Logo Search packages:      
Sourcecode: linux version File versions  Download package

direct.c

/*
 * linux/fs/nfs/direct.c
 *
 * Copyright (C) 2003 by Chuck Lever <cel@netapp.com>
 *
 * High-performance uncached I/O for the Linux NFS client
 *
 * There are important applications whose performance or correctness
 * depends on uncached access to file data.  Database clusters
 * (multiple copies of the same instance running on separate hosts)
 * implement their own cache coherency protocol that subsumes file
 * system cache protocols.  Applications that process datasets
 * considerably larger than the client's memory do not always benefit
 * from a local cache.  A streaming video server, for instance, has no
 * need to cache the contents of a file.
 *
 * When an application requests uncached I/O, all read and write requests
 * are made directly to the server; data stored or fetched via these
 * requests is not cached in the Linux page cache.  The client does not
 * correct unaligned requests from applications.  All requested bytes are
 * held on permanent storage before a direct write system call returns to
 * an application.
 *
 * Solaris implements an uncached I/O facility called directio() that
 * is used for backups and sequential I/O to very large files.  Solaris
 * also supports uncaching whole NFS partitions with "-o forcedirectio,"
 * an undocumented mount option.
 *
 * Designed by Jeff Kimmel, Chuck Lever, and Trond Myklebust, with
 * help from Andrew Morton.
 *
 * 18 Dec 2001    Initial implementation for 2.4  --cel
 * 08 Jul 2002    Version for 2.4.19, with bug fixes --trondmy
 * 08 Jun 2003    Port to 2.5 APIs  --cel
 * 31 Mar 2004    Handle direct I/O without VFS support  --cel
 * 15 Sep 2004    Parallel async reads  --cel
 * 04 May 2005    support O_DIRECT with aio  --cel
 *
 */

#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/file.h>
#include <linux/pagemap.h>
#include <linux/kref.h>

#include <linux/nfs_fs.h>
#include <linux/nfs_page.h>
#include <linux/sunrpc/clnt.h>

#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/atomic.h>

#include "internal.h"
#include "iostat.h"

#define NFSDBG_FACILITY       NFSDBG_VFS

static struct kmem_cache *nfs_direct_cachep;

/*
 * This represents a set of asynchronous requests that we're waiting on
 */
struct nfs_direct_req {
      struct kref       kref;       /* release manager */

      /* I/O parameters */
      struct nfs_open_context *ctx;       /* file open context info */
      struct kiocb *          iocb;       /* controlling i/o request */
      struct inode *          inode;            /* target file of i/o */

      /* completion state */
      atomic_t          io_count;   /* i/os we're waiting for */
      spinlock_t        lock;       /* protect completion state */
      ssize_t                 count,            /* bytes actually processed */
                        error;            /* any reported error */
      struct completion completion; /* wait for i/o completion */

      /* commit state */
      struct list_head  rewrite_list;     /* saved nfs_write_data structs */
      struct nfs_write_data * commit_data;      /* special write_data for commits */
      int               flags;
#define NFS_ODIRECT_DO_COMMIT       (1)   /* an unstable reply was received */
#define NFS_ODIRECT_RESCHED_WRITES  (2)   /* write verification failed */
      struct nfs_writeverf    verf;       /* unstable write verifier */
};

static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode);
static const struct rpc_call_ops nfs_write_direct_ops;

static inline void get_dreq(struct nfs_direct_req *dreq)
{
      atomic_inc(&dreq->io_count);
}

static inline int put_dreq(struct nfs_direct_req *dreq)
{
      return atomic_dec_and_test(&dreq->io_count);
}

/**
 * nfs_direct_IO - NFS address space operation for direct I/O
 * @rw: direction (read or write)
 * @iocb: target I/O control block
 * @iov: array of vectors that define I/O buffer
 * @pos: offset in file to begin the operation
 * @nr_segs: size of iovec array
 *
 * The presence of this routine in the address space ops vector means
 * the NFS client supports direct I/O.  However, we shunt off direct
 * read and write requests before the VFS gets them, so this method
 * should never be called.
 */
ssize_t nfs_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov, loff_t pos, unsigned long nr_segs)
{
      dprintk("NFS: nfs_direct_IO (%s) off/no(%Ld/%lu) EINVAL\n",
                  iocb->ki_filp->f_path.dentry->d_name.name,
                  (long long) pos, nr_segs);

      return -EINVAL;
}

static void nfs_direct_dirty_pages(struct page **pages, unsigned int pgbase, size_t count)
{
      unsigned int npages;
      unsigned int i;

      if (count == 0)
            return;
      pages += (pgbase >> PAGE_SHIFT);
      npages = (count + (pgbase & ~PAGE_MASK) + PAGE_SIZE - 1) >> PAGE_SHIFT;
      for (i = 0; i < npages; i++) {
            struct page *page = pages[i];
            if (!PageCompound(page))
                  set_page_dirty(page);
      }
}

static void nfs_direct_release_pages(struct page **pages, unsigned int npages)
{
      unsigned int i;
      for (i = 0; i < npages; i++)
            page_cache_release(pages[i]);
}

static inline struct nfs_direct_req *nfs_direct_req_alloc(void)
{
      struct nfs_direct_req *dreq;

      dreq = kmem_cache_alloc(nfs_direct_cachep, GFP_KERNEL);
      if (!dreq)
            return NULL;

      kref_init(&dreq->kref);
      kref_get(&dreq->kref);
      init_completion(&dreq->completion);
      INIT_LIST_HEAD(&dreq->rewrite_list);
      dreq->iocb = NULL;
      dreq->ctx = NULL;
      spin_lock_init(&dreq->lock);
      atomic_set(&dreq->io_count, 0);
      dreq->count = 0;
      dreq->error = 0;
      dreq->flags = 0;

      return dreq;
}

static void nfs_direct_req_free(struct kref *kref)
{
      struct nfs_direct_req *dreq = container_of(kref, struct nfs_direct_req, kref);

      if (dreq->ctx != NULL)
            put_nfs_open_context(dreq->ctx);
      kmem_cache_free(nfs_direct_cachep, dreq);
}

static void nfs_direct_req_release(struct nfs_direct_req *dreq)
{
      kref_put(&dreq->kref, nfs_direct_req_free);
}

/*
 * Collects and returns the final error value/byte-count.
 */
static ssize_t nfs_direct_wait(struct nfs_direct_req *dreq)
{
      ssize_t result = -EIOCBQUEUED;

      /* Async requests don't wait here */
      if (dreq->iocb)
            goto out;

      result = wait_for_completion_interruptible(&dreq->completion);

      if (!result)
            result = dreq->error;
      if (!result)
            result = dreq->count;

out:
      return (ssize_t) result;
}

/*
 * Synchronous I/O uses a stack-allocated iocb.  Thus we can't trust
 * the iocb is still valid here if this is a synchronous request.
 */
static void nfs_direct_complete(struct nfs_direct_req *dreq)
{
      if (dreq->iocb) {
            long res = (long) dreq->error;
            if (!res)
                  res = (long) dreq->count;
            aio_complete(dreq->iocb, res, 0);
      }
      complete_all(&dreq->completion);

      nfs_direct_req_release(dreq);
}

/*
 * We must hold a reference to all the pages in this direct read request
 * until the RPCs complete.  This could be long *after* we are woken up in
 * nfs_direct_wait (for instance, if someone hits ^C on a slow server).
 */
static void nfs_direct_read_result(struct rpc_task *task, void *calldata)
{
      struct nfs_read_data *data = calldata;
      struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req;

      if (nfs_readpage_result(task, data) != 0)
            return;

      spin_lock(&dreq->lock);
      if (unlikely(task->tk_status < 0)) {
            dreq->error = task->tk_status;
            spin_unlock(&dreq->lock);
      } else {
            dreq->count += data->res.count;
            spin_unlock(&dreq->lock);
            nfs_direct_dirty_pages(data->pagevec,
                        data->args.pgbase,
                        data->res.count);
      }
      nfs_direct_release_pages(data->pagevec, data->npages);

      if (put_dreq(dreq))
            nfs_direct_complete(dreq);
}

static const struct rpc_call_ops nfs_read_direct_ops = {
      .rpc_call_done = nfs_direct_read_result,
      .rpc_release = nfs_readdata_release,
};

/*
 * For each rsize'd chunk of the user's buffer, dispatch an NFS READ
 * operation.  If nfs_readdata_alloc() or get_user_pages() fails,
 * bail and stop sending more reads.  Read length accounting is
 * handled automatically by nfs_direct_read_result().  Otherwise, if
 * no requests have been sent, just return an error.
 */
static ssize_t nfs_direct_read_schedule_segment(struct nfs_direct_req *dreq,
                                    const struct iovec *iov,
                                    loff_t pos)
{
      struct nfs_open_context *ctx = dreq->ctx;
      struct inode *inode = ctx->path.dentry->d_inode;
      unsigned long user_addr = (unsigned long)iov->iov_base;
      size_t count = iov->iov_len;
      size_t rsize = NFS_SERVER(inode)->rsize;
      unsigned int pgbase;
      int result;
      ssize_t started = 0;

      do {
            struct nfs_read_data *data;
            size_t bytes;

            pgbase = user_addr & ~PAGE_MASK;
            bytes = min(rsize,count);

            result = -ENOMEM;
            data = nfs_readdata_alloc(nfs_page_array_len(pgbase, bytes));
            if (unlikely(!data))
                  break;

            down_read(&current->mm->mmap_sem);
            result = get_user_pages(current, current->mm, user_addr,
                              data->npages, 1, 0, data->pagevec, NULL);
            up_read(&current->mm->mmap_sem);
            if (result < 0) {
                  nfs_readdata_release(data);
                  break;
            }
            if ((unsigned)result < data->npages) {
                  bytes = result * PAGE_SIZE;
                  if (bytes <= pgbase) {
                        nfs_direct_release_pages(data->pagevec, result);
                        nfs_readdata_release(data);
                        break;
                  }
                  bytes -= pgbase;
                  data->npages = result;
            }

            get_dreq(dreq);

            data->req = (struct nfs_page *) dreq;
            data->inode = inode;
            data->cred = ctx->cred;
            data->args.fh = NFS_FH(inode);
            data->args.context = ctx;
            data->args.offset = pos;
            data->args.pgbase = pgbase;
            data->args.pages = data->pagevec;
            data->args.count = bytes;
            data->res.fattr = &data->fattr;
            data->res.eof = 0;
            data->res.count = bytes;

            rpc_init_task(&data->task, NFS_CLIENT(inode), RPC_TASK_ASYNC,
                        &nfs_read_direct_ops, data);
            NFS_PROTO(inode)->read_setup(data);

            data->task.tk_cookie = (unsigned long) inode;

            rpc_execute(&data->task);

            dprintk("NFS: %5u initiated direct read call "
                  "(req %s/%Ld, %zu bytes @ offset %Lu)\n",
                        data->task.tk_pid,
                        inode->i_sb->s_id,
                        (long long)NFS_FILEID(inode),
                        bytes,
                        (unsigned long long)data->args.offset);

            started += bytes;
            user_addr += bytes;
            pos += bytes;
            /* FIXME: Remove this unnecessary math from final patch */
            pgbase += bytes;
            pgbase &= ~PAGE_MASK;
            BUG_ON(pgbase != (user_addr & ~PAGE_MASK));

            count -= bytes;
      } while (count != 0);

      if (started)
            return started;
      return result < 0 ? (ssize_t) result : -EFAULT;
}

static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq,
                                    const struct iovec *iov,
                                    unsigned long nr_segs,
                                    loff_t pos)
{
      ssize_t result = -EINVAL;
      size_t requested_bytes = 0;
      unsigned long seg;

      get_dreq(dreq);

      for (seg = 0; seg < nr_segs; seg++) {
            const struct iovec *vec = &iov[seg];
            result = nfs_direct_read_schedule_segment(dreq, vec, pos);
            if (result < 0)
                  break;
            requested_bytes += result;
            if ((size_t)result < vec->iov_len)
                  break;
            pos += vec->iov_len;
      }

      if (put_dreq(dreq))
            nfs_direct_complete(dreq);

      if (requested_bytes != 0)
            return 0;

      if (result < 0)
            return result;
      return -EIO;
}

static ssize_t nfs_direct_read(struct kiocb *iocb, const struct iovec *iov,
                         unsigned long nr_segs, loff_t pos)
{
      ssize_t result = 0;
      sigset_t oldset;
      struct inode *inode = iocb->ki_filp->f_mapping->host;
      struct rpc_clnt *clnt = NFS_CLIENT(inode);
      struct nfs_direct_req *dreq;

      dreq = nfs_direct_req_alloc();
      if (!dreq)
            return -ENOMEM;

      dreq->inode = inode;
      dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
      if (!is_sync_kiocb(iocb))
            dreq->iocb = iocb;

      rpc_clnt_sigmask(clnt, &oldset);
      result = nfs_direct_read_schedule_iovec(dreq, iov, nr_segs, pos);
      if (!result)
            result = nfs_direct_wait(dreq);
      rpc_clnt_sigunmask(clnt, &oldset);
      nfs_direct_req_release(dreq);

      return result;
}

static void nfs_direct_free_writedata(struct nfs_direct_req *dreq)
{
      while (!list_empty(&dreq->rewrite_list)) {
            struct nfs_write_data *data = list_entry(dreq->rewrite_list.next, struct nfs_write_data, pages);
            list_del(&data->pages);
            nfs_direct_release_pages(data->pagevec, data->npages);
            nfs_writedata_release(data);
      }
}

#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
static void nfs_direct_write_reschedule(struct nfs_direct_req *dreq)
{
      struct inode *inode = dreq->inode;
      struct list_head *p;
      struct nfs_write_data *data;

      dreq->count = 0;
      get_dreq(dreq);

      list_for_each(p, &dreq->rewrite_list) {
            data = list_entry(p, struct nfs_write_data, pages);

            get_dreq(dreq);

            /*
             * Reset data->res.
             */
            nfs_fattr_init(&data->fattr);
            data->res.count = data->args.count;
            memset(&data->verf, 0, sizeof(data->verf));

            /*
             * Reuse data->task; data->args should not have changed
             * since the original request was sent.
             */
            rpc_init_task(&data->task, NFS_CLIENT(inode), RPC_TASK_ASYNC,
                        &nfs_write_direct_ops, data);
            NFS_PROTO(inode)->write_setup(data, FLUSH_STABLE);

            data->task.tk_priority = RPC_PRIORITY_NORMAL;
            data->task.tk_cookie = (unsigned long) inode;

            /*
             * We're called via an RPC callback, so BKL is already held.
             */
            rpc_execute(&data->task);

            dprintk("NFS: %5u rescheduled direct write call (req %s/%Ld, %u bytes @ offset %Lu)\n",
                        data->task.tk_pid,
                        inode->i_sb->s_id,
                        (long long)NFS_FILEID(inode),
                        data->args.count,
                        (unsigned long long)data->args.offset);
      }

      if (put_dreq(dreq))
            nfs_direct_write_complete(dreq, inode);
}

static void nfs_direct_commit_result(struct rpc_task *task, void *calldata)
{
      struct nfs_write_data *data = calldata;
      struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req;

      /* Call the NFS version-specific code */
      if (NFS_PROTO(data->inode)->commit_done(task, data) != 0)
            return;
      if (unlikely(task->tk_status < 0)) {
            dprintk("NFS: %5u commit failed with error %d.\n",
                        task->tk_pid, task->tk_status);
            dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
      } else if (memcmp(&dreq->verf, &data->verf, sizeof(data->verf))) {
            dprintk("NFS: %5u commit verify failed\n", task->tk_pid);
            dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
      }

      dprintk("NFS: %5u commit returned %d\n", task->tk_pid, task->tk_status);
      nfs_direct_write_complete(dreq, data->inode);
}

static const struct rpc_call_ops nfs_commit_direct_ops = {
      .rpc_call_done = nfs_direct_commit_result,
      .rpc_release = nfs_commit_release,
};

static void nfs_direct_commit_schedule(struct nfs_direct_req *dreq)
{
      struct nfs_write_data *data = dreq->commit_data;

      data->inode = dreq->inode;
      data->cred = dreq->ctx->cred;

      data->args.fh = NFS_FH(data->inode);
      data->args.offset = 0;
      data->args.count = 0;
      data->res.count = 0;
      data->res.fattr = &data->fattr;
      data->res.verf = &data->verf;

      rpc_init_task(&data->task, NFS_CLIENT(dreq->inode), RPC_TASK_ASYNC,
                        &nfs_commit_direct_ops, data);
      NFS_PROTO(data->inode)->commit_setup(data, 0);

      data->task.tk_priority = RPC_PRIORITY_NORMAL;
      data->task.tk_cookie = (unsigned long)data->inode;
      /* Note: task.tk_ops->rpc_release will free dreq->commit_data */
      dreq->commit_data = NULL;

      dprintk("NFS: %5u initiated commit call\n", data->task.tk_pid);

      rpc_execute(&data->task);
}

static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode)
{
      int flags = dreq->flags;

      dreq->flags = 0;
      switch (flags) {
            case NFS_ODIRECT_DO_COMMIT:
                  nfs_direct_commit_schedule(dreq);
                  break;
            case NFS_ODIRECT_RESCHED_WRITES:
                  nfs_direct_write_reschedule(dreq);
                  break;
            default:
                  if (dreq->commit_data != NULL)
                        nfs_commit_free(dreq->commit_data);
                  nfs_direct_free_writedata(dreq);
                  nfs_zap_mapping(inode, inode->i_mapping);
                  nfs_direct_complete(dreq);
      }
}

static void nfs_alloc_commit_data(struct nfs_direct_req *dreq)
{
      dreq->commit_data = nfs_commit_alloc();
      if (dreq->commit_data != NULL)
            dreq->commit_data->req = (struct nfs_page *) dreq;
}
#else
static inline void nfs_alloc_commit_data(struct nfs_direct_req *dreq)
{
      dreq->commit_data = NULL;
}

static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode)
{
      nfs_direct_free_writedata(dreq);
      nfs_zap_mapping(inode, inode->i_mapping);
      nfs_direct_complete(dreq);
}
#endif

static void nfs_direct_write_result(struct rpc_task *task, void *calldata)
{
      struct nfs_write_data *data = calldata;
      struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req;
      int status = task->tk_status;

      if (nfs_writeback_done(task, data) != 0)
            return;

      spin_lock(&dreq->lock);

      if (unlikely(status < 0)) {
            /* An error has occurred, so we should not commit */
            dreq->flags = 0;
            dreq->error = status;
      }
      if (unlikely(dreq->error != 0))
            goto out_unlock;

      dreq->count += data->res.count;

      if (data->res.verf->committed != NFS_FILE_SYNC) {
            switch (dreq->flags) {
                  case 0:
                        memcpy(&dreq->verf, &data->verf, sizeof(dreq->verf));
                        dreq->flags = NFS_ODIRECT_DO_COMMIT;
                        break;
                  case NFS_ODIRECT_DO_COMMIT:
                        if (memcmp(&dreq->verf, &data->verf, sizeof(dreq->verf))) {
                              dprintk("NFS: %5u write verify failed\n", task->tk_pid);
                              dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
                        }
            }
      }
out_unlock:
      spin_unlock(&dreq->lock);
}

/*
 * NB: Return the value of the first error return code.  Subsequent
 *     errors after the first one are ignored.
 */
static void nfs_direct_write_release(void *calldata)
{
      struct nfs_write_data *data = calldata;
      struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req;

      if (put_dreq(dreq))
            nfs_direct_write_complete(dreq, data->inode);
}

static const struct rpc_call_ops nfs_write_direct_ops = {
      .rpc_call_done = nfs_direct_write_result,
      .rpc_release = nfs_direct_write_release,
};

/*
 * For each wsize'd chunk of the user's buffer, dispatch an NFS WRITE
 * operation.  If nfs_writedata_alloc() or get_user_pages() fails,
 * bail and stop sending more writes.  Write length accounting is
 * handled automatically by nfs_direct_write_result().  Otherwise, if
 * no requests have been sent, just return an error.
 */
static ssize_t nfs_direct_write_schedule_segment(struct nfs_direct_req *dreq,
                                     const struct iovec *iov,
                                     loff_t pos, int sync)
{
      struct nfs_open_context *ctx = dreq->ctx;
      struct inode *inode = ctx->path.dentry->d_inode;
      unsigned long user_addr = (unsigned long)iov->iov_base;
      size_t count = iov->iov_len;
      size_t wsize = NFS_SERVER(inode)->wsize;
      unsigned int pgbase;
      int result;
      ssize_t started = 0;

      do {
            struct nfs_write_data *data;
            size_t bytes;

            pgbase = user_addr & ~PAGE_MASK;
            bytes = min(wsize,count);

            result = -ENOMEM;
            data = nfs_writedata_alloc(nfs_page_array_len(pgbase, bytes));
            if (unlikely(!data))
                  break;

            down_read(&current->mm->mmap_sem);
            result = get_user_pages(current, current->mm, user_addr,
                              data->npages, 0, 0, data->pagevec, NULL);
            up_read(&current->mm->mmap_sem);
            if (result < 0) {
                  nfs_writedata_release(data);
                  break;
            }
            if ((unsigned)result < data->npages) {
                  bytes = result * PAGE_SIZE;
                  if (bytes <= pgbase) {
                        nfs_direct_release_pages(data->pagevec, result);
                        nfs_writedata_release(data);
                        break;
                  }
                  bytes -= pgbase;
                  data->npages = result;
            }

            get_dreq(dreq);

            list_move_tail(&data->pages, &dreq->rewrite_list);

            data->req = (struct nfs_page *) dreq;
            data->inode = inode;
            data->cred = ctx->cred;
            data->args.fh = NFS_FH(inode);
            data->args.context = ctx;
            data->args.offset = pos;
            data->args.pgbase = pgbase;
            data->args.pages = data->pagevec;
            data->args.count = bytes;
            data->res.fattr = &data->fattr;
            data->res.count = bytes;
            data->res.verf = &data->verf;

            rpc_init_task(&data->task, NFS_CLIENT(inode), RPC_TASK_ASYNC,
                        &nfs_write_direct_ops, data);
            NFS_PROTO(inode)->write_setup(data, sync);

            data->task.tk_priority = RPC_PRIORITY_NORMAL;
            data->task.tk_cookie = (unsigned long) inode;

            rpc_execute(&data->task);

            dprintk("NFS: %5u initiated direct write call "
                  "(req %s/%Ld, %zu bytes @ offset %Lu)\n",
                        data->task.tk_pid,
                        inode->i_sb->s_id,
                        (long long)NFS_FILEID(inode),
                        bytes,
                        (unsigned long long)data->args.offset);

            started += bytes;
            user_addr += bytes;
            pos += bytes;

            /* FIXME: Remove this useless math from the final patch */
            pgbase += bytes;
            pgbase &= ~PAGE_MASK;
            BUG_ON(pgbase != (user_addr & ~PAGE_MASK));

            count -= bytes;
      } while (count != 0);

      if (started)
            return started;
      return result < 0 ? (ssize_t) result : -EFAULT;
}

static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq,
                                     const struct iovec *iov,
                                     unsigned long nr_segs,
                                     loff_t pos, int sync)
{
      ssize_t result = 0;
      size_t requested_bytes = 0;
      unsigned long seg;

      get_dreq(dreq);

      for (seg = 0; seg < nr_segs; seg++) {
            const struct iovec *vec = &iov[seg];
            result = nfs_direct_write_schedule_segment(dreq, vec,
                                             pos, sync);
            if (result < 0)
                  break;
            requested_bytes += result;
            if ((size_t)result < vec->iov_len)
                  break;
            pos += vec->iov_len;
      }

      if (put_dreq(dreq))
            nfs_direct_write_complete(dreq, dreq->inode);

      if (requested_bytes != 0)
            return 0;

      if (result < 0)
            return result;
      return -EIO;
}

static ssize_t nfs_direct_write(struct kiocb *iocb, const struct iovec *iov,
                        unsigned long nr_segs, loff_t pos,
                        size_t count)
{
      ssize_t result = 0;
      sigset_t oldset;
      struct inode *inode = iocb->ki_filp->f_mapping->host;
      struct rpc_clnt *clnt = NFS_CLIENT(inode);
      struct nfs_direct_req *dreq;
      size_t wsize = NFS_SERVER(inode)->wsize;
      int sync = 0;

      dreq = nfs_direct_req_alloc();
      if (!dreq)
            return -ENOMEM;
      nfs_alloc_commit_data(dreq);

      if (dreq->commit_data == NULL || count < wsize)
            sync = FLUSH_STABLE;

      dreq->inode = inode;
      dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
      if (!is_sync_kiocb(iocb))
            dreq->iocb = iocb;

      rpc_clnt_sigmask(clnt, &oldset);
      result = nfs_direct_write_schedule_iovec(dreq, iov, nr_segs, pos, sync);
      if (!result)
            result = nfs_direct_wait(dreq);
      rpc_clnt_sigunmask(clnt, &oldset);
      nfs_direct_req_release(dreq);

      return result;
}

/**
 * nfs_file_direct_read - file direct read operation for NFS files
 * @iocb: target I/O control block
 * @iov: vector of user buffers into which to read data
 * @nr_segs: size of iov vector
 * @pos: byte offset in file where reading starts
 *
 * We use this function for direct reads instead of calling
 * generic_file_aio_read() in order to avoid gfar's check to see if
 * the request starts before the end of the file.  For that check
 * to work, we must generate a GETATTR before each direct read, and
 * even then there is a window between the GETATTR and the subsequent
 * READ where the file size could change.  Our preference is simply
 * to do all reads the application wants, and the server will take
 * care of managing the end of file boundary.
 *
 * This function also eliminates unnecessarily updating the file's
 * atime locally, as the NFS server sets the file's atime, and this
 * client must read the updated atime from the server back into its
 * cache.
 */
ssize_t nfs_file_direct_read(struct kiocb *iocb, const struct iovec *iov,
                        unsigned long nr_segs, loff_t pos)
{
      ssize_t retval = -EINVAL;
      struct file *file = iocb->ki_filp;
      struct address_space *mapping = file->f_mapping;
      size_t count;

      count = iov_length(iov, nr_segs);
      nfs_add_stats(mapping->host, NFSIOS_DIRECTREADBYTES, count);

      dprintk("nfs: direct read(%s/%s, %zd@%Ld)\n",
            file->f_path.dentry->d_parent->d_name.name,
            file->f_path.dentry->d_name.name,
            count, (long long) pos);

      retval = 0;
      if (!count)
            goto out;

      retval = nfs_sync_mapping(mapping);
      if (retval)
            goto out;

      retval = nfs_direct_read(iocb, iov, nr_segs, pos);
      if (retval > 0)
            iocb->ki_pos = pos + retval;

out:
      return retval;
}

/**
 * nfs_file_direct_write - file direct write operation for NFS files
 * @iocb: target I/O control block
 * @iov: vector of user buffers from which to write data
 * @nr_segs: size of iov vector
 * @pos: byte offset in file where writing starts
 *
 * We use this function for direct writes instead of calling
 * generic_file_aio_write() in order to avoid taking the inode
 * semaphore and updating the i_size.  The NFS server will set
 * the new i_size and this client must read the updated size
 * back into its cache.  We let the server do generic write
 * parameter checking and report problems.
 *
 * We also avoid an unnecessary invocation of generic_osync_inode(),
 * as it is fairly meaningless to sync the metadata of an NFS file.
 *
 * We eliminate local atime updates, see direct read above.
 *
 * We avoid unnecessary page cache invalidations for normal cached
 * readers of this file.
 *
 * Note that O_APPEND is not supported for NFS direct writes, as there
 * is no atomic O_APPEND write facility in the NFS protocol.
 */
ssize_t nfs_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
                        unsigned long nr_segs, loff_t pos)
{
      ssize_t retval = -EINVAL;
      struct file *file = iocb->ki_filp;
      struct address_space *mapping = file->f_mapping;
      size_t count;

      count = iov_length(iov, nr_segs);
      nfs_add_stats(mapping->host, NFSIOS_DIRECTWRITTENBYTES, count);

      dfprintk(VFS, "nfs: direct write(%s/%s, %zd@%Ld)\n",
            file->f_path.dentry->d_parent->d_name.name,
            file->f_path.dentry->d_name.name,
            count, (long long) pos);

      retval = generic_write_checks(file, &pos, &count, 0);
      if (retval)
            goto out;

      retval = -EINVAL;
      if ((ssize_t) count < 0)
            goto out;
      retval = 0;
      if (!count)
            goto out;

      retval = nfs_sync_mapping(mapping);
      if (retval)
            goto out;

      retval = nfs_direct_write(iocb, iov, nr_segs, pos, count);

      if (retval > 0)
            iocb->ki_pos = pos + retval;

out:
      return retval;
}

/**
 * nfs_init_directcache - create a slab cache for nfs_direct_req structures
 *
 */
int __init nfs_init_directcache(void)
{
      nfs_direct_cachep = kmem_cache_create("nfs_direct_cache",
                                    sizeof(struct nfs_direct_req),
                                    0, (SLAB_RECLAIM_ACCOUNT|
                                          SLAB_MEM_SPREAD),
                                    NULL);
      if (nfs_direct_cachep == NULL)
            return -ENOMEM;

      return 0;
}

/**
 * nfs_destroy_directcache - destroy the slab cache for nfs_direct_req structures
 *
 */
void nfs_destroy_directcache(void)
{
      kmem_cache_destroy(nfs_direct_cachep);
}

Generated by  Doxygen 1.6.0   Back to index