| /* |
| * 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; |
| unsigned int rpages = (rsize + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; |
| |
| 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(rpages); |
| |
| 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(NFS_SERVER(inode)->wpages); |
| 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"); |
| } |