/* * 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_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); } /* * 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; nfs_readpage_result(task, data); } static void nfs_direct_read_release(void *calldata) { struct nfs_read_data *data = calldata; struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req; int status = data->task.tk_status; spin_lock(&dreq->lock); if (unlikely(status < 0)) { dreq->error = 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); nfs_readdata_release(calldata); } static const struct rpc_call_ops nfs_read_direct_ops = { .rpc_call_done = nfs_direct_read_result, .rpc_release = nfs_direct_read_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; struct rpc_task *task; struct rpc_message msg = { .rpc_cred = ctx->cred, }; struct rpc_task_setup task_setup_data = { .rpc_client = NFS_CLIENT(inode), .rpc_message = &msg, .callback_ops = &nfs_read_direct_ops, .workqueue = nfsiod_workqueue, .flags = RPC_TASK_ASYNC, }; 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(¤t->mm->mmap_sem); result = get_user_pages(current, current->mm, user_addr, data->npages, 1, 0, data->pagevec, NULL); up_read(¤t->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 = msg.rpc_cred; data->args.fh = NFS_FH(inode); data->args.context = get_nfs_open_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; msg.rpc_argp = &data->args; msg.rpc_resp = &data->res; task_setup_data.task = &data->task; task_setup_data.callback_data = data; NFS_PROTO(inode)->read_setup(data, &msg); task = rpc_run_task(&task_setup_data); if (IS_ERR(task)) break; rpc_put_task(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; struct inode *inode = iocb->ki_filp->f_mapping->host; 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; result = nfs_direct_read_schedule_iovec(dreq, iov, nr_segs, pos); if (!result) result = nfs_direct_wait(dreq); 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; struct rpc_task *task; struct rpc_message msg = { .rpc_cred = dreq->ctx->cred, }; struct rpc_task_setup task_setup_data = { .rpc_client = NFS_CLIENT(inode), .callback_ops = &nfs_write_direct_ops, .workqueue = nfsiod_workqueue, .flags = RPC_TASK_ASYNC, }; 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); /* Use stable writes */ data->args.stable = NFS_FILE_SYNC; /* * 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. */ task_setup_data.task = &data->task; task_setup_data.callback_data = data; msg.rpc_argp = &data->args; msg.rpc_resp = &data->res; NFS_PROTO(inode)->write_setup(data, &msg); /* * We're called via an RPC callback, so BKL is already held. */ task = rpc_run_task(&task_setup_data); if (!IS_ERR(task)) rpc_put_task(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; /* Call the NFS version-specific code */ NFS_PROTO(data->inode)->commit_done(task, data); } static void nfs_direct_commit_release(void *calldata) { struct nfs_write_data *data = calldata; struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req; int status = data->task.tk_status; 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); nfs_direct_write_complete(dreq, data->inode); nfs_commitdata_release(calldata); } static const struct rpc_call_ops nfs_commit_direct_ops = { .rpc_call_done = nfs_direct_commit_result, .rpc_release = nfs_direct_commit_release, }; static void nfs_direct_commit_schedule(struct nfs_direct_req *dreq) { struct nfs_write_data *data = dreq->commit_data; struct rpc_task *task; struct rpc_message msg = { .rpc_argp = &data->args, .rpc_resp = &data->res, .rpc_cred = dreq->ctx->cred, }; struct rpc_task_setup task_setup_data = { .task = &data->task, .rpc_client = NFS_CLIENT(dreq->inode), .rpc_message = &msg, .callback_ops = &nfs_commit_direct_ops, .callback_data = data, .workqueue = nfsiod_workqueue, .flags = RPC_TASK_ASYNC, }; data->inode = dreq->inode; data->cred = msg.rpc_cred; data->args.fh = NFS_FH(data->inode); data->args.offset = 0; data->args.count = 0; data->args.context = get_nfs_open_context(dreq->ctx); data->res.count = 0; data->res.fattr = &data->fattr; data->res.verf = &data->verf; NFS_PROTO(data->inode)->commit_setup(data, &msg); /* 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); task = rpc_run_task(&task_setup_data); if (!IS_ERR(task)) rpc_put_task(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_commitdata_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; if (nfs_writeback_done(task, data) != 0) return; } /* * 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; int status = data->task.tk_status; 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", data->task.tk_pid); dreq->flags = NFS_ODIRECT_RESCHED_WRITES; } } } out_unlock: spin_unlock(&dreq->lock); 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; struct rpc_task *task; struct rpc_message msg = { .rpc_cred = ctx->cred, }; struct rpc_task_setup task_setup_data = { .rpc_client = NFS_CLIENT(inode), .rpc_message = &msg, .callback_ops = &nfs_write_direct_ops, .workqueue = nfsiod_workqueue, .flags = RPC_TASK_ASYNC, }; 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(¤t->mm->mmap_sem); result = get_user_pages(current, current->mm, user_addr, data->npages, 0, 0, data->pagevec, NULL); up_read(¤t->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 = msg.rpc_cred; data->args.fh = NFS_FH(inode); data->args.context = get_nfs_open_context(ctx); data->args.offset = pos; data->args.pgbase = pgbase; data->args.pages = data->pagevec; data->args.count = bytes; data->args.stable = sync; data->res.fattr = &data->fattr; data->res.count = bytes; data->res.verf = &data->verf; task_setup_data.task = &data->task; task_setup_data.callback_data = data; msg.rpc_argp = &data->args; msg.rpc_resp = &data->res; NFS_PROTO(inode)->write_setup(data, &msg); task = rpc_run_task(&task_setup_data); if (IS_ERR(task)) break; rpc_put_task(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; struct inode *inode = iocb->ki_filp->f_mapping->host; struct nfs_direct_req *dreq; size_t wsize = NFS_SERVER(inode)->wsize; int sync = NFS_UNSTABLE; dreq = nfs_direct_req_alloc(); if (!dreq) return -ENOMEM; nfs_alloc_commit_data(dreq); if (dreq->commit_data == NULL || count < wsize) sync = NFS_FILE_SYNC; dreq->inode = inode; dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp)); if (!is_sync_kiocb(iocb)) dreq->iocb = iocb; result = nfs_direct_write_schedule_iovec(dreq, iov, nr_segs, pos, sync); if (!result) result = nfs_direct_wait(dreq); 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); }