From 6818173bd658439b83896a2a7586f64ab51bf29c Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Thu, 7 May 2009 15:37:36 +0200 Subject: splice: implement default splice_read method If f_op->splice_read() is not implemented, fall back to a plain read. Use vfs_readv() to read into previously allocated pages. This will allow splice and functions using splice, such as the loop device, to work on all filesystems. This includes "direct_io" files in fuse which bypass the page cache. Signed-off-by: Miklos Szeredi Signed-off-by: Jens Axboe --- fs/splice.c | 120 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 115 insertions(+), 5 deletions(-) (limited to 'fs/splice.c') diff --git a/fs/splice.c b/fs/splice.c index e405cf552f5c..3bd9cb21b38e 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -507,9 +507,116 @@ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos, return ret; } - EXPORT_SYMBOL(generic_file_splice_read); +static const struct pipe_buf_operations default_pipe_buf_ops = { + .can_merge = 0, + .map = generic_pipe_buf_map, + .unmap = generic_pipe_buf_unmap, + .confirm = generic_pipe_buf_confirm, + .release = generic_pipe_buf_release, + .steal = generic_pipe_buf_steal, + .get = generic_pipe_buf_get, +}; + +static ssize_t kernel_readv(struct file *file, const struct iovec *vec, + unsigned long vlen, loff_t offset) +{ + mm_segment_t old_fs; + loff_t pos = offset; + ssize_t res; + + old_fs = get_fs(); + set_fs(get_ds()); + /* The cast to a user pointer is valid due to the set_fs() */ + res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos); + set_fs(old_fs); + + return res; +} + +ssize_t default_file_splice_read(struct file *in, loff_t *ppos, + struct pipe_inode_info *pipe, size_t len, + unsigned int flags) +{ + unsigned int nr_pages; + unsigned int nr_freed; + size_t offset; + struct page *pages[PIPE_BUFFERS]; + struct partial_page partial[PIPE_BUFFERS]; + struct iovec vec[PIPE_BUFFERS]; + pgoff_t index; + ssize_t res; + size_t this_len; + int error; + int i; + struct splice_pipe_desc spd = { + .pages = pages, + .partial = partial, + .flags = flags, + .ops = &default_pipe_buf_ops, + .spd_release = spd_release_page, + }; + + index = *ppos >> PAGE_CACHE_SHIFT; + offset = *ppos & ~PAGE_CACHE_MASK; + nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; + + for (i = 0; i < nr_pages && i < PIPE_BUFFERS && len; i++) { + struct page *page; + + page = alloc_page(GFP_HIGHUSER); + error = -ENOMEM; + if (!page) + goto err; + + this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset); + vec[i].iov_base = (void __user *) kmap(page); + vec[i].iov_len = this_len; + pages[i] = page; + spd.nr_pages++; + len -= this_len; + offset = 0; + } + + res = kernel_readv(in, vec, spd.nr_pages, *ppos); + if (res < 0) + goto err; + + error = 0; + if (!res) + goto err; + + nr_freed = 0; + for (i = 0; i < spd.nr_pages; i++) { + kunmap(pages[i]); + this_len = min_t(size_t, vec[i].iov_len, res); + partial[i].offset = 0; + partial[i].len = this_len; + if (!this_len) { + __free_page(pages[i]); + pages[i] = NULL; + nr_freed++; + } + res -= this_len; + } + spd.nr_pages -= nr_freed; + + res = splice_to_pipe(pipe, &spd); + if (res > 0) + *ppos += res; + + return res; + +err: + for (i = 0; i < spd.nr_pages; i++) { + kunmap(pages[i]); + __free_page(pages[i]); + } + return error; +} +EXPORT_SYMBOL(default_file_splice_read); + /* * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos' * using sendpage(). Return the number of bytes sent. @@ -933,11 +1040,10 @@ static long do_splice_to(struct file *in, loff_t *ppos, struct pipe_inode_info *pipe, size_t len, unsigned int flags) { + ssize_t (*splice_read)(struct file *, loff_t *, + struct pipe_inode_info *, size_t, unsigned int); int ret; - if (unlikely(!in->f_op || !in->f_op->splice_read)) - return -EINVAL; - if (unlikely(!(in->f_mode & FMODE_READ))) return -EBADF; @@ -945,7 +1051,11 @@ static long do_splice_to(struct file *in, loff_t *ppos, if (unlikely(ret < 0)) return ret; - return in->f_op->splice_read(in, ppos, pipe, len, flags); + splice_read = in->f_op->splice_read; + if (!splice_read) + splice_read = default_file_splice_read; + + return splice_read(in, ppos, pipe, len, flags); } /** -- cgit v1.2.3