Re: [PATCH] erofs: force inplace I/O under low memory scenario
From: Gao Xiang
Date: Wed Dec 09 2020 - 06:38:41 EST
Hi Chao,
On Wed, Dec 09, 2020 at 06:07:08PM +0800, Chao Yu wrote:
> On 2020/12/8 13:46, Gao Xiang wrote:
...
> > bool standalone = true;
> > + gfp_t gfp = mapping_gfp_constraint(mc, GFP_KERNEL) & ~__GFP_DIRECT_RECLAIM;
>
> Could be local as there is only one place uses it.
This line is somewhat too long, I have no idea how to deal
with it inlined properly... I think I might leave it as-is
or find a better way to fold in it without generating too
long lines....
Thanks,
Gao Xiang
>
> Reviewed-by: Chao Yu <yuchao0@xxxxxxxxxx>
>
> Thanks,
>
> > if (clt->mode < COLLECT_PRIMARY_FOLLOWED)
> > return;
> > @@ -168,6 +175,7 @@ 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 +187,17 @@ 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) {
> > + gfp |= __GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN;
> > +
> > + 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 +207,12 @@ 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 */
> > @@ -560,7 +582,7 @@ 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);
> > @@ -613,11 +635,12 @@ 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:
> > /*
> > @@ -1011,6 +1034,16 @@ 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);
> > /*
> > @@ -1073,7 +1106,7 @@ 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 */
> > set_page_private(page, Z_EROFS_SHORTLIVED_PAGE);
> > @@ -1282,7 +1315,7 @@ 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 */
> > @@ -1336,7 +1369,7 @@ 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",
> >
>