dev.c

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/*
  FUSE: Filesystem in Userspace
  Copyright (C) 2001-2008  Miklos Szeredi <[email protected]>

  This program can be distributed under the terms of the GNU GPL.
  See the file COPYING.
*/

#include "fuse_i.h"

#include <linux/init.h>
#include <linux/module.h>
#include <linux/poll.h>
#include <linux/uio.h>
#include <linux/miscdevice.h>
#include <linux/pagemap.h>
#include <linux/file.h>
#include <linux/slab.h>
#include <linux/pipe_fs_i.h>
#include <linux/swap.h>
#include <linux/splice.h>

MODULE_ALIAS_MISCDEV(FUSE_MINOR);
MODULE_ALIAS("devname:fuse");

static struct kmem_cache *fuse_req_cachep;

static struct fuse_conn *fuse_get_conn(struct file *file)
{
    /*
     * Lockless access is OK, because file->private data is set
     * once during mount and is valid until the file is released.
     */
    return file->private_data;
}

static void fuse_request_init(struct fuse_req *req)
{
    memset(req, 0, sizeof(*req));
    INIT_LIST_HEAD(&req->list);
    INIT_LIST_HEAD(&req->intr_entry);
    init_waitqueue_head(&req->waitq);
    atomic_set(&req->count, 1);
}

struct fuse_req *fuse_request_alloc(void)
{
    struct fuse_req *req = kmem_cache_alloc(fuse_req_cachep, GFP_KERNEL);
    if (req)
        fuse_request_init(req);
    return req;
}
EXPORT_SYMBOL_GPL(fuse_request_alloc);

struct fuse_req *fuse_request_alloc_nofs(void)
{
    struct fuse_req *req = kmem_cache_alloc(fuse_req_cachep, GFP_NOFS);
    if (req)
        fuse_request_init(req);
    return req;
}

void fuse_request_free(struct fuse_req *req)
{
    kmem_cache_free(fuse_req_cachep, req);
}

static void block_sigs(sigset_t *oldset)
{
    sigset_t mask;

    siginitsetinv(&mask, sigmask(SIGKILL));
    sigprocmask(SIG_BLOCK, &mask, oldset);
}

static void restore_sigs(sigset_t *oldset)
{
    sigprocmask(SIG_SETMASK, oldset, NULL);
}

static void __fuse_get_request(struct fuse_req *req)
{
    atomic_inc(&req->count);
}

/* Must be called with > 1 refcount */
static void __fuse_put_request(struct fuse_req *req)
{
    BUG_ON(atomic_read(&req->count) < 2);
    atomic_dec(&req->count);
}

static void fuse_req_init_context(struct fuse_req *req)
{
    req->in.h.uid = current_fsuid();
    req->in.h.gid = current_fsgid();
    req->in.h.pid = current->pid;
}

struct fuse_req *fuse_get_req(struct fuse_conn *fc)
{
    struct fuse_req *req;
    sigset_t oldset;
    int intr;
    int err;

    atomic_inc(&fc->num_waiting);
    block_sigs(&oldset);
    intr = wait_event_interruptible(fc->blocked_waitq, !fc->blocked);
    restore_sigs(&oldset);
    err = -EINTR;
    if (intr)
        goto out;

    err = -ENOTCONN;
    if (!fc->connected)
        goto out;

    req = fuse_request_alloc();
    err = -ENOMEM;
    if (!req)
        goto out;

    fuse_req_init_context(req);
    req->waiting = 1;
    return req;

 out:
    atomic_dec(&fc->num_waiting);
    return ERR_PTR(err);
}
EXPORT_SYMBOL_GPL(fuse_get_req);

/*
 * Return request in fuse_file->reserved_req.  However that may
 * currently be in use.  If that is the case, wait for it to become
 * available.
 */
static struct fuse_req *get_reserved_req(struct fuse_conn *fc,
                     struct file *file)
{
    struct fuse_req *req = NULL;
    struct fuse_file *ff = file->private_data;

    do {
        wait_event(fc->reserved_req_waitq, ff->reserved_req);
        spin_lock(&fc->lock);
        if (ff->reserved_req) {
            req = ff->reserved_req;
            ff->reserved_req = NULL;
            req->stolen_file = get_file(file);
        }
        spin_unlock(&fc->lock);
    } while (!req);

    return req;
}

/*
 * Put stolen request back into fuse_file->reserved_req
 */
static void put_reserved_req(struct fuse_conn *fc, struct fuse_req *req)
{
    struct file *file = req->stolen_file;
    struct fuse_file *ff = file->private_data;

    spin_lock(&fc->lock);
    fuse_request_init(req);
    BUG_ON(ff->reserved_req);
    ff->reserved_req = req;
    wake_up_all(&fc->reserved_req_waitq);
    spin_unlock(&fc->lock);
    fput(file);
}

/*
 * Gets a requests for a file operation, always succeeds
 *
 * This is used for sending the FLUSH request, which must get to
 * userspace, due to POSIX locks which may need to be unlocked.
 *
 * If allocation fails due to OOM, use the reserved request in
 * fuse_file.
 *
 * This is very unlikely to deadlock accidentally, since the
 * filesystem should not have it's own file open.  If deadlock is
 * intentional, it can still be broken by "aborting" the filesystem.
 */
struct fuse_req *fuse_get_req_nofail(struct fuse_conn *fc, struct file *file)
{
    struct fuse_req *req;

    atomic_inc(&fc->num_waiting);
    wait_event(fc->blocked_waitq, !fc->blocked);
    req = fuse_request_alloc();
    if (!req)
        req = get_reserved_req(fc, file);

    fuse_req_init_context(req);
    req->waiting = 1;
    return req;
}

void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req)
{
    if (atomic_dec_and_test(&req->count)) {
        if (req->waiting)
            atomic_dec(&fc->num_waiting);

        if (req->stolen_file)
            put_reserved_req(fc, req);
        else
            fuse_request_free(req);
    }
}
EXPORT_SYMBOL_GPL(fuse_put_request);

static unsigned len_args(unsigned numargs, struct fuse_arg *args)
{
    unsigned nbytes = 0;
    unsigned i;

    for (i = 0; i < numargs; i++)
        nbytes += args[i].size;

    return nbytes;
}

static u64 fuse_get_unique(struct fuse_conn *fc)
{
    fc->reqctr++;
    /* zero is special */
    if (fc->reqctr == 0)
        fc->reqctr = 1;

    return fc->reqctr;
}

static void queue_request(struct fuse_conn *fc, struct fuse_req *req)
{
    req->in.h.len = sizeof(struct fuse_in_header) +
        len_args(req->in.numargs, (struct fuse_arg *) req->in.args);
    list_add_tail(&req->list, &fc->pending);
    req->state = FUSE_REQ_PENDING;
    if (!req->waiting) {
        req->waiting = 1;
        atomic_inc(&fc->num_waiting);
    }
    wake_up(&fc->waitq);
    kill_fasync(&fc->fasync, SIGIO, POLL_IN);
}

void fuse_queue_forget(struct fuse_conn *fc, struct fuse_forget_link *forget,
               u64 nodeid, u64 nlookup)
{
    forget->forget_one.nodeid = nodeid;
    forget->forget_one.nlookup = nlookup;

    spin_lock(&fc->lock);
    if (fc->connected) {
        fc->forget_list_tail->next = forget;
        fc->forget_list_tail = forget;
        wake_up(&fc->waitq);
        kill_fasync(&fc->fasync, SIGIO, POLL_IN);
    } else {
        kfree(forget);
    }
    spin_unlock(&fc->lock);
}

static void flush_bg_queue(struct fuse_conn *fc)
{
    while (fc->active_background < fc->max_background &&
           !list_empty(&fc->bg_queue)) {
        struct fuse_req *req;

        req = list_entry(fc->bg_queue.next, struct fuse_req, list);
        list_del(&req->list);
        fc->active_background++;
        req->in.h.unique = fuse_get_unique(fc);
        queue_request(fc, req);
    }
}

/*
 * This function is called when a request is finished.  Either a reply
 * has arrived or it was aborted (and not yet sent) or some error
 * occurred during communication with userspace, or the device file
 * was closed.  The requester thread is woken up (if still waiting),
 * the 'end' callback is called if given, else the reference to the
 * request is released
 *
 * Called with fc->lock, unlocks it
 */
static void request_end(struct fuse_conn *fc, struct fuse_req *req)
__releases(fc->lock)
{
    void (*end) (struct fuse_conn *, struct fuse_req *) = req->end;
    req->end = NULL;
    list_del(&req->list);
    list_del(&req->intr_entry);
    req->state = FUSE_REQ_FINISHED;
    if (req->background) {
        if (fc->num_background == fc->max_background) {
            fc->blocked = 0;
            wake_up_all(&fc->blocked_waitq);
        }
        if (fc->num_background == fc->congestion_threshold &&
            fc->connected && fc->bdi_initialized) {
            clear_bdi_congested(&fc->bdi, BLK_RW_SYNC);
            clear_bdi_congested(&fc->bdi, BLK_RW_ASYNC);
        }
        fc->num_background--;
        fc->active_background--;
        flush_bg_queue(fc);
    }
    spin_unlock(&fc->lock);
    wake_up(&req->waitq);
    if (end)
        end(fc, req);
    fuse_put_request(fc, req);
}

static void wait_answer_interruptible(struct fuse_conn *fc,
                      struct fuse_req *req)
__releases(fc->lock)
__acquires(fc->lock)
{
    if (signal_pending(current))
        return;

    spin_unlock(&fc->lock);
    wait_event_interruptible(req->waitq, req->state == FUSE_REQ_FINISHED);
    spin_lock(&fc->lock);
}

static void queue_interrupt(struct fuse_conn *fc, struct fuse_req *req)
{
    list_add_tail(&req->intr_entry, &fc->interrupts);
    wake_up(&fc->waitq);
    kill_fasync(&fc->fasync, SIGIO, POLL_IN);
}

static void request_wait_answer(struct fuse_conn *fc, struct fuse_req *req)
__releases(fc->lock)
__acquires(fc->lock)
{
    if (!fc->no_interrupt) {
        /* Any signal may interrupt this */
        wait_answer_interruptible(fc, req);

        if (req->aborted)
            goto aborted;
        if (req->state == FUSE_REQ_FINISHED)
            return;

        req->interrupted = 1;
        if (req->state == FUSE_REQ_SENT)
            queue_interrupt(fc, req);
    }

    if (!req->force) {
        sigset_t oldset;

        /* Only fatal signals may interrupt this */
        block_sigs(&oldset);
        wait_answer_interruptible(fc, req);
        restore_sigs(&oldset);

        if (req->aborted)
            goto aborted;
        if (req->state == FUSE_REQ_FINISHED)
            return;

        /* Request is not yet in userspace, bail out */
        if (req->state == FUSE_REQ_PENDING) {
            list_del(&req->list);
            __fuse_put_request(req);
            req->out.h.error = -EINTR;
            return;
        }
    }

    /*
     * Either request is already in userspace, or it was forced.
     * Wait it out.
     */
    spin_unlock(&fc->lock);
    wait_event(req->waitq, req->state == FUSE_REQ_FINISHED);
    spin_lock(&fc->lock);

    if (!req->aborted)
        return;

 aborted:
    BUG_ON(req->state != FUSE_REQ_FINISHED);
    if (req->locked) {
        /* This is uninterruptible sleep, because data is
           being copied to/from the buffers of req.  During
           locked state, there mustn't be any filesystem
           operation (e.g. page fault), since that could lead
           to deadlock */
        spin_unlock(&fc->lock);
        wait_event(req->waitq, !req->locked);
        spin_lock(&fc->lock);
    }
}

void fuse_request_send(struct fuse_conn *fc, struct fuse_req *req)
{
    req->isreply = 1;
    spin_lock(&fc->lock);
    if (!fc->connected)
        req->out.h.error = -ENOTCONN;
    else if (fc->conn_error)
        req->out.h.error = -ECONNREFUSED;
    else {
        req->in.h.unique = fuse_get_unique(fc);
        queue_request(fc, req);
        /* acquire extra reference, since request is still needed
           after request_end() */
        __fuse_get_request(req);

        request_wait_answer(fc, req);
    }
    spin_unlock(&fc->lock);
}
EXPORT_SYMBOL_GPL(fuse_request_send);

static void fuse_request_send_nowait_locked(struct fuse_conn *fc,
                        struct fuse_req *req)
{
    req->background = 1;
    fc->num_background++;
    if (fc->num_background == fc->max_background)
        fc->blocked = 1;
    if (fc->num_background == fc->congestion_threshold &&
        fc->bdi_initialized) {
        set_bdi_congested(&fc->bdi, BLK_RW_SYNC);
        set_bdi_congested(&fc->bdi, BLK_RW_ASYNC);
    }
    list_add_tail(&req->list, &fc->bg_queue);
    flush_bg_queue(fc);
}

static void fuse_request_send_nowait(struct fuse_conn *fc, struct fuse_req *req)
{
    spin_lock(&fc->lock);
    if (fc->connected) {
        fuse_request_send_nowait_locked(fc, req);
        spin_unlock(&fc->lock);
    } else {
        req->out.h.error = -ENOTCONN;
        request_end(fc, req);
    }
}

void fuse_request_send_background(struct fuse_conn *fc, struct fuse_req *req)
{
    req->isreply = 1;
    fuse_request_send_nowait(fc, req);
}
EXPORT_SYMBOL_GPL(fuse_request_send_background);

static int fuse_request_send_notify_reply(struct fuse_conn *fc,
                      struct fuse_req *req, u64 unique)
{
    int err = -ENODEV;

    req->isreply = 0;
    req->in.h.unique = unique;
    spin_lock(&fc->lock);
    if (fc->connected) {
        queue_request(fc, req);
        err = 0;
    }
    spin_unlock(&fc->lock);

    return err;
}

/*
 * Called under fc->lock
 *
 * fc->connected must have been checked previously
 */
void fuse_request_send_background_locked(struct fuse_conn *fc,
                     struct fuse_req *req)
{
    req->isreply = 1;
    fuse_request_send_nowait_locked(fc, req);
}

/*
 * Lock the request.  Up to the next unlock_request() there mustn't be
 * anything that could cause a page-fault.  If the request was already
 * aborted bail out.
 */
static int lock_request(struct fuse_conn *fc, struct fuse_req *req)
{
    int err = 0;
    if (req) {
        spin_lock(&fc->lock);
        if (req->aborted)
            err = -ENOENT;
        else
            req->locked = 1;
        spin_unlock(&fc->lock);
    }
    return err;
}

/*
 * Unlock request.  If it was aborted during being locked, the
 * requester thread is currently waiting for it to be unlocked, so
 * wake it up.
 */
static void unlock_request(struct fuse_conn *fc, struct fuse_req *req)
{
    if (req) {
        spin_lock(&fc->lock);
        req->locked = 0;
        if (req->aborted)
            wake_up(&req->waitq);
        spin_unlock(&fc->lock);
    }
}

struct fuse_copy_state {
    struct fuse_conn *fc;
    int write;
    struct fuse_req *req;
    const struct iovec *iov;
    struct pipe_buffer *pipebufs;
    struct pipe_buffer *currbuf;
    struct pipe_inode_info *pipe;
    unsigned long nr_segs;
    unsigned long seglen;
    unsigned long addr;
    struct page *pg;
    void *mapaddr;
    void *buf;
    unsigned len;
    unsigned move_pages:1;
};

static void fuse_copy_init(struct fuse_copy_state *cs, struct fuse_conn *fc,
               int write,
               const struct iovec *iov, unsigned long nr_segs)
{
    memset(cs, 0, sizeof(*cs));
    cs->fc = fc;
    cs->write = write;
    cs->iov = iov;
    cs->nr_segs = nr_segs;
}

/* Unmap and put previous page of userspace buffer */
static void fuse_copy_finish(struct fuse_copy_state *cs)
{
    if (cs->currbuf) {
        struct pipe_buffer *buf = cs->currbuf;

        if (!cs->write) {
            buf->ops->unmap(cs->pipe, buf, cs->mapaddr);
        } else {
            kunmap(buf->page);
            buf->len = PAGE_SIZE - cs->len;
        }
        cs->currbuf = NULL;
        cs->mapaddr = NULL;
    } else if (cs->mapaddr) {
        kunmap(cs->pg);
        if (cs->write) {
            flush_dcache_page(cs->pg);
            set_page_dirty_lock(cs->pg);
        }
        put_page(cs->pg);
        cs->mapaddr = NULL;
    }
}

/*
 * Get another pagefull of userspace buffer, and map it to kernel
 * address space, and lock request
 */
static int fuse_copy_fill(struct fuse_copy_state *cs)
{
    unsigned long offset;
    int err;

    unlock_request(cs->fc, cs->req);
    fuse_copy_finish(cs);
    if (cs->pipebufs) {
        struct pipe_buffer *buf = cs->pipebufs;

        if (!cs->write) {
            err = buf->ops->confirm(cs->pipe, buf);
            if (err)
                return err;

            BUG_ON(!cs->nr_segs);
            cs->currbuf = buf;
            cs->mapaddr = buf->ops->map(cs->pipe, buf, 0);
            cs->len = buf->len;
            cs->buf = cs->mapaddr + buf->offset;
            cs->pipebufs++;
            cs->nr_segs--;
        } else {
            struct page *page;

            if (cs->nr_segs == cs->pipe->buffers)
                return -EIO;

            page = alloc_page(GFP_HIGHUSER);
            if (!page)
                return -ENOMEM;

            buf->page = page;
            buf->offset = 0;
            buf->len = 0;

            cs->currbuf = buf;
            cs->mapaddr = kmap(page);
            cs->buf = cs->mapaddr;
            cs->len = PAGE_SIZE;
            cs->pipebufs++;
            cs->nr_segs++;
        }
    } else {
        if (!cs->seglen) {
            BUG_ON(!cs->nr_segs);
            cs->seglen = cs->iov[0].iov_len;
            cs->addr = (unsigned long) cs->iov[0].iov_base;
            cs->iov++;
            cs->nr_segs--;
        }
        err = get_user_pages_fast(cs->addr, 1, cs->write, &cs->pg);
        if (err < 0)
            return err;
        BUG_ON(err != 1);
        offset = cs->addr % PAGE_SIZE;
        cs->mapaddr = kmap(cs->pg);
        cs->buf = cs->mapaddr + offset;
        cs->len = min(PAGE_SIZE - offset, cs->seglen);
        cs->seglen -= cs->len;
        cs->addr += cs->len;
    }

    return lock_request(cs->fc, cs->req);
}

/* Do as much copy to/from userspace buffer as we can */
static int fuse_copy_do(struct fuse_copy_state *cs, void **val, unsigned *size)
{
    unsigned ncpy = min(*size, cs->len);
    if (val) {
        if (cs->write)
            memcpy(cs->buf, *val, ncpy);
        else
            memcpy(*val, cs->buf, ncpy);
        *val += ncpy;
    }
    *size -= ncpy;
    cs->len -= ncpy;
    cs->buf += ncpy;
    return ncpy;
}

static int fuse_check_page(struct page *page)
{
    if (page_mapcount(page) ||
        page->mapping != NULL ||
        page_count(page) != 1 ||
        (page->flags & PAGE_FLAGS_CHECK_AT_PREP &
         ~(1 << PG_locked |
           1 << PG_referenced |
           1 << PG_uptodate |
           1 << PG_lru |
           1 << PG_active |
           1 << PG_reclaim))) {
        printk(KERN_WARNING "fuse: trying to steal weird page\n");
        printk(KERN_WARNING "  page=%p index=%li flags=%08lx, count=%i, mapcount=%i, mapping=%p\n", page, page->index, page->flags, page_count(page), page_mapcount(page), page->mapping);
        return 1;
    }
    return 0;
}

static int fuse_try_move_page(struct fuse_copy_state *cs, struct page **pagep)
{
    int err;
    struct page *oldpage = *pagep;
    struct page *newpage;
    struct pipe_buffer *buf = cs->pipebufs;
    struct address_space *mapping;
    pgoff_t index;

    unlock_request(cs->fc, cs->req);
    fuse_copy_finish(cs);

    err = buf->ops->confirm(cs->pipe, buf);
    if (err)
        return err;

    BUG_ON(!cs->nr_segs);
    cs->currbuf = buf;
    cs->len = buf->len;
    cs->pipebufs++;
    cs->nr_segs--;

    if (cs->len != PAGE_SIZE)
        goto out_fallback;

    if (buf->ops->steal(cs->pipe, buf) != 0)
        goto out_fallback;

    newpage = buf->page;

    if (WARN_ON(!PageUptodate(newpage)))
        return -EIO;

    ClearPageMappedToDisk(newpage);

    if (fuse_check_page(newpage) != 0)
        goto out_fallback_unlock;

    mapping = oldpage->mapping;
    index = oldpage->index;

    /*
     * This is a new and locked page, it shouldn't be mapped or
     * have any special flags on it
     */
    if (WARN_ON(page_mapped(oldpage)))
        goto out_fallback_unlock;
    if (WARN_ON(page_has_private(oldpage)))
        goto out_fallback_unlock;
    if (WARN_ON(PageDirty(oldpage) || PageWriteback(oldpage)))
        goto out_fallback_unlock;
    if (WARN_ON(PageMlocked(oldpage)))
        goto out_fallback_unlock;

    err = replace_page_cache_page(oldpage, newpage, GFP_KERNEL);
    if (err) {
        unlock_page(newpage);
        return err;
    }

    page_cache_get(newpage);

    if (!(buf->flags & PIPE_BUF_FLAG_LRU))
        lru_cache_add_file(newpage);

    err = 0;
    spin_lock(&cs->fc->lock);
    if (cs->req->aborted)
        err = -ENOENT;
    else
        *pagep = newpage;
    spin_unlock(&cs->fc->lock);

    if (err) {
        unlock_page(newpage);
        page_cache_release(newpage);
        return err;
    }

    unlock_page(oldpage);
    page_cache_release(oldpage);
    cs->len = 0;

    return 0;

out_fallback_unlock:
    unlock_page(newpage);
out_fallback:
    cs->mapaddr = buf->ops->map(cs->pipe, buf, 1);
    cs->buf = cs->mapaddr + buf->offset;

    err = lock_request(cs->fc, cs->req);
    if (err)
        return err;

    return 1;
}

static int fuse_ref_page(struct fuse_copy_state *cs, struct page *page,
             unsigned offset, unsigned count)
{
    struct pipe_buffer *buf;

    if (cs->nr_segs == cs->pipe->buffers)
        return -EIO;

    unlock_request(cs->fc, cs->req);
    fuse_copy_finish(cs);

    buf = cs->pipebufs;
    page_cache_get(page);
    buf->page = page;
    buf->offset = offset;
    buf->len = count;

    cs->pipebufs++;
    cs->nr_segs++;
    cs->len = 0;

    return 0;
}

/*
 * Copy a page in the request to/from the userspace buffer.  Must be
 * done atomically
 */
static int fuse_copy_page(struct fuse_copy_state *cs, struct page **pagep,
              unsigned offset, unsigned count, int zeroing)
{
    int err;
    struct page *page = *pagep;

    if (page && zeroing && count < PAGE_SIZE)
        clear_highpage(page);

    while (count) {
        if (cs->write && cs->pipebufs && page) {
            return fuse_ref_page(cs, page, offset, count);
        } else if (!cs->len) {
            if (cs->move_pages && page &&
                offset == 0 && count == PAGE_SIZE) {
                err = fuse_try_move_page(cs, pagep);
                if (err <= 0)
                    return err;
            } else {
                err = fuse_copy_fill(cs);
                if (err)
                    return err;
            }
        }
        if (page) {
            void *mapaddr = kmap_atomic(page);
            void *buf = mapaddr + offset;
            offset += fuse_copy_do(cs, &buf, &count);
            kunmap_atomic(mapaddr);
        } else
            offset += fuse_copy_do(cs, NULL, &count);
    }
    if (page && !cs->write)
        flush_dcache_page(page);
    return 0;
}

/* Copy pages in the request to/from userspace buffer */
static int fuse_copy_pages(struct fuse_copy_state *cs, unsigned nbytes,
               int zeroing)
{
    unsigned i;
    struct fuse_req *req = cs->req;
    unsigned offset = req->page_offset;
    unsigned count = min(nbytes, (unsigned) PAGE_SIZE - offset);

    for (i = 0; i < req->num_pages && (nbytes || zeroing); i++) {
        int err;

        err = fuse_copy_page(cs, &req->pages[i], offset, count,
                     zeroing);
        if (err)
            return err;

        nbytes -= count;
        count = min(nbytes, (unsigned) PAGE_SIZE);
        offset = 0;
    }
    return 0;
}

/* Copy a single argument in the request to/from userspace buffer */
static int fuse_copy_one(struct fuse_copy_state *cs, void *val, unsigned size)
{
    while (size) {
        if (!cs->len) {
            int err = fuse_copy_fill(cs);
            if (err)
                return err;
        }
        fuse_copy_do(cs, &val, &size);
    }
    return 0;
}

/* Copy request arguments to/from userspace buffer */
static int fuse_copy_args(struct fuse_copy_state *cs, unsigned numargs,
              unsigned argpages, struct fuse_arg *args,
              int zeroing)
{
    int err = 0;
    unsigned i;

    for (i = 0; !err && i < numargs; i++)  {
        struct fuse_arg *arg = &args[i];
        if (i == numargs - 1 && argpages)
            err = fuse_copy_pages(cs, arg->size, zeroing);
        else
            err = fuse_copy_one(cs, arg->value, arg->size);
    }
    return err;
}

static int forget_pending(struct fuse_conn *fc)
{
    return fc->forget_list_head.next != NULL;
}

static int request_pending(struct fuse_conn *fc)
{
    return !list_empty(&fc->pending) || !list_empty(&fc->interrupts) ||
        forget_pending(fc);
}

/* Wait until a request is available on the pending list */
static void request_wait(struct fuse_conn *fc)
__releases(fc->lock)
__acquires(fc->lock)
{
    DECLARE_WAITQUEUE(wait, current);

    add_wait_queue_exclusive(&fc->waitq, &wait);
    while (fc->connected && !request_pending(fc)) {
        set_current_state(TASK_INTERRUPTIBLE);
        if (signal_pending(current))
            break;

        spin_unlock(&fc->lock);
        schedule();
        spin_lock(&fc->lock);
    }
    set_current_state(TASK_RUNNING);
    remove_wait_queue(&fc->waitq, &wait);
}

/*
 * Transfer an interrupt request to userspace
 *
 * Unlike other requests this is assembled on demand, without a need
 * to allocate a separate fuse_req structure.
 *
 * Called with fc->lock held, releases it
 */
static int fuse_read_interrupt(struct fuse_conn *fc, struct fuse_copy_state *cs,
                   size_t nbytes, struct fuse_req *req)
__releases(fc->lock)
{
    struct fuse_in_header ih;
    struct fuse_interrupt_in arg;
    unsigned reqsize = sizeof(ih) + sizeof(arg);
    int err;

    list_del_init(&req->intr_entry);
    req->intr_unique = fuse_get_unique(fc);
    memset(&ih, 0, sizeof(ih));
    memset(&arg, 0, sizeof(arg));
    ih.len = reqsize;
    ih.opcode = FUSE_INTERRUPT;
    ih.unique = req->intr_unique;
    arg.unique = req->in.h.unique;

    spin_unlock(&fc->lock);
    if (nbytes < reqsize)
        return -EINVAL;

    err = fuse_copy_one(cs, &ih, sizeof(ih));
    if (!err)
        err = fuse_copy_one(cs, &arg, sizeof(arg));
    fuse_copy_finish(cs);

    return err ? err : reqsize;
}

static struct fuse_forget_link *dequeue_forget(struct fuse_conn *fc,
                           unsigned max,
                           unsigned *countp)
{
    struct fuse_forget_link *head = fc->forget_list_head.next;
    struct fuse_forget_link **newhead = &head;
    unsigned count;

    for (count = 0; *newhead != NULL && count < max; count++)
        newhead = &(*newhead)->next;

    fc->forget_list_head.next = *newhead;
    *newhead = NULL;
    if (fc->forget_list_head.next == NULL)
        fc->forget_list_tail = &fc->forget_list_head;

    if (countp != NULL)
        *countp = count;

    return head;
}

static int fuse_read_single_forget(struct fuse_conn *fc,
                   struct fuse_copy_state *cs,
                   size_t nbytes)
__releases(fc->lock)
{
    int err;
    struct fuse_forget_link *forget = dequeue_forget(fc, 1, NULL);
    struct fuse_forget_in arg = {
        .nlookup = forget->forget_one.nlookup,
    };
    struct fuse_in_header ih = {
        .opcode = FUSE_FORGET,
        .nodeid = forget->forget_one.nodeid,
        .unique = fuse_get_unique(fc),
        .len = sizeof(ih) + sizeof(arg),
    };

    spin_unlock(&fc->lock);
    kfree(forget);
    if (nbytes < ih.len)
        return -EINVAL;

    err = fuse_copy_one(cs, &ih, sizeof(ih));
    if (!err)
        err = fuse_copy_one(cs, &arg, sizeof(arg));
    fuse_copy_finish(cs);

    if (err)
        return err;

    return ih.len;
}

static int fuse_read_batch_forget(struct fuse_conn *fc,
                   struct fuse_copy_state *cs, size_t nbytes)
__releases(fc->lock)
{
    int err;
    unsigned max_forgets;
    unsigned count;
    struct fuse_forget_link *head;
    struct fuse_batch_forget_in arg = { .count = 0 };
    struct fuse_in_header ih = {
        .opcode = FUSE_BATCH_FORGET,
        .unique = fuse_get_unique(fc),
        .len = sizeof(ih) + sizeof(arg),
    };

    if (nbytes < ih.len) {
        spin_unlock(&fc->lock);
        return -EINVAL;
    }

    max_forgets = (nbytes - ih.len) / sizeof(struct fuse_forget_one);
    head = dequeue_forget(fc, max_forgets, &count);
    spin_unlock(&fc->lock);

    arg.count = count;
    ih.len += count * sizeof(struct fuse_forget_one);
    err = fuse_copy_one(cs, &ih, sizeof(ih));
    if (!err)
        err = fuse_copy_one(cs, &arg, sizeof(arg));

    while (head) {
        struct fuse_forget_link *forget = head;

        if (!err) {
            err = fuse_copy_one(cs, &forget->forget_one,
                        sizeof(forget->forget_one));
        }
        head = forget->next;
        kfree(forget);
    }

    fuse_copy_finish(cs);

    if (err)
        return err;

    return ih.len;
}

static int fuse_read_forget(struct fuse_conn *fc, struct fuse_copy_state *cs,
                size_t nbytes)
__releases(fc->lock)
{
    if (fc->minor < 16 || fc->forget_list_head.next->next == NULL)
        return fuse_read_single_forget(fc, cs, nbytes);
    else
        return fuse_read_batch_forget(fc, cs, nbytes);
}

/*
 * Read a single request into the userspace filesystem's buffer.  This
 * function waits until a request is available, then removes it from
 * the pending list and copies request data to userspace buffer.  If
 * no reply is needed (FORGET) or request has been aborted or there
 * was an error during the copying then it's finished by calling
 * request_end().  Otherwise add it to the processing list, and set
 * the 'sent' flag.
 */
static ssize_t fuse_dev_do_read(struct fuse_conn *fc, struct file *file,
                struct fuse_copy_state *cs, size_t nbytes)
{
    int err;
    struct fuse_req *req;
    struct fuse_in *in;
    unsigned reqsize;

 restart:
    spin_lock(&fc->lock);
    err = -EAGAIN;
    if ((file->f_flags & O_NONBLOCK) && fc->connected &&
        !request_pending(fc))
        goto err_unlock;

    request_wait(fc);
    err = -ENODEV;
    if (!fc->connected)
        goto err_unlock;
    err = -ERESTARTSYS;
    if (!request_pending(fc))
        goto err_unlock;

    if (!list_empty(&fc->interrupts)) {
        req = list_entry(fc->interrupts.next, struct fuse_req,
                 intr_entry);
        return fuse_read_interrupt(fc, cs, nbytes, req);
    }

    if (forget_pending(fc)) {
        if (list_empty(&fc->pending) || fc->forget_batch-- > 0)
            return fuse_read_forget(fc, cs, nbytes);

        if (fc->forget_batch <= -8)
            fc->forget_batch = 16;
    }

    req = list_entry(fc->pending.next, struct fuse_req, list);
    req->state = FUSE_REQ_READING;
    list_move(&req->list, &fc->io);

    in = &req->in;
    reqsize = in->h.len;
    /* If request is too large, reply with an error and restart the read */
    if (nbytes < reqsize) {
        req->out.h.error = -EIO;
        /* SETXATTR is special, since it may contain too large data */
        if (in->h.opcode == FUSE_SETXATTR)
            req->out.h.error = -E2BIG;
        request_end(fc, req);
        goto restart;
    }
    spin_unlock(&fc->lock);
    cs->req = req;
    err = fuse_copy_one(cs, &in->h, sizeof(in->h));
    if (!err)
        err = fuse_copy_args(cs, in->numargs, in->argpages,
                     (struct fuse_arg *) in->args, 0);
    fuse_copy_finish(cs);
    spin_lock(&fc->lock);
    req->locked = 0;
    if (req->aborted) {
        request_end(fc, req);
        return -ENODEV;
    }
    if (err) {
        req->out.h.error = -EIO;
        request_end(fc, req);
        return err;
    }
    if (!req->isreply)
        request_end(fc, req);
    else {
        req->state = FUSE_REQ_SENT;
        list_move_tail(&req->list, &fc->processing);
        if (req->interrupted)
            queue_interrupt(fc, req);
        spin_unlock(&fc->lock);
    }
    return reqsize;

 err_unlock:
    spin_unlock(&fc->lock);
    return err;
}

static ssize_t fuse_dev_read(struct kiocb *iocb, const struct iovec *iov,
                  unsigned long nr_segs, loff_t pos)
{
    struct fuse_copy_state cs;
    struct file *file = iocb->ki_filp;
    struct fuse_conn *fc = fuse_get_conn(file);
    if (!fc)
        return -EPERM;

    fuse_copy_init(&cs, fc, 1, iov, nr_segs);

    return fuse_dev_do_read(fc, file, &cs, iov_length(iov, nr_segs));
}

static int fuse_dev_pipe_buf_steal(struct pipe_inode_info *pipe,
                   struct pipe_buffer *buf)
{
    return 1;
}

static const struct pipe_buf_operations fuse_dev_pipe_buf_ops = {
    .can_merge = 0,
    .map = generic_pipe_buf_map,
    .unmap = generic_pipe_buf_unmap,
    .confirm = generic_pipe_buf_confirm,
    .release = generic_pipe_buf_release,
    .steal = fuse_dev_pipe_buf_steal,
    .get = generic_pipe_buf_get,
};

static ssize_t fuse_dev_splice_read(struct file *in, loff_t *ppos,
                    struct pipe_inode_info *pipe,
                    size_t len, unsigned int flags)
{
    int ret;
    int page_nr = 0;
    int do_wakeup = 0;
    struct pipe_buffer *bufs;
    struct fuse_copy_state cs;
    struct fuse_conn *fc = fuse_get_conn(in);
    if (!fc)
        return -EPERM;

    bufs = kmalloc(pipe->buffers * sizeof(struct pipe_buffer), GFP_KERNEL);
    if (!bufs)
        return -ENOMEM;

    fuse_copy_init(&cs, fc, 1, NULL, 0);
    cs.pipebufs = bufs;
    cs.pipe = pipe;
    ret = fuse_dev_do_read(fc, in, &cs, len);
    if (ret < 0)
        goto out;

    ret = 0;
    pipe_lock(pipe);

    if (!pipe->readers) {
        send_sig(SIGPIPE, current, 0);
        if (!ret)
            ret = -EPIPE;
        goto out_unlock;
    }

    if (pipe->nrbufs + cs.nr_segs > pipe->buffers) {
        ret = -EIO;
        goto out_unlock;
    }

    while (page_nr < cs.nr_segs) {
        int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
        struct pipe_buffer *buf = pipe->bufs + newbuf;

        buf->page = bufs[page_nr].page;
        buf->offset = bufs[page_nr].offset;
        buf->len = bufs[page_nr].len;
        buf->ops = &fuse_dev_pipe_buf_ops;

        pipe->nrbufs++;
        page_nr++;
        ret += buf->len;

        if (pipe->inode)
            do_wakeup = 1;
    }

out_unlock:
    pipe_unlock(pipe);

    if (do_wakeup) {
        smp_mb();
        if (waitqueue_active(&pipe->wait))
            wake_up_interruptible(&pipe->wait);
        kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
    }

out:
    for (; page_nr < cs.nr_segs; page_nr++)
        page_cache_release(bufs[page_nr].page);

    kfree(bufs);
    return ret;
}

static int fuse_notify_poll(struct fuse_conn *fc, unsigned int size,
                struct fuse_copy_state *cs)
{
    struct fuse_notify_poll_wakeup_out outarg;
    int err = -EINVAL;

    if (size != sizeof(outarg))
        goto err;

    err = fuse_copy_one(cs, &outarg, sizeof(outarg));
    if (err)
        goto err;

    fuse_copy_finish(cs);
    return fuse_notify_poll_wakeup(fc, &outarg);

err:
    fuse_copy_finish(cs);
    return err;
}

static int fuse_notify_inval_inode(struct fuse_conn *fc, unsigned int size,
                   struct fuse_copy_state *cs)
{
    struct fuse_notify_inval_inode_out outarg;
    int err = -EINVAL;

    if (size != sizeof(outarg))
        goto err;

    err = fuse_copy_one(cs, &outarg, sizeof(outarg));
    if (err)
        goto err;
    fuse_copy_finish(cs);

    down_read(&fc->killsb);
    err = -ENOENT;
    if (fc->sb) {
        err = fuse_reverse_inval_inode(fc->sb, outarg.ino,
                           outarg.off, outarg.len);
    }
    up_read(&fc->killsb);
    return err;

err:
    fuse_copy_finish(cs);
    return err;
}

static int fuse_notify_inval_entry(struct fuse_conn *fc, unsigned int size,
                   struct fuse_copy_state *cs)
{
    struct fuse_notify_inval_entry_out outarg;
    int err = -ENOMEM;
    char *buf;
    struct qstr name;

    buf = kzalloc(FUSE_NAME_MAX + 1, GFP_KERNEL);
    if (!buf)
        goto err;

    err = -EINVAL;
    if (size < sizeof(outarg))
        goto err;

    err = fuse_copy_one(cs, &outarg, sizeof(outarg));
    if (err)
        goto err;

    err = -ENAMETOOLONG;
    if (outarg.namelen > FUSE_NAME_MAX)
        goto err;

    err = -EINVAL;
    if (size != sizeof(outarg) + outarg.namelen + 1)
        goto err;

    name.name = buf;
    name.len = outarg.namelen;
    err = fuse_copy_one(cs, buf, outarg.namelen + 1);
    if (err)
        goto err;
    fuse_copy_finish(cs);
    buf[outarg.namelen] = 0;
    name.hash = full_name_hash(name.name, name.len);

    down_read(&fc->killsb);
    err = -ENOENT;
    if (fc->sb)
        err = fuse_reverse_inval_entry(fc->sb, outarg.parent, 0, &name);
    up_read(&fc->killsb);
    kfree(buf);
    return err;

err:
    kfree(buf);
    fuse_copy_finish(cs);
    return err;
}

static int fuse_notify_delete(struct fuse_conn *fc, unsigned int size,
                  struct fuse_copy_state *cs)
{
    struct fuse_notify_delete_out outarg;
    int err = -ENOMEM;
    char *buf;
    struct qstr name;

    buf = kzalloc(FUSE_NAME_MAX + 1, GFP_KERNEL);
    if (!buf)
        goto err;

    err = -EINVAL;
    if (size < sizeof(outarg))
        goto err;

    err = fuse_copy_one(cs, &outarg, sizeof(outarg));
    if (err)
        goto err;

    err = -ENAMETOOLONG;
    if (outarg.namelen > FUSE_NAME_MAX)
        goto err;

    err = -EINVAL;
    if (size != sizeof(outarg) + outarg.namelen + 1)
        goto err;

    name.name = buf;
    name.len = outarg.namelen;
    err = fuse_copy_one(cs, buf, outarg.namelen + 1);
    if (err)
        goto err;
    fuse_copy_finish(cs);
    buf[outarg.namelen] = 0;
    name.hash = full_name_hash(name.name, name.len);

    down_read(&fc->killsb);
    err = -ENOENT;
    if (fc->sb)
        err = fuse_reverse_inval_entry(fc->sb, outarg.parent,
                           outarg.child, &name);
    up_read(&fc->killsb);
    kfree(buf);
    return err;

err:
    kfree(buf);
    fuse_copy_finish(cs);
    return err;
}

static int fuse_notify_store(struct fuse_conn *fc, unsigned int size,
                 struct fuse_copy_state *cs)
{
    struct fuse_notify_store_out outarg;
    struct inode *inode;
    struct address_space *mapping;
    u64 nodeid;
    int err;
    pgoff_t index;
    unsigned int offset;
    unsigned int num;
    loff_t file_size;
    loff_t end;

    err = -EINVAL;
    if (size < sizeof(outarg))
        goto out_finish;

    err = fuse_copy_one(cs, &outarg, sizeof(outarg));
    if (err)
        goto out_finish;

    err = -EINVAL;
    if (size - sizeof(outarg) != outarg.size)
        goto out_finish;

    nodeid = outarg.nodeid;

    down_read(&fc->killsb);

    err = -ENOENT;
    if (!fc->sb)
        goto out_up_killsb;

    inode = ilookup5(fc->sb, nodeid, fuse_inode_eq, &nodeid);
    if (!inode)
        goto out_up_killsb;

    mapping = inode->i_mapping;
    index = outarg.offset >> PAGE_CACHE_SHIFT;
    offset = outarg.offset & ~PAGE_CACHE_MASK;
    file_size = i_size_read(inode);
    end = outarg.offset + outarg.size;
    if (end > file_size) {
        file_size = end;
        fuse_write_update_size(inode, file_size);
    }

    num = outarg.size;
    while (num) {
        struct page *page;
        unsigned int this_num;

        err = -ENOMEM;
        page = find_or_create_page(mapping, index,
                       mapping_gfp_mask(mapping));
        if (!page)
            goto out_iput;

        this_num = min_t(unsigned, num, PAGE_CACHE_SIZE - offset);
        err = fuse_copy_page(cs, &page, offset, this_num, 0);
        if (!err && offset == 0 && (num != 0 || file_size == end))
            SetPageUptodate(page);
        unlock_page(page);
        page_cache_release(page);

        if (err)
            goto out_iput;

        num -= this_num;
        offset = 0;
        index++;
    }

    err = 0;

out_iput:
    iput(inode);
out_up_killsb:
    up_read(&fc->killsb);
out_finish:
    fuse_copy_finish(cs);
    return err;
}

static void fuse_retrieve_end(struct fuse_conn *fc, struct fuse_req *req)
{
    release_pages(req->pages, req->num_pages, 0);
}

static int fuse_retrieve(struct fuse_conn *fc, struct inode *inode,
             struct fuse_notify_retrieve_out *outarg)
{
    int err;
    struct address_space *mapping = inode->i_mapping;
    struct fuse_req *req;
    pgoff_t index;
    loff_t file_size;
    unsigned int num;
    unsigned int offset;
    size_t total_len = 0;

    req = fuse_get_req(fc);
    if (IS_ERR(req))
        return PTR_ERR(req);

    offset = outarg->offset & ~PAGE_CACHE_MASK;

    req->in.h.opcode = FUSE_NOTIFY_REPLY;
    req->in.h.nodeid = outarg->nodeid;
    req->in.numargs = 2;
    req->in.argpages = 1;
    req->page_offset = offset;
    req->end = fuse_retrieve_end;

    index = outarg->offset >> PAGE_CACHE_SHIFT;
    file_size = i_size_read(inode);
    num = outarg->size;
    if (outarg->offset > file_size)
        num = 0;
    else if (outarg->offset + num > file_size)
        num = file_size - outarg->offset;

    while (num && req->num_pages < FUSE_MAX_PAGES_PER_REQ) {
        struct page *page;
        unsigned int this_num;

        page = find_get_page(mapping, index);
        if (!page)
            break;

        this_num = min_t(unsigned, num, PAGE_CACHE_SIZE - offset);
        req->pages[req->num_pages] = page;
        req->num_pages++;

        offset = 0;
        num -= this_num;
        total_len += this_num;
        index++;
    }
    req->misc.retrieve_in.offset = outarg->offset;
    req->misc.retrieve_in.size = total_len;
    req->in.args[0].size = sizeof(req->misc.retrieve_in);
    req->in.args[0].value = &req->misc.retrieve_in;
    req->in.args[1].size = total_len;

    err = fuse_request_send_notify_reply(fc, req, outarg->notify_unique);
    if (err)
        fuse_retrieve_end(fc, req);

    return err;
}

static int fuse_notify_retrieve(struct fuse_conn *fc, unsigned int size,
                struct fuse_copy_state *cs)
{
    struct fuse_notify_retrieve_out outarg;
    struct inode *inode;
    int err;

    err = -EINVAL;
    if (size != sizeof(outarg))
        goto copy_finish;

    err = fuse_copy_one(cs, &outarg, sizeof(outarg));
    if (err)
        goto copy_finish;

    fuse_copy_finish(cs);

    down_read(&fc->killsb);
    err = -ENOENT;
    if (fc->sb) {
        u64 nodeid = outarg.nodeid;

        inode = ilookup5(fc->sb, nodeid, fuse_inode_eq, &nodeid);
        if (inode) {
            err = fuse_retrieve(fc, inode, &outarg);
            iput(inode);
        }
    }
    up_read(&fc->killsb);

    return err;

copy_finish:
    fuse_copy_finish(cs);
    return err;
}

static int fuse_notify(struct fuse_conn *fc, enum fuse_notify_code code,
               unsigned int size, struct fuse_copy_state *cs)
{
    switch (code) {
    case FUSE_NOTIFY_POLL:
        return fuse_notify_poll(fc, size, cs);

    case FUSE_NOTIFY_INVAL_INODE:
        return fuse_notify_inval_inode(fc, size, cs);

    case FUSE_NOTIFY_INVAL_ENTRY:
        return fuse_notify_inval_entry(fc, size, cs);

    case FUSE_NOTIFY_STORE:
        return fuse_notify_store(fc, size, cs);

    case FUSE_NOTIFY_RETRIEVE:
        return fuse_notify_retrieve(fc, size, cs);

    case FUSE_NOTIFY_DELETE:
        return fuse_notify_delete(fc, size, cs);

    default:
        fuse_copy_finish(cs);
        return -EINVAL;
    }
}

/* Look up request on processing list by unique ID */
static struct fuse_req *request_find(struct fuse_conn *fc, u64 unique)
{
    struct list_head *entry;

    list_for_each(entry, &fc->processing) {
        struct fuse_req *req;
        req = list_entry(entry, struct fuse_req, list);
        if (req->in.h.unique == unique || req->intr_unique == unique)
            return req;
    }
    return NULL;
}

static int copy_out_args(struct fuse_copy_state *cs, struct fuse_out *out,
             unsigned nbytes)
{
    unsigned reqsize = sizeof(struct fuse_out_header);

    if (out->h.error)
        return nbytes != reqsize ? -EINVAL : 0;

    reqsize += len_args(out->numargs, out->args);

    if (reqsize < nbytes || (reqsize > nbytes && !out->argvar))
        return -EINVAL;
    else if (reqsize > nbytes) {
        struct fuse_arg *lastarg = &out->args[out->numargs-1];
        unsigned diffsize = reqsize - nbytes;
        if (diffsize > lastarg->size)
            return -EINVAL;
        lastarg->size -= diffsize;
    }
    return fuse_copy_args(cs, out->numargs, out->argpages, out->args,
                  out->page_zeroing);
}

/*
 * Write a single reply to a request.  First the header is copied from
 * the write buffer.  The request is then searched on the processing
 * list by the unique ID found in the header.  If found, then remove
 * it from the list and copy the rest of the buffer to the request.
 * The request is finished by calling request_end()
 */
static ssize_t fuse_dev_do_write(struct fuse_conn *fc,
                 struct fuse_copy_state *cs, size_t nbytes)
{
    int err;
    struct fuse_req *req;
    struct fuse_out_header oh;

    if (nbytes < sizeof(struct fuse_out_header))
        return -EINVAL;

    err = fuse_copy_one(cs, &oh, sizeof(oh));
    if (err)
        goto err_finish;

    err = -EINVAL;
    if (oh.len != nbytes)
        goto err_finish;

    /*
     * Zero oh.unique indicates unsolicited notification message
     * and error contains notification code.
     */
    if (!oh.unique) {
        err = fuse_notify(fc, oh.error, nbytes - sizeof(oh), cs);
        return err ? err : nbytes;
    }

    err = -EINVAL;
    if (oh.error <= -1000 || oh.error > 0)
        goto err_finish;

    spin_lock(&fc->lock);
    err = -ENOENT;
    if (!fc->connected)
        goto err_unlock;

    req = request_find(fc, oh.unique);
    if (!req)
        goto err_unlock;

    if (req->aborted) {
        spin_unlock(&fc->lock);
        fuse_copy_finish(cs);
        spin_lock(&fc->lock);
        request_end(fc, req);
        return -ENOENT;
    }
    /* Is it an interrupt reply? */
    if (req->intr_unique == oh.unique) {
        err = -EINVAL;
        if (nbytes != sizeof(struct fuse_out_header))
            goto err_unlock;

        if (oh.error == -ENOSYS)
            fc->no_interrupt = 1;
        else if (oh.error == -EAGAIN)
            queue_interrupt(fc, req);

        spin_unlock(&fc->lock);
        fuse_copy_finish(cs);
        return nbytes;
    }

    req->state = FUSE_REQ_WRITING;
    list_move(&req->list, &fc->io);
    req->out.h = oh;
    req->locked = 1;
    cs->req = req;
    if (!req->out.page_replace)
        cs->move_pages = 0;
    spin_unlock(&fc->lock);

    err = copy_out_args(cs, &req->out, nbytes);
    fuse_copy_finish(cs);

    spin_lock(&fc->lock);
    req->locked = 0;
    if (!err) {
        if (req->aborted)
            err = -ENOENT;
    } else if (!req->aborted)
        req->out.h.error = -EIO;
    request_end(fc, req);

    return err ? err : nbytes;

 err_unlock:
    spin_unlock(&fc->lock);
 err_finish:
    fuse_copy_finish(cs);
    return err;
}

static ssize_t fuse_dev_write(struct kiocb *iocb, const struct iovec *iov,
                  unsigned long nr_segs, loff_t pos)
{
    struct fuse_copy_state cs;
    struct fuse_conn *fc = fuse_get_conn(iocb->ki_filp);
    if (!fc)
        return -EPERM;

    fuse_copy_init(&cs, fc, 0, iov, nr_segs);

    return fuse_dev_do_write(fc, &cs, iov_length(iov, nr_segs));
}

static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe,
                     struct file *out, loff_t *ppos,
                     size_t len, unsigned int flags)
{
    unsigned nbuf;
    unsigned idx;
    struct pipe_buffer *bufs;
    struct fuse_copy_state cs;
    struct fuse_conn *fc;
    size_t rem;
    ssize_t ret;

    fc = fuse_get_conn(out);
    if (!fc)
        return -EPERM;

    bufs = kmalloc(pipe->buffers * sizeof(struct pipe_buffer), GFP_KERNEL);
    if (!bufs)
        return -ENOMEM;

    pipe_lock(pipe);
    nbuf = 0;
    rem = 0;
    for (idx = 0; idx < pipe->nrbufs && rem < len; idx++)
        rem += pipe->bufs[(pipe->curbuf + idx) & (pipe->buffers - 1)].len;

    ret = -EINVAL;
    if (rem < len) {
        pipe_unlock(pipe);
        goto out;
    }

    rem = len;
    while (rem) {
        struct pipe_buffer *ibuf;
        struct pipe_buffer *obuf;

        BUG_ON(nbuf >= pipe->buffers);
        BUG_ON(!pipe->nrbufs);
        ibuf = &pipe->bufs[pipe->curbuf];
        obuf = &bufs[nbuf];

        if (rem >= ibuf->len) {
            *obuf = *ibuf;
            ibuf->ops = NULL;
            pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
            pipe->nrbufs--;
        } else {
            ibuf->ops->get(pipe, ibuf);
            *obuf = *ibuf;
            obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
            obuf->len = rem;
            ibuf->offset += obuf->len;
            ibuf->len -= obuf->len;
        }
        nbuf++;
        rem -= obuf->len;
    }
    pipe_unlock(pipe);

    fuse_copy_init(&cs, fc, 0, NULL, nbuf);
    cs.pipebufs = bufs;
    cs.pipe = pipe;

    if (flags & SPLICE_F_MOVE)
        cs.move_pages = 1;

    ret = fuse_dev_do_write(fc, &cs, len);

    for (idx = 0; idx < nbuf; idx++) {
        struct pipe_buffer *buf = &bufs[idx];
        buf->ops->release(pipe, buf);
    }
out:
    kfree(bufs);
    return ret;
}

static unsigned fuse_dev_poll(struct file *file, poll_table *wait)
{
    unsigned mask = POLLOUT | POLLWRNORM;
    struct fuse_conn *fc = fuse_get_conn(file);
    if (!fc)
        return POLLERR;

    poll_wait(file, &fc->waitq, wait);

    spin_lock(&fc->lock);
    if (!fc->connected)
        mask = POLLERR;
    else if (request_pending(fc))
        mask |= POLLIN | POLLRDNORM;
    spin_unlock(&fc->lock);

    return mask;
}

/*
 * Abort all requests on the given list (pending or processing)
 *
 * This function releases and reacquires fc->lock
 */
static void end_requests(struct fuse_conn *fc, struct list_head *head)
__releases(fc->lock)
__acquires(fc->lock)
{
    while (!list_empty(head)) {
        struct fuse_req *req;
        req = list_entry(head->next, struct fuse_req, list);
        req->out.h.error = -ECONNABORTED;
        request_end(fc, req);
        spin_lock(&fc->lock);
    }
}

/*
 * Abort requests under I/O
 *
 * The requests are set to aborted and finished, and the request
 * waiter is woken up.  This will make request_wait_answer() wait
 * until the request is unlocked and then return.
 *
 * If the request is asynchronous, then the end function needs to be
 * called after waiting for the request to be unlocked (if it was
 * locked).
 */
static void end_io_requests(struct fuse_conn *fc)
__releases(fc->lock)
__acquires(fc->lock)
{
    while (!list_empty(&fc->io)) {
        struct fuse_req *req =
            list_entry(fc->io.next, struct fuse_req, list);
        void (*end) (struct fuse_conn *, struct fuse_req *) = req->end;

        req->aborted = 1;
        req->out.h.error = -ECONNABORTED;
        req->state = FUSE_REQ_FINISHED;
        list_del_init(&req->list);
        wake_up(&req->waitq);
        if (end) {
            req->end = NULL;
            __fuse_get_request(req);
            spin_unlock(&fc->lock);
            wait_event(req->waitq, !req->locked);
            end(fc, req);
            fuse_put_request(fc, req);
            spin_lock(&fc->lock);
        }
    }
}

static void end_queued_requests(struct fuse_conn *fc)
__releases(fc->lock)
__acquires(fc->lock)
{
    fc->max_background = UINT_MAX;
    flush_bg_queue(fc);
    end_requests(fc, &fc->pending);
    end_requests(fc, &fc->processing);
    while (forget_pending(fc))
        kfree(dequeue_forget(fc, 1, NULL));
}

static void end_polls(struct fuse_conn *fc)
{
    struct rb_node *p;

    p = rb_first(&fc->polled_files);

    while (p) {
        struct fuse_file *ff;
        ff = rb_entry(p, struct fuse_file, polled_node);
        wake_up_interruptible_all(&ff->poll_wait);

        p = rb_next(p);
    }
}

/*
 * Abort all requests.
 *
 * Emergency exit in case of a malicious or accidental deadlock, or
 * just a hung filesystem.
 *
 * The same effect is usually achievable through killing the
 * filesystem daemon and all users of the filesystem.  The exception
 * is the combination of an asynchronous request and the tricky
 * deadlock (see Documentation/filesystems/fuse.txt).
 *
 * During the aborting, progression of requests from the pending and
 * processing lists onto the io list, and progression of new requests
 * onto the pending list is prevented by req->connected being false.
 *
 * Progression of requests under I/O to the processing list is
 * prevented by the req->aborted flag being true for these requests.
 * For this reason requests on the io list must be aborted first.
 */
void fuse_abort_conn(struct fuse_conn *fc)
{
    spin_lock(&fc->lock);
    if (fc->connected) {
        fc->connected = 0;
        fc->blocked = 0;
        end_io_requests(fc);
        end_queued_requests(fc);
        end_polls(fc);
        wake_up_all(&fc->waitq);
        wake_up_all(&fc->blocked_waitq);
        kill_fasync(&fc->fasync, SIGIO, POLL_IN);
    }
    spin_unlock(&fc->lock);
}
EXPORT_SYMBOL_GPL(fuse_abort_conn);

int fuse_dev_release(struct inode *inode, struct file *file)
{
    struct fuse_conn *fc = fuse_get_conn(file);
    if (fc) {
        spin_lock(&fc->lock);
        fc->connected = 0;
        fc->blocked = 0;
        end_queued_requests(fc);
        end_polls(fc);
        wake_up_all(&fc->blocked_waitq);
        spin_unlock(&fc->lock);
        fuse_conn_put(fc);
    }

    return 0;
}
EXPORT_SYMBOL_GPL(fuse_dev_release);

static int fuse_dev_fasync(int fd, struct file *file, int on)
{
    struct fuse_conn *fc = fuse_get_conn(file);
    if (!fc)
        return -EPERM;

    /* No locking - fasync_helper does its own locking */
    return fasync_helper(fd, file, on, &fc->fasync);
}

const struct file_operations fuse_dev_operations = {
    .owner      = THIS_MODULE,
    .llseek     = no_llseek,
    .read       = do_sync_read,
    .aio_read   = fuse_dev_read,
    .splice_read    = fuse_dev_splice_read,
    .write      = do_sync_write,
    .aio_write  = fuse_dev_write,
    .splice_write   = fuse_dev_splice_write,
    .poll       = fuse_dev_poll,
    .release    = fuse_dev_release,
    .fasync     = fuse_dev_fasync,
};
EXPORT_SYMBOL_GPL(fuse_dev_operations);

static struct miscdevice fuse_miscdevice = {
    .minor = FUSE_MINOR,
    .name  = "fuse",
    .fops = &fuse_dev_operations,
};

int __init fuse_dev_init(void)
{
    int err = -ENOMEM;
    fuse_req_cachep = kmem_cache_create("fuse_request",
                        sizeof(struct fuse_req),
                        0, 0, NULL);
    if (!fuse_req_cachep)
        goto out;

    err = misc_register(&fuse_miscdevice);
    if (err)
        goto out_cache_clean;

    return 0;

 out_cache_clean:
    kmem_cache_destroy(fuse_req_cachep);
 out:
    return err;
}

void fuse_dev_cleanup(void)
{
    misc_deregister(&fuse_miscdevice);
    kmem_cache_destroy(fuse_req_cachep);
}