/* * 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 "internal.h" #include "iostat.h" #include "pnfs.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 nfs_lock_context *l_ctx; /* Lock 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 nfs_mds_commit_info mds_cinfo; /* Storage for cinfo */ struct pnfs_ds_commit_info ds_cinfo; /* Storage for cinfo */ struct work_struct work; 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 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, struct inode *inode); 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); } /** * 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_release_pages(struct page **pages, unsigned int npages) { unsigned int i; for (i = 0; i < npages; i++) page_cache_release(pages[i]); } void nfs_init_cinfo_from_dreq(struct nfs_commit_info *cinfo, struct nfs_direct_req *dreq) { cinfo->lock = &dreq->lock; 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_alloc(nfs_direct_cachep, GFP_KERNEL); if (!dreq) return NULL; kref_init(&dreq->kref); kref_get(&dreq->kref); init_completion(&dreq->completion); dreq->mds_cinfo.ncommit = 0; atomic_set(&dreq->mds_cinfo.rpcs_out, 0); INIT_LIST_HEAD(&dreq->mds_cinfo.list); INIT_WORK(&dreq->work, nfs_direct_write_schedule_work); memset(&dreq->ds_cinfo, 0, sizeof(dreq->ds_cinfo)); dreq->iocb = NULL; dreq->ctx = NULL; dreq->l_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->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); } /* * 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->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); } void nfs_direct_readpage_release(struct nfs_page *req) { dprintk("NFS: direct read done (%s/%lld %d@%lld)\n", req->wb_context->dentry->d_inode->i_sb->s_id, (long long)NFS_FILEID(req->wb_context->dentry->d_inode), req->wb_bytes, (long long)req_offset(req)); nfs_release_request(req); } static void nfs_direct_read_completion(struct nfs_pgio_header *hdr) { unsigned long bytes = 0; struct nfs_direct_req *dreq = hdr->dreq; if (test_bit(NFS_IOHDR_REDO, &hdr->flags)) goto out_put; spin_lock(&dreq->lock); if (test_bit(NFS_IOHDR_ERROR, &hdr->flags) && (hdr->good_bytes == 0)) dreq->error = hdr->error; else dreq->count += hdr->good_bytes; spin_unlock(&dreq->lock); if (!test_bit(NFS_IOHDR_ERROR, &hdr->flags)) { while (!list_empty(&hdr->pages)) { struct nfs_page *req = nfs_list_entry(hdr->pages.next); struct page *page = req->wb_page; if (test_bit(NFS_IOHDR_EOF, &hdr->flags)) { if (bytes > hdr->good_bytes) zero_user(page, 0, PAGE_SIZE); else if (hdr->good_bytes - bytes < PAGE_SIZE) zero_user_segment(page, hdr->good_bytes & ~PAGE_MASK, PAGE_SIZE); } bytes += req->wb_bytes; nfs_list_remove_request(req); nfs_direct_readpage_release(req); if (!PageCompound(page)) set_page_dirty(page); page_cache_release(page); } } else { while (!list_empty(&hdr->pages)) { struct nfs_page *req = nfs_list_entry(hdr->pages.next); if (bytes < hdr->good_bytes) if (!PageCompound(req->wb_page)) set_page_dirty(req->wb_page); bytes += req->wb_bytes; page_cache_release(req->wb_page); nfs_list_remove_request(req); nfs_direct_readpage_release(req); } } out_put: if (put_dreq(dreq)) nfs_direct_complete(dreq); hdr->release(hdr); } static void nfs_sync_pgio_error(struct list_head *head) { 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_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_segment(struct nfs_pageio_descriptor *desc, const struct iovec *iov, loff_t pos) { struct nfs_direct_req *dreq = desc->pg_dreq; struct nfs_open_context *ctx = dreq->ctx; struct inode *inode = ctx->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; struct page **pagevec = NULL; unsigned int npages; do { size_t bytes; int i; pgbase = user_addr & ~PAGE_MASK; bytes = min(max(rsize, PAGE_SIZE), count); result = -ENOMEM; npages = nfs_page_array_len(pgbase, bytes); if (!pagevec) pagevec = kmalloc(npages * sizeof(struct page *), GFP_KERNEL); if (!pagevec) break; down_read(¤t->mm->mmap_sem); result = get_user_pages(current, current->mm, user_addr, npages, 1, 0, pagevec, NULL); up_read(¤t->mm->mmap_sem); if (result < 0) break; if ((unsigned)result < npages) { bytes = result * PAGE_SIZE; if (bytes <= pgbase) { nfs_direct_release_pages(pagevec, result); break; } bytes -= pgbase; npages = result; } for (i = 0; i < npages; i++) { struct nfs_page *req; unsigned int req_len = min(bytes, PAGE_SIZE - pgbase); /* XXX do we need to do the eof zeroing found in async_filler? */ req = nfs_create_request(dreq->ctx, dreq->inode, pagevec[i], pgbase, req_len); if (IS_ERR(req)) { nfs_direct_release_pages(pagevec + i, npages - i); 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); nfs_direct_release_pages(pagevec + i, npages - i); break; } pgbase = 0; bytes -= req_len; started += req_len; user_addr += req_len; pos += req_len; count -= req_len; } } while (count != 0); kfree(pagevec); 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) { struct nfs_pageio_descriptor desc; ssize_t result = -EINVAL; size_t requested_bytes = 0; unsigned long seg; nfs_pageio_init_read(&desc, dreq->inode, &nfs_direct_read_completion_ops); get_dreq(dreq); desc.pg_dreq = dreq; for (seg = 0; seg < nr_segs; seg++) { const struct iovec *vec = &iov[seg]; result = nfs_direct_read_schedule_segment(&desc, vec, pos); if (result < 0) break; requested_bytes += result; if ((size_t)result < vec->iov_len) break; pos += vec->iov_len; } nfs_pageio_complete(&desc); /* * If no bytes were started, return the error, and let the * generic layer handle the completion. */ if (requested_bytes == 0) { nfs_direct_req_release(dreq); return result < 0 ? result : -EIO; } if (put_dreq(dreq)) nfs_direct_complete(dreq); return 0; } static ssize_t nfs_direct_read(struct kiocb *iocb, const struct iovec *iov, unsigned long nr_segs, loff_t pos) { ssize_t result = -ENOMEM; struct inode *inode = iocb->ki_filp->f_mapping->host; struct nfs_direct_req *dreq; dreq = nfs_direct_req_alloc(); if (dreq == NULL) goto out; dreq->inode = inode; dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp)); dreq->l_ctx = nfs_get_lock_context(dreq->ctx); if (dreq->l_ctx == NULL) goto out_release; if (!is_sync_kiocb(iocb)) dreq->iocb = iocb; result = nfs_direct_read_schedule_iovec(dreq, iov, nr_segs, pos); if (!result) result = nfs_direct_wait(dreq); out_release: nfs_direct_req_release(dreq); out: return result; } #if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4) 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); pnfs_recover_commit_reqs(dreq->inode, &reqs, &cinfo); spin_lock(cinfo.lock); nfs_scan_commit_list(&cinfo.mds->list, &reqs, &cinfo, 0); spin_unlock(cinfo.lock); dreq->count = 0; get_dreq(dreq); nfs_pageio_init_write(&desc, dreq->inode, FLUSH_STABLE, &nfs_direct_write_completion_ops); desc.pg_dreq = dreq; list_for_each_entry_safe(req, tmp, &reqs, wb_list) { if (!nfs_pageio_add_request(&desc, req)) { nfs_list_add_request(req, &failed); spin_lock(cinfo.lock); dreq->flags = 0; dreq->error = -EIO; spin_unlock(cinfo.lock); } } nfs_pageio_complete(&desc); while (!list_empty(&failed)) { page_cache_release(req->wb_page); nfs_release_request(req); nfs_unlock_request(req); } if (put_dreq(dreq)) nfs_direct_write_complete(dreq, dreq->inode); } static void nfs_direct_commit_complete(struct nfs_commit_data *data) { struct nfs_direct_req *dreq = data->dreq; struct nfs_commit_info cinfo; struct nfs_page *req; int status = data->task.tk_status; nfs_init_cinfo_from_dreq(&cinfo, dreq); if (status < 0) { dprintk("NFS: %5u commit failed with error %d.\n", data->task.tk_pid, status); dreq->flags = NFS_ODIRECT_RESCHED_WRITES; } else if (memcmp(&dreq->verf, &data->verf, sizeof(data->verf))) { dprintk("NFS: %5u commit verify failed\n", data->task.tk_pid); dreq->flags = NFS_ODIRECT_RESCHED_WRITES; } dprintk("NFS: %5u commit returned %d\n", data->task.tk_pid, status); while (!list_empty(&data->pages)) { req = nfs_list_entry(data->pages.next); nfs_list_remove_request(req); if (dreq->flags == NFS_ODIRECT_RESCHED_WRITES) { /* Note the rewrite will go through mds */ nfs_mark_request_commit(req, NULL, &cinfo); } else { page_cache_release(req->wb_page); nfs_release_request(req); } nfs_unlock_request(req); } if (atomic_dec_and_test(&cinfo.mds->rpcs_out)) nfs_direct_write_complete(dreq, data->inode); } static void nfs_direct_error_cleanup(struct nfs_inode *nfsi) { /* There is no lock to clear */ } static const struct nfs_commit_completion_ops nfs_direct_commit_completion_ops = { .completion = nfs_direct_commit_complete, .error_cleanup = nfs_direct_error_cleanup, }; 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_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_zap_mapping(dreq->inode, dreq->inode->i_mapping); nfs_direct_complete(dreq); } } static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode) { schedule_work(&dreq->work); /* Calls nfs_direct_write_schedule_work */ } #else static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode) { nfs_zap_mapping(inode, inode->i_mapping); nfs_direct_complete(dreq); } #endif /* * 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_segment(struct nfs_pageio_descriptor *desc, const struct iovec *iov, loff_t pos) { struct nfs_direct_req *dreq = desc->pg_dreq; struct nfs_open_context *ctx = dreq->ctx; struct inode *inode = ctx->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; struct page **pagevec = NULL; unsigned int npages; do { size_t bytes; int i; pgbase = user_addr & ~PAGE_MASK; bytes = min(max(wsize, PAGE_SIZE), count); result = -ENOMEM; npages = nfs_page_array_len(pgbase, bytes); if (!pagevec) pagevec = kmalloc(npages * sizeof(struct page *), GFP_KERNEL); if (!pagevec) break; down_read(¤t->mm->mmap_sem); result = get_user_pages(current, current->mm, user_addr, npages, 0, 0, pagevec, NULL); up_read(¤t->mm->mmap_sem); if (result < 0) break; if ((unsigned)result < npages) { bytes = result * PAGE_SIZE; if (bytes <= pgbase) { nfs_direct_release_pages(pagevec, result); break; } bytes -= pgbase; npages = result; } for (i = 0; i < npages; i++) { struct nfs_page *req; unsigned int req_len = min(bytes, PAGE_SIZE - pgbase); req = nfs_create_request(dreq->ctx, dreq->inode, pagevec[i], pgbase, req_len); if (IS_ERR(req)) { nfs_direct_release_pages(pagevec + i, npages - i); result = PTR_ERR(req); 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_request(req); nfs_release_request(req); nfs_direct_release_pages(pagevec + i, npages - i); } pgbase = 0; bytes -= req_len; started += req_len; user_addr += req_len; pos += req_len; count -= req_len; } } while (count != 0); kfree(pagevec); if (started) return started; return result < 0 ? (ssize_t) result : -EFAULT; } static void nfs_direct_write_completion(struct nfs_pgio_header *hdr) { struct nfs_direct_req *dreq = hdr->dreq; struct nfs_commit_info cinfo; int bit = -1; struct nfs_page *req = nfs_list_entry(hdr->pages.next); if (test_bit(NFS_IOHDR_REDO, &hdr->flags)) goto out_put; nfs_init_cinfo_from_dreq(&cinfo, dreq); spin_lock(&dreq->lock); if (test_bit(NFS_IOHDR_ERROR, &hdr->flags)) { dreq->flags = 0; dreq->error = hdr->error; } if (dreq->error != 0) bit = NFS_IOHDR_ERROR; else { dreq->count += hdr->good_bytes; if (test_bit(NFS_IOHDR_NEED_RESCHED, &hdr->flags)) { dreq->flags = NFS_ODIRECT_RESCHED_WRITES; bit = NFS_IOHDR_NEED_RESCHED; } else if (test_bit(NFS_IOHDR_NEED_COMMIT, &hdr->flags)) { if (dreq->flags == NFS_ODIRECT_RESCHED_WRITES) bit = NFS_IOHDR_NEED_RESCHED; else if (dreq->flags == 0) { memcpy(&dreq->verf, &req->wb_verf, sizeof(dreq->verf)); bit = NFS_IOHDR_NEED_COMMIT; dreq->flags = NFS_ODIRECT_DO_COMMIT; } else if (dreq->flags == NFS_ODIRECT_DO_COMMIT) { if (memcmp(&dreq->verf, &req->wb_verf, sizeof(dreq->verf))) { dreq->flags = NFS_ODIRECT_RESCHED_WRITES; bit = NFS_IOHDR_NEED_RESCHED; } else bit = NFS_IOHDR_NEED_COMMIT; } } } spin_unlock(&dreq->lock); while (!list_empty(&hdr->pages)) { req = nfs_list_entry(hdr->pages.next); nfs_list_remove_request(req); switch (bit) { case NFS_IOHDR_NEED_RESCHED: case NFS_IOHDR_NEED_COMMIT: nfs_mark_request_commit(req, hdr->lseg, &cinfo); break; default: page_cache_release(req->wb_page); nfs_release_request(req); } nfs_unlock_request(req); } out_put: if (put_dreq(dreq)) nfs_direct_write_complete(dreq, hdr->inode); hdr->release(hdr); } static const struct nfs_pgio_completion_ops nfs_direct_write_completion_ops = { .error_cleanup = nfs_sync_pgio_error, .init_hdr = nfs_direct_pgio_init, .completion = nfs_direct_write_completion, }; static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq, const struct iovec *iov, unsigned long nr_segs, loff_t pos) { struct nfs_pageio_descriptor desc; ssize_t result = 0; size_t requested_bytes = 0; unsigned long seg; nfs_pageio_init_write(&desc, dreq->inode, FLUSH_COND_STABLE, &nfs_direct_write_completion_ops); desc.pg_dreq = dreq; get_dreq(dreq); for (seg = 0; seg < nr_segs; seg++) { const struct iovec *vec = &iov[seg]; result = nfs_direct_write_schedule_segment(&desc, vec, pos); if (result < 0) break; requested_bytes += result; if ((size_t)result < vec->iov_len) break; pos += vec->iov_len; } nfs_pageio_complete(&desc); /* * If no bytes were started, return the error, and let the * generic layer handle the completion. */ if (requested_bytes == 0) { nfs_direct_req_release(dreq); return result < 0 ? result : -EIO; } if (put_dreq(dreq)) nfs_direct_write_complete(dreq, dreq->inode); return 0; } 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 = -ENOMEM; struct inode *inode = iocb->ki_filp->f_mapping->host; struct nfs_direct_req *dreq; dreq = nfs_direct_req_alloc(); if (!dreq) goto out; dreq->inode = inode; dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp)); dreq->l_ctx = nfs_get_lock_context(dreq->ctx); if (dreq->l_ctx == NULL) goto out_release; if (!is_sync_kiocb(iocb)) dreq->iocb = iocb; result = nfs_direct_write_schedule_iovec(dreq, iov, nr_segs, pos); if (!result) result = nfs_direct_wait(dreq); out_release: nfs_direct_req_release(dreq); out: 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); dfprintk(FILE, "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; task_io_account_read(count); 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 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(FILE, "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; task_io_account_write(count); retval = nfs_direct_write(iocb, iov, nr_segs, pos, count); if (retval > 0) { struct inode *inode = mapping->host; iocb->ki_pos = pos + retval; spin_lock(&inode->i_lock); if (i_size_read(inode) < iocb->ki_pos) i_size_write(inode, iocb->ki_pos); spin_unlock(&inode->i_lock); } 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); }