/* * 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 * */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define NFSDBG_FACILITY NFSDBG_VFS #define MAX_DIRECTIO_SIZE (4096UL << PAGE_SHIFT) static kmem_cache_t *nfs_direct_cachep; /* * This represents a set of asynchronous requests that we're waiting on */ struct nfs_direct_req { struct kref kref; /* release manager */ struct list_head list; /* nfs_read_data structs */ wait_queue_head_t wait; /* wait for i/o completion */ struct page ** pages; /* pages in our buffer */ unsigned int npages; /* count of pages */ atomic_t complete, /* i/os we're waiting for */ count, /* bytes actually processed */ error; /* any reported error */ }; /** * nfs_get_user_pages - find and set up pages underlying user's buffer * rw: direction (read or write) * user_addr: starting address of this segment of user's buffer * count: size of this segment * @pages: returned array of page struct pointers underlying user's buffer */ static inline int nfs_get_user_pages(int rw, unsigned long user_addr, size_t size, struct page ***pages) { int result = -ENOMEM; unsigned long page_count; size_t array_size; /* set an arbitrary limit to prevent type overflow */ /* XXX: this can probably be as large as INT_MAX */ if (size > MAX_DIRECTIO_SIZE) { *pages = NULL; return -EFBIG; } page_count = (user_addr + size + PAGE_SIZE - 1) >> PAGE_SHIFT; page_count -= user_addr >> PAGE_SHIFT; array_size = (page_count * sizeof(struct page *)); *pages = kmalloc(array_size, GFP_KERNEL); if (*pages) { down_read(¤t->mm->mmap_sem); result = get_user_pages(current, current->mm, user_addr, page_count, (rw == READ), 0, *pages, NULL); up_read(¤t->mm->mmap_sem); } return result; } /** * nfs_free_user_pages - tear down page struct array * @pages: array of page struct pointers underlying target buffer * @npages: number of pages in the array * @do_dirty: dirty the pages as we release them */ static void nfs_free_user_pages(struct page **pages, int npages, int do_dirty) { int i; for (i = 0; i < npages; i++) { if (do_dirty) set_page_dirty_lock(pages[i]); page_cache_release(pages[i]); } kfree(pages); } /** * nfs_direct_req_release - release nfs_direct_req structure for direct read * @kref: kref object embedded in an nfs_direct_req structure * */ static void nfs_direct_req_release(struct kref *kref) { struct nfs_direct_req *dreq = container_of(kref, struct nfs_direct_req, kref); kmem_cache_free(nfs_direct_cachep, dreq); } /** * nfs_direct_read_alloc - allocate nfs_read_data structures for direct read * @count: count of bytes for the read request * @rsize: local rsize setting * * Note we also set the number of requests we have in the dreq when we are * done. This prevents races with I/O completion so we will always wait * until all requests have been dispatched and completed. */ static struct nfs_direct_req *nfs_direct_read_alloc(size_t nbytes, unsigned int rsize) { struct list_head *list; struct nfs_direct_req *dreq; unsigned int reads = 0; dreq = kmem_cache_alloc(nfs_direct_cachep, SLAB_KERNEL); if (!dreq) return NULL; kref_init(&dreq->kref); init_waitqueue_head(&dreq->wait); INIT_LIST_HEAD(&dreq->list); atomic_set(&dreq->count, 0); atomic_set(&dreq->error, 0); list = &dreq->list; for(;;) { struct nfs_read_data *data = nfs_readdata_alloc(); if (unlikely(!data)) { while (!list_empty(list)) { data = list_entry(list->next, struct nfs_read_data, pages); list_del(&data->pages); nfs_readdata_free(data); } kref_put(&dreq->kref, nfs_direct_req_release); return NULL; } INIT_LIST_HEAD(&data->pages); list_add(&data->pages, list); data->req = (struct nfs_page *) dreq; reads++; if (nbytes <= rsize) break; nbytes -= rsize; } kref_get(&dreq->kref); atomic_set(&dreq->complete, reads); return dreq; } /** * nfs_direct_read_result - handle a read reply for a direct read request * @data: address of NFS READ operation control block * @status: status of this NFS READ operation * * 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_read_wait (for instance, if someone hits ^C on a slow server). */ static void nfs_direct_read_result(struct nfs_read_data *data, int status) { struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req; if (likely(status >= 0)) atomic_add(data->res.count, &dreq->count); else atomic_set(&dreq->error, status); if (unlikely(atomic_dec_and_test(&dreq->complete))) { nfs_free_user_pages(dreq->pages, dreq->npages, 1); wake_up(&dreq->wait); kref_put(&dreq->kref, nfs_direct_req_release); } } /** * nfs_direct_read_schedule - dispatch NFS READ operations for a direct read * @dreq: address of nfs_direct_req struct for this request * @inode: target inode * @ctx: target file open context * @user_addr: starting address of this segment of user's buffer * @count: size of this segment * @file_offset: offset in file to begin the operation * * For each nfs_read_data struct that was allocated on the list, dispatch * an NFS READ operation */ static void nfs_direct_read_schedule(struct nfs_direct_req *dreq, struct inode *inode, struct nfs_open_context *ctx, unsigned long user_addr, size_t count, loff_t file_offset) { struct list_head *list = &dreq->list; struct page **pages = dreq->pages; unsigned int curpage, pgbase; unsigned int rsize = NFS_SERVER(inode)->rsize; curpage = 0; pgbase = user_addr & ~PAGE_MASK; do { struct nfs_read_data *data; unsigned int bytes; bytes = rsize; if (count < rsize) bytes = count; data = list_entry(list->next, struct nfs_read_data, pages); list_del_init(&data->pages); data->inode = inode; data->cred = ctx->cred; data->args.fh = NFS_FH(inode); data->args.context = ctx; data->args.offset = file_offset; data->args.pgbase = pgbase; data->args.pages = &pages[curpage]; data->args.count = bytes; data->res.fattr = &data->fattr; data->res.eof = 0; data->res.count = bytes; NFS_PROTO(inode)->read_setup(data); data->task.tk_cookie = (unsigned long) inode; data->complete = nfs_direct_read_result; lock_kernel(); rpc_execute(&data->task); unlock_kernel(); dfprintk(VFS, "NFS: %4d initiated direct read call (req %s/%Ld, %u 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); file_offset += bytes; pgbase += bytes; curpage += pgbase >> PAGE_SHIFT; pgbase &= ~PAGE_MASK; count -= bytes; } while (count != 0); } /** * nfs_direct_read_wait - wait for I/O completion for direct reads * @dreq: request on which we are to wait * @intr: whether or not this wait can be interrupted * * Collects and returns the final error value/byte-count. */ static ssize_t nfs_direct_read_wait(struct nfs_direct_req *dreq, int intr) { int result = 0; if (intr) { result = wait_event_interruptible(dreq->wait, (atomic_read(&dreq->complete) == 0)); } else { wait_event(dreq->wait, (atomic_read(&dreq->complete) == 0)); } if (!result) result = atomic_read(&dreq->error); if (!result) result = atomic_read(&dreq->count); kref_put(&dreq->kref, nfs_direct_req_release); return (ssize_t) result; } /** * nfs_direct_read_seg - Read in one iov segment. Generate separate * read RPCs for each "rsize" bytes. * @inode: target inode * @ctx: target file open context * @user_addr: starting address of this segment of user's buffer * @count: size of this segment * @file_offset: offset in file to begin the operation * @pages: array of addresses of page structs defining user's buffer * @nr_pages: number of pages in the array * */ static ssize_t nfs_direct_read_seg(struct inode *inode, struct nfs_open_context *ctx, unsigned long user_addr, size_t count, loff_t file_offset, struct page **pages, unsigned int nr_pages) { ssize_t result; sigset_t oldset; struct rpc_clnt *clnt = NFS_CLIENT(inode); struct nfs_direct_req *dreq; dreq = nfs_direct_read_alloc(count, NFS_SERVER(inode)->rsize); if (!dreq) return -ENOMEM; dreq->pages = pages; dreq->npages = nr_pages; rpc_clnt_sigmask(clnt, &oldset); nfs_direct_read_schedule(dreq, inode, ctx, user_addr, count, file_offset); result = nfs_direct_read_wait(dreq, clnt->cl_intr); rpc_clnt_sigunmask(clnt, &oldset); return result; } /** * nfs_direct_read - For each iov segment, map the user's buffer * then generate read RPCs. * @inode: target inode * @ctx: target file open context * @iov: array of vectors that define I/O buffer * file_offset: offset in file to begin the operation * nr_segs: size of iovec array * * We've already pushed out any non-direct writes so that this read * will see them when we read from the server. */ static ssize_t nfs_direct_read(struct inode *inode, struct nfs_open_context *ctx, const struct iovec *iov, loff_t file_offset, unsigned long nr_segs) { ssize_t tot_bytes = 0; unsigned long seg = 0; while ((seg < nr_segs) && (tot_bytes >= 0)) { ssize_t result; int page_count; struct page **pages; const struct iovec *vec = &iov[seg++]; unsigned long user_addr = (unsigned long) vec->iov_base; size_t size = vec->iov_len; page_count = nfs_get_user_pages(READ, user_addr, size, &pages); if (page_count < 0) { nfs_free_user_pages(pages, 0, 0); if (tot_bytes > 0) break; return page_count; } result = nfs_direct_read_seg(inode, ctx, user_addr, size, file_offset, pages, page_count); if (result <= 0) { if (tot_bytes > 0) break; return result; } tot_bytes += result; file_offset += result; if (result < size) break; } return tot_bytes; } /** * nfs_direct_write_seg - Write out one iov segment. Generate separate * write RPCs for each "wsize" bytes, then commit. * @inode: target inode * @ctx: target file open context * user_addr: starting address of this segment of user's buffer * count: size of this segment * file_offset: offset in file to begin the operation * @pages: array of addresses of page structs defining user's buffer * nr_pages: size of pages array */ static ssize_t nfs_direct_write_seg(struct inode *inode, struct nfs_open_context *ctx, unsigned long user_addr, size_t count, loff_t file_offset, struct page **pages, int nr_pages) { const unsigned int wsize = NFS_SERVER(inode)->wsize; size_t request; int curpage, need_commit; ssize_t result, tot_bytes; struct nfs_writeverf first_verf; struct nfs_write_data *wdata; wdata = nfs_writedata_alloc(); if (!wdata) return -ENOMEM; wdata->inode = inode; wdata->cred = ctx->cred; wdata->args.fh = NFS_FH(inode); wdata->args.context = ctx; wdata->args.stable = NFS_UNSTABLE; if (IS_SYNC(inode) || NFS_PROTO(inode)->version == 2 || count <= wsize) wdata->args.stable = NFS_FILE_SYNC; wdata->res.fattr = &wdata->fattr; wdata->res.verf = &wdata->verf; nfs_begin_data_update(inode); retry: need_commit = 0; tot_bytes = 0; curpage = 0; request = count; wdata->args.pgbase = user_addr & ~PAGE_MASK; wdata->args.offset = file_offset; do { wdata->args.count = request; if (wdata->args.count > wsize) wdata->args.count = wsize; wdata->args.pages = &pages[curpage]; dprintk("NFS: direct write: c=%u o=%Ld ua=%lu, pb=%u, cp=%u\n", wdata->args.count, (long long) wdata->args.offset, user_addr + tot_bytes, wdata->args.pgbase, curpage); lock_kernel(); result = NFS_PROTO(inode)->write(wdata); unlock_kernel(); if (result <= 0) { if (tot_bytes > 0) break; goto out; } if (tot_bytes == 0) memcpy(&first_verf.verifier, &wdata->verf.verifier, sizeof(first_verf.verifier)); if (wdata->verf.committed != NFS_FILE_SYNC) { need_commit = 1; if (memcmp(&first_verf.verifier, &wdata->verf.verifier, sizeof(first_verf.verifier))); goto sync_retry; } tot_bytes += result; /* in case of a short write: stop now, let the app recover */ if (result < wdata->args.count) break; wdata->args.offset += result; wdata->args.pgbase += result; curpage += wdata->args.pgbase >> PAGE_SHIFT; wdata->args.pgbase &= ~PAGE_MASK; request -= result; } while (request != 0); /* * Commit data written so far, even in the event of an error */ if (need_commit) { wdata->args.count = tot_bytes; wdata->args.offset = file_offset; lock_kernel(); result = NFS_PROTO(inode)->commit(wdata); unlock_kernel(); if (result < 0 || memcmp(&first_verf.verifier, &wdata->verf.verifier, sizeof(first_verf.verifier)) != 0) goto sync_retry; } result = tot_bytes; out: nfs_end_data_update(inode); nfs_writedata_free(wdata); return result; sync_retry: wdata->args.stable = NFS_FILE_SYNC; goto retry; } /** * nfs_direct_write - For each iov segment, map the user's buffer * then generate write and commit RPCs. * @inode: target inode * @ctx: target file open context * @iov: array of vectors that define I/O buffer * file_offset: offset in file to begin the operation * nr_segs: size of iovec array * * Upon return, generic_file_direct_IO invalidates any cached pages * that non-direct readers might access, so they will pick up these * writes immediately. */ static ssize_t nfs_direct_write(struct inode *inode, struct nfs_open_context *ctx, const struct iovec *iov, loff_t file_offset, unsigned long nr_segs) { ssize_t tot_bytes = 0; unsigned long seg = 0; while ((seg < nr_segs) && (tot_bytes >= 0)) { ssize_t result; int page_count; struct page **pages; const struct iovec *vec = &iov[seg++]; unsigned long user_addr = (unsigned long) vec->iov_base; size_t size = vec->iov_len; page_count = nfs_get_user_pages(WRITE, user_addr, size, &pages); if (page_count < 0) { nfs_free_user_pages(pages, 0, 0); if (tot_bytes > 0) break; return page_count; } result = nfs_direct_write_seg(inode, ctx, user_addr, size, file_offset, pages, page_count); nfs_free_user_pages(pages, page_count, 0); if (result <= 0) { if (tot_bytes > 0) break; return result; } tot_bytes += result; file_offset += result; if (result < size) break; } return tot_bytes; } /** * 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 * file_offset: offset in file to begin the operation * nr_segs: size of iovec array * */ ssize_t nfs_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov, loff_t file_offset, unsigned long nr_segs) { ssize_t result = -EINVAL; struct file *file = iocb->ki_filp; struct nfs_open_context *ctx; struct dentry *dentry = file->f_dentry; struct inode *inode = dentry->d_inode; /* * No support for async yet */ if (!is_sync_kiocb(iocb)) return result; ctx = (struct nfs_open_context *)file->private_data; switch (rw) { case READ: dprintk("NFS: direct_IO(read) (%s) off/no(%Lu/%lu)\n", dentry->d_name.name, file_offset, nr_segs); result = nfs_direct_read(inode, ctx, iov, file_offset, nr_segs); break; case WRITE: dprintk("NFS: direct_IO(write) (%s) off/no(%Lu/%lu)\n", dentry->d_name.name, file_offset, nr_segs); result = nfs_direct_write(inode, ctx, iov, file_offset, nr_segs); break; default: break; } return result; } /** * nfs_file_direct_read - file direct read operation for NFS files * @iocb: target I/O control block * @buf: user's buffer into which to read data * count: number of bytes to read * 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. So 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, char __user *buf, size_t count, loff_t pos) { ssize_t retval = -EINVAL; loff_t *ppos = &iocb->ki_pos; struct file *file = iocb->ki_filp; struct nfs_open_context *ctx = (struct nfs_open_context *) file->private_data; struct address_space *mapping = file->f_mapping; struct inode *inode = mapping->host; struct iovec iov = { .iov_base = buf, .iov_len = count, }; dprintk("nfs: direct read(%s/%s, %lu@%Ld)\n", file->f_dentry->d_parent->d_name.name, file->f_dentry->d_name.name, (unsigned long) count, (long long) pos); if (!is_sync_kiocb(iocb)) goto out; if (count < 0) goto out; retval = -EFAULT; if (!access_ok(VERIFY_WRITE, iov.iov_base, iov.iov_len)) goto out; retval = 0; if (!count) goto out; retval = nfs_sync_mapping(mapping); if (retval) goto out; retval = nfs_direct_read(inode, ctx, &iov, pos, 1); if (retval > 0) *ppos = pos + retval; out: return retval; } /** * nfs_file_direct_write - file direct write operation for NFS files * @iocb: target I/O control block * @buf: user's buffer from which to write data * count: number of bytes to write * 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 char __user *buf, size_t count, loff_t pos) { ssize_t retval; struct file *file = iocb->ki_filp; struct nfs_open_context *ctx = (struct nfs_open_context *) file->private_data; struct address_space *mapping = file->f_mapping; struct inode *inode = mapping->host; struct iovec iov = { .iov_base = (char __user *)buf, }; dfprintk(VFS, "nfs: direct write(%s/%s, %lu@%Ld)\n", file->f_dentry->d_parent->d_name.name, file->f_dentry->d_name.name, (unsigned long) count, (long long) pos); retval = -EINVAL; if (!is_sync_kiocb(iocb)) goto out; 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; iov.iov_len = count, retval = -EFAULT; if (!access_ok(VERIFY_READ, iov.iov_base, iov.iov_len)) goto out; retval = nfs_sync_mapping(mapping); if (retval) goto out; retval = nfs_direct_write(inode, ctx, &iov, pos, 1); if (mapping->nrpages) invalidate_inode_pages2(mapping); if (retval > 0) iocb->ki_pos = pos + retval; out: return retval; } int nfs_init_directcache(void) { nfs_direct_cachep = kmem_cache_create("nfs_direct_cache", sizeof(struct nfs_direct_req), 0, SLAB_RECLAIM_ACCOUNT, NULL, NULL); if (nfs_direct_cachep == NULL) return -ENOMEM; return 0; } void nfs_destroy_directcache(void) { if (kmem_cache_destroy(nfs_direct_cachep)) printk(KERN_INFO "nfs_direct_cache: not all structures were freed\n"); }