From 912d35f86781e64d73be1ef358f703c08905ac37 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Wed, 26 Apr 2006 10:59:21 +0200 Subject: [PATCH] Add support for the sys_vmsplice syscall sys_splice() moves data to/from pipes with a file input/output. sys_vmsplice() moves data to a pipe, with the input being a user address range instead. This uses an approach suggested by Linus, where we can hold partial ranges inside the pages[] map. Hopefully this will be useful for network receive support as well. Signed-off-by: Jens Axboe --- fs/splice.c | 292 ++++++++++++++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 253 insertions(+), 39 deletions(-) (limited to 'fs/splice.c') diff --git a/fs/splice.c b/fs/splice.c index 8c6030c762e2..0b2c1f060cae 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -27,6 +27,7 @@ #include #include #include +#include /* * Passed to the actors @@ -38,6 +39,22 @@ struct splice_desc { loff_t pos; /* file position */ }; +struct partial_page { + unsigned int offset; + unsigned int len; +}; + +/* + * Passed to move_to_pipe + */ +struct splice_pipe_desc { + struct page **pages; /* page map */ + struct partial_page *partial; /* pages[] may not be contig */ + int nr_pages; /* number of pages in map */ + unsigned int flags; /* splice flags */ + struct pipe_buf_operations *ops;/* ops associated with output pipe */ +}; + /* * 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 @@ -128,6 +145,19 @@ static void page_cache_pipe_buf_unmap(struct pipe_inode_info *info, kunmap(buf->page); } +static void *user_page_pipe_buf_map(struct file *file, + struct pipe_inode_info *pipe, + struct pipe_buffer *buf) +{ + return kmap(buf->page); +} + +static void user_page_pipe_buf_unmap(struct pipe_inode_info *pipe, + struct pipe_buffer *buf) +{ + kunmap(buf->page); +} + static void page_cache_pipe_buf_get(struct pipe_inode_info *info, struct pipe_buffer *buf) { @@ -143,19 +173,33 @@ static struct pipe_buf_operations page_cache_pipe_buf_ops = { .get = page_cache_pipe_buf_get, }; +static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe, + struct pipe_buffer *buf) +{ + return 1; +} + +static struct pipe_buf_operations user_page_pipe_buf_ops = { + .can_merge = 0, + .map = user_page_pipe_buf_map, + .unmap = user_page_pipe_buf_unmap, + .release = page_cache_pipe_buf_release, + .steal = user_page_pipe_buf_steal, + .get = page_cache_pipe_buf_get, +}; + /* * 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 pipe_inode_info *pipe, struct page **pages, - int nr_pages, unsigned long len, - unsigned int offset, unsigned int flags) +static ssize_t move_to_pipe(struct pipe_inode_info *pipe, + struct splice_pipe_desc *spd) { - int ret, do_wakeup, i; + int ret, do_wakeup, page_nr; ret = 0; do_wakeup = 0; - i = 0; + page_nr = 0; if (pipe->inode) mutex_lock(&pipe->inode->i_mutex); @@ -171,27 +215,19 @@ static ssize_t move_to_pipe(struct pipe_inode_info *pipe, struct page **pages, if (pipe->nrbufs < PIPE_BUFFERS) { int newbuf = (pipe->curbuf + pipe->nrbufs) & (PIPE_BUFFERS - 1); struct pipe_buffer *buf = pipe->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; + buf->page = spd->pages[page_nr]; + buf->offset = spd->partial[page_nr].offset; + buf->len = spd->partial[page_nr].len; + buf->ops = spd->ops; pipe->nrbufs++; + page_nr++; + ret += buf->len; + if (pipe->inode) do_wakeup = 1; - ret += this_len; - len -= this_len; - offset = 0; - if (!--nr_pages) - break; - if (!len) + if (!--spd->nr_pages) break; if (pipe->nrbufs < PIPE_BUFFERS) continue; @@ -199,7 +235,7 @@ static ssize_t move_to_pipe(struct pipe_inode_info *pipe, struct page **pages, break; } - if (flags & SPLICE_F_NONBLOCK) { + if (spd->flags & SPLICE_F_NONBLOCK) { if (!ret) ret = -EAGAIN; break; @@ -234,8 +270,8 @@ static ssize_t move_to_pipe(struct pipe_inode_info *pipe, struct page **pages, kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); } - while (i < nr_pages) - page_cache_release(pages[i++]); + while (page_nr < spd->nr_pages) + page_cache_release(spd->pages[page_nr++]); return ret; } @@ -246,17 +282,24 @@ __generic_file_splice_read(struct file *in, loff_t *ppos, unsigned int flags) { struct address_space *mapping = in->f_mapping; - unsigned int loff, offset, nr_pages; + unsigned int loff, nr_pages; struct page *pages[PIPE_BUFFERS]; + struct partial_page partial[PIPE_BUFFERS]; struct page *page; pgoff_t index, end_index; loff_t isize; - size_t bytes; - int i, error; + size_t total_len; + int error; + struct splice_pipe_desc spd = { + .pages = pages, + .partial = partial, + .flags = flags, + .ops = &page_cache_pipe_buf_ops, + }; index = *ppos >> PAGE_CACHE_SHIFT; - loff = offset = *ppos & ~PAGE_CACHE_MASK; - nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; + loff = *ppos & ~PAGE_CACHE_MASK; + nr_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; if (nr_pages > PIPE_BUFFERS) nr_pages = PIPE_BUFFERS; @@ -266,15 +309,15 @@ __generic_file_splice_read(struct file *in, loff_t *ppos, * read-ahead if this is a non-zero offset (we are likely doing small * chunk splice and the page is already there) for a single page. */ - if (!offset || nr_pages > 1) - do_page_cache_readahead(mapping, in, index, nr_pages); + if (!loff || spd.nr_pages > 1) + do_page_cache_readahead(mapping, in, index, spd.nr_pages); /* * Now fill in the holes: */ error = 0; - bytes = 0; - for (i = 0; i < nr_pages; i++, index++) { + total_len = 0; + for (spd.nr_pages = 0; spd.nr_pages < nr_pages; spd.nr_pages++, index++) { unsigned int this_len; if (!len) @@ -367,26 +410,29 @@ readpage: */ if (end_index == index) { loff = PAGE_CACHE_SIZE - (isize & ~PAGE_CACHE_MASK); - if (bytes + loff > isize) { + if (total_len + loff > isize) { page_cache_release(page); break; } /* * force quit after adding this page */ - nr_pages = i; + nr_pages = spd.nr_pages; this_len = min(this_len, loff); + loff = 0; } } fill_it: - pages[i] = page; - bytes += this_len; + pages[spd.nr_pages] = page; + partial[spd.nr_pages].offset = loff; + partial[spd.nr_pages].len = this_len; len -= this_len; + total_len += this_len; loff = 0; } - if (i) - return move_to_pipe(pipe, pages, i, bytes, offset, flags); + if (spd.nr_pages) + return move_to_pipe(pipe, &spd); return error; } @@ -1018,6 +1064,174 @@ static long do_splice(struct file *in, loff_t __user *off_in, return -EINVAL; } +/* + * Map an iov into an array of pages and offset/length tupples. With the + * partial_page structure, we can map several non-contiguous ranges into + * our ones pages[] map instead of splitting that operation into pieces. + * Could easily be exported as a generic helper for other users, in which + * case one would probably want to add a 'max_nr_pages' parameter as well. + */ +static int get_iovec_page_array(const struct iovec __user *iov, + unsigned int nr_vecs, struct page **pages, + struct partial_page *partial) +{ + int buffers = 0, error = 0; + + /* + * It's ok to take the mmap_sem for reading, even + * across a "get_user()". + */ + down_read(¤t->mm->mmap_sem); + + while (nr_vecs) { + unsigned long off, npages; + void __user *base; + size_t len; + int i; + + /* + * Get user address base and length for this iovec. + */ + error = get_user(base, &iov->iov_base); + if (unlikely(error)) + break; + error = get_user(len, &iov->iov_len); + if (unlikely(error)) + break; + + /* + * Sanity check this iovec. 0 read succeeds. + */ + if (unlikely(!len)) + break; + error = -EFAULT; + if (unlikely(!base)) + break; + + /* + * Get this base offset and number of pages, then map + * in the user pages. + */ + off = (unsigned long) base & ~PAGE_MASK; + npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT; + if (npages > PIPE_BUFFERS - buffers) + npages = PIPE_BUFFERS - buffers; + + error = get_user_pages(current, current->mm, + (unsigned long) base, npages, 0, 0, + &pages[buffers], NULL); + + if (unlikely(error <= 0)) + break; + + /* + * Fill this contiguous range into the partial page map. + */ + for (i = 0; i < error; i++) { + const int plen = min_t(size_t, len, PAGE_SIZE) - off; + + partial[buffers].offset = off; + partial[buffers].len = plen; + + off = 0; + len -= plen; + buffers++; + } + + /* + * We didn't complete this iov, stop here since it probably + * means we have to move some of this into a pipe to + * be able to continue. + */ + if (len) + break; + + /* + * Don't continue if we mapped fewer pages than we asked for, + * or if we mapped the max number of pages that we have + * room for. + */ + if (error < npages || buffers == PIPE_BUFFERS) + break; + + nr_vecs--; + iov++; + } + + up_read(¤t->mm->mmap_sem); + + if (buffers) + return buffers; + + return error; +} + +/* + * vmsplice splices a user address range into a pipe. It can be thought of + * as splice-from-memory, where the regular splice is splice-from-file (or + * to file). In both cases the output is a pipe, naturally. + * + * Note that vmsplice only supports splicing _from_ user memory to a pipe, + * not the other way around. Splicing from user memory is a simple operation + * that can be supported without any funky alignment restrictions or nasty + * vm tricks. We simply map in the user memory and fill them into a pipe. + * The reverse isn't quite as easy, though. There are two possible solutions + * for that: + * + * - memcpy() the data internally, at which point we might as well just + * do a regular read() on the buffer anyway. + * - Lots of nasty vm tricks, that are neither fast nor flexible (it + * has restriction limitations on both ends of the pipe). + * + * Alas, it isn't here. + * + */ +static long do_vmsplice(struct file *file, const struct iovec __user *iov, + unsigned long nr_segs, unsigned int flags) +{ + struct pipe_inode_info *pipe = file->f_dentry->d_inode->i_pipe; + struct page *pages[PIPE_BUFFERS]; + struct partial_page partial[PIPE_BUFFERS]; + struct splice_pipe_desc spd = { + .pages = pages, + .partial = partial, + .flags = flags, + .ops = &user_page_pipe_buf_ops, + }; + + if (unlikely(!pipe)) + return -EBADF; + if (unlikely(nr_segs > UIO_MAXIOV)) + return -EINVAL; + else if (unlikely(!nr_segs)) + return 0; + + spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial); + if (spd.nr_pages <= 0) + return spd.nr_pages; + + return move_to_pipe(pipe, &spd); +} + +asmlinkage long sys_vmsplice(int fd, const struct iovec __user *iov, + unsigned long nr_segs, unsigned int flags) +{ + struct file *file; + long error; + int fput; + + error = -EBADF; + file = fget_light(fd, &fput); + if (file) { + if (file->f_mode & FMODE_WRITE) + error = do_vmsplice(file, iov, nr_segs, flags); + + fput_light(file, fput); + } + + return error; +} + asmlinkage long sys_splice(int fd_in, loff_t __user *off_in, int fd_out, loff_t __user *off_out, size_t len, unsigned int flags) -- cgit v1.2.3