diff options
Diffstat (limited to 'fs/splice.c')
| -rw-r--r-- | fs/splice.c | 612 |
1 files changed, 612 insertions, 0 deletions
diff --git a/fs/splice.c b/fs/splice.c new file mode 100644 index 000000000000..efa47c1c4e13 --- /dev/null +++ b/fs/splice.c @@ -0,0 +1,612 @@ +/* + * "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> + +/* + * 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 */ +}; + +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, +}; + +static ssize_t move_to_pipe(struct inode *inode, struct page **pages, + int nr_pages, unsigned long offset, + unsigned long len) +{ + 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 (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) +{ + 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, i * sizeof(struct page *)); + for (j = 0, pidx = index; j < i; pidx++, j++) + shadow[pages[j]->index - pidx] = 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); +} + +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); + + if (ret <= 0) + break; + + in->f_pos += ret; + len -= ret; + spliced += ret; + } + + if (spliced) + return spliced; + + return ret; +} + +/* + * Send 'len' bytes to socket from 'file' at position '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; + + /* + * 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; + + ret = file->f_op->sendpage(file, buf->page, offset, sd->len, &pos, + sd->len < sd->total_len); + + 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. + * + * For now we just do the slower thing and always copy pages over, it's + * easier than migrating pages from the pipe to the target file. For the + * case of doing file | file splicing, the migrate approach had some LRU + * nastiness... + */ +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; + char *src, *dst; + pgoff_t index; + int ret; + + /* + * 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; + +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) + goto out; + + 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 < 0) + goto out; + + set_page_dirty(page); + ret = write_one_page(page, 0); +out: + if (ret < 0) + unlock_page(page); + page_cache_release(page); + buf->ops->unmap(info, buf); + return ret; +} + +typedef int (splice_actor)(struct pipe_inode_info *, struct pipe_buffer *, + struct splice_desc *); + +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 (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; + +} + +ssize_t generic_file_splice_write(struct inode *inode, struct file *out, + size_t len, unsigned int flags) +{ + return move_from_pipe(inode, out, len, flags, pipe_to_file); +} + +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); +} + +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); +} + +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); +} + +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; +} |