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Date: Wed, 14 Sep 2016 10:37:14 +0200
From: Miklos Szeredi <mszeredi@...hat.com>
To: linux-fsdevel@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>
Subject: [PATCH 09/11] splice: use get_page_for_read()
What __generic_file_splice_read() does is get a series of uptodate pages
and put them into the pipe buffer.
The get_page_for_read() helper can now be used to get the pages,
simplifying the code and making sure the splice(2) stays in sync with
read(2).
For example get_page_for_read() can handle partially uptodate pages and now
splice can take advantage of these as well.
Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
---
fs/splice.c | 169 +++++-------------------------------------------------------
1 file changed, 12 insertions(+), 157 deletions(-)
diff --git a/fs/splice.c b/fs/splice.c
index dc4648ba6e8d..e7757b363b6c 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -265,14 +265,12 @@ __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;
+ pgoff_t index;
+ int error;
struct splice_pipe_desc spd = {
.pages = pages,
.partial = partial,
@@ -290,168 +288,25 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
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;
+ while (spd.nr_pages < nr_pages && len) {
+ long ret;
- 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)
+ ret = get_page_for_read(in, loff, len, index, &page);
+ if (ret <= 0) {
+ error = ret;
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.pages[spd.nr_pages] = page;
+ spd.partial[spd.nr_pages].offset = loff;
+ spd.partial[spd.nr_pages].len = ret;
spd.nr_pages++;
index++;
+ len -= ret;
+ loff = 0;
}
- /*
- * 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)
--
2.5.5
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