[PATCH v2] erofs: force inplace I/O under low memory scenario
From: Gao Xiang
Date: Wed Dec 09 2020 - 07:38:54 EST
From: Gao Xiang <hsiangkao@xxxxxxxxxx>
Try to forcely switch to inplace I/O under low memory scenario in
order to avoid direct memory reclaim due to cached page allocation.
Reviewed-by: Chao Yu <yuchao0@xxxxxxxxxx>
Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxx>
---
v2:
refine the gfp definition.
fs/erofs/compress.h | 3 +++
fs/erofs/zdata.c | 48 +++++++++++++++++++++++++++++++++++++--------
2 files changed, 43 insertions(+), 8 deletions(-)
diff --git a/fs/erofs/compress.h b/fs/erofs/compress.h
index 4dadde18cdf1..aea129ddda74 100644
--- a/fs/erofs/compress.h
+++ b/fs/erofs/compress.h
@@ -28,11 +28,13 @@ struct z_erofs_decompress_req {
/* some special page->private (unsigned long, see below) */
#define Z_EROFS_SHORTLIVED_PAGE (-1UL << 2)
+#define Z_EROFS_PREALLOCATED_PAGE (-2UL << 2)
/*
* For all pages in a pcluster, page->private should be one of
* Type Last 2bits page->private
* short-lived page 00 Z_EROFS_SHORTLIVED_PAGE
+ * preallocated page (tryalloc) 00 Z_EROFS_PREALLOCATED_PAGE
* cached/managed page 00 pointer to z_erofs_pcluster
* online page (file-backed, 01/10/11 sub-index << 2 | count
* some pages can be used for inplace I/O)
@@ -40,6 +42,7 @@ struct z_erofs_decompress_req {
* page->mapping should be one of
* Type page->mapping
* short-lived page NULL
+ * preallocated page NULL
* cached/managed page non-NULL or NULL (invalidated/truncated page)
* online page non-NULL
*
diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index 777790038bc9..6cb356c4217b 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -20,6 +20,11 @@
enum z_erofs_cache_alloctype {
DONTALLOC, /* don't allocate any cached pages */
DELAYEDALLOC, /* delayed allocation (at the time of submitting io) */
+ /*
+ * try to use cached I/O if page allocation succeeds or fallback
+ * to in-place I/O instead to avoid any direct reclaim.
+ */
+ TRYALLOC,
};
/*
@@ -154,13 +159,16 @@ static DEFINE_MUTEX(z_pagemap_global_lock);
static void preload_compressed_pages(struct z_erofs_collector *clt,
struct address_space *mc,
- enum z_erofs_cache_alloctype type)
+ enum z_erofs_cache_alloctype type,
+ struct list_head *pagepool)
{
const struct z_erofs_pcluster *pcl = clt->pcl;
const unsigned int clusterpages = BIT(pcl->clusterbits);
struct page **pages = clt->compressedpages;
pgoff_t index = pcl->obj.index + (pages - pcl->compressed_pages);
bool standalone = true;
+ gfp_t gfp = (mapping_gfp_mask(mc) & ~__GFP_DIRECT_RECLAIM) |
+ __GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN;
if (clt->mode < COLLECT_PRIMARY_FOLLOWED)
return;
@@ -168,6 +176,7 @@ static void preload_compressed_pages(struct z_erofs_collector *clt,
for (; pages < pcl->compressed_pages + clusterpages; ++pages) {
struct page *page;
compressed_page_t t;
+ struct page *newpage = NULL;
/* the compressed page was loaded before */
if (READ_ONCE(*pages))
@@ -179,7 +188,15 @@ static void preload_compressed_pages(struct z_erofs_collector *clt,
t = tag_compressed_page_justfound(page);
} else if (type == DELAYEDALLOC) {
t = tagptr_init(compressed_page_t, PAGE_UNALLOCATED);
+ } else if (type == TRYALLOC) {
+ newpage = erofs_allocpage(pagepool, gfp);
+ if (!newpage)
+ goto dontalloc;
+
+ set_page_private(newpage, Z_EROFS_PREALLOCATED_PAGE);
+ t = tag_compressed_page_justfound(newpage);
} else { /* DONTALLOC */
+dontalloc:
if (standalone)
clt->compressedpages = pages;
standalone = false;
@@ -189,8 +206,12 @@ static void preload_compressed_pages(struct z_erofs_collector *clt,
if (!cmpxchg_relaxed(pages, NULL, tagptr_cast_ptr(t)))
continue;
- if (page)
+ if (page) {
put_page(page);
+ } else if (newpage) {
+ set_page_private(newpage, 0);
+ list_add(&newpage->lru, pagepool);
+ }
}
if (standalone) /* downgrade to PRIMARY_FOLLOWED_NOINPLACE */
@@ -554,7 +575,7 @@ static bool should_alloc_managed_pages(struct z_erofs_decompress_frontend *fe,
}
static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
- struct page *page)
+ struct page *page, struct list_head *pagepool)
{
struct inode *const inode = fe->inode;
struct erofs_sb_info *const sbi = EROFS_I_SB(inode);
@@ -607,11 +628,12 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
/* preload all compressed pages (maybe downgrade role if necessary) */
if (should_alloc_managed_pages(fe, sbi->ctx.cache_strategy, map->m_la))
- cache_strategy = DELAYEDALLOC;
+ cache_strategy = TRYALLOC;
else
cache_strategy = DONTALLOC;
- preload_compressed_pages(clt, MNGD_MAPPING(sbi), cache_strategy);
+ preload_compressed_pages(clt, MNGD_MAPPING(sbi),
+ cache_strategy, pagepool);
hitted:
/*
@@ -1005,6 +1027,16 @@ static struct page *pickup_page_for_submission(struct z_erofs_pcluster *pcl,
justfound = tagptr_unfold_tags(t);
page = tagptr_unfold_ptr(t);
+ /*
+ * preallocated cached pages, which is used to avoid direct reclaim
+ * otherwise, it will go inplace I/O path instead.
+ */
+ if (page->private == Z_EROFS_PREALLOCATED_PAGE) {
+ WRITE_ONCE(pcl->compressed_pages[nr], page);
+ set_page_private(page, 0);
+ tocache = true;
+ goto out_tocache;
+ }
mapping = READ_ONCE(page->mapping);
/*
@@ -1067,7 +1099,7 @@ static struct page *pickup_page_for_submission(struct z_erofs_pcluster *pcl,
cond_resched();
goto repeat;
}
-
+out_tocache:
if (!tocache || add_to_page_cache_lru(page, mc, index + nr, gfp)) {
/* turn into temporary page if fails (1 ref) */
set_page_private(page, Z_EROFS_SHORTLIVED_PAGE);
@@ -1278,7 +1310,7 @@ static int z_erofs_readpage(struct file *file, struct page *page)
f.headoffset = (erofs_off_t)page->index << PAGE_SHIFT;
- err = z_erofs_do_read_page(&f, page);
+ err = z_erofs_do_read_page(&f, page, &pagepool);
(void)z_erofs_collector_end(&f.clt);
/* if some compressed cluster ready, need submit them anyway */
@@ -1332,7 +1364,7 @@ static void z_erofs_readahead(struct readahead_control *rac)
/* traversal in reverse order */
head = (void *)page_private(page);
- err = z_erofs_do_read_page(&f, page);
+ err = z_erofs_do_read_page(&f, page, &pagepool);
if (err)
erofs_err(inode->i_sb,
"readahead error at page %lu @ nid %llu",
--
2.24.0