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authorMiklos Szeredi <miklos@szeredi.hu>2009-05-07 15:37:36 +0200
committerJens Axboe <jens.axboe@oracle.com>2009-05-11 14:13:10 +0200
commit6818173bd658439b83896a2a7586f64ab51bf29c (patch)
tree17d25ee77485af18da1a80cb7f1d8ec581c6abfc /fs/splice.c
parent7c77f0b3f9208c339a4b40737bb2cb0f0319bb8d (diff)
downloadlinux-6818173bd658439b83896a2a7586f64ab51bf29c.tar.bz2
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 <mszeredi@suse.cz> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'fs/splice.c')
-rw-r--r--fs/splice.c120
1 files changed, 115 insertions, 5 deletions
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);
}
/**