| /* |
| * "splice": joining two ropes together by interweaving their strands. |
| * |
| * This is the "extended pipe" functionality, where a pipe is used as |
| * an arbitrary in-memory buffer. Think of a pipe as a small kernel |
| * buffer that you can use to transfer data from one end to the other. |
| * |
| * The traditional unix read/write is extended with a "splice()" operation |
| * that transfers data buffers to or from a pipe buffer. |
| * |
| * Named by Larry McVoy, original implementation from Linus, extended by |
| * Jens to support splicing to files and fixing the initial implementation |
| * bugs. |
| * |
| * Copyright (C) 2005 Jens Axboe <axboe@suse.de> |
| * Copyright (C) 2005 Linus Torvalds <torvalds@osdl.org> |
| * |
| */ |
| #include <linux/fs.h> |
| #include <linux/file.h> |
| #include <linux/pagemap.h> |
| #include <linux/pipe_fs_i.h> |
| #include <linux/mm_inline.h> |
| #include <linux/swap.h> |
| #include <linux/writeback.h> |
| #include <linux/buffer_head.h> |
| #include <linux/module.h> |
| #include <linux/syscalls.h> |
| |
| /* |
| * Passed to the actors |
| */ |
| struct splice_desc { |
| unsigned int len, total_len; /* current and remaining length */ |
| unsigned int flags; /* splice flags */ |
| struct file *file; /* file to read/write */ |
| loff_t pos; /* file position */ |
| }; |
| |
| /* |
| * Attempt to steal a page from a pipe buffer. This should perhaps go into |
| * a vm helper function, it's already simplified quite a bit by the |
| * addition of remove_mapping(). If success is returned, the caller may |
| * attempt to reuse this page for another destination. |
| */ |
| static int page_cache_pipe_buf_steal(struct pipe_inode_info *info, |
| struct pipe_buffer *buf) |
| { |
| struct page *page = buf->page; |
| struct address_space *mapping = page_mapping(page); |
| |
| WARN_ON(!PageLocked(page)); |
| WARN_ON(!PageUptodate(page)); |
| |
| if (PagePrivate(page)) |
| try_to_release_page(page, mapping_gfp_mask(mapping)); |
| |
| if (!remove_mapping(mapping, page)) |
| return 1; |
| |
| if (PageLRU(page)) { |
| struct zone *zone = page_zone(page); |
| |
| spin_lock_irq(&zone->lru_lock); |
| BUG_ON(!PageLRU(page)); |
| __ClearPageLRU(page); |
| del_page_from_lru(zone, page); |
| spin_unlock_irq(&zone->lru_lock); |
| } |
| |
| return 0; |
| } |
| |
| static void page_cache_pipe_buf_release(struct pipe_inode_info *info, |
| struct pipe_buffer *buf) |
| { |
| page_cache_release(buf->page); |
| buf->page = NULL; |
| } |
| |
| static void *page_cache_pipe_buf_map(struct file *file, |
| struct pipe_inode_info *info, |
| struct pipe_buffer *buf) |
| { |
| struct page *page = buf->page; |
| |
| lock_page(page); |
| |
| if (!PageUptodate(page)) { |
| unlock_page(page); |
| return ERR_PTR(-EIO); |
| } |
| |
| if (!page->mapping) { |
| unlock_page(page); |
| return ERR_PTR(-ENODATA); |
| } |
| |
| return kmap(buf->page); |
| } |
| |
| static void page_cache_pipe_buf_unmap(struct pipe_inode_info *info, |
| struct pipe_buffer *buf) |
| { |
| unlock_page(buf->page); |
| kunmap(buf->page); |
| } |
| |
| static struct pipe_buf_operations page_cache_pipe_buf_ops = { |
| .can_merge = 0, |
| .map = page_cache_pipe_buf_map, |
| .unmap = page_cache_pipe_buf_unmap, |
| .release = page_cache_pipe_buf_release, |
| .steal = page_cache_pipe_buf_steal, |
| }; |
| |
| /* |
| * Pipe output worker. This sets up our pipe format with the page cache |
| * pipe buffer operations. Otherwise very similar to the regular pipe_writev(). |
| */ |
| static ssize_t move_to_pipe(struct inode *inode, struct page **pages, |
| int nr_pages, unsigned long offset, |
| unsigned long len, unsigned int flags) |
| { |
| struct pipe_inode_info *info; |
| int ret, do_wakeup, i; |
| |
| ret = 0; |
| do_wakeup = 0; |
| i = 0; |
| |
| mutex_lock(PIPE_MUTEX(*inode)); |
| |
| info = inode->i_pipe; |
| for (;;) { |
| int bufs; |
| |
| if (!PIPE_READERS(*inode)) { |
| send_sig(SIGPIPE, current, 0); |
| if (!ret) |
| ret = -EPIPE; |
| break; |
| } |
| |
| bufs = info->nrbufs; |
| if (bufs < PIPE_BUFFERS) { |
| int newbuf = (info->curbuf + bufs) & (PIPE_BUFFERS - 1); |
| struct pipe_buffer *buf = info->bufs + newbuf; |
| struct page *page = pages[i++]; |
| unsigned long this_len; |
| |
| this_len = PAGE_CACHE_SIZE - offset; |
| if (this_len > len) |
| this_len = len; |
| |
| buf->page = page; |
| buf->offset = offset; |
| buf->len = this_len; |
| buf->ops = &page_cache_pipe_buf_ops; |
| info->nrbufs = ++bufs; |
| do_wakeup = 1; |
| |
| ret += this_len; |
| len -= this_len; |
| offset = 0; |
| if (!--nr_pages) |
| break; |
| if (!len) |
| break; |
| if (bufs < PIPE_BUFFERS) |
| continue; |
| |
| break; |
| } |
| |
| if (flags & SPLICE_F_NONBLOCK) { |
| if (!ret) |
| ret = -EAGAIN; |
| break; |
| } |
| |
| if (signal_pending(current)) { |
| if (!ret) |
| ret = -ERESTARTSYS; |
| break; |
| } |
| |
| if (do_wakeup) { |
| wake_up_interruptible_sync(PIPE_WAIT(*inode)); |
| kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, |
| POLL_IN); |
| do_wakeup = 0; |
| } |
| |
| PIPE_WAITING_WRITERS(*inode)++; |
| pipe_wait(inode); |
| PIPE_WAITING_WRITERS(*inode)--; |
| } |
| |
| mutex_unlock(PIPE_MUTEX(*inode)); |
| |
| if (do_wakeup) { |
| wake_up_interruptible(PIPE_WAIT(*inode)); |
| kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, POLL_IN); |
| } |
| |
| while (i < nr_pages) |
| page_cache_release(pages[i++]); |
| |
| return ret; |
| } |
| |
| static int __generic_file_splice_read(struct file *in, struct inode *pipe, |
| size_t len, unsigned int flags) |
| { |
| struct address_space *mapping = in->f_mapping; |
| unsigned int offset, nr_pages; |
| struct page *pages[PIPE_BUFFERS], *shadow[PIPE_BUFFERS]; |
| struct page *page; |
| pgoff_t index, pidx; |
| int i, j; |
| |
| index = in->f_pos >> PAGE_CACHE_SHIFT; |
| offset = in->f_pos & ~PAGE_CACHE_MASK; |
| nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; |
| |
| if (nr_pages > PIPE_BUFFERS) |
| nr_pages = PIPE_BUFFERS; |
| |
| /* |
| * initiate read-ahead on this page range |
| */ |
| do_page_cache_readahead(mapping, in, index, nr_pages); |
| |
| /* |
| * Get as many pages from the page cache as possible.. |
| * Start IO on the page cache entries we create (we |
| * can assume that any pre-existing ones we find have |
| * already had IO started on them). |
| */ |
| i = find_get_pages(mapping, index, nr_pages, pages); |
| |
| /* |
| * common case - we found all pages and they are contiguous, |
| * kick them off |
| */ |
| if (i && (pages[i - 1]->index == index + i - 1)) |
| goto splice_them; |
| |
| /* |
| * fill shadow[] with pages at the right locations, so we only |
| * have to fill holes |
| */ |
| memset(shadow, 0, nr_pages * sizeof(struct page *)); |
| for (j = 0; j < i; j++) |
| shadow[pages[j]->index - index] = pages[j]; |
| |
| /* |
| * now fill in the holes |
| */ |
| for (i = 0, pidx = index; i < nr_pages; pidx++, i++) { |
| int error; |
| |
| if (shadow[i]) |
| continue; |
| |
| /* |
| * no page there, look one up / create it |
| */ |
| page = find_or_create_page(mapping, pidx, |
| mapping_gfp_mask(mapping)); |
| if (!page) |
| break; |
| |
| if (PageUptodate(page)) |
| unlock_page(page); |
| else { |
| error = mapping->a_ops->readpage(in, page); |
| |
| if (unlikely(error)) { |
| page_cache_release(page); |
| break; |
| } |
| } |
| shadow[i] = page; |
| } |
| |
| if (!i) { |
| for (i = 0; i < nr_pages; i++) { |
| if (shadow[i]) |
| page_cache_release(shadow[i]); |
| } |
| return 0; |
| } |
| |
| memcpy(pages, shadow, i * sizeof(struct page *)); |
| |
| /* |
| * Now we splice them into the pipe.. |
| */ |
| splice_them: |
| return move_to_pipe(pipe, pages, i, offset, len, flags); |
| } |
| |
| /** |
| * generic_file_splice_read - splice data from file to a pipe |
| * @in: file to splice from |
| * @pipe: pipe to splice to |
| * @len: number of bytes to splice |
| * @flags: splice modifier flags |
| * |
| * Will read pages from given file and fill them into a pipe. |
| * |
| */ |
| ssize_t generic_file_splice_read(struct file *in, struct inode *pipe, |
| size_t len, unsigned int flags) |
| { |
| ssize_t spliced; |
| int ret; |
| |
| ret = 0; |
| spliced = 0; |
| while (len) { |
| ret = __generic_file_splice_read(in, pipe, len, flags); |
| |
| if (ret <= 0) |
| break; |
| |
| in->f_pos += ret; |
| len -= ret; |
| spliced += ret; |
| |
| if (!(flags & SPLICE_F_NONBLOCK)) |
| continue; |
| ret = -EAGAIN; |
| break; |
| } |
| |
| if (spliced) |
| return spliced; |
| |
| return ret; |
| } |
| |
| /* |
| * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos' |
| * using sendpage(). |
| */ |
| static int pipe_to_sendpage(struct pipe_inode_info *info, |
| struct pipe_buffer *buf, struct splice_desc *sd) |
| { |
| struct file *file = sd->file; |
| loff_t pos = sd->pos; |
| unsigned int offset; |
| ssize_t ret; |
| void *ptr; |
| int more; |
| |
| /* |
| * sub-optimal, but we are limited by the pipe ->map. we don't |
| * need a kmap'ed buffer here, we just want to make sure we |
| * have the page pinned if the pipe page originates from the |
| * page cache |
| */ |
| ptr = buf->ops->map(file, info, buf); |
| if (IS_ERR(ptr)) |
| return PTR_ERR(ptr); |
| |
| offset = pos & ~PAGE_CACHE_MASK; |
| more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len; |
| |
| ret = file->f_op->sendpage(file, buf->page, offset, sd->len, &pos,more); |
| |
| buf->ops->unmap(info, buf); |
| if (ret == sd->len) |
| return 0; |
| |
| return -EIO; |
| } |
| |
| /* |
| * This is a little more tricky than the file -> pipe splicing. There are |
| * basically three cases: |
| * |
| * - Destination page already exists in the address space and there |
| * are users of it. For that case we have no other option that |
| * copying the data. Tough luck. |
| * - Destination page already exists in the address space, but there |
| * are no users of it. Make sure it's uptodate, then drop it. Fall |
| * through to last case. |
| * - Destination page does not exist, we can add the pipe page to |
| * the page cache and avoid the copy. |
| * |
| * If asked to move pages to the output file (SPLICE_F_MOVE is set in |
| * sd->flags), we attempt to migrate pages from the pipe to the output |
| * file address space page cache. This is possible if no one else has |
| * the pipe page referenced outside of the pipe and page cache. If |
| * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create |
| * a new page in the output file page cache and fill/dirty that. |
| */ |
| static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf, |
| struct splice_desc *sd) |
| { |
| struct file *file = sd->file; |
| struct address_space *mapping = file->f_mapping; |
| unsigned int offset; |
| struct page *page; |
| pgoff_t index; |
| char *src; |
| int ret, stolen; |
| |
| /* |
| * after this, page will be locked and unmapped |
| */ |
| src = buf->ops->map(file, info, buf); |
| if (IS_ERR(src)) |
| return PTR_ERR(src); |
| |
| index = sd->pos >> PAGE_CACHE_SHIFT; |
| offset = sd->pos & ~PAGE_CACHE_MASK; |
| stolen = 0; |
| |
| /* |
| * reuse buf page, if SPLICE_F_MOVE is set |
| */ |
| if (sd->flags & SPLICE_F_MOVE) { |
| /* |
| * If steal succeeds, buf->page is now pruned from the vm |
| * side (LRU and page cache) and we can reuse it. |
| */ |
| if (buf->ops->steal(info, buf)) |
| goto find_page; |
| |
| page = buf->page; |
| stolen = 1; |
| if (add_to_page_cache_lru(page, mapping, index, |
| mapping_gfp_mask(mapping))) |
| goto find_page; |
| } else { |
| find_page: |
| ret = -ENOMEM; |
| page = find_or_create_page(mapping, index, |
| mapping_gfp_mask(mapping)); |
| if (!page) |
| goto out; |
| |
| /* |
| * If the page is uptodate, it is also locked. If it isn't |
| * uptodate, we can mark it uptodate if we are filling the |
| * full page. Otherwise we need to read it in first... |
| */ |
| if (!PageUptodate(page)) { |
| if (sd->len < PAGE_CACHE_SIZE) { |
| ret = mapping->a_ops->readpage(file, page); |
| if (unlikely(ret)) |
| goto out; |
| |
| lock_page(page); |
| |
| if (!PageUptodate(page)) { |
| /* |
| * page got invalidated, repeat |
| */ |
| if (!page->mapping) { |
| unlock_page(page); |
| page_cache_release(page); |
| goto find_page; |
| } |
| ret = -EIO; |
| goto out; |
| } |
| } else { |
| WARN_ON(!PageLocked(page)); |
| SetPageUptodate(page); |
| } |
| } |
| } |
| |
| ret = mapping->a_ops->prepare_write(file, page, 0, sd->len); |
| if (ret == AOP_TRUNCATED_PAGE) { |
| page_cache_release(page); |
| goto find_page; |
| } else if (ret) |
| goto out; |
| |
| if (!stolen) { |
| char *dst = kmap_atomic(page, KM_USER0); |
| |
| memcpy(dst + offset, src + buf->offset, sd->len); |
| flush_dcache_page(page); |
| kunmap_atomic(dst, KM_USER0); |
| } |
| |
| ret = mapping->a_ops->commit_write(file, page, 0, sd->len); |
| if (ret == AOP_TRUNCATED_PAGE) { |
| page_cache_release(page); |
| goto find_page; |
| } else if (ret) |
| goto out; |
| |
| balance_dirty_pages_ratelimited(mapping); |
| out: |
| if (!stolen) { |
| page_cache_release(page); |
| unlock_page(page); |
| } |
| buf->ops->unmap(info, buf); |
| return ret; |
| } |
| |
| typedef int (splice_actor)(struct pipe_inode_info *, struct pipe_buffer *, |
| struct splice_desc *); |
| |
| /* |
| * Pipe input worker. Most of this logic works like a regular pipe, the |
| * key here is the 'actor' worker passed in that actually moves the data |
| * to the wanted destination. See pipe_to_file/pipe_to_sendpage above. |
| */ |
| static ssize_t move_from_pipe(struct inode *inode, struct file *out, |
| size_t len, unsigned int flags, |
| splice_actor *actor) |
| { |
| struct pipe_inode_info *info; |
| int ret, do_wakeup, err; |
| struct splice_desc sd; |
| |
| ret = 0; |
| do_wakeup = 0; |
| |
| sd.total_len = len; |
| sd.flags = flags; |
| sd.file = out; |
| sd.pos = out->f_pos; |
| |
| mutex_lock(PIPE_MUTEX(*inode)); |
| |
| info = inode->i_pipe; |
| for (;;) { |
| int bufs = info->nrbufs; |
| |
| if (bufs) { |
| int curbuf = info->curbuf; |
| struct pipe_buffer *buf = info->bufs + curbuf; |
| struct pipe_buf_operations *ops = buf->ops; |
| |
| sd.len = buf->len; |
| if (sd.len > sd.total_len) |
| sd.len = sd.total_len; |
| |
| err = actor(info, buf, &sd); |
| if (err) { |
| if (!ret && err != -ENODATA) |
| ret = err; |
| |
| break; |
| } |
| |
| ret += sd.len; |
| buf->offset += sd.len; |
| buf->len -= sd.len; |
| if (!buf->len) { |
| buf->ops = NULL; |
| ops->release(info, buf); |
| curbuf = (curbuf + 1) & (PIPE_BUFFERS - 1); |
| info->curbuf = curbuf; |
| info->nrbufs = --bufs; |
| do_wakeup = 1; |
| } |
| |
| sd.pos += sd.len; |
| sd.total_len -= sd.len; |
| if (!sd.total_len) |
| break; |
| } |
| |
| if (bufs) |
| continue; |
| if (!PIPE_WRITERS(*inode)) |
| break; |
| if (!PIPE_WAITING_WRITERS(*inode)) { |
| if (ret) |
| break; |
| } |
| |
| if (flags & SPLICE_F_NONBLOCK) { |
| if (!ret) |
| ret = -EAGAIN; |
| break; |
| } |
| |
| if (signal_pending(current)) { |
| if (!ret) |
| ret = -ERESTARTSYS; |
| break; |
| } |
| |
| if (do_wakeup) { |
| wake_up_interruptible_sync(PIPE_WAIT(*inode)); |
| kill_fasync(PIPE_FASYNC_WRITERS(*inode),SIGIO,POLL_OUT); |
| do_wakeup = 0; |
| } |
| |
| pipe_wait(inode); |
| } |
| |
| mutex_unlock(PIPE_MUTEX(*inode)); |
| |
| if (do_wakeup) { |
| wake_up_interruptible(PIPE_WAIT(*inode)); |
| kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT); |
| } |
| |
| mutex_lock(&out->f_mapping->host->i_mutex); |
| out->f_pos = sd.pos; |
| mutex_unlock(&out->f_mapping->host->i_mutex); |
| return ret; |
| |
| } |
| |
| /** |
| * generic_file_splice_write - splice data from a pipe to a file |
| * @inode: pipe inode |
| * @out: file to write to |
| * @len: number of bytes to splice |
| * @flags: splice modifier flags |
| * |
| * Will either move or copy pages (determined by @flags options) from |
| * the given pipe inode to the given file. |
| * |
| */ |
| ssize_t generic_file_splice_write(struct inode *inode, struct file *out, |
| size_t len, unsigned int flags) |
| { |
| struct address_space *mapping = out->f_mapping; |
| ssize_t ret = move_from_pipe(inode, out, len, flags, pipe_to_file); |
| |
| /* |
| * if file or inode is SYNC and we actually wrote some data, sync it |
| */ |
| if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(mapping->host)) |
| && ret > 0) { |
| struct inode *inode = mapping->host; |
| int err; |
| |
| mutex_lock(&inode->i_mutex); |
| err = generic_osync_inode(mapping->host, mapping, |
| OSYNC_METADATA|OSYNC_DATA); |
| mutex_unlock(&inode->i_mutex); |
| |
| if (err) |
| ret = err; |
| } |
| |
| return ret; |
| } |
| |
| /** |
| * generic_splice_sendpage - splice data from a pipe to a socket |
| * @inode: pipe inode |
| * @out: socket to write to |
| * @len: number of bytes to splice |
| * @flags: splice modifier flags |
| * |
| * Will send @len bytes from the pipe to a network socket. No data copying |
| * is involved. |
| * |
| */ |
| ssize_t generic_splice_sendpage(struct inode *inode, struct file *out, |
| size_t len, unsigned int flags) |
| { |
| return move_from_pipe(inode, out, len, flags, pipe_to_sendpage); |
| } |
| |
| EXPORT_SYMBOL(generic_file_splice_write); |
| EXPORT_SYMBOL(generic_file_splice_read); |
| |
| /* |
| * Attempt to initiate a splice from pipe to file. |
| */ |
| static long do_splice_from(struct inode *pipe, struct file *out, size_t len, |
| unsigned int flags) |
| { |
| loff_t pos; |
| int ret; |
| |
| if (!out->f_op || !out->f_op->splice_write) |
| return -EINVAL; |
| |
| if (!(out->f_mode & FMODE_WRITE)) |
| return -EBADF; |
| |
| pos = out->f_pos; |
| ret = rw_verify_area(WRITE, out, &pos, len); |
| if (unlikely(ret < 0)) |
| return ret; |
| |
| return out->f_op->splice_write(pipe, out, len, flags); |
| } |
| |
| /* |
| * Attempt to initiate a splice from a file to a pipe. |
| */ |
| static long do_splice_to(struct file *in, struct inode *pipe, size_t len, |
| unsigned int flags) |
| { |
| loff_t pos, isize, left; |
| int ret; |
| |
| if (!in->f_op || !in->f_op->splice_read) |
| return -EINVAL; |
| |
| if (!(in->f_mode & FMODE_READ)) |
| return -EBADF; |
| |
| pos = in->f_pos; |
| ret = rw_verify_area(READ, in, &pos, len); |
| if (unlikely(ret < 0)) |
| return ret; |
| |
| isize = i_size_read(in->f_mapping->host); |
| if (unlikely(in->f_pos >= isize)) |
| return 0; |
| |
| left = isize - in->f_pos; |
| if (left < len) |
| len = left; |
| |
| return in->f_op->splice_read(in, pipe, len, flags); |
| } |
| |
| /* |
| * Determine where to splice to/from. |
| */ |
| static long do_splice(struct file *in, struct file *out, size_t len, |
| unsigned int flags) |
| { |
| struct inode *pipe; |
| |
| pipe = in->f_dentry->d_inode; |
| if (pipe->i_pipe) |
| return do_splice_from(pipe, out, len, flags); |
| |
| pipe = out->f_dentry->d_inode; |
| if (pipe->i_pipe) |
| return do_splice_to(in, pipe, len, flags); |
| |
| return -EINVAL; |
| } |
| |
| asmlinkage long sys_splice(int fdin, int fdout, size_t len, unsigned int flags) |
| { |
| long error; |
| struct file *in, *out; |
| int fput_in, fput_out; |
| |
| if (unlikely(!len)) |
| return 0; |
| |
| error = -EBADF; |
| in = fget_light(fdin, &fput_in); |
| if (in) { |
| if (in->f_mode & FMODE_READ) { |
| out = fget_light(fdout, &fput_out); |
| if (out) { |
| if (out->f_mode & FMODE_WRITE) |
| error = do_splice(in, out, len, flags); |
| fput_light(out, fput_out); |
| } |
| } |
| |
| fput_light(in, fput_in); |
| } |
| |
| return error; |
| } |