[PATCH] splice: make the read-side do batched page lookups
Use the new find_get_pages_contig() to potentially look up the entire
splice range in one single call. This speeds up generic_file_splice_read()
quite a bit.
Signed-off-by: Jens Axboe <axboe@suse.de>
diff --git a/fs/splice.c b/fs/splice.c
index dc205f6..a46ddd2 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -279,7 +279,7 @@
pgoff_t index, end_index;
loff_t isize;
size_t total_len;
- int error;
+ int error, page_nr;
struct splice_pipe_desc spd = {
.pages = pages,
.partial = partial,
@@ -307,7 +307,56 @@
*/
error = 0;
total_len = 0;
- for (spd.nr_pages = 0; spd.nr_pages < nr_pages; spd.nr_pages++, index++) {
+
+ /*
+ * Lookup the (hopefully) full range of pages we need.
+ */
+ spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages);
+
+ /*
+ * If find_get_pages_contig() returned fewer pages than we needed,
+ * allocate the rest.
+ */
+ index += spd.nr_pages;
+ 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_mask(mapping));
+ if (unlikely(error)) {
+ page_cache_release(page);
+ break;
+ }
+ /*
+ * add_to_page_cache() locks the page, unlock it
+ * to avoid convoluting the logic below even more.
+ */
+ unlock_page(page);
+ }
+
+ 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_CACHE_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)
@@ -317,28 +366,7 @@
* this_len is the max we'll use from this page
*/
this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
-find_page:
- /*
- * lookup the page for this index
- */
- 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_mask(mapping));
- if (unlikely(error)) {
- page_cache_release(page);
- break;
- }
-
- goto readpage;
- }
+ page = pages[page_nr];
/*
* If the page isn't uptodate, we may need to start io on it
@@ -360,7 +388,6 @@
*/
if (!page->mapping) {
unlock_page(page);
- page_cache_release(page);
break;
}
/*
@@ -371,16 +398,20 @@
goto fill_it;
}
-readpage:
/*
* need to read in the page
*/
error = mapping->a_ops->readpage(in, page);
-
if (unlikely(error)) {
- page_cache_release(page);
+ /*
+ * We really should re-lookup the page here,
+ * but it complicates things a lot. Instead
+ * lets just do what we already stored, and
+ * we'll get it the next time we are called.
+ */
if (error == AOP_TRUNCATED_PAGE)
- goto find_page;
+ error = 0;
+
break;
}
@@ -389,10 +420,8 @@
*/
isize = i_size_read(mapping->host);
end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
- if (unlikely(!isize || index > end_index)) {
- page_cache_release(page);
+ if (unlikely(!isize || index > end_index))
break;
- }
/*
* if this is the last page, see if we need to shrink
@@ -400,27 +429,33 @@
*/
if (end_index == index) {
loff = PAGE_CACHE_SIZE - (isize & ~PAGE_CACHE_MASK);
- if (total_len + loff > isize) {
- page_cache_release(page);
+ if (total_len + loff > isize)
break;
- }
/*
* force quit after adding this page
*/
- nr_pages = spd.nr_pages;
+ len = this_len;
this_len = min(this_len, loff);
loff = 0;
}
}
fill_it:
- pages[spd.nr_pages] = page;
- partial[spd.nr_pages].offset = loff;
- partial[spd.nr_pages].len = this_len;
+ partial[page_nr].offset = loff;
+ partial[page_nr].len = this_len;
len -= this_len;
total_len += this_len;
loff = 0;
+ spd.nr_pages++;
+ index++;
}
+ /*
+ * Release any pages at the end, if we quit early. 'i' is how far
+ * we got, 'nr_pages' is how many pages are in the map.
+ */
+ while (page_nr < nr_pages)
+ page_cache_release(pages[page_nr++]);
+
if (spd.nr_pages)
return splice_to_pipe(pipe, &spd);