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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * 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/slab.h>
 #include <linux/task_io_accounting_ops.h>
 #include <linux/module.h>
 
 #include <linux/nfs_fs.h>
 #include <linux/nfs_page.h>
 #include <linux/sunrpc/clnt.h>
 
 #include <linux/uaccess.h>
 #include <linux/atomic.h>
 
 #include "internal.h"
 #include "iostat.h"
 #include "pnfs.h"
 #include "fscache.h"
 #include "nfstrace.h"
 
 #define NFSDBG_FACILITY     NFSDBG_VFS
 
 static struct kmem_cache *nfs_direct_cachep;
 
 static const struct nfs_pgio_completion_ops nfs_direct_write_completion_ops;
 static const struct nfs_commit_completion_ops nfs_direct_commit_completion_ops;
 static void nfs_direct_write_complete(struct nfs_direct_req *dreq);
 static void nfs_direct_write_schedule_work(struct work_struct *work);
 
 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);
 }
 
 static void
 nfs_direct_handle_truncated(struct nfs_direct_req *dreq,
                 const struct nfs_pgio_header *hdr,
                 ssize_t dreq_len)
 {
     if (!(test_bit(NFS_IOHDR_ERROR, &hdr->flags) ||
           test_bit(NFS_IOHDR_EOF, &hdr->flags)))
         return;
     if (dreq->max_count >= dreq_len) {
         dreq->max_count = dreq_len;
         if (dreq->count > dreq_len)
             dreq->count = dreq_len;
 
         if (test_bit(NFS_IOHDR_ERROR, &hdr->flags))
             dreq->error = hdr->error;
         else /* Clear outstanding error if this is EOF */
             dreq->error = 0;
     }
 }
 
 static void
 nfs_direct_count_bytes(struct nfs_direct_req *dreq,
                const struct nfs_pgio_header *hdr)
 {
     loff_t hdr_end = hdr->io_start + hdr->good_bytes;
     ssize_t dreq_len = 0;
 
     if (hdr_end > dreq->io_start)
         dreq_len = hdr_end - dreq->io_start;
 
     nfs_direct_handle_truncated(dreq, hdr, dreq_len);
 
     if (dreq_len > dreq->max_count)
         dreq_len = dreq->max_count;
 
     if (dreq->count < dreq_len)
         dreq->count = dreq_len;
 }
 
 /**
  * nfs_swap_rw - NFS address space operation for swap I/O
  * @iocb: target I/O control block
  * @iter: I/O buffer
  *
  * Perform IO to the swap-file.  This is much like direct IO.
  */
 int nfs_swap_rw(struct kiocb *iocb, struct iov_iter *iter)
 {
     ssize_t ret;
 
     VM_BUG_ON(iov_iter_count(iter) != PAGE_SIZE);
 
     if (iov_iter_rw(iter) == READ)
         ret = nfs_file_direct_read(iocb, iter, true);
     else
         ret = nfs_file_direct_write(iocb, iter, true);
     if (ret < 0)
         return ret;
     return 0;
 }
 
 static void nfs_direct_release_pages(struct page **pages, unsigned int npages)
 {
     unsigned int i;
     for (i = 0; i < npages; i++)
         put_page(pages[i]);
 }
 
 void nfs_init_cinfo_from_dreq(struct nfs_commit_info *cinfo,
                   struct nfs_direct_req *dreq)
 {
     cinfo->inode = dreq->inode;
     cinfo->mds = &dreq->mds_cinfo;
     cinfo->ds = &dreq->ds_cinfo;
     cinfo->dreq = dreq;
     cinfo->completion_ops = &nfs_direct_commit_completion_ops;
 }
 
 static inline struct nfs_direct_req *nfs_direct_req_alloc(void)
 {
     struct nfs_direct_req *dreq;
 
     dreq = kmem_cache_zalloc(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->mds_cinfo.list);
     pnfs_init_ds_commit_info(&dreq->ds_cinfo);
     INIT_WORK(&dreq->work, nfs_direct_write_schedule_work);
     spin_lock_init(&dreq->lock);
 
     return dreq;
 }
 
 static void nfs_direct_req_free(struct kref *kref)
 {
     struct nfs_direct_req *dreq = container_of(kref, struct nfs_direct_req, kref);
 
     pnfs_release_ds_info(&dreq->ds_cinfo, dreq->inode);
     if (dreq->l_ctx != NULL)
         nfs_put_lock_context(dreq->l_ctx);
     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);
 }
 
 ssize_t nfs_dreq_bytes_left(struct nfs_direct_req *dreq)
 {
     return dreq->bytes_left;
 }
 EXPORT_SYMBOL_GPL(nfs_dreq_bytes_left);
 
 /*
  * 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_killable(&dreq->completion);
 
     if (!result) {
         result = dreq->count;
         WARN_ON_ONCE(dreq->count < 0);
     }
     if (!result)
         result = dreq->error;
 
 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)
 {
     struct inode *inode = dreq->inode;
 
     inode_dio_end(inode);
 
     if (dreq->iocb) {
         long res = (long) dreq->error;
         if (dreq->count != 0) {
             res = (long) dreq->count;
             WARN_ON_ONCE(dreq->count < 0);
         }
         dreq->iocb->ki_complete(dreq->iocb, res);
     }
 
     complete(&dreq->completion);
 
     nfs_direct_req_release(dreq);
 }
 
 static void nfs_direct_read_completion(struct nfs_pgio_header *hdr)
 {
     unsigned long bytes = 0;
     struct nfs_direct_req *dreq = hdr->dreq;
 
     spin_lock(&dreq->lock);
     if (test_bit(NFS_IOHDR_REDO, &hdr->flags)) {
         spin_unlock(&dreq->lock);
         goto out_put;
     }
 
     nfs_direct_count_bytes(dreq, hdr);
     spin_unlock(&dreq->lock);
 
     while (!list_empty(&hdr->pages)) {
         struct nfs_page *req = nfs_list_entry(hdr->pages.next);
         struct page *page = req->wb_page;
 
         if (!PageCompound(page) && bytes < hdr->good_bytes &&
             (dreq->flags == NFS_ODIRECT_SHOULD_DIRTY))
             set_page_dirty(page);
         bytes += req->wb_bytes;
         nfs_list_remove_request(req);
         nfs_release_request(req);
     }
 out_put:
     if (put_dreq(dreq))
         nfs_direct_complete(dreq);
     hdr->release(hdr);
 }
 
 static void nfs_read_sync_pgio_error(struct list_head *head, int error)
 {
     struct nfs_page *req;
 
     while (!list_empty(head)) {
         req = nfs_list_entry(head->next);
         nfs_list_remove_request(req);
         nfs_release_request(req);
     }
 }
 
 static void nfs_direct_pgio_init(struct nfs_pgio_header *hdr)
 {
     get_dreq(hdr->dreq);
 }
 
 static const struct nfs_pgio_completion_ops nfs_direct_read_completion_ops = {
     .error_cleanup = nfs_read_sync_pgio_error,
     .init_hdr = nfs_direct_pgio_init,
     .completion = nfs_direct_read_completion,
 };
 
 /*
  * 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_iovec(struct nfs_direct_req *dreq,
                           struct iov_iter *iter,
                           loff_t pos)
 {
     struct nfs_pageio_descriptor desc;
     struct inode *inode = dreq->inode;
     ssize_t result = -EINVAL;
     size_t requested_bytes = 0;
     size_t rsize = max_t(size_t, NFS_SERVER(inode)->rsize, PAGE_SIZE);
 
     nfs_pageio_init_read(&desc, dreq->inode, false,
                  &nfs_direct_read_completion_ops);
     get_dreq(dreq);
     desc.pg_dreq = dreq;
     inode_dio_begin(inode);
 
     while (iov_iter_count(iter)) {
         struct page **pagevec;
         size_t bytes;
         size_t pgbase;
         unsigned npages, i;
 
         result = iov_iter_get_pages_alloc2(iter, &pagevec,
                           rsize, &pgbase);
         if (result < 0)
             break;
     
         bytes = result;
         npages = (result + pgbase + PAGE_SIZE - 1) / PAGE_SIZE;
         for (i = 0; i < npages; i++) {
             struct nfs_page *req;
             unsigned int req_len = min_t(size_t, bytes, PAGE_SIZE - pgbase);
             /* XXX do we need to do the eof zeroing found in async_filler? */
             req = nfs_create_request(dreq->ctx, pagevec[i],
                          pgbase, req_len);
             if (IS_ERR(req)) {
                 result = PTR_ERR(req);
                 break;
             }
             req->wb_index = pos >> PAGE_SHIFT;
             req->wb_offset = pos & ~PAGE_MASK;
             if (!nfs_pageio_add_request(&desc, req)) {
                 result = desc.pg_error;
                 nfs_release_request(req);
                 break;
             }
             pgbase = 0;
             bytes -= req_len;
             requested_bytes += req_len;
             pos += req_len;
             dreq->bytes_left -= req_len;
         }
         nfs_direct_release_pages(pagevec, npages);
         kvfree(pagevec);
         if (result < 0)
             break;
     }
 
     nfs_pageio_complete(&desc);
 
     /*
      * If no bytes were started, return the error, and let the
      * generic layer handle the completion.
      */
     if (requested_bytes == 0) {
         inode_dio_end(inode);
         nfs_direct_req_release(dreq);
         return result < 0 ? result : -EIO;
     }
 
     if (put_dreq(dreq))
         nfs_direct_complete(dreq);
     return requested_bytes;
 }
 
 /**
  * nfs_file_direct_read - file direct read operation for NFS files
  * @iocb: target I/O control block
  * @iter: vector of user buffers into which to read data
  * @swap: flag indicating this is swap IO, not O_DIRECT IO
  *
  * 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, struct iov_iter *iter,
                  bool swap)
 {
     struct file *file = iocb->ki_filp;
     struct address_space *mapping = file->f_mapping;
     struct inode *inode = mapping->host;
     struct nfs_direct_req *dreq;
     struct nfs_lock_context *l_ctx;
     ssize_t result, requested;
     size_t count = iov_iter_count(iter);
     nfs_add_stats(mapping->host, NFSIOS_DIRECTREADBYTES, count);
 
     dfprintk(FILE, "NFS: direct read(%pD2, %zd@%Ld)\n",
         file, count, (long long) iocb->ki_pos);
 
     result = 0;
     if (!count)
         goto out;
 
     task_io_account_read(count);
 
     result = -ENOMEM;
     dreq = nfs_direct_req_alloc();
     if (dreq == NULL)
         goto out;
 
     dreq->inode = inode;
     dreq->bytes_left = dreq->max_count = count;
     dreq->io_start = iocb->ki_pos;
     dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
     l_ctx = nfs_get_lock_context(dreq->ctx);
     if (IS_ERR(l_ctx)) {
         result = PTR_ERR(l_ctx);
         nfs_direct_req_release(dreq);
         goto out_release;
     }
     dreq->l_ctx = l_ctx;
     if (!is_sync_kiocb(iocb))
         dreq->iocb = iocb;
 
     if (user_backed_iter(iter))
         dreq->flags = NFS_ODIRECT_SHOULD_DIRTY;
 
     if (!swap)
         nfs_start_io_direct(inode);
 
     NFS_I(inode)->read_io += count;
     requested = nfs_direct_read_schedule_iovec(dreq, iter, iocb->ki_pos);
 
     if (!swap)
         nfs_end_io_direct(inode);
 
     if (requested > 0) {
         result = nfs_direct_wait(dreq);
         if (result > 0) {
             requested -= result;
             iocb->ki_pos += result;
         }
         iov_iter_revert(iter, requested);
     } else {
         result = requested;
     }
 
 out_release:
     nfs_direct_req_release(dreq);
 out:
     return result;
 }
 
 static void
 nfs_direct_join_group(struct list_head *list, struct inode *inode)
 {
     struct nfs_page *req, *next;
 
     list_for_each_entry(req, list, wb_list) {
         if (req->wb_head != req || req->wb_this_page == req)
             continue;
         for (next = req->wb_this_page;
                 next != req->wb_head;
                 next = next->wb_this_page) {
             nfs_list_remove_request(next);
             nfs_release_request(next);
         }
         nfs_join_page_group(req, inode);
     }
 }
 
 static void
 nfs_direct_write_scan_commit_list(struct inode *inode,
                   struct list_head *list,
                   struct nfs_commit_info *cinfo)
 {
     mutex_lock(&NFS_I(cinfo->inode)->commit_mutex);
     pnfs_recover_commit_reqs(list, cinfo);
     nfs_scan_commit_list(&cinfo->mds->list, list, cinfo, 0);
     mutex_unlock(&NFS_I(cinfo->inode)->commit_mutex);
 }
 
 static void nfs_direct_write_reschedule(struct nfs_direct_req *dreq)
 {
     struct nfs_pageio_descriptor desc;
     struct nfs_page *req, *tmp;
     LIST_HEAD(reqs);
     struct nfs_commit_info cinfo;
     LIST_HEAD(failed);
 
     nfs_init_cinfo_from_dreq(&cinfo, dreq);
     nfs_direct_write_scan_commit_list(dreq->inode, &reqs, &cinfo);
 
     nfs_direct_join_group(&reqs, dreq->inode);
 
     dreq->count = 0;
     dreq->max_count = 0;
     list_for_each_entry(req, &reqs, wb_list)
         dreq->max_count += req->wb_bytes;
     nfs_clear_pnfs_ds_commit_verifiers(&dreq->ds_cinfo);
     get_dreq(dreq);
 
     nfs_pageio_init_write(&desc, dreq->inode, FLUSH_STABLE, false,
                   &nfs_direct_write_completion_ops);
     desc.pg_dreq = dreq;
 
     list_for_each_entry_safe(req, tmp, &reqs, wb_list) {
         /* Bump the transmission count */
         req->wb_nio++;
         if (!nfs_pageio_add_request(&desc, req)) {
             nfs_list_move_request(req, &failed);
             spin_lock(&cinfo.inode->i_lock);
             dreq->flags = 0;
             if (desc.pg_error < 0)
                 dreq->error = desc.pg_error;
             else
                 dreq->error = -EIO;
             spin_unlock(&cinfo.inode->i_lock);
         }
         nfs_release_request(req);
     }
     nfs_pageio_complete(&desc);
 
     while (!list_empty(&failed)) {
         req = nfs_list_entry(failed.next);
         nfs_list_remove_request(req);
         nfs_unlock_and_release_request(req);
     }
 
     if (put_dreq(dreq))
         nfs_direct_write_complete(dreq);
 }
 
 static void nfs_direct_commit_complete(struct nfs_commit_data *data)
 {
     const struct nfs_writeverf *verf = data->res.verf;
     struct nfs_direct_req *dreq = data->dreq;
     struct nfs_commit_info cinfo;
     struct nfs_page *req;
     int status = data->task.tk_status;
 
     trace_nfs_direct_commit_complete(dreq);
 
     if (status < 0) {
         /* Errors in commit are fatal */
         dreq->error = status;
         dreq->max_count = 0;
         dreq->count = 0;
         dreq->flags = NFS_ODIRECT_DONE;
     } else {
         status = dreq->error;
     }
 
     nfs_init_cinfo_from_dreq(&cinfo, dreq);
 
     while (!list_empty(&data->pages)) {
         req = nfs_list_entry(data->pages.next);
         nfs_list_remove_request(req);
         if (status >= 0 && !nfs_write_match_verf(verf, req)) {
             dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
             /*
              * Despite the reboot, the write was successful,
              * so reset wb_nio.
              */
             req->wb_nio = 0;
             nfs_mark_request_commit(req, NULL, &cinfo, 0);
         } else /* Error or match */
             nfs_release_request(req);
         nfs_unlock_and_release_request(req);
     }
 
     if (nfs_commit_end(cinfo.mds))
         nfs_direct_write_complete(dreq);
 }
 
 static void nfs_direct_resched_write(struct nfs_commit_info *cinfo,
         struct nfs_page *req)
 {
     struct nfs_direct_req *dreq = cinfo->dreq;
 
     trace_nfs_direct_resched_write(dreq);
 
     spin_lock(&dreq->lock);
     if (dreq->flags != NFS_ODIRECT_DONE)
         dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
     spin_unlock(&dreq->lock);
     nfs_mark_request_commit(req, NULL, cinfo, 0);
 }
 
 static const struct nfs_commit_completion_ops nfs_direct_commit_completion_ops = {
     .completion = nfs_direct_commit_complete,
     .resched_write = nfs_direct_resched_write,
 };
 
 static void nfs_direct_commit_schedule(struct nfs_direct_req *dreq)
 {
     int res;
     struct nfs_commit_info cinfo;
     LIST_HEAD(mds_list);
 
     nfs_init_cinfo_from_dreq(&cinfo, dreq);
     nfs_scan_commit(dreq->inode, &mds_list, &cinfo);
     res = nfs_generic_commit_list(dreq->inode, &mds_list, 0, &cinfo);
     if (res < 0) /* res == -ENOMEM */
         nfs_direct_write_reschedule(dreq);
 }
 
 static void nfs_direct_write_clear_reqs(struct nfs_direct_req *dreq)
 {
     struct nfs_commit_info cinfo;
     struct nfs_page *req;
     LIST_HEAD(reqs);
 
     nfs_init_cinfo_from_dreq(&cinfo, dreq);
     nfs_direct_write_scan_commit_list(dreq->inode, &reqs, &cinfo);
 
     while (!list_empty(&reqs)) {
         req = nfs_list_entry(reqs.next);
         nfs_list_remove_request(req);
         nfs_release_request(req);
         nfs_unlock_and_release_request(req);
     }
 }
 
 static void nfs_direct_write_schedule_work(struct work_struct *work)
 {
     struct nfs_direct_req *dreq = container_of(work, struct nfs_direct_req, work);
     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:
             nfs_direct_write_clear_reqs(dreq);
             nfs_zap_mapping(dreq->inode, dreq->inode->i_mapping);
             nfs_direct_complete(dreq);
     }
 }
 
 static void nfs_direct_write_complete(struct nfs_direct_req *dreq)
 {
     trace_nfs_direct_write_complete(dreq);
     queue_work(nfsiod_workqueue, &dreq->work); /* Calls nfs_direct_write_schedule_work */
 }
 
 static void nfs_direct_write_completion(struct nfs_pgio_header *hdr)
 {
     struct nfs_direct_req *dreq = hdr->dreq;
     struct nfs_commit_info cinfo;
     struct nfs_page *req = nfs_list_entry(hdr->pages.next);
     int flags = NFS_ODIRECT_DONE;
 
     trace_nfs_direct_write_completion(dreq);
 
     nfs_init_cinfo_from_dreq(&cinfo, dreq);
 
     spin_lock(&dreq->lock);
     if (test_bit(NFS_IOHDR_REDO, &hdr->flags)) {
         spin_unlock(&dreq->lock);
         goto out_put;
     }
 
     nfs_direct_count_bytes(dreq, hdr);
     if (test_bit(NFS_IOHDR_UNSTABLE_WRITES, &hdr->flags)) {
         if (!dreq->flags)
             dreq->flags = NFS_ODIRECT_DO_COMMIT;
         flags = dreq->flags;
     }
     spin_unlock(&dreq->lock);
 
     while (!list_empty(&hdr->pages)) {
 
         req = nfs_list_entry(hdr->pages.next);
         nfs_list_remove_request(req);
         if (flags == NFS_ODIRECT_DO_COMMIT) {
             kref_get(&req->wb_kref);
             memcpy(&req->wb_verf, &hdr->verf.verifier,
                    sizeof(req->wb_verf));
             nfs_mark_request_commit(req, hdr->lseg, &cinfo,
                 hdr->ds_commit_idx);
         } else if (flags == NFS_ODIRECT_RESCHED_WRITES) {
             kref_get(&req->wb_kref);
             nfs_mark_request_commit(req, NULL, &cinfo, 0);
         }
         nfs_unlock_and_release_request(req);
     }
 
 out_put:
     if (put_dreq(dreq))
         nfs_direct_write_complete(dreq);
     hdr->release(hdr);
 }
 
 static void nfs_write_sync_pgio_error(struct list_head *head, int error)
 {
     struct nfs_page *req;
 
     while (!list_empty(head)) {
         req = nfs_list_entry(head->next);
         nfs_list_remove_request(req);
         nfs_unlock_and_release_request(req);
     }
 }
 
 static void nfs_direct_write_reschedule_io(struct nfs_pgio_header *hdr)
 {
     struct nfs_direct_req *dreq = hdr->dreq;
 
     trace_nfs_direct_write_reschedule_io(dreq);
 
     spin_lock(&dreq->lock);
     if (dreq->error == 0) {
         dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
         /* fake unstable write to let common nfs resend pages */
         hdr->verf.committed = NFS_UNSTABLE;
         hdr->good_bytes = hdr->args.offset + hdr->args.count -
             hdr->io_start;
     }
     spin_unlock(&dreq->lock);
 }
 
 static const struct nfs_pgio_completion_ops nfs_direct_write_completion_ops = {
     .error_cleanup = nfs_write_sync_pgio_error,
     .init_hdr = nfs_direct_pgio_init,
     .completion = nfs_direct_write_completion,
     .reschedule_io = nfs_direct_write_reschedule_io,
 };
 
 
 /*
  * NB: Return the value of the first error return code.  Subsequent
  *     errors after the first one are ignored.
  */
 /*
  * 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_iovec(struct nfs_direct_req *dreq,
                            struct iov_iter *iter,
                            loff_t pos, int ioflags)
 {
     struct nfs_pageio_descriptor desc;
     struct inode *inode = dreq->inode;
     ssize_t result = 0;
     size_t requested_bytes = 0;
     size_t wsize = max_t(size_t, NFS_SERVER(inode)->wsize, PAGE_SIZE);
 
     trace_nfs_direct_write_schedule_iovec(dreq);
 
     nfs_pageio_init_write(&desc, inode, ioflags, false,
                   &nfs_direct_write_completion_ops);
     desc.pg_dreq = dreq;
     get_dreq(dreq);
     inode_dio_begin(inode);
 
     NFS_I(inode)->write_io += iov_iter_count(iter);
     while (iov_iter_count(iter)) {
         struct page **pagevec;
         size_t bytes;
         size_t pgbase;
         unsigned npages, i;
 
         result = iov_iter_get_pages_alloc2(iter, &pagevec,
                           wsize, &pgbase);
         if (result < 0)
             break;
 
         bytes = result;
         npages = (result + pgbase + PAGE_SIZE - 1) / PAGE_SIZE;
         for (i = 0; i < npages; i++) {
             struct nfs_page *req;
             unsigned int req_len = min_t(size_t, bytes, PAGE_SIZE - pgbase);
 
             req = nfs_create_request(dreq->ctx, pagevec[i],
                          pgbase, req_len);
             if (IS_ERR(req)) {
                 result = PTR_ERR(req);
                 break;
             }
 
             if (desc.pg_error < 0) {
                 nfs_free_request(req);
                 result = desc.pg_error;
                 break;
             }
 
             nfs_lock_request(req);
             req->wb_index = pos >> PAGE_SHIFT;
             req->wb_offset = pos & ~PAGE_MASK;
             if (!nfs_pageio_add_request(&desc, req)) {
                 result = desc.pg_error;
                 nfs_unlock_and_release_request(req);
                 break;
             }
             pgbase = 0;
             bytes -= req_len;
             requested_bytes += req_len;
             pos += req_len;
             dreq->bytes_left -= req_len;
         }
         nfs_direct_release_pages(pagevec, npages);
         kvfree(pagevec);
         if (result < 0)
             break;
     }
     nfs_pageio_complete(&desc);
 
     /*
      * If no bytes were started, return the error, and let the
      * generic layer handle the completion.
      */
     if (requested_bytes == 0) {
         inode_dio_end(inode);
         nfs_direct_req_release(dreq);
         return result < 0 ? result : -EIO;
     }
 
     if (put_dreq(dreq))
         nfs_direct_write_complete(dreq);
     return requested_bytes;
 }
 
 /**
  * nfs_file_direct_write - file direct write operation for NFS files
  * @iocb: target I/O control block
  * @iter: vector of user buffers from which to write data
  * @swap: flag indicating this is swap IO, not O_DIRECT IO
  *
  * 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 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, struct iov_iter *iter,
                   bool swap)
 {
     ssize_t result, requested;
     size_t count;
     struct file *file = iocb->ki_filp;
     struct address_space *mapping = file->f_mapping;
     struct inode *inode = mapping->host;
     struct nfs_direct_req *dreq;
     struct nfs_lock_context *l_ctx;
     loff_t pos, end;
 
     dfprintk(FILE, "NFS: direct write(%pD2, %zd@%Ld)\n",
         file, iov_iter_count(iter), (long long) iocb->ki_pos);
 
     if (swap)
         /* bypass generic checks */
         result =  iov_iter_count(iter);
     else
         result = generic_write_checks(iocb, iter);
     if (result <= 0)
         return result;
     count = result;
     nfs_add_stats(mapping->host, NFSIOS_DIRECTWRITTENBYTES, count);
 
     pos = iocb->ki_pos;
     end = (pos + iov_iter_count(iter) - 1) >> PAGE_SHIFT;
 
     task_io_account_write(count);
 
     result = -ENOMEM;
     dreq = nfs_direct_req_alloc();
     if (!dreq)
         goto out;
 
     dreq->inode = inode;
     dreq->bytes_left = dreq->max_count = count;
     dreq->io_start = pos;
     dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
     l_ctx = nfs_get_lock_context(dreq->ctx);
     if (IS_ERR(l_ctx)) {
         result = PTR_ERR(l_ctx);
         nfs_direct_req_release(dreq);
         goto out_release;
     }
     dreq->l_ctx = l_ctx;
     if (!is_sync_kiocb(iocb))
         dreq->iocb = iocb;
     pnfs_init_ds_commit_info_ops(&dreq->ds_cinfo, inode);
 
     if (swap) {
         requested = nfs_direct_write_schedule_iovec(dreq, iter, pos,
                                 FLUSH_STABLE);
     } else {
         nfs_start_io_direct(inode);
 
         requested = nfs_direct_write_schedule_iovec(dreq, iter, pos,
                                 FLUSH_COND_STABLE);
 
         if (mapping->nrpages) {
             invalidate_inode_pages2_range(mapping,
                               pos >> PAGE_SHIFT, end);
         }
 
         nfs_end_io_direct(inode);
     }
 
     if (requested > 0) {
         result = nfs_direct_wait(dreq);
         if (result > 0) {
             requested -= result;
             iocb->ki_pos = pos + result;
             /* XXX: should check the generic_write_sync retval */
             generic_write_sync(iocb, result);
         }
         iov_iter_revert(iter, requested);
     } else {
         result = requested;
     }
     nfs_fscache_invalidate(inode, FSCACHE_INVAL_DIO_WRITE);
 out_release:
     nfs_direct_req_release(dreq);
 out:
     return result;
 }
 
 /**
  * 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);
 }

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