diff options
Diffstat (limited to 'fs/nfs/direct.c')
| -rw-r--r-- | fs/nfs/direct.c | 808 |
1 files changed, 808 insertions, 0 deletions
diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c new file mode 100644 index 000000000000..68df803f27ca --- /dev/null +++ b/fs/nfs/direct.c @@ -0,0 +1,808 @@ +/* + * 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 + * + */ + +#include <linux/config.h> +#include <linux/errno.h> +#include <linux/sched.h> +#include <linux/kernel.h> +#include <linux/smp_lock.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> + +#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->task.tk_calldata = data; + data->task.tk_release = nfs_readdata_release; + 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_defer(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 dentry *dentry = file->f_dentry; + 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@%lu)\n", + dentry->d_parent->d_name.name, dentry->d_name.name, + (unsigned long) count, (unsigned 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; + + if (mapping->nrpages) { + retval = filemap_fdatawrite(mapping); + if (retval == 0) + retval = nfs_wb_all(inode); + if (retval == 0) + retval = filemap_fdatawait(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 = -EINVAL; + loff_t *ppos = &iocb->ki_pos; + unsigned long limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur; + struct file *file = iocb->ki_filp; + struct nfs_open_context *ctx = + (struct nfs_open_context *) file->private_data; + struct dentry *dentry = file->f_dentry; + struct address_space *mapping = file->f_mapping; + struct inode *inode = mapping->host; + struct iovec iov = { + .iov_base = (char __user *)buf, + .iov_len = count, + }; + + dfprintk(VFS, "nfs: direct write(%s/%s(%ld), %lu@%lu)\n", + dentry->d_parent->d_name.name, dentry->d_name.name, + inode->i_ino, (unsigned long) count, (unsigned long) pos); + + if (!is_sync_kiocb(iocb)) + goto out; + if (count < 0) + goto out; + if (pos < 0) + goto out; + retval = -EFAULT; + if (!access_ok(VERIFY_READ, iov.iov_base, iov.iov_len)) + goto out; + if (file->f_error) { + retval = file->f_error; + file->f_error = 0; + goto out; + } + retval = -EFBIG; + if (limit != RLIM_INFINITY) { + if (pos >= limit) { + send_sig(SIGXFSZ, current, 0); + goto out; + } + if (count > limit - (unsigned long) pos) + count = limit - (unsigned long) pos; + } + retval = 0; + if (!count) + goto out; + + if (mapping->nrpages) { + retval = filemap_fdatawrite(mapping); + if (retval == 0) + retval = nfs_wb_all(inode); + if (retval == 0) + retval = filemap_fdatawait(mapping); + if (retval) + goto out; + } + + retval = nfs_direct_write(inode, ctx, &iov, pos, 1); + if (mapping->nrpages) + invalidate_inode_pages2(mapping); + if (retval > 0) + *ppos = 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"); +} |