// SPDX-License-Identifier: GPL-2.0-only /* * linux/fs/nfs/direct.c * * Copyright (C) 2003 by Chuck Lever * * 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 #include #include #include #include #include #include #include #include #include #include #include #include #include #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) dreq->error = hdr->error; } 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; } static void nfs_direct_truncate_request(struct nfs_direct_req *dreq, struct nfs_page *req) { loff_t offs = req_offset(req); size_t req_start = (size_t)(offs - dreq->io_start); if (req_start < dreq->max_count) dreq->max_count = req_start; if (req_start < dreq->count) dreq->count = req_start; } /** * 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, loff_t offset) { loff_t start = offset - dreq->io_start; return dreq->max_count - start; } 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_page_create_from_page(dreq->ctx, pagevec[i], pgbase, pos, req_len); if (IS_ERR(req)) { result = PTR_ERR(req); break; } 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_add_page_head(struct list_head *list, struct nfs_page *req) { struct nfs_page *head = req->wb_head; if (!list_empty(&head->wb_list) || !nfs_lock_request(head)) return; if (!list_empty(&head->wb_list)) { nfs_unlock_request(head); return; } list_add(&head->wb_list, list); kref_get(&head->wb_kref); kref_get(&head->wb_kref); } static void nfs_direct_join_group(struct list_head *list, struct nfs_commit_info *cinfo, struct inode *inode) { struct nfs_page *req, *subreq; list_for_each_entry(req, list, wb_list) { if (req->wb_head != req) { nfs_direct_add_page_head(&req->wb_list, req); continue; } subreq = req->wb_this_page; if (subreq == req) continue; do { /* * Remove subrequests from this list before freeing * them in the call to nfs_join_page_group(). */ if (!list_empty(&subreq->wb_list)) { nfs_list_remove_request(subreq); nfs_release_request(subreq); } } while ((subreq = subreq->wb_this_page) != req); nfs_join_page_group(req, cinfo, 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; LIST_HEAD(reqs); struct nfs_commit_info cinfo; nfs_init_cinfo_from_dreq(&cinfo, dreq); nfs_direct_write_scan_commit_list(dreq->inode, &reqs, &cinfo); nfs_direct_join_group(&reqs, &cinfo, dreq->inode); 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; while (!list_empty(&reqs)) { req = nfs_list_entry(reqs.next); /* Bump the transmission count */ req->wb_nio++; if (!nfs_pageio_add_request(&desc, req)) { spin_lock(&dreq->lock); if (dreq->error < 0) { desc.pg_error = dreq->error; } else if (desc.pg_error != -EAGAIN) { dreq->flags = 0; if (!desc.pg_error) desc.pg_error = -EIO; dreq->error = desc.pg_error; } else dreq->flags = NFS_ODIRECT_RESCHED_WRITES; spin_unlock(&dreq->lock); break; } nfs_release_request(req); } nfs_pageio_complete(&desc); while (!list_empty(&reqs)) { req = nfs_list_entry(reqs.next); nfs_list_remove_request(req); nfs_unlock_and_release_request(req); if (desc.pg_error == -EAGAIN) { nfs_mark_request_commit(req, NULL, &cinfo, 0); } else { spin_lock(&dreq->lock); nfs_direct_truncate_request(dreq, req); spin_unlock(&dreq->lock); nfs_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->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) { spin_lock(&dreq->lock); nfs_direct_truncate_request(dreq, req); spin_unlock(&dreq->lock); nfs_release_request(req); } else if (!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 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_commit_begin(cinfo.mds); nfs_scan_commit(dreq->inode, &mds_list, &cinfo); res = nfs_generic_commit_list(dreq->inode, &mds_list, 0, &cinfo); if (res < 0) { /* res == -ENOMEM */ spin_lock(&dreq->lock); if (dreq->flags == 0) dreq->flags = NFS_ODIRECT_RESCHED_WRITES; spin_unlock(&dreq->lock); } if (nfs_commit_end(cinfo.mds)) nfs_direct_write_complete(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_direct_truncate_request(dreq, 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) && !test_bit(NFS_IOHDR_ERROR, &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; struct nfs_page *req; struct nfs_commit_info cinfo; trace_nfs_direct_write_reschedule_io(dreq); nfs_init_cinfo_from_dreq(&cinfo, dreq); spin_lock(&dreq->lock); if (dreq->error == 0) dreq->flags = NFS_ODIRECT_RESCHED_WRITES; set_bit(NFS_IOHDR_REDO, &hdr->flags); spin_unlock(&dreq->lock); while (!list_empty(&hdr->pages)) { req = nfs_list_entry(hdr->pages.next); nfs_list_remove_request(req); nfs_unlock_request(req); nfs_mark_request_commit(req, NULL, &cinfo, 0); } } 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; struct nfs_commit_info cinfo; ssize_t result = 0; size_t requested_bytes = 0; size_t wsize = max_t(size_t, NFS_SERVER(inode)->wsize, PAGE_SIZE); bool defer = false; 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_page_create_from_page(dreq->ctx, pagevec[i], pgbase, pos, 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; } pgbase = 0; bytes -= req_len; requested_bytes += req_len; pos += req_len; dreq->bytes_left -= req_len; if (defer) { nfs_mark_request_commit(req, NULL, &cinfo, 0); continue; } nfs_lock_request(req); if (nfs_pageio_add_request(&desc, req)) continue; /* Exit on hard errors */ if (desc.pg_error < 0 && desc.pg_error != -EAGAIN) { result = desc.pg_error; nfs_unlock_and_release_request(req); break; } /* If the error is soft, defer remaining requests */ nfs_init_cinfo_from_dreq(&cinfo, dreq); spin_lock(&dreq->lock); dreq->flags = NFS_ODIRECT_RESCHED_WRITES; spin_unlock(&dreq->lock); nfs_unlock_request(req); nfs_mark_request_commit(req, NULL, &cinfo, 0); desc.pg_error = 0; defer = true; } 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); }