[PATCH 4/4] erofs: convert z_erofs_bind_cache() to folios

Gao Xiang
2025-01-14T03:44:43Z

The managed cache uses a pseudo inode to keep (necessary) compressed
data.

Currently, it still uses zero-order folios, so this is just a trivial
conversion, except that the use of the pagepool is temporarily dropped.

Drop some obsoleted comments too.

Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
---
fs/erofs/compress.h | 23 +-------------------
fs/erofs/zdata.c | 51 ++++++++++++++++++---------------------------
2 files changed, 21 insertions(+), 53 deletions(-)

diff --git a/fs/erofs/compress.h b/fs/erofs/compress.h
index 7bfe251680ec..65ff39401020 100644
--- a/fs/erofs/compress.h
+++ b/fs/erofs/compress.h
@@ -29,29 +29,8 @@ struct z_erofs_decompressor {
char *name;
};

-/* 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)
- *
- * 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
- *
- * For all managed pages, PG_private should be set with 1 extra refcount,
- * which is used for page reclaim / migration.
- */
+#define Z_EROFS_PREALLOCATED_FOLIO ((void *)(-2UL << 2))

/*
* Currently, short-lived pages are pages directly from buddy system
diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index dcbb692ac058..b3fb18d1a9c8 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -516,13 +516,11 @@ static void z_erofs_bind_cache(struct z_erofs_frontend *fe)
struct z_erofs_pcluster *pcl = fe->pcl;
unsigned int pclusterpages = z_erofs_pclusterpages(pcl);
bool shouldalloc = z_erofs_should_alloc_cache(fe);
- bool standalone = true;
- /*
- * optimistic allocation without direct reclaim since inplace I/O
- * can be used if low memory otherwise.
- */
+ bool may_bypass = true;
+ /* Optimistic allocation, as in-place I/O can be used as a fallback */
gfp_t gfp = (mapping_gfp_mask(mc) & ~__GFP_DIRECT_RECLAIM) |
__GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN;
+ struct folio *folio, *newfolio;
unsigned int i;

if (i_blocksize(fe->inode) != PAGE_SIZE ||
@@ -530,47 +528,42 @@ static void z_erofs_bind_cache(struct z_erofs_frontend *fe)
return;

for (i = 0; i < pclusterpages; ++i) {
- struct page *page, *newpage;
-
/* Inaccurate check w/o locking to avoid unneeded lookups */
if (READ_ONCE(pcl->compressed_bvecs[i].page))
continue;

- page = find_get_page(mc, pcl->index + i);
- if (!page) {
- /* I/O is needed, no possible to decompress directly */
- standalone = false;
+ folio = filemap_get_folio(mc, pcl->index + i);
+ if (IS_ERR(folio)) {
+ may_bypass = false;
if (!shouldalloc)
continue;

/*
- * Try cached I/O if allocation succeeds or fallback to
- * in-place I/O instead to avoid any direct reclaim.
+ * Allocate a managed folio for cached I/O, or it may be
+ * then filled with a file-backed folio for in-place I/O
*/
- newpage = erofs_allocpage(&fe->pagepool, gfp);
- if (!newpage)
+ newfolio = filemap_alloc_folio(gfp, 0);
+ if (!newfolio)
continue;
- set_page_private(newpage, Z_EROFS_PREALLOCATED_PAGE);
+ newfolio->private = Z_EROFS_PREALLOCATED_FOLIO;
+ folio = NULL;
}
spin_lock(&pcl->lockref.lock);
if (!pcl->compressed_bvecs[i].page) {
- pcl->compressed_bvecs[i].page = page ? page : newpage;
+ pcl->compressed_bvecs[i].page =
+ folio_page(folio ?: newfolio, 0);
spin_unlock(&pcl->lockref.lock);
continue;
}
spin_unlock(&pcl->lockref.lock);
-
- if (page)
- put_page(page);
- else if (newpage)
- erofs_pagepool_add(&fe->pagepool, newpage);
+ folio_put(folio ?: newfolio);
}

/*
- * 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.
+ * Don't perform in-place I/O if all compressed pages are available in
+ * the managed cache, as the pcluster can be moved to the bypass queue.
*/
- if (standalone)
+ if (may_bypass)
fe->mode = Z_EROFS_PCLUSTER_FOLLOWED_NOINPLACE;
}

@@ -1481,12 +1474,8 @@ static void z_erofs_fill_bio_vec(struct bio_vec *bvec,
DBG_BUGON(z_erofs_is_shortlived_page(bvec->bv_page));

folio = page_folio(zbv.page);
- /*
- * Handle preallocated cached folios. We tried to allocate such folios
- * without triggering direct reclaim. If allocation failed, inplace
- * file-backed folios will be used instead.
- */
- if (folio->private == (void *)Z_EROFS_PREALLOCATED_PAGE) {
+ /* For preallocated managed folios, add them to page cache here */
+ if (folio->private == Z_EROFS_PREALLOCATED_FOLIO) {
tocache = true;
goto out_tocache;
}
--
2.43.5