The patch titled
Subject: mm: put readahead pages in cache earlier
has been added to the -mm tree. Its filename is
mm-put-readahead-pages-in-cache-earlier.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-put-readahead-pages-in-cache-earlier.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-put-readahead-pages-in-cache-earlier.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Subject: mm: put readahead pages in cache earlier
When populating the page cache for readahead, mappings that use
->readpages must populate the page cache themselves as the pages are
passed on a linked list which would normally be used for the page cache's
LRU. For mappings that use ->readpage or the upcoming ->readahead method,
we can put the pages into the page cache as soon as they're allocated,
which solves a race between readahead and direct IO. It also lets us
remove the gfp argument from read_pages().
Use the new readahead_page() API to implement the repeated calls to
->readpage(), just like most filesystems will.
Link: http://lkml.kernel.org/r/20200414150233.24495-11-willy@xxxxxxxxxxxxx
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: William Kucharski <william.kucharski@xxxxxxxxxx>
Cc: Chao Yu <yuchao0@xxxxxxxxxx>
Cc: Cong Wang <xiyou.wangcong@xxxxxxxxx>
Cc: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Cc: Dave Chinner <dchinner@xxxxxxxxxx>
Cc: Eric Biggers <ebiggers@xxxxxxxxxx>
Cc: Gao Xiang <gaoxiang25@xxxxxxxxxx>
Cc: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx>
Cc: Junxiao Bi <junxiao.bi@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Zi Yan <ziy@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/readahead.c | 46 ++++++++++++++++++++++++++++------------------
1 file changed, 28 insertions(+), 18 deletions(-)
--- a/mm/readahead.c~mm-put-readahead-pages-in-cache-earlier
+++ a/mm/readahead.c
@@ -114,14 +114,14 @@ int read_cache_pages(struct address_spac
EXPORT_SYMBOL(read_cache_pages);
static void read_pages(struct readahead_control *rac, struct list_head *pages,
- gfp_t gfp)
+ bool skip_page)
{
const struct address_space_operations *aops = rac->mapping->a_ops;
+ struct page *page;
struct blk_plug plug;
- unsigned page_idx;
if (!readahead_count(rac))
- return;
+ goto out;
blk_start_plug(&plug);
@@ -130,23 +130,23 @@ static void read_pages(struct readahead_
readahead_count(rac));
/* Clean up the remaining pages */
put_pages_list(pages);
- goto out;
- }
-
- for (page_idx = 0; page_idx < readahead_count(rac); page_idx++) {
- struct page *page = lru_to_page(pages);
- list_del(&page->lru);
- if (!add_to_page_cache_lru(page, rac->mapping, page->index,
- gfp))
+ rac->_index += rac->_nr_pages;
+ rac->_nr_pages = 0;
+ } else {
+ while ((page = readahead_page(rac))) {
aops->readpage(rac->file, page);
- put_page(page);
+ put_page(page);
+ }
}
-out:
blk_finish_plug(&plug);
BUG_ON(!list_empty(pages));
- rac->_nr_pages = 0;
+ BUG_ON(readahead_count(rac));
+
+out:
+ if (skip_page)
+ rac->_index++;
}
/*
@@ -168,6 +168,7 @@ void __do_page_cache_readahead(struct ad
struct readahead_control rac = {
.mapping = mapping,
.file = filp,
+ ._index = index,
};
unsigned long i;
@@ -183,6 +184,8 @@ void __do_page_cache_readahead(struct ad
if (index + i > end_index)
break;
+ BUG_ON(index + i != rac._index + rac._nr_pages);
+
page = xa_load(&mapping->i_pages, index + i);
if (page && !xa_is_value(page)) {
/*
@@ -190,15 +193,22 @@ void __do_page_cache_readahead(struct ad
* contiguous pages before continuing with the next
* batch.
*/
- read_pages(&rac, &page_pool, gfp_mask);
+ read_pages(&rac, &page_pool, true);
continue;
}
page = __page_cache_alloc(gfp_mask);
if (!page)
break;
- page->index = index + i;
- list_add(&page->lru, &page_pool);
+ if (mapping->a_ops->readpages) {
+ page->index = index + i;
+ list_add(&page->lru, &page_pool);
+ } else if (add_to_page_cache_lru(page, mapping, index + i,
+ gfp_mask) < 0) {
+ put_page(page);
+ read_pages(&rac, &page_pool, true);
+ continue;
+ }
if (i == nr_to_read - lookahead_size)
SetPageReadahead(page);
rac._nr_pages++;
@@ -209,7 +219,7 @@ void __do_page_cache_readahead(struct ad
* uptodate then the caller will launch readpage again, and
* will then handle the error.
*/
- read_pages(&rac, &page_pool, gfp_mask);
+ read_pages(&rac, &page_pool, false);
}
/*
_
Patches currently in -mm which might be from willy@xxxxxxxxxxxxx are
mm-move-readahead-prototypes-from-mmh.patch
mm-return-void-from-various-readahead-functions.patch
mm-ignore-return-value-of-readpages.patch
mm-move-readahead-nr_pages-check-into-read_pages.patch
mm-add-new-readahead_control-api.patch
mm-use-readahead_control-to-pass-arguments.patch
mm-rename-various-offset-parameters-to-index.patch
mm-rename-readahead-loop-variable-to-i.patch
mm-remove-page_offset-from-readahead-loop.patch
mm-put-readahead-pages-in-cache-earlier.patch
mm-add-readahead-address-space-operation.patch
mm-move-end_index-check-out-of-readahead-loop.patch
mm-add-page_cache_readahead_unbounded.patch
mm-document-why-we-dont-set-pagereadahead.patch
mm-use-memalloc_nofs_save-in-readahead-path.patch
fs-convert-mpage_readpages-to-mpage_readahead.patch
btrfs-convert-from-readpages-to-readahead.patch
erofs-convert-uncompressed-files-from-readpages-to-readahead.patch
erofs-convert-compressed-files-from-readpages-to-readahead.patch
ext4-convert-from-readpages-to-readahead.patch
ext4-pass-the-inode-to-ext4_mpage_readpages.patch
f2fs-convert-from-readpages-to-readahead.patch
f2fs-pass-the-inode-to-f2fs_mpage_readpages.patch
fuse-convert-from-readpages-to-readahead.patch
iomap-convert-from-readpages-to-readahead.patch
