brain-hackers_pepepper-mirror/linux-brain
1
0
Fork 0
mirror of https://github.com/brain-hackers/linux-brain.git synced 2024-06-09 15:26:21 +09:00
Code Issues Projects Releases Wiki Activity

switch default_file_splice_read() to use of pipe-backed iov_iter

Browse Source 
we only use iov_iter_get_pages_alloc() and iov_iter_advance() -
pages are filled by kernel_readv() via a kvec array (as we used
to do all along), so iov_iter here is used only as a way of
arranging for those pages to be in pipe.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2016-09-23 15:34:57 -04:00
parent 82c156f853
commit 523ac9afc7
1 changed files with 40 additions and 71 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

111
fs/splice.c
View File

@ -361,7 +361,7 @@ const struct pipe_buf_operations nosteal_pipe_buf_ops = {
};
EXPORT_SYMBOL(nosteal_pipe_buf_ops);
static ssize_t kernel_readv(struct file *file, const struct iovec *vec,
static ssize_t kernel_readv(struct file *file, const struct kvec *vec,
unsigned long vlen, loff_t offset)
{
mm_segment_t old_fs;
@ -397,96 +397,65 @@ static ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len,
unsigned int flags)
{
struct kvec *vec, __vec[PIPE_DEF_BUFFERS];
struct iov_iter to;
struct page **pages;
unsigned int nr_pages;
unsigned int nr_freed;
size_t offset;
struct page *pages[PIPE_DEF_BUFFERS];
struct partial_page partial[PIPE_DEF_BUFFERS];
struct iovec *vec, __vec[PIPE_DEF_BUFFERS];
size_t offset, dummy, copied = 0;
ssize_t res;
size_t this_len;
int error;
int i;
struct splice_pipe_desc spd = {
.pages = pages,
.partial = partial,
.nr_pages_max = PIPE_DEF_BUFFERS,
.flags = flags,
.ops = &default_pipe_buf_ops,
.spd_release = spd_release_page,
};
if (splice_grow_spd(pipe, &spd))
if (pipe->nrbufs == pipe->buffers)
return -EAGAIN;
/*
* Try to keep page boundaries matching to source pagecache ones -
* it probably won't be much help, but...
*/
offset = *ppos & ~PAGE_MASK;
iov_iter_pipe(&to, ITER_PIPE | READ, pipe, len + offset);
res = iov_iter_get_pages_alloc(&to, &pages, len + offset, &dummy);
if (res <= 0)
return -ENOMEM;
res = -ENOMEM;
nr_pages = res / PAGE_SIZE;
vec = __vec;
if (spd.nr_pages_max > PIPE_DEF_BUFFERS) {
vec = kmalloc(spd.nr_pages_max * sizeof(struct iovec), GFP_KERNEL);
if (!vec)
goto shrink_ret;
if (nr_pages > PIPE_DEF_BUFFERS) {
vec = kmalloc(nr_pages * sizeof(struct kvec), GFP_KERNEL);
if (unlikely(!vec)) {
res = -ENOMEM;
goto out;
}
}
offset = *ppos & ~PAGE_MASK;
nr_pages = (len + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
pipe->bufs[to.idx].offset = offset;
pipe->bufs[to.idx].len -= offset;
for (i = 0; i < nr_pages && i < spd.nr_pages_max && len; i++) {
struct page *page;
page = alloc_page(GFP_USER);
error = -ENOMEM;
if (!page)
goto err;
this_len = min_t(size_t, len, PAGE_SIZE - offset);
vec[i].iov_base = (void __user *) page_address(page);
for (i = 0; i < nr_pages; i++) {
size_t this_len = min_t(size_t, len, PAGE_SIZE - offset);
vec[i].iov_base = page_address(pages[i]) + offset;
vec[i].iov_len = this_len;
spd.pages[i] = page;
spd.nr_pages++;
len -= this_len;
offset = 0;
}
res = kernel_readv(in, vec, spd.nr_pages, *ppos);
if (res < 0) {
error = res;
goto err;
}
error = 0;
if (!res)
goto err;
nr_freed = 0;
for (i = 0; i < spd.nr_pages; i++) {
this_len = min_t(size_t, vec[i].iov_len, res);
spd.partial[i].offset = 0;
spd.partial[i].len = this_len;
if (!this_len) {
__free_page(spd.pages[i]);
spd.pages[i] = NULL;
nr_freed++;
}
res -= this_len;
}
spd.nr_pages -= nr_freed;
res = splice_to_pipe(pipe, &spd);
if (res > 0)
res = kernel_readv(in, vec, nr_pages, *ppos);
if (res > 0) {
copied = res;
*ppos += res;
}
shrink_ret:
if (vec != __vec)
kfree(vec);
splice_shrink_spd(&spd);
out:
for (i = 0; i < nr_pages; i++)
put_page(pages[i]);
kvfree(pages);
iov_iter_advance(&to, copied); /* truncates and discards */
return res;
err:
for (i = 0; i < spd.nr_pages; i++)
__free_page(spd.pages[i]);
res = error;
goto shrink_ret;
}
/*