[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>
This commit is contained in:
Jens Axboe
parent
ebf43500ef
commit
eb20796bf6
113
fs/splice.c
113
fs/splice.c
@ -279,7 +279,7 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
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pgoff_t index, end_index;
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loff_t isize;
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size_t total_len;
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int error;
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int error, page_nr;
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struct splice_pipe_desc spd = {
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.pages = pages,
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.partial = partial,
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@ -307,7 +307,56 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
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*/
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error = 0;
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total_len = 0;
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for (spd.nr_pages = 0; spd.nr_pages < nr_pages; spd.nr_pages++, index++) {
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/*
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* Lookup the (hopefully) full range of pages we need.
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*/
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spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages);
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/*
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* If find_get_pages_contig() returned fewer pages than we needed,
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* allocate the rest.
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*/
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index += spd.nr_pages;
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while (spd.nr_pages < nr_pages) {
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/*
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* Page could be there, find_get_pages_contig() breaks on
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* the first hole.
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*/
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page = find_get_page(mapping, index);
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if (!page) {
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/*
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* page didn't exist, allocate one.
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*/
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page = page_cache_alloc_cold(mapping);
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if (!page)
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break;
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error = add_to_page_cache_lru(page, mapping, index,
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mapping_gfp_mask(mapping));
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if (unlikely(error)) {
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page_cache_release(page);
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break;
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}
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/*
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* add_to_page_cache() locks the page, unlock it
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* to avoid convoluting the logic below even more.
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*/
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unlock_page(page);
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}
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pages[spd.nr_pages++] = page;
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index++;
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}
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/*
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* Now loop over the map and see if we need to start IO on any
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* pages, fill in the partial map, etc.
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*/
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index = *ppos >> PAGE_CACHE_SHIFT;
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nr_pages = spd.nr_pages;
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spd.nr_pages = 0;
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for (page_nr = 0; page_nr < nr_pages; page_nr++) {
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unsigned int this_len;
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if (!len)
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@ -317,28 +366,7 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
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* this_len is the max we'll use from this page
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*/
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this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
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find_page:
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/*
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* lookup the page for this index
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*/
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page = find_get_page(mapping, index);
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if (!page) {
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/*
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* page didn't exist, allocate one
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*/
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page = page_cache_alloc_cold(mapping);
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if (!page)
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break;
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error = add_to_page_cache_lru(page, mapping, index,
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mapping_gfp_mask(mapping));
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if (unlikely(error)) {
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page_cache_release(page);
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break;
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}
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goto readpage;
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}
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page = pages[page_nr];
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/*
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* If the page isn't uptodate, we may need to start io on it
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@ -360,7 +388,6 @@ find_page:
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*/
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if (!page->mapping) {
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unlock_page(page);
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page_cache_release(page);
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break;
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}
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/*
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@ -371,16 +398,20 @@ find_page:
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goto fill_it;
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}
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readpage:
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/*
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* need to read in the page
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*/
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error = mapping->a_ops->readpage(in, page);
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if (unlikely(error)) {
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page_cache_release(page);
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/*
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* We really should re-lookup the page here,
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* but it complicates things a lot. Instead
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* lets just do what we already stored, and
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* we'll get it the next time we are called.
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*/
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if (error == AOP_TRUNCATED_PAGE)
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goto find_page;
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error = 0;
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break;
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}
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@ -389,10 +420,8 @@ readpage:
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*/
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isize = i_size_read(mapping->host);
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end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
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if (unlikely(!isize || index > end_index)) {
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page_cache_release(page);
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if (unlikely(!isize || index > end_index))
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break;
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}
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/*
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* if this is the last page, see if we need to shrink
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@ -400,27 +429,33 @@ readpage:
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*/
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if (end_index == index) {
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loff = PAGE_CACHE_SIZE - (isize & ~PAGE_CACHE_MASK);
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if (total_len + loff > isize) {
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page_cache_release(page);
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if (total_len + loff > isize)
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break;
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}
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/*
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* force quit after adding this page
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*/
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nr_pages = spd.nr_pages;
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len = this_len;
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this_len = min(this_len, loff);
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loff = 0;
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}
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}
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fill_it:
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pages[spd.nr_pages] = page;
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partial[spd.nr_pages].offset = loff;
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partial[spd.nr_pages].len = this_len;
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partial[page_nr].offset = loff;
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partial[page_nr].len = this_len;
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len -= this_len;
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total_len += this_len;
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loff = 0;
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spd.nr_pages++;
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index++;
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}
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/*
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* Release any pages at the end, if we quit early. 'i' is how far
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* we got, 'nr_pages' is how many pages are in the map.
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*/
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while (page_nr < nr_pages)
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page_cache_release(pages[page_nr++]);
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if (spd.nr_pages)
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return splice_to_pipe(pipe, &spd);
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