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switch generic_file_splice_read() to use of ->read_iter()

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... and kill the ->splice_read() instances that can be switched to it

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
2016-09-22 23:35:42 -04:00
parent 241699cd72
commit 82c156f853
16 changed files with 58 additions and 605 deletions
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244
fs/splice.c
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@@ -281,207 +281,6 @@ void splice_shrink_spd(struct splice_pipe_desc *spd)
kfree(spd->partial);
}
static int
__generic_file_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len,
unsigned int flags)
{
struct address_space *mapping = in->f_mapping;
unsigned int loff, nr_pages, req_pages;
struct page *pages[PIPE_DEF_BUFFERS];
struct partial_page partial[PIPE_DEF_BUFFERS];
struct page *page;
pgoff_t index, end_index;
loff_t isize;
int error, page_nr;
struct splice_pipe_desc spd = {
.pages = pages,
.partial = partial,
.nr_pages_max = PIPE_DEF_BUFFERS,
.flags = flags,
.ops = &page_cache_pipe_buf_ops,
.spd_release = spd_release_page,
};
if (splice_grow_spd(pipe, &spd))
return -ENOMEM;
index = *ppos >> PAGE_SHIFT;
loff = *ppos & ~PAGE_MASK;
req_pages = (len + loff + PAGE_SIZE - 1) >> PAGE_SHIFT;
nr_pages = min(req_pages, spd.nr_pages_max);
/*
* Lookup the (hopefully) full range of pages we need.
*/
spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, spd.pages);
index += spd.nr_pages;
/*
* If find_get_pages_contig() returned fewer pages than we needed,
* readahead/allocate the rest and fill in the holes.
*/
if (spd.nr_pages < nr_pages)
page_cache_sync_readahead(mapping, &in->f_ra, in,
index, req_pages - spd.nr_pages);
error = 0;
while (spd.nr_pages < nr_pages) {
/*
* Page could be there, find_get_pages_contig() breaks on
* the first hole.
*/
page = find_get_page(mapping, index);
if (!page) {
/*
* page didn't exist, allocate one.
*/
page = page_cache_alloc_cold(mapping);
if (!page)
break;
error = add_to_page_cache_lru(page, mapping, index,
mapping_gfp_constraint(mapping, GFP_KERNEL));
if (unlikely(error)) {
put_page(page);
if (error == -EEXIST)
continue;
break;
}
/*
* add_to_page_cache() locks the page, unlock it
* to avoid convoluting the logic below even more.
*/
unlock_page(page);
}
spd.pages[spd.nr_pages++] = page;
index++;
}
/*
* Now loop over the map and see if we need to start IO on any
* pages, fill in the partial map, etc.
*/
index = *ppos >> PAGE_SHIFT;
nr_pages = spd.nr_pages;
spd.nr_pages = 0;
for (page_nr = 0; page_nr < nr_pages; page_nr++) {
unsigned int this_len;
if (!len)
break;
/*
* this_len is the max we'll use from this page
*/
this_len = min_t(unsigned long, len, PAGE_SIZE - loff);
page = spd.pages[page_nr];
if (PageReadahead(page))
page_cache_async_readahead(mapping, &in->f_ra, in,
page, index, req_pages - page_nr);
/*
* If the page isn't uptodate, we may need to start io on it
*/
if (!PageUptodate(page)) {
lock_page(page);
/*
* Page was truncated, or invalidated by the
* filesystem. Redo the find/create, but this time the
* page is kept locked, so there's no chance of another
* race with truncate/invalidate.
*/
if (!page->mapping) {
unlock_page(page);
retry_lookup:
page = find_or_create_page(mapping, index,
mapping_gfp_mask(mapping));
if (!page) {
error = -ENOMEM;
break;
}
put_page(spd.pages[page_nr]);
spd.pages[page_nr] = page;
}
/*
* page was already under io and is now done, great
*/
if (PageUptodate(page)) {
unlock_page(page);
goto fill_it;
}
/*
* need to read in the page
*/
error = mapping->a_ops->readpage(in, page);
if (unlikely(error)) {
/*
* Re-lookup the page
*/
if (error == AOP_TRUNCATED_PAGE)
goto retry_lookup;
break;
}
}
fill_it:
/*
* i_size must be checked after PageUptodate.
*/
isize = i_size_read(mapping->host);
end_index = (isize - 1) >> PAGE_SHIFT;
if (unlikely(!isize || index > end_index))
break;
/*
* if this is the last page, see if we need to shrink
* the length and stop
*/
if (end_index == index) {
unsigned int plen;
/*
* max good bytes in this page
*/
plen = ((isize - 1) & ~PAGE_MASK) + 1;
if (plen <= loff)
break;
/*
* force quit after adding this page
*/
this_len = min(this_len, plen - loff);
len = this_len;
}
spd.partial[page_nr].offset = loff;
spd.partial[page_nr].len = this_len;
len -= this_len;
loff = 0;
spd.nr_pages++;
index++;
}
/*
* Release any pages at the end, if we quit early. 'page_nr' is how far
* we got, 'nr_pages' is how many pages are in the map.
*/
while (page_nr < nr_pages)
put_page(spd.pages[page_nr++]);
in->f_ra.prev_pos = (loff_t)index << PAGE_SHIFT;
if (spd.nr_pages)
error = splice_to_pipe(pipe, &spd);
splice_shrink_spd(&spd);
return error;
}
/**
* generic_file_splice_read - splice data from file to a pipe
* @in: file to splice from
@@ -492,32 +291,46 @@ fill_it:
*
* Description:
* Will read pages from given file and fill them into a pipe. Can be
* used as long as the address_space operations for the source implements
* a readpage() hook.
* used as long as it has more or less sane ->read_iter().
*
*/
ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len,
unsigned int flags)
{
loff_t isize, left;
int ret;
if (IS_DAX(in->f_mapping->host))
return default_file_splice_read(in, ppos, pipe, len, flags);
struct iov_iter to;
struct kiocb kiocb;
loff_t isize;
int idx, ret;
isize = i_size_read(in->f_mapping->host);
if (unlikely(*ppos >= isize))
return 0;
left = isize - *ppos;
if (unlikely(left < len))
len = left;
ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
iov_iter_pipe(&to, ITER_PIPE | READ, pipe, len);
idx = to.idx;
init_sync_kiocb(&kiocb, in);
kiocb.ki_pos = *ppos;
ret = in->f_op->read_iter(&kiocb, &to);
if (ret > 0) {
*ppos += ret;
*ppos = kiocb.ki_pos;
file_accessed(in);
} else if (ret < 0) {
if (WARN_ON(to.idx != idx || to.iov_offset)) {
/*
* a bogus ->read_iter() has copied something and still
* returned an error instead of a short read.
*/
to.idx = idx;
to.iov_offset = 0;
iov_iter_advance(&to, 0); /* to free what was emitted */
}
/*
* callers of ->splice_read() expect -EAGAIN on
* "can't put anything in there", rather than -EFAULT.
*/
if (ret == -EFAULT)
ret = -EAGAIN;
}
return ret;
@@ -580,7 +393,7 @@ ssize_t kernel_write(struct file *file, const char *buf, size_t count,
}
EXPORT_SYMBOL(kernel_write);
ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
static ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len,
unsigned int flags)
{
@@ -675,7 +488,6 @@ err:
res = error;
goto shrink_ret;
}
EXPORT_SYMBOL(default_file_splice_read);
/*
* Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'