(struct p9_fid *fid, struct p9_wstat *wst)
{
        int err;
        struct p9_req_t *req;
        struct p9_client *clnt;

        err = 0;
        clnt = fid->clnt;
        wst->size = p9_client_statsize(wst, clnt->proto_version);
        p9_debug(P9_DEBUG_9P, ">>> TWSTAT fid %d\n",
                 fid->fid);
        p9_debug(P9_DEBUG_9P,
                 "     sz=%x type=%x dev=%x qid=%x.%llx.%x\n"
                 "     mode=%8.8x atime=%8.8x mtime=%8.8x length=%llx\n"
                 "     name=%s uid=%s gid=%s muid=%s extension=(%s)\n"
                 "     uid=%d gid=%d n_muid=%d\n",
                 wst->size, wst->type, wst->dev, wst->qid.type,
                 wst->qid.path, wst->qid.version,
                 wst->mode, wst->atime, wst->mtime, wst->length,
                 wst->name, wst->uid, wst->gid, wst->muid, wst->extension,
                 from_kuid(&init_user_ns, wst->n_uid),
                 from_kgid(&init_user_ns, wst->n_gid),
                 from_kuid(&init_user_ns, wst->n_muid));

        req = p9_client_rpc(clnt, P9_TWSTAT, "dwS",
                            fid->fid, wst->size + 2, wst);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto error;
        }

        p9_debug(P9_DEBUG_9P, "<<< RWSTAT fid %d\n", fid->fid);

        p9_tag_remove(clnt, req);
error:
        return err;
}
EXPORT_SYMBOL(p9_client_wstat);

int p9_client_setattr(struct p9_fid *fid, struct p9_iattr_dotl *p9attr)
{
        int err;
        struct p9_req_t *req;
        struct p9_client *clnt;

        err = 0;
        clnt = fid->clnt;
        p9_debug(P9_DEBUG_9P, ">>> TSETATTR fid %d\n", fid->fid);
        p9_debug(P9_DEBUG_9P, "    valid=%x mode=%x uid=%d gid=%d size=%lld\n",
                 p9attr->valid, p9attr->mode,
                 from_kuid(&init_user_ns, p9attr->uid),
                 from_kgid(&init_user_ns, p9attr->gid),
                 p9attr->size);
        p9_debug(P9_DEBUG_9P, "    atime_sec=%lld atime_nsec=%lld\n",
                 p9attr->atime_sec, p9attr->atime_nsec);
        p9_debug(P9_DEBUG_9P, "    mtime_sec=%lld mtime_nsec=%lld\n",
                 p9attr->mtime_sec, p9attr->mtime_nsec);

        req = p9_client_rpc(clnt, P9_TSETATTR, "dI", fid->fid, p9attr);

        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto error;
        }
        p9_debug(P9_DEBUG_9P, "<<< RSETATTR fid %d\n", fid->fid);
        p9_tag_remove(clnt, req);
error:
        return err;
}
EXPORT_SYMBOL(p9_client_setattr);

int p9_client_statfs(struct p9_fid *fid, struct p9_rstatfs *sb)
{
        int err;
        struct p9_req_t *req;
        struct p9_client *clnt;

        err = 0;
        clnt = fid->clnt;

        p9_debug(P9_DEBUG_9P, ">>> TSTATFS fid %d\n", fid->fid);

        req = p9_client_rpc(clnt, P9_TSTATFS, "d", fid->fid);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto error;
        }

        err = p9pdu_readf(&req->rc, clnt->proto_version, "ddqqqqqqd", &sb->type,
                          &sb->bsize, &sb->blocks, &sb->bfree, &sb->bavail,
                          &sb->files, &sb->ffree, &sb->fsid, &sb->namelen);
        if (err) {
                trace_9p_protocol_dump(clnt, &req->rc);
                p9_tag_remove(clnt, req);
                goto error;
        }

        p9_debug(P9_DEBUG_9P,
                 "<<< RSTATFS fid %d type 0x%x bsize %u blocks %llu bfree %llu bavail %llu files %llu ffree %llu fsid %llu namelen %u\n",
                 fid->fid, sb->type, sb->bsize, sb->blocks, sb->bfree,
                 sb->bavail, sb->files, sb->ffree, sb->fsid, sb->namelen);

        p9_tag_remove(clnt, req);
error:
        return err;
}
EXPORT_SYMBOL(p9_client_statfs);

int p9_client_rename(struct p9_fid *fid,
                     struct p9_fid *newdirfid, const char *name)
{
        int err;
        struct p9_req_t *req;
        struct p9_client *clnt;

        err = 0;
        clnt = fid->clnt;

        p9_debug(P9_DEBUG_9P, ">>> TRENAME fid %d newdirfid %d name %s\n",
                 fid->fid, newdirfid->fid, name);

        req = p9_client_rpc(clnt, P9_TRENAME, "dds", fid->fid,
                            newdirfid->fid, name);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto error;
        }

        p9_debug(P9_DEBUG_9P, "<<< RRENAME fid %d\n", fid->fid);

        p9_tag_remove(clnt, req);
error:
        return err;
}
EXPORT_SYMBOL(p9_client_rename);

int p9_client_renameat(struct p9_fid *olddirfid, const char *old_name,
                       struct p9_fid *newdirfid, const char *new_name)
{
        int err;
        struct p9_req_t *req;
        struct p9_client *clnt;

        err = 0;
        clnt = olddirfid->clnt;

        p9_debug(P9_DEBUG_9P,
                 ">>> TRENAMEAT olddirfid %d old name %s newdirfid %d new name %s\n",
                 olddirfid->fid, old_name, newdirfid->fid, new_name);

        req = p9_client_rpc(clnt, P9_TRENAMEAT, "dsds", olddirfid->fid,
                            old_name, newdirfid->fid, new_name);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto error;
        }

        p9_debug(P9_DEBUG_9P, "<<< RRENAMEAT newdirfid %d new name %s\n",
                 newdirfid->fid, new_name);

        p9_tag_remove(clnt, req);
error:
        return err;
}
EXPORT_SYMBOL(p9_client_renameat);

/* An xattrwalk without @attr_name gives the fid for the lisxattr namespace
 */
struct p9_fid *p9_client_xattrwalk(struct p9_fid *file_fid,
                                   const char *attr_name, u64 *attr_size)
{
        int err;
        struct p9_req_t *req;
        struct p9_client *clnt;
        struct p9_fid *attr_fid;

        err = 0;
        clnt = file_fid->clnt;
        attr_fid = p9_fid_create(clnt);
        if (!attr_fid) {
                err = -ENOMEM;
                goto error;
        }
        p9_debug(P9_DEBUG_9P,
                 ">>> TXATTRWALK file_fid %d, attr_fid %d name %s\n",
                 file_fid->fid, attr_fid->fid, attr_name);

        req = p9_client_rpc(clnt, P9_TXATTRWALK, "dds",
                            file_fid->fid, attr_fid->fid, attr_name);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto error;
        }
        err = p9pdu_readf(&req->rc, clnt->proto_version, "q", attr_size);
        if (err) {
                trace_9p_protocol_dump(clnt, &req->rc);
                p9_tag_remove(clnt, req);
                goto clunk_fid;
        }
        p9_tag_remove(clnt, req);
        p9_debug(P9_DEBUG_9P, "<<<  RXATTRWALK fid %d size %llu\n",
                 attr_fid->fid, *attr_size);
        return attr_fid;
clunk_fid:
        p9_client_clunk(attr_fid);
        attr_fid = NULL;
error:
        if (attr_fid && attr_fid != file_fid)
                p9_fid_destroy(attr_fid);

        return ERR_PTR(err);
}
EXPORT_SYMBOL_GPL(p9_client_xattrwalk);

int p9_client_xattrcreate(struct p9_fid *fid, const char *name,
                          u64 attr_size, int flags)
{
        int err;
        struct p9_req_t *req;
        struct p9_client *clnt;

        p9_debug(P9_DEBUG_9P,
                 ">>> TXATTRCREATE fid %d name  %s size %llu flag %d\n",
                 fid->fid, name, attr_size, flags);
        err = 0;
        clnt = fid->clnt;
        req = p9_client_rpc(clnt, P9_TXATTRCREATE, "dsqd",
                            fid->fid, name, attr_size, flags);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto error;
        }
        p9_debug(P9_DEBUG_9P, "<<< RXATTRCREATE fid %d\n", fid->fid);
        p9_tag_remove(clnt, req);
error:
        return err;
}
EXPORT_SYMBOL_GPL(p9_client_xattrcreate);

int p9_client_readdir(struct p9_fid *fid, char *data, u32 count, u64 offset)
{
        int err, rsize, non_zc = 0;
        struct p9_client *clnt;
        struct p9_req_t *req;
        char *dataptr;
        struct kvec kv = {.iov_base = data, .iov_len = count};
        struct iov_iter to;

        iov_iter_kvec(&to, READ, &kv, 1, count);

        p9_debug(P9_DEBUG_9P, ">>> TREADDIR fid %d offset %llu count %d\n",
                 fid->fid, offset, count);

        err = 0;
        clnt = fid->clnt;

        rsize = fid->iounit;
        if (!rsize || rsize > clnt->msize - P9_READDIRHDRSZ)
                rsize = clnt->msize - P9_READDIRHDRSZ;

        if (count < rsize)
                rsize = count;

        /* Don't bother zerocopy for small IO (< 1024) */
        if (clnt->trans_mod->zc_request && rsize > 1024) {
                /* response header len is 11
                 * PDU Header(7) + IO Size (4)
                 */
                req = p9_client_zc_rpc(clnt, P9_TREADDIR, &to, NULL, rsize, 0,
                                       11, "dqd", fid->fid, offset, rsize);
        } else {
                non_zc = 1;
                req = p9_client_rpc(clnt, P9_TREADDIR, "dqd", fid->fid,
                                    offset, rsize);
        }
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto error;
        }

        err = p9pdu_readf(&req->rc, clnt->proto_version, "D", &count, &dataptr);
        if (err) {
                trace_9p_protocol_dump(clnt, &req->rc);
                goto free_and_error;
        }
        if (rsize < count) {
                pr_err("bogus RREADDIR count (%d > %d)\n", count, rsize);
                count = rsize;
        }

        p9_debug(P9_DEBUG_9P, "<<< RREADDIR count %d\n", count);

        if (non_zc)
                memmove(data, dataptr, count);

        p9_tag_remove(clnt, req);
        return count;

free_and_error:
        p9_tag_remove(clnt, req);
error:
        return err;
}
EXPORT_SYMBOL(p9_client_readdir);

int p9_client_mknod_dotl(struct p9_fid *fid, const char *name, int mode,
                         dev_t rdev, kgid_t gid, struct p9_qid *qid)
{
        int err;
        struct p9_client *clnt;
        struct p9_req_t *req;

        err = 0;
        clnt = fid->clnt;
        p9_debug(P9_DEBUG_9P,
                 ">>> TMKNOD fid %d name %s mode %d major %d minor %d\n",
                 fid->fid, name, mode, MAJOR(rdev), MINOR(rdev));
        req = p9_client_rpc(clnt, P9_TMKNOD, "dsdddg", fid->fid, name, mode,
                            MAJOR(rdev), MINOR(rdev), gid);
        if (IS_ERR(req))
                return PTR_ERR(req);

        err = p9pdu_readf(&req->rc, clnt->proto_version, "Q", qid);
        if (err) {
                trace_9p_protocol_dump(clnt, &req->rc);
                goto error;
        }
        p9_debug(P9_DEBUG_9P, "<<< RMKNOD qid %x.%llx.%x\n",
                 qid->type, qid->path, qid->version);

error:
        p9_tag_remove(clnt, req);
        return err;
}
EXPORT_SYMBOL(p9_client_mknod_dotl);

int p9_client_mkdir_dotl(struct p9_fid *fid, const char *name, int mode,
                         kgid_t gid, struct p9_qid *qid)
{
        int err;
        struct p9_client *clnt;
        struct p9_req_t *req;

        err = 0;
        clnt = fid->clnt;
        p9_debug(P9_DEBUG_9P, ">>> TMKDIR fid %d name %s mode %d gid %d\n",
                 fid->fid, name, mode, from_kgid(&init_user_ns, gid));
        req = p9_client_rpc(clnt, P9_TMKDIR, "dsdg",
                            fid->fid, name, mode, gid);
        if (IS_ERR(req))
                return PTR_ERR(req);

        err = p9pdu_readf(&req->rc, clnt->proto_version, "Q", qid);
        if (err) {
                trace_9p_protocol_dump(clnt, &req->rc);
                goto error;
        }
        p9_debug(P9_DEBUG_9P, "<<< RMKDIR qid %x.%llx.%x\n", qid->type,
                 qid->path, qid->version);

error:
        p9_tag_remove(clnt, req);
        return err;
}
EXPORT_SYMBOL(p9_client_mkdir_dotl);

int p9_client_lock_dotl(struct p9_fid *fid, struct p9_flock *flock, u8 *status)
{
        int err;
        struct p9_client *clnt;
        struct p9_req_t *req;

        err = 0;
        clnt = fid->clnt;
        p9_debug(P9_DEBUG_9P,
                 ">>> TLOCK fid %d type %i flags %d start %lld length %lld proc_id %d client_id %s\n",
                 fid->fid, flock->type, flock->flags, flock->start,
                 flock->length, flock->proc_id, flock->client_id);

        req = p9_client_rpc(clnt, P9_TLOCK, "dbdqqds", fid->fid, flock->type,
                            flock->flags, flock->start, flock->length,
                            flock->proc_id, flock->client_id);

        if (IS_ERR(req))
                return PTR_ERR(req);

        err = p9pdu_readf(&req->rc, clnt->proto_version, "b", status);
        if (err) {
                trace_9p_protocol_dump(clnt, &req->rc);
                goto error;
        }
        p9_debug(P9_DEBUG_9P, "<<< RLOCK status %i\n", *status);
error:
        p9_tag_remove(clnt, req);
        return err;
}
EXPORT_SYMBOL(p9_client_lock_dotl);

int p9_client_getlock_dotl(struct p9_fid *fid, struct p9_getlock *glock)
{
        int err;
        struct p9_client *clnt;
        struct p9_req_t *req;

        err = 0;
        clnt = fid->clnt;
        p9_debug(P9_DEBUG_9P,
                 ">>> TGETLOCK fid %d, type %i start %lld length %lld proc_id %d client_id %s\n",
                 fid->fid, glock->type, glock->start, glock->length,
                 glock->proc_id, glock->client_id);

        req = p9_client_rpc(clnt, P9_TGETLOCK, "dbqqds", fid->fid,
                            glock->type, glock->start, glock->length,
                            glock->proc_id, glock->client_id);

        if (IS_ERR(req))
                return PTR_ERR(req);

        err = p9pdu_readf(&req->rc, clnt->proto_version, "bqqds", &glock->type,
                          &glock->start, &glock->length, &glock->proc_id,
                          &glock->client_id);
        if (err) {
                trace_9p_protocol_dump(clnt, &req->rc);
                goto error;
        }
        p9_debug(P9_DEBUG_9P,
                 "<<< RGETLOCK type %i start %lld length %lld proc_id %d client_id %s\n",
                 glock->type, glock->start, glock->length,
                 glock->proc_id, glock->client_id);
error:
        p9_tag_remove(clnt, req);
        return err;
}
EXPORT_SYMBOL(p9_client_getlock_dotl);

int p9_client_readlink(struct p9_fid *fid, char **target)
{
        int err;
        struct p9_client *clnt;
        struct p9_req_t *req;

        err = 0;
        clnt = fid->clnt;
        p9_debug(P9_DEBUG_9P, ">>> TREADLINK fid %d\n", fid->fid);

        req = p9_client_rpc(clnt, P9_TREADLINK, "d", fid->fid);
        if (IS_ERR(req))
                return PTR_ERR(req);

        err = p9pdu_readf(&req->rc, clnt->proto_version, "s", target);
        if (err) {
                trace_9p_protocol_dump(clnt, &req->rc);
                goto error;
        }
        p9_debug(P9_DEBUG_9P, "<<< RREADLINK target %s\n", *target);
error:
        p9_tag_remove(clnt, req);
        return err;
}
EXPORT_SYMBOL(p9_client_readlink);

int __init p9_client_init(void)
{
        p9_req_cache = KMEM_CACHE(p9_req_t, SLAB_TYPESAFE_BY_RCU);
        return p9_req_cache ? 0 : -ENOMEM;
}

void __exit p9_client_exit(void)
{
        kmem_cache_destroy(p9_req_cache);
}