From 0b964600d3aae56ff9d5bdd710a79f39a44c572c Mon Sep 17 00:00:00 2001 From: Gao Xiang Date: Mon, 22 Mar 2021 02:32:27 +0800 Subject: [PATCH] erofs: complete a missing case for inplace I/O Add a missing case which could cause unnecessary page allocation but not directly use inplace I/O instead, which increases runtime extra memory footprint. The detail is, considering an online file-backed page, the right half of the page is chosen to be cached (e.g. the end page of a readahead request) and some of its data doesn't exist in managed cache, so the pcluster will be definitely kept in the submission chain. (IOWs, it cannot be decompressed without I/O, e.g., due to the bypass queue). Currently, DELAYEDALLOC/TRYALLOC cases can be downgraded as NOINPLACE, and stop online pages from inplace I/O. After this patch, unneeded page allocations won't be observed in pickup_page_for_submission() then. Link: https://lore.kernel.org/r/20210321183227.5182-1-hsiangkao@aol.com Signed-off-by: Gao Xiang --- fs/erofs/zdata.c | 44 +++++++++++++++++++++++++++++--------------- 1 file changed, 29 insertions(+), 15 deletions(-) diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c index 7ab8a4e3dfcb..cd9b76216925 100644 --- a/fs/erofs/zdata.c +++ b/fs/erofs/zdata.c @@ -104,6 +104,12 @@ enum z_erofs_collectmode { * |_______PRIMARY_FOLLOWED_______|________PRIMARY_HOOKED___________| */ COLLECT_PRIMARY_HOOKED, + /* + * a weak form of COLLECT_PRIMARY_FOLLOWED, the difference is that it + * could be dispatched into bypass queue later due to uptodated managed + * pages. All related online pages cannot be reused for inplace I/O (or + * pagevec) since it can be directly decoded without I/O submission. + */ COLLECT_PRIMARY_FOLLOWED_NOINPLACE, /* * The current collection has been linked with the owned chain, and @@ -186,21 +192,25 @@ static void preload_compressed_pages(struct z_erofs_collector *clt, if (page) { 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; + } else { + /* I/O is needed, no possible to decompress directly */ standalone = false; - continue; + switch (type) { + case DELAYEDALLOC: + t = tagptr_init(compressed_page_t, + PAGE_UNALLOCATED); + break; + case TRYALLOC: + newpage = erofs_allocpage(pagepool, gfp); + if (!newpage) + continue; + set_page_private(newpage, + Z_EROFS_PREALLOCATED_PAGE); + t = tag_compressed_page_justfound(newpage); + break; + default: /* DONTALLOC */ + continue; + } } if (!cmpxchg_relaxed(pages, NULL, tagptr_cast_ptr(t))) @@ -214,7 +224,11 @@ dontalloc: } } - if (standalone) /* downgrade to PRIMARY_FOLLOWED_NOINPLACE */ + /* + * don't do inplace I/O if all compressed pages are available in + * managed cache since it can be moved to the bypass queue instead. + */ + if (standalone) clt->mode = COLLECT_PRIMARY_FOLLOWED_NOINPLACE; }